Prof. Dr. Corinna Hess
Academic Research Focus
- Inorganic and bioinorganic chemistry
Fields of Application
Photo-(electro)catalysis
Publications
5.
K Rickmeyer, M Huber, C R Hess
Influence of a neighbouring Cu centre on electro- and photocatalytic CO2 reduction by Fe-Mabiq Journal Article
In: Chemical Communications, 2023, ISSN: 1359-7345.
@article{nokey,
title = {Influence of a neighbouring Cu centre on electro- and photocatalytic CO2 reduction by Fe-Mabiq},
author = {K Rickmeyer and M Huber and C R Hess},
url = {http://dx.doi.org/10.1039/D3CC04777F},
doi = {10.1039/D3CC04777F},
issn = {1359-7345},
year = {2023},
date = {2023-12-14},
journal = {Chemical Communications},
abstract = {Electrocatalytic and photocatalytic CO2 reduction by a heterobimetallic Cu/Fe\textendashMabiq complex were examined and compared to the monometallic [Fe(Mabiq)]+. The neighbouring Cu\textendashXantphos unit leads to marked changes in the electrocatalytic mechanism and enhanced photocatalytic performance.},
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pubstate = {published},
tppubtype = {article}
}
Electrocatalytic and photocatalytic CO2 reduction by a heterobimetallic Cu/Fe–Mabiq complex were examined and compared to the monometallic [Fe(Mabiq)]+. The neighbouring Cu–Xantphos unit leads to marked changes in the electrocatalytic mechanism and enhanced photocatalytic performance.
4.
K Rickmeyer, L Niederegger, M Keilwerth, C R Hess
Multifaceted Role of the Noninnocent Mabiq Ligand in Promoting Selective Reduction of CO2 to CO Journal Article
In: ACS Catalysis, pp. 3046-3057, 2022.
@article{nokey,
title = {Multifaceted Role of the Noninnocent Mabiq Ligand in Promoting Selective Reduction of CO2 to CO},
author = {K Rickmeyer and L Niederegger and M Keilwerth and C R Hess},
url = {https://doi.org/10.1021/acscatal.1c04636},
doi = {10.1021/acscatal.1c04636},
year = {2022},
date = {2022-02-21},
journal = {ACS Catalysis},
pages = {3046-3057},
abstract = {We have investigated the ability of Co\textendash and Fe\textendashMabiq complexes (Mabiq = 2\textendash4:6\textendash8-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) to act as electrocatalysts for CO2 reduction. We observed marked differences in activity when switching the metal center, as the Fe complex outperforms its Co-containing analogue, both in terms of overpotential (η) and faradaic efficiency (FE). [Fe(Mabiq)2(MeCN)2]PF6 ([2]+) selectively reduces CO2 to CO with an overpotential requirement of 500 mV. We have synthesized and fully characterized the two-electron reduced Na(OEt2)[Fe(Mabiq)] ([2]\textendash), which consists of an intermediate spin FeII center coupled to a ligand biradical and exhibits a unique S = 1 spin state. Both electrochemical and reactivity studies with [2]\textendash point toward a protonated precatalytic intermediate (IPhOH). The molecular structure of IPhOH indicates the diketiminate carbon as the site of protonation and the ability of the Mabiq ligand to engage in hydrogen bonding interactions. The noninnocent Mabiq ligand, therefore, acts not only as an electron reservoir but also as a proton storage site. Our ligand system uniquely combines two beneficial features, a redox-active unit and a proton donor site, that in combination with the metal ion reduces overpotentials and facilitates selective CO2 conversion.},
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pubstate = {published},
tppubtype = {article}
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We have investigated the ability of Co– and Fe–Mabiq complexes (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) to act as electrocatalysts for CO2 reduction. We observed marked differences in activity when switching the metal center, as the Fe complex outperforms its Co-containing analogue, both in terms of overpotential (η) and faradaic efficiency (FE). [Fe(Mabiq)2(MeCN)2]PF6 ([2]+) selectively reduces CO2 to CO with an overpotential requirement of 500 mV. We have synthesized and fully characterized the two-electron reduced Na(OEt2)[Fe(Mabiq)] ([2]–), which consists of an intermediate spin FeII center coupled to a ligand biradical and exhibits a unique S = 1 spin state. Both electrochemical and reactivity studies with [2]– point toward a protonated precatalytic intermediate (IPhOH). The molecular structure of IPhOH indicates the diketiminate carbon as the site of protonation and the ability of the Mabiq ligand to engage in hydrogen bonding interactions. The noninnocent Mabiq ligand, therefore, acts not only as an electron reservoir but also as a proton storage site. Our ligand system uniquely combines two beneficial features, a redox-active unit and a proton donor site, that in combination with the metal ion reduces overpotentials and facilitates selective CO2 conversion.
