Prof. Dr. Jürgen Hauer
Academic Research Focus
- Dynamic spectroscopy
- Photosynthetic systems and their constituents
- Molecular J Aggregates
- Photochemistry and Photophysics
- 2D-Materials and inorganic systems
- Photosynthetic systems and their constituents
- Molecular J Aggregates
- Photochemistry and Photophysics
- 2D-Materials and inorganic systems
Fields of Application
Nanomaterials, Photo-(electro)catalysis, Photonics
Publications
28.
M Binzer, F Šanda, L Mewes, E Thyrhaug, J Hauer
Broadband shot-to-shot transient absorption anisotropy Journal Article
In: The Journal of Chemical Physics, vol. 162, no. 23, pp. 234201, 2025, ISSN: 0021-9606.
@article{nokey,
title = {Broadband shot-to-shot transient absorption anisotropy},
author = {M Binzer and F \v{S}anda and L Mewes and E Thyrhaug and J Hauer},
url = {https://doi.org/10.1063/5.0268081},
doi = {10.1063/5.0268081},
issn = {0021-9606},
year = {2025},
date = {2025-06-16},
journal = {The Journal of Chemical Physics},
volume = {162},
number = {23},
pages = {234201},
abstract = {Transient absorption (TA) is the most widespread method to follow ultrafast dynamics in molecules and materials. The related method of TA anisotropy (TAA) reports on the ultrafast reorientation dynamics of transition dipole moments, reporting on phenomena ranging from electronic dephasing to orientational diffusion. While these are fundamental aspects complementary to TA, TAA is generally less widely used. The main reason is that TAA signals are usually not measured directly but are retrieved from two consecutive TA measurements with parallel (R‖) and perpendicular (R⊥) polarization of pump and probe pulses. This means that even minor systematic errors in these measurements lead to drastic changes in the TAA signal. In this work, the authors demonstrate alternating shot-to-shot detection of R‖ and R⊥, minimizing systematic errors due to laser fluctuations. The employed broadband detection lets us discuss effects dependent on detection wavelength in the ultrafast anisotropy decay of 2,3-naphthalocyanine, a system previously scrutinized by David Jonas and co-workers. In particular, we compare timescales of population relaxation and decoherence and support the proposals for isotropic type of relaxation in square symmetric molecules.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Transient absorption (TA) is the most widespread method to follow ultrafast dynamics in molecules and materials. The related method of TA anisotropy (TAA) reports on the ultrafast reorientation dynamics of transition dipole moments, reporting on phenomena ranging from electronic dephasing to orientational diffusion. While these are fundamental aspects complementary to TA, TAA is generally less widely used. The main reason is that TAA signals are usually not measured directly but are retrieved from two consecutive TA measurements with parallel (R‖) and perpendicular (R⊥) polarization of pump and probe pulses. This means that even minor systematic errors in these measurements lead to drastic changes in the TAA signal. In this work, the authors demonstrate alternating shot-to-shot detection of R‖ and R⊥, minimizing systematic errors due to laser fluctuations. The employed broadband detection lets us discuss effects dependent on detection wavelength in the ultrafast anisotropy decay of 2,3-naphthalocyanine, a system previously scrutinized by David Jonas and co-workers. In particular, we compare timescales of population relaxation and decoherence and support the proposals for isotropic type of relaxation in square symmetric molecules.
27.
H Hao, P Malý, Y Cui, M Binzer, E Thyrhaug, J Hauer
Fluorescence-Detected Pump–Probe Spectroscopy for Artifact-Free Detection of Stokes Shift Dynamics Journal Article
In: The Journal of Physical Chemistry Letters, pp. 4861-4868, 2025.
@article{nokey,
title = {Fluorescence-Detected Pump\textendashProbe Spectroscopy for Artifact-Free Detection of Stokes Shift Dynamics},
author = {H Hao and P Mal\'{y} and Y Cui and M Binzer and E Thyrhaug and J Hauer},
url = {https://doi.org/10.1021/acs.jpclett.5c00646},
doi = {10.1021/acs.jpclett.5c00646},
year = {2025},
date = {2025-05-09},
journal = {The Journal of Physical Chemistry Letters},
pages = {4861-4868},
abstract = {Fluorescence-detected pump\textendashprobe (F-PP) spectroscopy is a recently developed method to study excited-state dynamics. F-PP combines the temporal resolution of conventional transient absorption (TA) spectroscopy with the sensitivity of fluorescence detection. In this work, we demonstrate inherently phase-stable F-PP spectroscopy using 20 fs pulses to monitor the ultrafast Stokes shift dynamics of a solvated fluorophore (Y12). We observed a shift in the stimulated emission maximum with a time constant of 84 fs. In contrast to TA, F-PP provides a coherent artifact-free view of this process. Using quantitative signal background subtraction, as discussed in this work, F-PP uncovers the pure stimulated emission spectrum and its ultrafast dynamics. This signal isolation is a clear advantage over TA, where different contributions often overlap heavily. We compare results from F-PP and TA on an equal footing using the same excitation pulses, emphasizing the features and advantages of the F-PP technique.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Fluorescence-detected pump–probe (F-PP) spectroscopy is a recently developed method to study excited-state dynamics. F-PP combines the temporal resolution of conventional transient absorption (TA) spectroscopy with the sensitivity of fluorescence detection. In this work, we demonstrate inherently phase-stable F-PP spectroscopy using 20 fs pulses to monitor the ultrafast Stokes shift dynamics of a solvated fluorophore (Y12). We observed a shift in the stimulated emission maximum with a time constant of 84 fs. In contrast to TA, F-PP provides a coherent artifact-free view of this process. Using quantitative signal background subtraction, as discussed in this work, F-PP uncovers the pure stimulated emission spectrum and its ultrafast dynamics. This signal isolation is a clear advantage over TA, where different contributions often overlap heavily. We compare results from F-PP and TA on an equal footing using the same excitation pulses, emphasizing the features and advantages of the F-PP technique.
26.
E Keil, A Kumar, L Bäuml, S Reiter, E Thyrhaug, S Moser, C D P Duffy, R De Vivie-Riedle, J Hauer
Reassessing the role and lifetime of Qx in the energy transfer dynamics of chlorophyll a Journal Article
In: Chemical Science, 2024, ISSN: 2041-6520.
@article{nokey,
title = {Reassessing the role and lifetime of Qx in the energy transfer dynamics of chlorophyll a},
author = {E Keil and A Kumar and L B\"{a}uml and S Reiter and E Thyrhaug and S Moser and C D P Duffy and R De Vivie-Riedle and J Hauer},
url = {http://dx.doi.org/10.1039/D4SC06441K},
doi = {10.1039/D4SC06441K},
issn = {2041-6520},
year = {2024},
date = {2024-11-27},
journal = {Chemical Science},
abstract = {Chlorophylls are photoactive molecular building blocks essential to most photosynthetic systems. They have comparatively simple optical spectra defined by states with near-orthogonal transition dipole moments, referred to as Bx and By in the blue/green spectral region, and Qx and Qy in the red. Underlying these spectra is a surprisingly complex electronic structure, where strong electronic-vibrational interactions are crucial to the description of state characters. Following photoexcitation, energy-relaxation between these states is extremely fast and connected to only modest changes in spectral shapes. This has pushed conventional theoretical and experimental methods to their limits and left the energy transfer pathway under debate. In this work, we address the electronic structure and photodynamics of chlorophyll a using polarization-controlled static \textendash and ultrafast \textendash optical spectroscopies. We support the experimental data analysis with quantum dynamical simulations and effective heat dissipation models. We find clear evidence for B → Q transfer on a timescale of ∼100 fs and identify Qx signatures within fluorescence excitation and transient spectra. However, Qx is populated only fleetingly, with a lifetime well below our ∼30 fs experimental time resolution. Outside of these timescales, the kinetics are determined by vibrational relaxation and cooling. Despite its ultrashort lifetime, our theoretical analysis suggests that Qx plays a crucial role as a bridging state in B → Q energy transfer. In summary, our findings present a unified and consistent picture of chlorophyll relaxation dynamics based on ultrafast and polarization-resolved spectroscopic techniques supported by extensive theoretical models; they clarify the role of Qx in the energy deactivation network of chlorophyll a.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Chlorophylls are photoactive molecular building blocks essential to most photosynthetic systems. They have comparatively simple optical spectra defined by states with near-orthogonal transition dipole moments, referred to as Bx and By in the blue/green spectral region, and Qx and Qy in the red. Underlying these spectra is a surprisingly complex electronic structure, where strong electronic-vibrational interactions are crucial to the description of state characters. Following photoexcitation, energy-relaxation between these states is extremely fast and connected to only modest changes in spectral shapes. This has pushed conventional theoretical and experimental methods to their limits and left the energy transfer pathway under debate. In this work, we address the electronic structure and photodynamics of chlorophyll a using polarization-controlled static – and ultrafast – optical spectroscopies. We support the experimental data analysis with quantum dynamical simulations and effective heat dissipation models. We find clear evidence for B → Q transfer on a timescale of ∼100 fs and identify Qx signatures within fluorescence excitation and transient spectra. However, Qx is populated only fleetingly, with a lifetime well below our ∼30 fs experimental time resolution. Outside of these timescales, the kinetics are determined by vibrational relaxation and cooling. Despite its ultrashort lifetime, our theoretical analysis suggests that Qx plays a crucial role as a bridging state in B → Q energy transfer. In summary, our findings present a unified and consistent picture of chlorophyll relaxation dynamics based on ultrafast and polarization-resolved spectroscopic techniques supported by extensive theoretical models; they clarify the role of Qx in the energy deactivation network of chlorophyll a.
