Header

UZH-Logo

Maintenance Infos

Geminate Recombination versus Cage Escape in the Reductive Quenching of a Re(I) Carbonyl Complex on Mesoporous ZrO2


Oppelt, Kerstin; Fernández-Terán, Ricardo; Pfister, Rolf; Hamm, Peter (2019). Geminate Recombination versus Cage Escape in the Reductive Quenching of a Re(I) Carbonyl Complex on Mesoporous ZrO2. Journal of Physical Chemistry C, 123(32):19952-19961.

Abstract

In the wider context of artificial photosynthesis, this work aims to explore the functionality and characteristics of rhenium tricarbonyl complexes as photosensitizers in heterogeneous water reduction systems. To that end, the reductive quenching of an excited ReICl(2,2′‐bipyridine‐4,4′‐bisphosphonic acid)(CO)3 adsorbed on a redox-neutral scaffold by phenothiazine was observed by transient IR spectroscopy. From the spectroscopic and time response, the full reaction cycle could be elucidated, and the intrinsic lifetime of the excited Re complex, together with rates for reductive quenching, cage escape, as well as geminate recombination and secondary back electron transfer could be determined. Three different scenarios have been explored, which decrease the mobility of the reactants in the system in a stepwise manner: Starting from a reference system with all compounds in solution, first the Re complex was immobilized on the surface, and in a second step also the quencher. The overall reaction cycle for all reactants in solution is preserved as long as the quencher is in solution, with relatively minor changes of the rates of the individual reaction steps. The overall cage escape yield was found to be larger on the surface. As soon as the quencher is co-adsorbed alongside the Re-complex, however, the reaction cycle changes completely. Electron transfer occurred only from quencher molecules that sit next to an excited Re complex, and there is no possibility of cage escape. Varying the ratio of quencher molecules and Re-complexes, it is concluded that molecules do not cluster on the surface, and that excitation energy migration is not a very efficient process.

Abstract

In the wider context of artificial photosynthesis, this work aims to explore the functionality and characteristics of rhenium tricarbonyl complexes as photosensitizers in heterogeneous water reduction systems. To that end, the reductive quenching of an excited ReICl(2,2′‐bipyridine‐4,4′‐bisphosphonic acid)(CO)3 adsorbed on a redox-neutral scaffold by phenothiazine was observed by transient IR spectroscopy. From the spectroscopic and time response, the full reaction cycle could be elucidated, and the intrinsic lifetime of the excited Re complex, together with rates for reductive quenching, cage escape, as well as geminate recombination and secondary back electron transfer could be determined. Three different scenarios have been explored, which decrease the mobility of the reactants in the system in a stepwise manner: Starting from a reference system with all compounds in solution, first the Re complex was immobilized on the surface, and in a second step also the quencher. The overall reaction cycle for all reactants in solution is preserved as long as the quencher is in solution, with relatively minor changes of the rates of the individual reaction steps. The overall cage escape yield was found to be larger on the surface. As soon as the quencher is co-adsorbed alongside the Re-complex, however, the reaction cycle changes completely. Electron transfer occurred only from quencher molecules that sit next to an excited Re complex, and there is no possibility of cage escape. Varying the ratio of quencher molecules and Re-complexes, it is concluded that molecules do not cluster on the surface, and that excitation energy migration is not a very efficient process.

Statistics

Citations

Altmetrics

Downloads

2 downloads since deposited on 07 Feb 2020
2 downloads since 12 months
Detailed statistics

Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Uncontrolled Keywords:General Energy, Physical and Theoretical Chemistry, Electronic, Optical and Magnetic Materials, Surfaces, Coatings and Films
Language:English
Date:15 August 2019
Deposited On:07 Feb 2020 11:33
Last Modified:07 Feb 2020 11:58
Publisher:American Chemical Society (ACS)
ISSN:1932-7447
Additional Information:This document is the Accepted Manuscript version of a Published Work that appeared in final form inThe Journal of Physical Chemistry C © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org10.1021/acs.jpcc.9b04950
OA Status:Closed
Publisher DOI:https://doi.org/10.1021/acs.jpcc.9b04950
Project Information:
  • : FunderSwiss National Science Foundation
  • : Grant IDCRSII2_160801/1
  • : Project Title
  • : FunderUniversity Research Priority Program (URPP)
  • : Grant ID
  • : Project TitleLightChEC

Download

Closed Access: Download allowed only for UZH members