3.
F Haag, P S Deimel, P Knecht, L Niederegger, K Seufert, M G. Cuxart, Y Bao, A C Papageorgiou, M Muntwiler, W Auwärter, C R Hess, J V Barth, F Allegretti
The Flexible On-Surface Self-Assembly of a Low-Symmetry Mabiq Ligand: An Unconventional Metal-Assisted Phase Transformation on Ag(111) Journal Article
In: The Journal of Physical Chemistry C, vol. 125, no. 42, pp. 23178-23191, 2021, ISSN: 1932-7447.
@article{nokey,
title = {The Flexible On-Surface Self-Assembly of a Low-Symmetry Mabiq Ligand: An Unconventional Metal-Assisted Phase Transformation on Ag(111)},
author = {F Haag and P S Deimel and P Knecht and L Niederegger and K Seufert and M G. Cuxart and Y Bao and A C Papageorgiou and M Muntwiler and W Auw\"{a}rter and C R Hess and J V Barth and F Allegretti},
url = {https://doi.org/10.1021/acs.jpcc.1c07400},
doi = {10.1021/acs.jpcc.1c07400},
issn = {1932-7447},
year = {2021},
date = {2021-10-12},
journal = {The Journal of Physical Chemistry C},
volume = {125},
number = {42},
pages = {23178-23191},
abstract = {The self-assembly of metal\textendashorganic complexes and networks of increasing complexity on solid surfaces is important for their application in a variety of fields, such as catalysis, sensing, and molecular magnetism. Here, we have selected a low-symmetry, free-base macrocyclic biquinazoline ligand, H-Mabiq, which upon metalation has the potential to incorporate cations in two different coordination sites, affording multi-valency and multi-electron transfer capacity. We show that H-Mabiq molecules readily self-assemble onto the Ag(111) surface at room temperature, forming a well-ordered monolayer of closely packed molecules. Upon increasing the temperature, a new phase with a different long-range order and molecular packing is obtained. By means of scanning tunneling microscopy and photoelectron spectroscopy, we show that this new phase is characterized by a distinctive silver-bridged dimeric motif, entailing a Ag adatom accommodated at the peripheral coordination site of two opposing H-Mabiq molecules. Thus, the present work reveals the ability of the bio-inspired Mabiq ligands to form surface-confined two-dimensional assemblies incorporating metal adatoms. The results bode promise for the use of metal-containing Mabiq compounds to engineer regular bimetallic arrays with atomic precision.},
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pubstate = {published},
tppubtype = {article}
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The self-assembly of metal–organic complexes and networks of increasing complexity on solid surfaces is important for their application in a variety of fields, such as catalysis, sensing, and molecular magnetism. Here, we have selected a low-symmetry, free-base macrocyclic biquinazoline ligand, H-Mabiq, which upon metalation has the potential to incorporate cations in two different coordination sites, affording multi-valency and multi-electron transfer capacity. We show that H-Mabiq molecules readily self-assemble onto the Ag(111) surface at room temperature, forming a well-ordered monolayer of closely packed molecules. Upon increasing the temperature, a new phase with a different long-range order and molecular packing is obtained. By means of scanning tunneling microscopy and photoelectron spectroscopy, we show that this new phase is characterized by a distinctive silver-bridged dimeric motif, entailing a Ag adatom accommodated at the peripheral coordination site of two opposing H-Mabiq molecules. Thus, the present work reveals the ability of the bio-inspired Mabiq ligands to form surface-confined two-dimensional assemblies incorporating metal adatoms. The results bode promise for the use of metal-containing Mabiq compounds to engineer regular bimetallic arrays with atomic precision.