25.
S Reiter, I Gordiy, K L Kollmannsberger, F Liu, E Thyrhaug, D Leister, J Warnan, J Hauer, R De Vivie-Riedle
Molecular interactions of photosystem I and ZIF-8 in bio-nanohybrid materials Journal Article
In: Physical Chemistry Chemical Physics, vol. 26, no. 35, pp. 23228-23239, 2024, ISSN: 1463-9076.
@article{nokey,
title = {Molecular interactions of photosystem I and ZIF-8 in bio-nanohybrid materials},
author = {S Reiter and I Gordiy and K L Kollmannsberger and F Liu and E Thyrhaug and D Leister and J Warnan and J Hauer and R De Vivie-Riedle},
url = {http://dx.doi.org/10.1039/D4CP03021D},
doi = {10.1039/D4CP03021D},
issn = {1463-9076},
year = {2024},
date = {2024-08-22},
journal = {Physical Chemistry Chemical Physics},
volume = {26},
number = {35},
pages = {23228-23239},
abstract = {Bio-nanohybrid devices featuring natural photocatalysts bound to a nanostructure hold great promise in the search for sustainable energy conversion. One of the major challenges of integrating biological systems is protecting them against harsh environmental conditions while retaining, or ideally enhancing their photophysical properties. In this mainly computational work we investigate an assembly of cyanobacterial photosystem I (PS I) embedded in a metal\textendashorganic framework (MOF), namely the zeolitic imidazolate framework ZIF-8. This complex has been reported experimentally [Bennett et al., Nanoscale Adv., 2019, 1, 94] but so far the molecular interactions between PS I and the MOF remained elusive. We show via absorption spectroscopy that PS I remains intact throughout the encapsulation-release cycle. Molecular dynamics (MD) simulations further confirm that the encapsulation has no noticeable structural impact on the photosystem. However, the MOF building blocks frequently coordinate to the Mg2+ ions of chlorophylls in the periphery of the antenna complex. High-level quantum mechanical calculations reveal charge-transfer interactions, which affect the excitonic network and thereby may reversibly change the fluorescence properties of PS I. Nevertheless, our results highlight the stability of PS I in the MOF, as the reaction center remains unimpeded by the heterogeneous environment, paving the way for applications in the foreseeable future.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Bio-nanohybrid devices featuring natural photocatalysts bound to a nanostructure hold great promise in the search for sustainable energy conversion. One of the major challenges of integrating biological systems is protecting them against harsh environmental conditions while retaining, or ideally enhancing their photophysical properties. In this mainly computational work we investigate an assembly of cyanobacterial photosystem I (PS I) embedded in a metal–organic framework (MOF), namely the zeolitic imidazolate framework ZIF-8. This complex has been reported experimentally [Bennett et al., Nanoscale Adv., 2019, 1, 94] but so far the molecular interactions between PS I and the MOF remained elusive. We show via absorption spectroscopy that PS I remains intact throughout the encapsulation-release cycle. Molecular dynamics (MD) simulations further confirm that the encapsulation has no noticeable structural impact on the photosystem. However, the MOF building blocks frequently coordinate to the Mg2+ ions of chlorophylls in the periphery of the antenna complex. High-level quantum mechanical calculations reveal charge-transfer interactions, which affect the excitonic network and thereby may reversibly change the fluorescence properties of PS I. Nevertheless, our results highlight the stability of PS I in the MOF, as the reaction center remains unimpeded by the heterogeneous environment, paving the way for applications in the foreseeable future.
24.
Y Xu, M T Peschel, M Jänchen, R Foja, G Storch, E Thyrhaug, R De Vivie-Riedle, J Hauer
Determining Excited-State Absorption Properties of a Quinoid Flavin by Polarization-Resolved Transient Spectroscopy Journal Article
In: The Journal of Physical Chemistry A, vol. 128, no. 19, pp. 3830-3839, 2024, ISSN: 1089-5639.
@article{nokey,
title = {Determining Excited-State Absorption Properties of a Quinoid Flavin by Polarization-Resolved Transient Spectroscopy},
author = {Y Xu and M T Peschel and M J\"{a}nchen and R Foja and G Storch and E Thyrhaug and R De Vivie-Riedle and J Hauer},
url = {https://doi.org/10.1021/acs.jpca.4c01260},
doi = {10.1021/acs.jpca.4c01260},
issn = {1089-5639},
year = {2024},
date = {2024-05-16},
journal = {The Journal of Physical Chemistry A},
volume = {128},
number = {19},
pages = {3830-3839},
abstract = {As important naturally occurring chromophores, photophysical/chemical properties of quinoid flavins have been extensively studied both experimentally and theoretically. However, little is known about the transition dipole moment (TDM) orientation of excited-state absorption transitions of these important compounds. This aspect is of high interest in the fields of photocatalysis and quantum control studies. In this work, we employ polarization-associated spectra (PAS) to study the excited-state absorption transitions and the underlying TDM directions of a standard quinoid flavin compound. As compared to transient absorption anisotropy (TAA), an analysis based on PAS not only avoids diverging signals but also retrieves the relative angle for ESA transitions with respect to known TDM directions. Quantum chemical calculations of excited-state properties lead to good agreement with TA signals measured in magic angle configuration. Only when comparing experiment and theory for TAA spectra and PAS, do we find deviations when and only when the S0 → S1 of flavin is used as a reference. We attribute this to the vibronic coupling of this transition to a dark state. This effect is only observed in the employed polarization-controlled spectroscopy and would have gone unnoticed in conventional TA.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
As important naturally occurring chromophores, photophysical/chemical properties of quinoid flavins have been extensively studied both experimentally and theoretically. However, little is known about the transition dipole moment (TDM) orientation of excited-state absorption transitions of these important compounds. This aspect is of high interest in the fields of photocatalysis and quantum control studies. In this work, we employ polarization-associated spectra (PAS) to study the excited-state absorption transitions and the underlying TDM directions of a standard quinoid flavin compound. As compared to transient absorption anisotropy (TAA), an analysis based on PAS not only avoids diverging signals but also retrieves the relative angle for ESA transitions with respect to known TDM directions. Quantum chemical calculations of excited-state properties lead to good agreement with TA signals measured in magic angle configuration. Only when comparing experiment and theory for TAA spectra and PAS, do we find deviations when and only when the S0 → S1 of flavin is used as a reference. We attribute this to the vibronic coupling of this transition to a dark state. This effect is only observed in the employed polarization-controlled spectroscopy and would have gone unnoticed in conventional TA.
23.
S N Deger, Y Cui, J Warnan, R A Fischer, F Šanda, J Hauer, A Pöthig
Influence of Chromophore Packing on Multiphoton Absorption in Carbazole-Based Pillar-Layered Coordination Polymers Journal Article
In: ACS Applied Optical Materials, vol. 2, no. 9, pp. 1770-1779, 2024.
@article{nokey,
title = {Influence of Chromophore Packing on Multiphoton Absorption in Carbazole-Based Pillar-Layered Coordination Polymers},
author = {S N Deger and Y Cui and J Warnan and R A Fischer and F \v{S}anda and J Hauer and A P\"{o}thig},
url = {https://doi.org/10.1021/acsaom.4c00080},
doi = {10.1021/acsaom.4c00080},
year = {2024},
date = {2024-04-09},
journal = {ACS Applied Optical Materials},
volume = {2},
number = {9},
pages = {1770-1779},
abstract = {Coordination polymers (CP) and their subgroup metal\textendashorganic frameworks (MOF) are promising classes of modular multiphoton-absorption active materials. However, a detailed knowledge of the structure\textendashproperty relationship or generalized design principles remains elusive. This study examines how various packings of the chromophore linker 9,9′-stilbene-bis-carbazole-3,6-dicarboxylic acid in three synthesized zinc-based CPs affect their MPA activity. Different spatial chromophore arrangements are achieved by the so-called “pillar-layer” synthesis approach, using the chromophore and two different additional pillar linkers (4,4′-bipyridine and 1,2-bis(4-pyridyl)ethane) for CP formation. Two novel pillar-layered CPs, Zn2n(sbcd)(bpy)(DMAc)2n(H2O)3n and Zn2n(sbcd)(bpe)(DMAc)3n(H2O), are reported and examined in their two-photon-absorption-induced photoluminescence and compared to a previously synthesized CP Zn2n(sbcd)(DMAc)2n(H2O)1.5n, containing the same chromophore but no pillars. The comparison shows significant differences for the two-photon absorption cross-sections of the materials, improving it by incorporating the pillar. Our findings point toward the significance of controlling the chromophore orientation to tailor the nonlinear optical properties of the materials. These insights pave the way toward an aim-directed development of MOFs for advanced photonic applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Coordination polymers (CP) and their subgroup metal–organic frameworks (MOF) are promising classes of modular multiphoton-absorption active materials. However, a detailed knowledge of the structure–property relationship or generalized design principles remains elusive. This study examines how various packings of the chromophore linker 9,9′-stilbene-bis-carbazole-3,6-dicarboxylic acid in three synthesized zinc-based CPs affect their MPA activity. Different spatial chromophore arrangements are achieved by the so-called “pillar-layer” synthesis approach, using the chromophore and two different additional pillar linkers (4,4′-bipyridine and 1,2-bis(4-pyridyl)ethane) for CP formation. Two novel pillar-layered CPs, Zn2n(sbcd)(bpy)(DMAc)2n(H2O)3n and Zn2n(sbcd)(bpe)(DMAc)3n(H2O), are reported and examined in their two-photon-absorption-induced photoluminescence and compared to a previously synthesized CP Zn2n(sbcd)(DMAc)2n(H2O)1.5n, containing the same chromophore but no pillars. The comparison shows significant differences for the two-photon absorption cross-sections of the materials, improving it by incorporating the pillar. Our findings point toward the significance of controlling the chromophore orientation to tailor the nonlinear optical properties of the materials. These insights pave the way toward an aim-directed development of MOFs for advanced photonic applications.
22.
Y Xu, L Mewes, E Thyrhaug, V Sláma, F Šanda, H Langhals, J Hauer
Isolating Pure Donor and Acceptor Signals by Polarization-Controlled Transient Absorption Spectroscopy Journal Article
In: The Journal of Physical Chemistry Letters, vol. 14, no. 23, pp. 5390-5396, 2023.
@article{nokey,
title = {Isolating Pure Donor and Acceptor Signals by Polarization-Controlled Transient Absorption Spectroscopy},
author = {Y Xu and L Mewes and E Thyrhaug and V Sl\'{a}ma and F \v{S}anda and H Langhals and J Hauer},
url = {https://doi.org/10.1021/acs.jpclett.3c01451},
doi = {10.1021/acs.jpclett.3c01451},
year = {2023},
date = {2023-06-06},
journal = {The Journal of Physical Chemistry Letters},
volume = {14},
number = {23},
pages = {5390-5396},
abstract = {The optical spectra of molecules are often highly congested, inhibiting definite assignment of features and dynamics. In this work, we demonstrate and apply a polarization-based strategy for the decomposition of time-resolved optical spectra to analyze the electronic structure and energy transfer in a molecular donor\textendashacceptor (D\textendashA) dyad. We choose a dyad with orthogonal transition dipole moments for D and A and high fluorescence quantum yield to show that polarization-controlled ultrafast transient absorption spectra can isolate the pure D and A parts of the total signal. This provides a strategy to greatly reduce spectral congestion in complex systems and thus allows for detailed studies of electronic structure and electronic energy transfer.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The optical spectra of molecules are often highly congested, inhibiting definite assignment of features and dynamics. In this work, we demonstrate and apply a polarization-based strategy for the decomposition of time-resolved optical spectra to analyze the electronic structure and energy transfer in a molecular donor–acceptor (D–A) dyad. We choose a dyad with orthogonal transition dipole moments for D and A and high fluorescence quantum yield to show that polarization-controlled ultrafast transient absorption spectra can isolate the pure D and A parts of the total signal. This provides a strategy to greatly reduce spectral congestion in complex systems and thus allows for detailed studies of electronic structure and electronic energy transfer.
21.
C Wallach, Y Selic, F S Geitner, A Kumar, E Thyrhaug, J Hauer, A J Karttunen, T F Fässler
Probing Charge-Transfer Processes in a Covalently Linked [Ge9]-Cluster Imine Dyad Journal Article
In: Angewandte Chemie International Edition, vol. 62, no. 29, pp. e202304088, 2023, ISSN: 1433-7851.
@article{nokey,
title = {Probing Charge-Transfer Processes in a Covalently Linked [Ge9]-Cluster Imine Dyad},
author = {C Wallach and Y Selic and F S Geitner and A Kumar and E Thyrhaug and J Hauer and A J Karttunen and T F F\"{a}ssler},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202304088},
doi = {https://doi.org/10.1002/anie.202304088},
issn = {1433-7851},
year = {2023},
date = {2023-04-27},
journal = {Angewandte Chemie International Edition},
volume = {62},
number = {29},
pages = {e202304088},
abstract = {Abstract C60 donor dyads in which the carbon cage is covalently linked to an electron-donating unit have been discussed as one possibility for an electron-transfer system, and it has been shown that spherical [Ge9] cluster anions show a close relation to fullerenes with respect to their electronic structure. However, the optical properties of these clusters and of functionalized cluster derivatives are almost unknown. We now report on the synthesis of the intensely red [Ge9] cluster linked to an extended π-electron system. [Ge9Si(TMS)32CH3C=N-DAB(II)Dipp]− (1−) is formed upon the reaction of [Ge9Si(TMS)32]2− with bromo-diazaborole DAB(II)Dipp-Br in CH3CN (TMS=trimethylsilyl; DAB(II)=1,3,2-diazaborole with an unsaturated backbone; Dipp=2,6-di-iso-propylphenyl). Reversible protonation of the imine entity in 1− yields the deep green, zwitterionic cluster [Ge9Si(TMS)32CH3C=N(H)-DAB(II)Dipp] (1-H) and vice versa. Optical spectroscopy combined with time-dependent density functional theory suggests a charge-transfer excitation between the cluster and the antibonding π* orbital of the imine moiety as the cause of the intense coloration. An absorption maximum of 1-H in the red region of the electromagnetic spectrum and the corresponding lowest-energy excited state at λ=669 nm make the compound an interesting starting point for further investigations targeting the design of photo-active cluster compounds.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract C60 donor dyads in which the carbon cage is covalently linked to an electron-donating unit have been discussed as one possibility for an electron-transfer system, and it has been shown that spherical [Ge9] cluster anions show a close relation to fullerenes with respect to their electronic structure. However, the optical properties of these clusters and of functionalized cluster derivatives are almost unknown. We now report on the synthesis of the intensely red [Ge9] cluster linked to an extended π-electron system. [Ge9Si(TMS)32CH3C=N-DAB(II)Dipp]− (1−) is formed upon the reaction of [Ge9Si(TMS)32]2− with bromo-diazaborole DAB(II)Dipp-Br in CH3CN (TMS=trimethylsilyl; DAB(II)=1,3,2-diazaborole with an unsaturated backbone; Dipp=2,6-di-iso-propylphenyl). Reversible protonation of the imine entity in 1− yields the deep green, zwitterionic cluster [Ge9Si(TMS)32CH3C=N(H)-DAB(II)Dipp] (1-H) and vice versa. Optical spectroscopy combined with time-dependent density functional theory suggests a charge-transfer excitation between the cluster and the antibonding π* orbital of the imine moiety as the cause of the intense coloration. An absorption maximum of 1-H in the red region of the electromagnetic spectrum and the corresponding lowest-energy excited state at λ=669 nm make the compound an interesting starting point for further investigations targeting the design of photo-active cluster compounds.
20.
A Kumar, P Malevich, L Mewes, S Wu, J P Barham, J Hauer
In: The Journal of Chemical Physics, vol. 158, no. 14, pp. 144201, 2023.
@article{nokey,
title = {Transient absorption spectroscopy based on uncompressed hollow core fiber white light proves pre-association between a radical ion photocatalyst and substrate},
author = {A Kumar and P Malevich and L Mewes and S Wu and J P Barham and J Hauer},
url = {https://aip.scitation.org/doi/abs/10.1063/5.0142225},
doi = {10.1063/5.0142225},
year = {2023},
date = {2023-03-24},
journal = {The Journal of Chemical Physics},
volume = {158},
number = {14},
pages = {144201},
abstract = {We present a hollow-core fiber (HCF) based transient absorption experiment, with capabilities beyond common titanium:sapphire based setups. By spectral filtering of the HCF spectrum, we provide pump pulses centered at 425 nm with several hundred nJ of pulse energy at the sample position. By employing the red edge of the HCF output for seeding CaF2, we obtain smooth probing spectra in the range between 320 and 900 nm. We demonstrate the capabilities of our experiment by following the ultrafast relaxation dynamics of a radical cationic photocatalyst to prove its pre-association with an arene substrate, a phenomenon that was not detectable previously by steady-state spectroscopic techniques. The detected preassembly rationalizes the successful participation of radical ionic photocatalysts in single electron transfer reactions, a notion that has been subject to controversy in recent years.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We present a hollow-core fiber (HCF) based transient absorption experiment, with capabilities beyond common titanium:sapphire based setups. By spectral filtering of the HCF spectrum, we provide pump pulses centered at 425 nm with several hundred nJ of pulse energy at the sample position. By employing the red edge of the HCF output for seeding CaF2, we obtain smooth probing spectra in the range between 320 and 900 nm. We demonstrate the capabilities of our experiment by following the ultrafast relaxation dynamics of a radical cationic photocatalyst to prove its pre-association with an arene substrate, a phenomenon that was not detectable previously by steady-state spectroscopic techniques. The detected preassembly rationalizes the successful participation of radical ionic photocatalysts in single electron transfer reactions, a notion that has been subject to controversy in recent years.
19.
S Reiter, F L Kiss, J Hauer, R De Vivie-Riedle
Thermal site energy fluctuations in photosystem I: new insights from MD/QM/MM calculations Journal Article
In: Chemical Science, vol. 14, no. 12, pp. 3117-3131, 2023, ISSN: 2041-6520.