2.
G C Tok, S Reiter, A T S Freiberg, L Reinschlüssel, H A Gasteiger, R De Vivie-Riedle, C R Hess
H2 Evolution from Electrocatalysts with Redox-Active Ligands: Mechanistic Insights from Theory and Experiment vis-à-vis Co-Mabiq Journal Article
In: Inorganic Chemistry, 2021, ISSN: 0020-1669.
@article{,
title = {H2 Evolution from Electrocatalysts with Redox-Active Ligands: Mechanistic Insights from Theory and Experiment vis-\`{a}-vis Co-Mabiq},
author = {G C Tok and S Reiter and A T S Freiberg and L Reinschl\"{u}ssel and H A Gasteiger and R De Vivie-Riedle and C R Hess},
url = {https://doi.org/10.1021/acs.inorgchem.1c01157},
doi = {10.1021/acs.inorgchem.1c01157},
issn = {0020-1669},
year = {2021},
date = {2021-07-23},
urldate = {2021-07-23},
journal = {Inorganic Chemistry},
abstract = {Electrocatalytic hydrogen production via transition metal complexes offers a promising approach for chemical energy storage. Optimal platforms to effectively control the proton and electron transfer steps en route to H2 evolution still need to be established, and redox-active ligands could play an important role in this context. In this study, we explore the role of the redox-active Mabiq (Mabiq = 2\textendash4:6\textendash8-bis(3,3,4,4-tetramethlyldihydropyrrolo)-10\textendash15-(2,2-biquinazolino)-[15]-1,3,5,8,10,14-hexaene1,3,7,9,11,14-N6) ligand in the hydrogen evolution reaction (HER). Using spectro-electrochemical studies in conjunction with quantum chemical calculations, we identified two precatalytic intermediates formed upon the addition of two electrons and one proton to [CoII(Mabiq)(THF)](PF6) (CoMbq). We further examined the acid strength effect on the generation of the intermediates. The generation of the first intermediate, CoMbq-H1, involves proton addition to the bridging imine-nitrogen atom of the ligand and requires strong proton activity. The second intermediate, CoMbq-H2, acquires a proton at the diketiminate carbon for which a weaker proton activity is sufficient. We propose two decoupled H2 evolution pathways based on these two intermediates, which operate at different overpotentials. Our results show how the various protonation sites of the redox-active Mabiq ligand affect the energies and activities of HER intermediates.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Electrocatalytic hydrogen production via transition metal complexes offers a promising approach for chemical energy storage. Optimal platforms to effectively control the proton and electron transfer steps en route to H2 evolution still need to be established, and redox-active ligands could play an important role in this context. In this study, we explore the role of the redox-active Mabiq (Mabiq = 2–4:6–8-bis(3,3,4,4-tetramethlyldihydropyrrolo)-10–15-(2,2-biquinazolino)-[15]-1,3,5,8,10,14-hexaene1,3,7,9,11,14-N6) ligand in the hydrogen evolution reaction (HER). Using spectro-electrochemical studies in conjunction with quantum chemical calculations, we identified two precatalytic intermediates formed upon the addition of two electrons and one proton to [CoII(Mabiq)(THF)](PF6) (CoMbq). We further examined the acid strength effect on the generation of the intermediates. The generation of the first intermediate, CoMbq-H1, involves proton addition to the bridging imine-nitrogen atom of the ligand and requires strong proton activity. The second intermediate, CoMbq-H2, acquires a proton at the diketiminate carbon for which a weaker proton activity is sufficient. We propose two decoupled H2 evolution pathways based on these two intermediates, which operate at different overpotentials. Our results show how the various protonation sites of the redox-active Mabiq ligand affect the energies and activities of HER intermediates.
1.
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.