@article{nokey,
title = {Thermal site energy fluctuations in photosystem I: new insights from MD/QM/MM calculations},
author = {S Reiter and F L Kiss and J Hauer and R De Vivie-Riedle},
url = {http://dx.doi.org/10.1039/D2SC06160K},
doi = {10.1039/D2SC06160K},
issn = {2041-6520},
year = {2023},
date = {2023-02-06},
journal = {Chemical Science},
volume = {14},
number = {12},
pages = {3117-3131},
abstract = {Cyanobacterial photosystem I (PSI) is one of the most efficient photosynthetic machineries found in nature. Due to the large scale and complexity of the system, the energy transfer mechanism from the antenna complex to the reaction center is still not fully understood. A central element is the accurate evaluation of the individual chlorophyll excitation energies (site energies). Such an evaluation must include a detailed treatment of site specific environmental influences on structural and electrostatic properties, but also their evolution in the temporal domain, because of the dynamic nature of the energy transfer process. In this work, we calculate the site energies of all 96 chlorophylls in a membrane-embedded model of PSI. The employed hybrid QM/MM approach using the multireference DFT/MRCI method in the QM region allows to obtain accurate site energies under explicit consideration of the natural environment. We identify energy traps and barriers in the antenna complex and discuss their implications for energy transfer to the reaction center. Going beyond previous studies, our model also accounts for the molecular dynamics of the full trimeric PSI complex. Via statistical analysis we show that the thermal fluctuations of single chlorophylls prevent the formation of a single prominent energy funnel within the antenna complex. These findings are also supported by a dipole exciton model. We conclude that energy transfer pathways may form only transiently at physiological temperatures, as thermal fluctuations overcome energy barriers. The set of site energies provided in this work sets the stage for theoretical and experimental studies on the highly efficient energy transfer mechanisms in PSI.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Cyanobacterial photosystem I (PSI) is one of the most efficient photosynthetic machineries found in nature. Due to the large scale and complexity of the system, the energy transfer mechanism from the antenna complex to the reaction center is still not fully understood. A central element is the accurate evaluation of the individual chlorophyll excitation energies (site energies). Such an evaluation must include a detailed treatment of site specific environmental influences on structural and electrostatic properties, but also their evolution in the temporal domain, because of the dynamic nature of the energy transfer process. In this work, we calculate the site energies of all 96 chlorophylls in a membrane-embedded model of PSI. The employed hybrid QM/MM approach using the multireference DFT/MRCI method in the QM region allows to obtain accurate site energies under explicit consideration of the natural environment. We identify energy traps and barriers in the antenna complex and discuss their implications for energy transfer to the reaction center. Going beyond previous studies, our model also accounts for the molecular dynamics of the full trimeric PSI complex. Via statistical analysis we show that the thermal fluctuations of single chlorophylls prevent the formation of a single prominent energy funnel within the antenna complex. These findings are also supported by a dipole exciton model. We conclude that energy transfer pathways may form only transiently at physiological temperatures, as thermal fluctuations overcome energy barriers. The set of site energies provided in this work sets the stage for theoretical and experimental studies on the highly efficient energy transfer mechanisms in PSI.
18.
S Reiter, L Bäuml, J Hauer, R De Vivie-Riedle
Q-Band relaxation in chlorophyll: new insights from multireference quantum dynamics Journal Article
In: Physical Chemistry Chemical Physics, 2022, ISSN: 1463-9076.
@article{nokey,
title = {Q-Band relaxation in chlorophyll: new insights from multireference quantum dynamics},
author = {S Reiter and L B\"{a}uml and J Hauer and R De Vivie-Riedle},
url = {http://dx.doi.org/10.1039/D2CP02914F},
doi = {10.1039/D2CP02914F},
issn = {1463-9076},
year = {2022},
date = {2022-10-27},
journal = {Physical Chemistry Chemical Physics},
abstract = {The ultrafast relaxation within the Q-bands of chlorophyll plays a crucial role in photosynthetic light-harvesting. Yet, despite being the focus of many experimental and theoretical studies, it is still not fully understood. In this paper we look at the relaxation process from the perspective of non-adiabatic wave packet dynamics. For this purpose, we identify vibrational degrees of freedom which contribute most to the non-adiabatic coupling. Using a selection of normal modes, we construct four reduced-dimensional coordinate spaces and investigate the wave packet dynamics on XMS-CASPT2 potential energy surfaces. In this context, we discuss the associated computational challenges, as many quantum chemical methods overestimate the Qx\textendashQy energy gap. Our results show that the Qx and Qy potential energy surfaces do not cross in an energetically accessible region of the vibrational space. Instead, non-adiabatic coupling facilitates ultrafast population transfer across the potential energy surface. Moreover, we can identify the excited vibrational eigenstates that take part in the relaxation process. We conclude that the Q-band system of chlorophyll a should be viewed as a strongly coupled system, where population is easily transferred between the x and y-polarized electronic states. This suggests that both orientations may contribute to the electron transfer in the reaction center of photosynthetic light-harvesting systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The ultrafast relaxation within the Q-bands of chlorophyll plays a crucial role in photosynthetic light-harvesting. Yet, despite being the focus of many experimental and theoretical studies, it is still not fully understood. In this paper we look at the relaxation process from the perspective of non-adiabatic wave packet dynamics. For this purpose, we identify vibrational degrees of freedom which contribute most to the non-adiabatic coupling. Using a selection of normal modes, we construct four reduced-dimensional coordinate spaces and investigate the wave packet dynamics on XMS-CASPT2 potential energy surfaces. In this context, we discuss the associated computational challenges, as many quantum chemical methods overestimate the Qx–Qy energy gap. Our results show that the Qx and Qy potential energy surfaces do not cross in an energetically accessible region of the vibrational space. Instead, non-adiabatic coupling facilitates ultrafast population transfer across the potential energy surface. Moreover, we can identify the excited vibrational eigenstates that take part in the relaxation process. We conclude that the Q-band system of chlorophyll a should be viewed as a strongly coupled system, where population is easily transferred between the x and y-polarized electronic states. This suggests that both orientations may contribute to the electron transfer in the reaction center of photosynthetic light-harvesting systems.
17.
S J Weishäupl, Y Cui, S N Deger, H Syed, A Ovsianikov, J Hauer, A Pöthig, R A Fischer
Coordination Polymers Based on Carbazole-Derived Chromophore Linkers for Optimized Multiphoton Absorption: A Structural and Photophysical Study Journal Article
In: Chemistry of Materials, vol. 34, no. 16, pp. 7402-7411, 2022, ISSN: 0897-4756.
@article{nokey,
title = {Coordination Polymers Based on Carbazole-Derived Chromophore Linkers for Optimized Multiphoton Absorption: A Structural and Photophysical Study},
author = {S J Weish\"{a}upl and Y Cui and S N Deger and H Syed and A Ovsianikov and J Hauer and A P\"{o}thig and R A Fischer},
url = {https://doi.org/10.1021/acs.chemmater.2c01525},
doi = {10.1021/acs.chemmater.2c01525},
issn = {0897-4756},
year = {2022},
date = {2022-08-08},
journal = {Chemistry of Materials},
volume = {34},
number = {16},
pages = {7402-7411},
abstract = {Multiphoton absorption (MPA), as a subgroup of non-linear optical effects, is of high interest in modern materials research since it has a great applicability in optoelectronics. However, most of the commonly used materials featuring MPA properties are chromophore molecules, which are limited by their thermal stability and uncontrolled aggregation in high-concentration solutions. A prominent material class which could in principle overcome these problems are metal\textendashorganic frameworks and coordination polymers (CPs) as they can be modularly tuned to possess chemical and thermal stability. In addition, by incorporating chromophores as linkers in the framework, their molecular properties can be retained or even enhanced. In this article, we report the synthesis and characterization of three new and highly MPA-active CPs, Zn2(sbcd)(DMAc)2(H2O)1.5, Sr(fbcd)(DMAc)0.25(H2O)3.5, and Ba(fbcd)(DMAc)2.5(H2O)1.5, based on two carbazole-containing chromophore linkers: a previously reported 9,9′-stilbene-bis-carbazole-3,6-dicarboxylic acid (H4sbcd) and the new 2,7-fluorene-9,9′-dimethyl-bis-carbazole-3,6-dicarboxylic acid (H4fbcd). Single-crystal structure analysis of the zinc-based CP reveals a sql network, whereas the barium- and strontium-based CPs are isostructural, showing a 4,8-c network topology. Z-scan analysis of the networks shows large two-photon absorption cross-sections σ(2) of 2100 to 33,300 GM, which is an enhancement of up to 3 orders of magnitude in comparison to the solvated linker and is also one of the highest MPA-cross-sections reported for CPs up to date.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Multiphoton absorption (MPA), as a subgroup of non-linear optical effects, is of high interest in modern materials research since it has a great applicability in optoelectronics. However, most of the commonly used materials featuring MPA properties are chromophore molecules, which are limited by their thermal stability and uncontrolled aggregation in high-concentration solutions. A prominent material class which could in principle overcome these problems are metal–organic frameworks and coordination polymers (CPs) as they can be modularly tuned to possess chemical and thermal stability. In addition, by incorporating chromophores as linkers in the framework, their molecular properties can be retained or even enhanced. In this article, we report the synthesis and characterization of three new and highly MPA-active CPs, Zn2(sbcd)(DMAc)2(H2O)1.5, Sr(fbcd)(DMAc)0.25(H2O)3.5, and Ba(fbcd)(DMAc)2.5(H2O)1.5, based on two carbazole-containing chromophore linkers: a previously reported 9,9′-stilbene-bis-carbazole-3,6-dicarboxylic acid (H4sbcd) and the new 2,7-fluorene-9,9′-dimethyl-bis-carbazole-3,6-dicarboxylic acid (H4fbcd). Single-crystal structure analysis of the zinc-based CP reveals a sql network, whereas the barium- and strontium-based CPs are isostructural, showing a 4,8-c network topology. Z-scan analysis of the networks shows large two-photon absorption cross-sections σ(2) of 2100 to 33,300 GM, which is an enhancement of up to 3 orders of magnitude in comparison to the solvated linker and is also one of the highest MPA-cross-sections reported for CPs up to date.
16.
N Li, R Guo, A L Oechsle, M A Reus, S Liang, L Song, K Wang, D Yang, F Allegretti, A Kumar, M Nuber, J Berger, S Bernstorff, H Iglev, J Hauer, R A Fischer, J V Barth, P Müller-Buschbaum
Operando Study of Structure Degradation in Solid-State Dye-Sensitized Solar Cells with a TiO2 Photoanode Having Ordered Mesopore Arrays Journal Article
In: Solar RRL, vol. n/a, no. n/a, pp. 2200373, 2022, ISSN: 2367-198X.
@article{nokey,
title = {Operando Study of Structure Degradation in Solid-State Dye-Sensitized Solar Cells with a TiO2 Photoanode Having Ordered Mesopore Arrays},
author = {N Li and R Guo and A L Oechsle and M A Reus and S Liang and L Song and K Wang and D Yang and F Allegretti and A Kumar and M Nuber and J Berger and S Bernstorff and H Iglev and J Hauer and R A Fischer and J V Barth and P M\"{u}ller-Buschbaum},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/solr.202200373},
doi = {https://doi.org/10.1002/solr.202200373},
issn = {2367-198X},
year = {2022},
date = {2022-05-31},
journal = {Solar RRL},
volume = {n/a},
number = {n/a},
pages = {2200373},
abstract = {Via operando grazing-incidence small-angle X-ray scattering, the degradation mechanisms of solid-state dye-sensitized solar cells (ssDSSCs) using two types of ordered mesoporous TiO2 scaffolds with different pore sizes, and an exemplary dye D205, are investigated. The temporal evolution of the inner morphology shows a strong impact on device performance. The photoinduced dye aggregation on the TiO2 surface leads to an increase in the domain radius but a decreased spatial order of the photoactive layer during the burn-in stage. This dye aggregation on the TiO2 surface causes the short-circuit current density loss, which plays a major role in the power conversion efficiency decay. Finally, it is found that a larger surface area in the small-pore sample yields a faster short-circuit current density decay as compared with the big-pore sample. Therefore, a control of dye aggregation and the pore size of TiO2 photoelectrodes is crucial for the stability of TiO2-based ssDSSCs.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Via operando grazing-incidence small-angle X-ray scattering, the degradation mechanisms of solid-state dye-sensitized solar cells (ssDSSCs) using two types of ordered mesoporous TiO2 scaffolds with different pore sizes, and an exemplary dye D205, are investigated. The temporal evolution of the inner morphology shows a strong impact on device performance. The photoinduced dye aggregation on the TiO2 surface leads to an increase in the domain radius but a decreased spatial order of the photoactive layer during the burn-in stage. This dye aggregation on the TiO2 surface causes the short-circuit current density loss, which plays a major role in the power conversion efficiency decay. Finally, it is found that a larger surface area in the small-pore sample yields a faster short-circuit current density decay as compared with the big-pore sample. Therefore, a control of dye aggregation and the pore size of TiO2 photoelectrodes is crucial for the stability of TiO2-based ssDSSCs.
15.
V Šebelík, C D P Duffy, E Keil, T Polívka, J Hauer
Understanding Carotenoid Dynamics via the Vibronic Energy Relaxation Approach Journal Article
In: The Journal of Physical Chemistry B, 2022, ISSN: 1520-6106.
@article{nokey,
title = {Understanding Carotenoid Dynamics via the Vibronic Energy Relaxation Approach},
author = {V \v{S}ebel\'{i}k and C D P Duffy and E Keil and T Pol\'{i}vka and J Hauer},
url = {https://doi.org/10.1021/acs.jpcb.2c00996},
doi = {10.1021/acs.jpcb.2c00996},
issn = {1520-6106},
year = {2022},
date = {2022-05-24},
journal = {The Journal of Physical Chemistry B},
abstract = {Carotenoids are an integral part of natural photosynthetic complexes, with tasks ranging from light harvesting to photoprotection. Their underlying energy deactivation network of optically dark and bright excited states is extremely efficient: after excitation of light with up to 2.5 eV of photon energy, the system relaxes back to ground state on a time scale of a few picoseconds. In this article, we summarize how a model based on the vibrational energy relaxation approach (VERA) explains the main characteristics of relaxation dynamics after one-photon excitation with special emphasis on the so-called S* state. Lineshapes after two-photon excitation are beyond the current model of VERA. We outline this future line of research in our article. In terms of experimental method development, we discuss which techniques are needed to better describe energy dissipation effects in carotenoids and within the first solvation shell.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Carotenoids are an integral part of natural photosynthetic complexes, with tasks ranging from light harvesting to photoprotection. Their underlying energy deactivation network of optically dark and bright excited states is extremely efficient: after excitation of light with up to 2.5 eV of photon energy, the system relaxes back to ground state on a time scale of a few picoseconds. In this article, we summarize how a model based on the vibrational energy relaxation approach (VERA) explains the main characteristics of relaxation dynamics after one-photon excitation with special emphasis on the so-called S* state. Lineshapes after two-photon excitation are beyond the current model of VERA. We outline this future line of research in our article. In terms of experimental method development, we discuss which techniques are needed to better describe energy dissipation effects in carotenoids and within the first solvation shell.
14.
S J Weishäupl, D C Mayer, Y Cui, P Kumar, H Oberhofer, R A Fischer, J Hauer, A Pöthig
Recent advances of multiphoton absorption in metal–organic frameworks Journal Article
In: Journal of Materials Chemistry C, vol. 10, no. 18, pp. 6912-6934, 2022, ISSN: 2050-7526.
@article{nokey,
title = {Recent advances of multiphoton absorption in metal\textendashorganic frameworks},
author = {S J Weish\"{a}upl and D C Mayer and Y Cui and P Kumar and H Oberhofer and R A Fischer and J Hauer and A P\"{o}thig},
url = {http://dx.doi.org/10.1039/D2TC00191H},
doi = {10.1039/D2TC00191H},
issn = {2050-7526},
year = {2022},
date = {2022-04-14},
journal = {Journal of Materials Chemistry C},
volume = {10},
number = {18},
pages = {6912-6934},
abstract = {Inorganic\textendashorganic hybrid materials such as metal\textendashorganic frameworks (MOFs) or coordination polymers (CPs) are of high interest in chemistry and materials science due to their modular design and versatile applicability, for example in gas storage, catalysis and sensor systems. Moreover, their tunability allows for photophysically relevant applications, such as multiphoton absorption (MPA). MPA is one of the most important non-linear optical effects, employed in optical limiting and two-photon fluorescence microscopy as well as for three-dimensional data storage. In this review we outline recent advances of MOFs and CPs regarding their MPA response properties. In the first part, we discuss the theoretical background of MPA absorbing linker molecules and effect of excitonic coupling when aligned within a rigid framework assembly. Furthermore, different state-of-the-art scanning and non-scanning measurement techniques for two-photon absorption (TPA) spectroscopy are compared for their advantages as well as their limitations. Additionally, we comprehensively present the latest progress of linker-based MPA materials (MOFs or surface anchored MOFs) and the relation between their framework-structure and their MPA cross section. In the last part of this review, future applications and research directions for the above outlined materials are discussed and illustrated.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Inorganic–organic hybrid materials such as metal–organic frameworks (MOFs) or coordination polymers (CPs) are of high interest in chemistry and materials science due to their modular design and versatile applicability, for example in gas storage, catalysis and sensor systems. Moreover, their tunability allows for photophysically relevant applications, such as multiphoton absorption (MPA). MPA is one of the most important non-linear optical effects, employed in optical limiting and two-photon fluorescence microscopy as well as for three-dimensional data storage. In this review we outline recent advances of MOFs and CPs regarding their MPA response properties. In the first part, we discuss the theoretical background of MPA absorbing linker molecules and effect of excitonic coupling when aligned within a rigid framework assembly. Furthermore, different state-of-the-art scanning and non-scanning measurement techniques for two-photon absorption (TPA) spectroscopy are compared for their advantages as well as their limitations. Additionally, we comprehensively present the latest progress of linker-based MPA materials (MOFs or surface anchored MOFs) and the relation between their framework-structure and their MPA cross section. In the last part of this review, future applications and research directions for the above outlined materials are discussed and illustrated.
13.
C Heshmatpour, J Hauer, F Šanda
Correlated spectral fluctuations quantified by line shape analysis of fifth-order two-dimensional electronic spectra Journal Article
In: The Journal of Chemical Physics, vol. 156, no. 8, pp. 084114, 2022.
@article{nokey,
title = {Correlated spectral fluctuations quantified by line shape analysis of fifth-order two-dimensional electronic spectra},
author = {C Heshmatpour and J Hauer and F \v{S}anda},
url = {https://aip.scitation.org/doi/abs/10.1063/5.0081053},
doi = {10.1063/5.0081053},
year = {2022},
date = {2022-02-01},
journal = {The Journal of Chemical Physics},
volume = {156},
number = {8},
pages = {084114},
abstract = {Correlated spectral fluctuations were suggested to coordinate excitation transport inside natural light harvesting complexes. We demonstrate the capacities of 2D line shapes from fifth-order coherent electronic signals (R5-2D) to report on such fluctuations in molecular aggregates and present a stochastic approach to fluctuations in correlated site and bi-exciton binding energies in the optical dynamics of Frenkel excitons. The model is applied to R5-2D line shapes of a homodimer, and we show that the peak tilt dynamics are a measure for site energy disorder, inter-site correlation, and the strength of bi-exciton binding energy fluctuations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Correlated spectral fluctuations were suggested to coordinate excitation transport inside natural light harvesting complexes. We demonstrate the capacities of 2D line shapes from fifth-order coherent electronic signals (R5-2D) to report on such fluctuations in molecular aggregates and present a stochastic approach to fluctuations in correlated site and bi-exciton binding energies in the optical dynamics of Frenkel excitons. The model is applied to R5-2D line shapes of a homodimer, and we show that the peak tilt dynamics are a measure for site energy disorder, inter-site correlation, and the strength of bi-exciton binding energy fluctuations.
12.
E Keil, P Malevich, J Hauer
Achromatic frequency doubling of supercontinuum pulses for transient absorption spectroscopy Journal Article
In: Optics Express, vol. 29, no. 24, pp. 39042-39054, 2021.
@article{nokey,
title = {Achromatic frequency doubling of supercontinuum pulses for transient absorption spectroscopy},
author = {E Keil and P Malevich and J Hauer},
url = {http://www.osapublishing.org/oe/abstract.cfm?URI=oe-29-24-39042},
doi = {10.1364/OE.442400},
year = {2021},
date = {2021-11-22},
urldate = {2021-11-22},
journal = {Optics Express},
volume = {29},
number = {24},
pages = {39042-39054},
abstract = {We present achromatic frequency doubling of supercontinuum pulses from a hollow core fiber as a technique for obtaining tunable ultrashort pulses in the near UV and blue spectral range. Pulse energies are stable on a 1.1\% level, averaged over 100 000 shots. By the use of conventional optics only, we compress a 0.2 \µJ pulse at a center wavelength of 475 nm to a pulse duration of 12 fs, as measured by X-FROG. We test the capabilities of the approach by employing the ASHG-pulses as a pump in a transient absorption experiment on \β-carotene in solution.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We present achromatic frequency doubling of supercontinuum pulses from a hollow core fiber as a technique for obtaining tunable ultrashort pulses in the near UV and blue spectral range. Pulse energies are stable on a 1.1% level, averaged over 100 000 shots. By the use of conventional optics only, we compress a 0.2 µJ pulse at a center wavelength of 475 nm to a pulse duration of 12 fs, as measured by X-FROG. We test the capabilities of the approach by employing the ASHG-pulses as a pump in a transient absorption experiment on β-carotene in solution.
11.
R Lauenstein, S L Mader, H Derondeau, O Z Esezobor, M Block, A J Römer, C Jandl, E Riedle, V R I Kaila, J Hauer, E Thyrhaug, C R Hess
The central role of the metal ion for photoactivity: Zn– vs. Ni–Mabiq Journal Article
In: Chemical Science, 2021, ISSN: 2041-6520.
@article{,
title = {The central role of the metal ion for photoactivity: Zn\textendash vs. Ni\textendashMabiq},
author = {R Lauenstein and S L Mader and H Derondeau and O Z Esezobor and M Block and A J R\"{o}mer and C Jandl and E Riedle and V R I Kaila and J Hauer and E Thyrhaug and C R Hess},
url = {http://dx.doi.org/10.1039/D0SC06096H},
doi = {10.1039/D0SC06096H},
issn = {2041-6520},
year = {2021},
date = {2021-04-21},
journal = {Chemical Science},
abstract = {Photoredox catalysts are integral components of artificial photosystems, and have recently emerged as powerful tools for catalysing numerous organic reactions. However, the development of inexpensive and efficient earth-abundant photoredox catalysts remains a challenge. We here present the photochemical and photophysical properties of a Ni\textendashMabiq catalyst ([NiII(Mabiq)]OTf (1); Mabiq = 2-4:6-8-bis(3,3,4,4-tetramethyldihydropyrrolo)-10-15-(2,2-biquinazolino)-[15]-1,3,5,8,10,14-hexaene1,3,7,9,11,14-N6)\textemdashand of a Zn-containing analogue ([ZnII(Mabiq)OTf] (2))\textemdashusing steady state and time resolved optical spectroscopy, time-dependent density functional theory (TDDFT) calculations, and reactivity studies. The Ni and Zn complexes exhibit similar absorption spectra, but markedly different photochemical properties. These differences arise because the excited states of 2 are ligand-localized, whereas metal-centered states account for the photoactivity of 1. The distinct properties of the Ni and Zn complexes are manifest in their behavior in the photo-driven aza-Henry reaction and oxidative coupling of methoxybenzylamine.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Photoredox catalysts are integral components of artificial photosystems, and have recently emerged as powerful tools for catalysing numerous organic reactions. However, the development of inexpensive and efficient earth-abundant photoredox catalysts remains a challenge. We here present the photochemical and photophysical properties of a Ni–Mabiq catalyst ([NiII(Mabiq)]OTf (1); Mabiq = 2-4:6-8-bis(3,3,4,4-tetramethyldihydropyrrolo)-10-15-(2,2-biquinazolino)-[15]-1,3,5,8,10,14-hexaene1,3,7,9,11,14-N6)—and of a Zn-containing analogue ([ZnII(Mabiq)OTf] (2))—using steady state and time resolved optical spectroscopy, time-dependent density functional theory (TDDFT) calculations, and reactivity studies. The Ni and Zn complexes exhibit similar absorption spectra, but markedly different photochemical properties. These differences arise because the excited states of 2 are ligand-localized, whereas metal-centered states account for the photoactivity of 1. The distinct properties of the Ni and Zn complexes are manifest in their behavior in the photo-driven aza-Henry reaction and oxidative coupling of methoxybenzylamine.
10.
M Peschel, P Kabacinski, D P Schwinger, E Thyrhaug, G Cerullo, T Bach, J Hauer, R De Vivie-Riedle
Activation of 2-Cyclohexenone by BF3 Coordination: Mechanistic Insights from Theory and Experiment Journal Article
In: Angewandte Chemie International Edition, vol. n/a, no. n/a, 2021, ISSN: 1433-7851.
@article{,
title = {Activation of 2-Cyclohexenone by BF3 Coordination: Mechanistic Insights from Theory and Experiment},
author = {M Peschel and P Kabacinski and D P Schwinger and E Thyrhaug and G Cerullo and T Bach and J Hauer and R De Vivie-Riedle
},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202016653},
doi = {https://doi.org/10.1002/anie.202016653},
issn = {1433-7851},
year = {2021},
date = {2021-02-17},
urldate = {2021-02-17},
journal = {Angewandte Chemie International Edition},
volume = {n/a},
number = {n/a},
abstract = {Lewis acids have recently been recognized as catalysts enabling enantioselective photochemical transformations. Mechanistic studies on these systems are however rare, either due to their absorption at wavelengths shorter than 260 nm, or due to the limitations of theoretical dynamic studies for larger complexes. In this work, we overcome these challenges and employ sub-30-fs transient absorption in the UV, in combination with a highly accurate theoretical treatment on the XMS-CASPT2 level. We investigate 2-cyclohexenone and its complex to boron trifluoride and analyze the observed dynamics based on trajectory calculations including non-adiabatic coupling and intersystem crossing. This approach explains all ultrafast decay pathways observed in the complex. We show that the Lewis acid remains attached to the substrate in the triplet state, which in turn explains why chiral boron-based Lewis acids induce a high enantioselectivity in photocycloaddition reactions.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Lewis acids have recently been recognized as catalysts enabling enantioselective photochemical transformations. Mechanistic studies on these systems are however rare, either due to their absorption at wavelengths shorter than 260 nm, or due to the limitations of theoretical dynamic studies for larger complexes. In this work, we overcome these challenges and employ sub-30-fs transient absorption in the UV, in combination with a highly accurate theoretical treatment on the XMS-CASPT2 level. We investigate 2-cyclohexenone and its complex to boron trifluoride and analyze the observed dynamics based on trajectory calculations including non-adiabatic coupling and intersystem crossing. This approach explains all ultrafast decay pathways observed in the complex. We show that the Lewis acid remains attached to the substrate in the triplet state, which in turn explains why chiral boron-based Lewis acids induce a high enantioselectivity in photocycloaddition reactions.
9.
S J Weishäupl, D C Mayer, E Thyrhaug, J Hauer, A Pöthig, R A Fischer
In: Dyes and Pigments, vol. 186, pp. 109012, 2021, ISSN: 0143-7208.
@article{nokey,
title = {A nitrophenyl-carbazole based push-pull linker as a building block for non-linear optical active coordination polymers: A structural and photophysical study},
author = {S J Weish\"{a}upl and D C Mayer and E Thyrhaug and J Hauer and A P\"{o}thig and R A Fischer},
url = {https://www.sciencedirect.com/science/article/pii/S0143720820317095},
doi = {https://doi.org/10.1016/j.dyepig.2020.109012},
issn = {0143-7208},
year = {2021},
date = {2021-02-01},
journal = {Dyes and Pigments},
volume = {186},
pages = {109012},
abstract = {Non-linear optical effects (NLO) such as multi-photon absorption, second harmonic generation (SHG) etc. have a wide range of applications. Nevertheless, the performance of many NLO-active organic dyes is limited by their thermal stability and photobleaching. These problems can be overcome by integrating the dyes into coordination polymers or metal-organic frameworks. Here, we present a structural and photophysical study of dipropyl-9-(4-nitrophenyl)-carbazole-3,6-dicarboxylate, a new “push-pull” organic dye molecule designed as a chromophore linker for NLO-active coordination polymers. Structure determination of a single-crystal showed that it crystallizes in a monoclinic crystal system P 21/c. The solvated chromophore exhibits two aromatic absorption bands at 250 nm and 275 nm as well as broad long wavelength band at 350 nm, which we assign to an intramolecular charge transfer state. Photoluminescence measurements in solvents of different polarities revealed two main effects: In nonpolar solvents, the spectrum shows an emission band at 360 nm, whereas in solvents with a higher polarity, the emission maximum broadens and redshifts. Solid-state emission measurement of sample powder exhibits an emission band at 520 nm which is redshifted compared to the measurements in solution, due to excimer formation in the solid-state. The optical as well as solvation-related properties of the investigated pigment render it to be a versatile ligand in coordination polymers.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Non-linear optical effects (NLO) such as multi-photon absorption, second harmonic generation (SHG) etc. have a wide range of applications. Nevertheless, the performance of many NLO-active organic dyes is limited by their thermal stability and photobleaching. These problems can be overcome by integrating the dyes into coordination polymers or metal-organic frameworks. Here, we present a structural and photophysical study of dipropyl-9-(4-nitrophenyl)-carbazole-3,6-dicarboxylate, a new “push-pull” organic dye molecule designed as a chromophore linker for NLO-active coordination polymers. Structure determination of a single-crystal showed that it crystallizes in a monoclinic crystal system P 21/c. The solvated chromophore exhibits two aromatic absorption bands at 250 nm and 275 nm as well as broad long wavelength band at 350 nm, which we assign to an intramolecular charge transfer state. Photoluminescence measurements in solvents of different polarities revealed two main effects: In nonpolar solvents, the spectrum shows an emission band at 360 nm, whereas in solvents with a higher polarity, the emission maximum broadens and redshifts. Solid-state emission measurement of sample powder exhibits an emission band at 520 nm which is redshifted compared to the measurements in solution, due to excimer formation in the solid-state. The optical as well as solvation-related properties of the investigated pigment render it to be a versatile ligand in coordination polymers.
8.
P M Stanley, C Thomas, E Thyrhaug, A Urstoeger, M Schuster, J Hauer, B Rieger, J Warnan, R A Fischer
Entrapped Molecular Photocatalyst and Photosensitizer in Metal–Organic Framework Nanoreactors for Enhanced Solar CO2 Reduction Journal Article
In: ACS Catalysis, vol. 11, no. 2, pp. 871-882, 2021.
@article{,
title = {Entrapped Molecular Photocatalyst and Photosensitizer in Metal\textendashOrganic Framework Nanoreactors for Enhanced Solar CO2 Reduction},
author = {P M Stanley and C Thomas and E Thyrhaug and A Urstoeger and M Schuster and J Hauer and B Rieger and J Warnan and R A Fischer},
url = {https://doi.org/10.1021/acscatal.0c04673},
doi = {10.1021/acscatal.0c04673},
year = {2021},
date = {2021-01-05},
urldate = {2021-01-05},
journal = {ACS Catalysis},
volume = {11},
number = {2},
pages = {871-882},
abstract = {Herein, we report on a molecular catalyst embedding metal\textendashorganic framework (MOF) that enables enhanced photocatalytic CO2 reduction activity. A benchmark photocatalyst fac-ReBr(CO)3(4,4′-dcbpy) (dcbpy = dicarboxy-2,2′-bipyridine) and photosensitizer Ru(bpy)2(5,5′-dcbpy)Cl2 (bpy = 2,2′-bipyridine) were synergistically entrapped inside the cages of the nontoxic and inexpensive MIL-101-NH2(Al) through noncovalent host\textendashguest interactions. The heterogeneous material improved Re catalyst stabilization under photocatalytic CO2 reduction conditions as selective CO evolution was prolonged from 1.5 to 40 h compared to the MOF-free photosystem upon reactivation with additional photosensitizer. By varying ratios of immobilized catalyst to photosensitizer, we demonstrated and evaluated the effect of reaction environment modulation in defined MOF cages acting as a nanoreactor. This illustrated the optimal efficiency for two photosensitizers and one catalyst per cage and further led to the determination of ad hoc relationships between molecular complex size, MOF pore windows, and number of hostable molecules per cage. Differing from typical homogeneous systems, photosensitizer\textemdashand not catalyst\textemdashdegradation was identified as a major performance-limiting factor, providing a future route to higher turnover numbers via a rational choice of parameters.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Herein, we report on a molecular catalyst embedding metal–organic framework (MOF) that enables enhanced photocatalytic CO2 reduction activity. A benchmark photocatalyst fac-ReBr(CO)3(4,4′-dcbpy) (dcbpy = dicarboxy-2,2′-bipyridine) and photosensitizer Ru(bpy)2(5,5′-dcbpy)Cl2 (bpy = 2,2′-bipyridine) were synergistically entrapped inside the cages of the nontoxic and inexpensive MIL-101-NH2(Al) through noncovalent host–guest interactions. The heterogeneous material improved Re catalyst stabilization under photocatalytic CO2 reduction conditions as selective CO evolution was prolonged from 1.5 to 40 h compared to the MOF-free photosystem upon reactivation with additional photosensitizer. By varying ratios of immobilized catalyst to photosensitizer, we demonstrated and evaluated the effect of reaction environment modulation in defined MOF cages acting as a nanoreactor. This illustrated the optimal efficiency for two photosensitizers and one catalyst per cage and further led to the determination of ad hoc relationships between molecular complex size, MOF pore windows, and number of hostable molecules per cage. Differing from typical homogeneous systems, photosensitizer—and not catalyst—degradation was identified as a major performance-limiting factor, providing a future route to higher turnover numbers via a rational choice of parameters.
7.
L Wolz, C Heshmatpour, A Perri, D Polli, G Cerullo, J J Finley, E Thyrhaug, J Hauer, A V Stier
Time-domain photocurrent spectroscopy based on a common-path birefringent interferometer Journal Article
In: Review of Scientific Instruments, vol. 91, no. 12, pp. 123101, 2020.
@article{,
title = {Time-domain photocurrent spectroscopy based on a common-path birefringent interferometer},
author = {L Wolz and C Heshmatpour and A Perri and D Polli and G Cerullo and J J Finley and E Thyrhaug and J Hauer and A V Stier},
url = {https://aip.scitation.org/doi/abs/10.1063/5.0023543},
doi = {10.1063/5.0023543},
year = {2020},
date = {2020-12-02},
urldate = {2020-12-02},
journal = {Review of Scientific Instruments},
volume = {91},
number = {12},
pages = {123101},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
6.
V Sláma, V Perlík, H Langhals, A Walter, T Mančal, J Hauer, F Šanda
Anharmonic Molecular Motion Drives Resonance Energy Transfer in peri-Arylene Dyads Journal Article
In: Frontiers in Chemistry, vol. 8, 2020, ISSN: 2296-2646.
@article{nokey,
title = {Anharmonic Molecular Motion Drives Resonance Energy Transfer in peri-Arylene Dyads},
author = {V Sl\'{a}ma and V Perl\'{i}k and H Langhals and A Walter and T Man\v{c}al and J Hauer and F \v{S}anda},
url = {https://www.frontiersin.org/article/10.3389/fchem.2020.579166},
doi = {10.3389/fchem.2020.579166},
issn = {2296-2646},
year = {2020},
date = {2020-11-23},
urldate = {2020-11-23},
journal = {Frontiers in Chemistry},
volume = {8},
abstract = {Spectral and dynamical properties of molecular donor-acceptor systems strongly depend on the steric arrangement of the constituents with exciton coupling J as a key control parameter. In the present work we study two peri-arylene based dyads with orthogonal and parallel transition dipoles for donor and acceptor moieties, respectively. We show that the anharmonic multi-well character of the orthogonal dyad's intramolecular potential explains findings from both stationary and time-resolved absorption experiments. While for a parallel dyad, standard quantum chemical estimates of J at 0 K are in good agreement with experimental observations, J becomes vanishingly small for the orthogonal dyad, in contrast to its ultrafast experimental transfer times. This discrepancy is not resolved even by accounting for harmonic fluctuations along normal coordinates. We resolve this problem by supplementing quantum chemical approaches with dynamical sampling of fluctuating geometries. In contrast to the moderate Gaussian fluctuations of J for the parallel dyad, fluctuations for the orthogonal dyad are found to follow non-Gaussian statistics leading to significantly higher effective J in good agreement with experimental observations. In effort to apply a unified framework for treating the dynamics of optical coherence and excitonic populations of both dyads, we employ a vibronic approach treating electronic and selected vibrational degrees on an equal footing. This vibronic model is used to model absorption and fluorescence spectra as well as donor-acceptor transport dynamics and covers the more traditional categories of F\"{o}rster and Redfield transport as limiting cases.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Spectral and dynamical properties of molecular donor-acceptor systems strongly depend on the steric arrangement of the constituents with exciton coupling J as a key control parameter. In the present work we study two peri-arylene based dyads with orthogonal and parallel transition dipoles for donor and acceptor moieties, respectively. We show that the anharmonic multi-well character of the orthogonal dyad's intramolecular potential explains findings from both stationary and time-resolved absorption experiments. While for a parallel dyad, standard quantum chemical estimates of J at 0 K are in good agreement with experimental observations, J becomes vanishingly small for the orthogonal dyad, in contrast to its ultrafast experimental transfer times. This discrepancy is not resolved even by accounting for harmonic fluctuations along normal coordinates. We resolve this problem by supplementing quantum chemical approaches with dynamical sampling of fluctuating geometries. In contrast to the moderate Gaussian fluctuations of J for the parallel dyad, fluctuations for the orthogonal dyad are found to follow non-Gaussian statistics leading to significantly higher effective J in good agreement with experimental observations. In effort to apply a unified framework for treating the dynamics of optical coherence and excitonic populations of both dyads, we employ a vibronic approach treating electronic and selected vibrational degrees on an equal footing. This vibronic model is used to model absorption and fluorescence spectra as well as donor-acceptor transport dynamics and covers the more traditional categories of Förster and Redfield transport as limiting cases.
5.
C Heshmatpour, P Malevich, F Plasser, M Menger, C Lambert, F Šanda, J Hauer
Annihilation Dynamics of Molecular Excitons Measured at a Single Perturbative Excitation Energy Journal Article
In: The Journal of Physical Chemistry Letters, vol. 11, no. 18, pp. 7776-7781, 2020.
@article{,
title = {Annihilation Dynamics of Molecular Excitons Measured at a Single Perturbative Excitation Energy},
author = {C Heshmatpour and P Malevich and F Plasser and M Menger and C Lambert and F \v{S}anda and J Hauer},
url = {https://doi.org/10.1021/acs.jpclett.0c02141},
doi = {10.1021/acs.jpclett.0c02141},
year = {2020},
date = {2020-09-17},
journal = {The Journal of Physical Chemistry Letters},
volume = {11},
number = {18},
pages = {7776-7781},
abstract = {Exciton\textendashexciton annihilation (EEA) is a ubiquitous phenomenon, which may limit the efficiency of photovoltaic devices. Conventional methods of determining EEA time scales rely on measuring the intensity dependence of third-order signals. In this work, we directly extract the annihilation rate of molecular excitons in a covalently joined molecular trimer without the need to perform and analyze intensity dependent data by employing fifth-order coherent optical spectroscopy signals emitted into ±2k⃗1 ∓ 2k⃗2 + k⃗3 phase matching directions. Measured two-dimensional line shapes and their time traces are analyzed in the framework of the many-body version of the Frenkel exciton model, extended to incorporate annihilation dynamics. Combining double-sided Feynman diagrams with explicit simulations of the fifth-order response, we identify a single peak as a direct reporter of EEA. We retrieve an annihilation time of 30 fs for the investigated squaraine trimer.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Exciton–exciton annihilation (EEA) is a ubiquitous phenomenon, which may limit the efficiency of photovoltaic devices. Conventional methods of determining EEA time scales rely on measuring the intensity dependence of third-order signals. In this work, we directly extract the annihilation rate of molecular excitons in a covalently joined molecular trimer without the need to perform and analyze intensity dependent data by employing fifth-order coherent optical spectroscopy signals emitted into ±2k⃗1 ∓ 2k⃗2 + k⃗3 phase matching directions. Measured two-dimensional line shapes and their time traces are analyzed in the framework of the many-body version of the Frenkel exciton model, extended to incorporate annihilation dynamics. Combining double-sided Feynman diagrams with explicit simulations of the fifth-order response, we identify a single peak as a direct reporter of EEA. We retrieve an annihilation time of 30 fs for the investigated squaraine trimer.
4.
J Cao, R J Cogdell, D F Coker, H-G Duan, J Hauer, U Kleinekathöfer, T L C Jansen, T Mančal, R J D Miller, J P Ogilvie, V I Prokhorenko, T Renger, H-S Tan, R Tempelaar, M Thorwart, E Thyrhaug, S Westenhoff, D Zigmantas
Quantum biology revisited Journal Article
In: Science Advances, vol. 6, no. 14, pp. eaaz4888, 2020.
@article{,
title = {Quantum biology revisited},
author = {J Cao and R J Cogdell and D F Coker and H-G Duan and J Hauer and U Kleinekath\"{o}fer and T L C Jansen and T Man\v{c}al and R J D Miller and J P Ogilvie and V I Prokhorenko and T Renger and H-S Tan and R Tempelaar and M Thorwart and E Thyrhaug and S Westenhoff and D Zigmantas},
url = {http://advances.sciencemag.org/content/6/14/eaaz4888.abstract},
doi = {10.1126/sciadv.aaz4888},
year = {2020},
date = {2020-04-01},
journal = {Science Advances},
volume = {6},
number = {14},
pages = {eaaz4888},
abstract = {Photosynthesis is a highly optimized process from which valuable lessons can be learned about the operating principles in nature. Its primary steps involve energy transport operating near theoretical quantum limits in efficiency. Recently, extensive research was motivated by the hypothesis that nature used quantum coherences to direct energy transfer. This body of work, a cornerstone for the field of quantum biology, rests on the interpretation of small-amplitude oscillations in two-dimensional electronic spectra of photosynthetic complexes. This Review discusses recent work reexamining these claims and demonstrates that interexciton coherences are too short lived to have any functional significance in photosynthetic energy transfer. Instead, the observed long-lived coherences originate from impulsively excited vibrations, generally observed in femtosecond spectroscopy. These efforts, collectively, lead to a more detailed understanding of the quantum aspects of dissipation. Nature, rather than trying to avoid dissipation, exploits it via engineering of exciton-bath interaction to create efficient energy flow.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Photosynthesis is a highly optimized process from which valuable lessons can be learned about the operating principles in nature. Its primary steps involve energy transport operating near theoretical quantum limits in efficiency. Recently, extensive research was motivated by the hypothesis that nature used quantum coherences to direct energy transfer. This body of work, a cornerstone for the field of quantum biology, rests on the interpretation of small-amplitude oscillations in two-dimensional electronic spectra of photosynthetic complexes. This Review discusses recent work reexamining these claims and demonstrates that interexciton coherences are too short lived to have any functional significance in photosynthetic energy transfer. Instead, the observed long-lived coherences originate from impulsively excited vibrations, generally observed in femtosecond spectroscopy. These efforts, collectively, lead to a more detailed understanding of the quantum aspects of dissipation. Nature, rather than trying to avoid dissipation, exploits it via engineering of exciton-bath interaction to create efficient energy flow.
3.
S Oviedo-Casado, F Šanda, J Hauer, J Prior
Magnetic pulses enable multidimensional optical spectroscopy of dark states Journal Article
In: The Journal of Chemical Physics, vol. 152, no. 8, pp. 084201, 2020, ISSN: 0021-9606.
@article{,
title = {Magnetic pulses enable multidimensional optical spectroscopy of dark states},
author = {S Oviedo-Casado and F \v{S}anda and J Hauer and J Prior},
url = {https://doi.org/10.1063/1.5139409},
doi = {10.1063/1.5139409},
issn = {0021-9606},
year = {2020},
date = {2020-02-28},
journal = {The Journal of Chemical Physics},
volume = {152},
number = {8},
pages = {084201},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
2.
C Heshmatpour, J Hauer, F Sanda
Interplay of exciton annihilation and transport in fifth order electronic spectroscopy Journal Article
In: Chemical Physics, vol. 528, 2020, ISSN: 0301-0104.
@article{,
title = {Interplay of exciton annihilation and transport in fifth order electronic spectroscopy},
author = {C Heshmatpour and J Hauer and F Sanda},
url = {\<Go to ISI\>://WOS:000490758300009},
doi = {10.1016/j.chemphys.2019.110433},
issn = {0301-0104},
year = {2020},
date = {2020-01-01},
journal = {Chemical Physics},
volume = {528},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
1.
V Balevičius Jr, T Wei, D Di Tommaso, D Abramavicius, J Hauer, T Polívka, C D P Duffy
The full dynamics of energy relaxation in large organic molecules: from photo-excitation to solvent heating Journal Article
In: Chemical Science, vol. 10, no. 18, pp. 4792-4804, 2019, ISSN: 2041-6520.
@article{nokey,
title = {The full dynamics of energy relaxation in large organic molecules: from photo-excitation to solvent heating},
author = {V Balevi\v{c}ius Jr and T Wei and D Di Tommaso and D Abramavicius and J Hauer and T Pol\'{i}vka and C D P Duffy},
url = {http://dx.doi.org/10.1039/C9SC00410F},
doi = {10.1039/C9SC00410F},
issn = {2041-6520},
year = {2019},
date = {2019-04-02},
journal = {Chemical Science},
volume = {10},
number = {18},
pages = {4792-4804},
abstract = {In some molecular systems, such as nucleobases, polyenes or the active ingredients of sunscreens, substantial amounts of photo-excitation energy are dissipated on a sub-picosecond time scale, raising questions such as: where does this energy go or among which degrees of freedom it is being distributed at such early times? Here we use transient absorption spectroscopy to track excitation energy dispersing from the optically accessible vibronic subsystem into the remaining vibrational subsystem of the solute and solvent. Monitoring the flow of energy during vibrational redistribution enables quantification of local molecular heating. Subsequent heat dissipation away from the solute molecule is characterized by classical thermodynamics and molecular dynamics simulations. Hence, we present a holistic approach that tracks the internal temperature and vibronic distribution from the act of photo-excitation to the restoration of the global equilibrium. Within this framework internal vibrational redistribution and vibrational cooling are emergent phenomena. We demonstrate the validity of the framework by examining a highly controversial example, carotenoids. We show that correctly accounting for the local temperature unambiguously explains their energetically and temporally congested spectral dynamics without the ad hoc postulation of additional ‘dark’ states. An immediate further application of this approach would be to monitor the excitation and thermal dynamics of pigment\textendashprotein systems.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In some molecular systems, such as nucleobases, polyenes or the active ingredients of sunscreens, substantial amounts of photo-excitation energy are dissipated on a sub-picosecond time scale, raising questions such as: where does this energy go or among which degrees of freedom it is being distributed at such early times? Here we use transient absorption spectroscopy to track excitation energy dispersing from the optically accessible vibronic subsystem into the remaining vibrational subsystem of the solute and solvent. Monitoring the flow of energy during vibrational redistribution enables quantification of local molecular heating. Subsequent heat dissipation away from the solute molecule is characterized by classical thermodynamics and molecular dynamics simulations. Hence, we present a holistic approach that tracks the internal temperature and vibronic distribution from the act of photo-excitation to the restoration of the global equilibrium. Within this framework internal vibrational redistribution and vibrational cooling are emergent phenomena. We demonstrate the validity of the framework by examining a highly controversial example, carotenoids. We show that correctly accounting for the local temperature unambiguously explains their energetically and temporally congested spectral dynamics without the ad hoc postulation of additional ‘dark’ states. An immediate further application of this approach would be to monitor the excitation and thermal dynamics of pigment–protein systems.