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Tuning of Photocatalytic Hydrogen Production and Photoinduced Intramolecular Electron Transfer Rates by Regioselective Bridging Ligand Substitution

Karnahl, Michael ; Kuhnt, Christian ; Ma, Fei LU ; Yartsev, Arkady LU orcid ; Schmitt, Michael ; Dietzek, Benjamin ; Rau, Sven and Popp, Juergen (2011) In ChemPhysChem 12(11). p.2101-2109
Abstract
Artificial photosynthesis based on supramolecular photocatalysts offers the unique possibility to study the molecular processes underlying catalytic conversion of photons into chemical fuels in great detail and to tune the properties of the photocatalyst by alterations of the molecular framework. Herein we focus on both possibilities in studying the photocatalytic reduction of protons by derivatives of the well-known photocatalyst [(tbbpy)(2)Ru(tpphz)PdCl2](PF6)(2) [4,4'-di-tert-butyl-2,2'-bipyridine (tbbpy), tetrapyrido[3,2-a:2',3'-c:3 '',2 ''-h:2'", 3'"-j]phenazine (tpphz)]. We report on a modified photocatalyst where the crucial bridging ligand tpphz is substituted by bromine and investigate the effect of the structural variation on the... (More)
Artificial photosynthesis based on supramolecular photocatalysts offers the unique possibility to study the molecular processes underlying catalytic conversion of photons into chemical fuels in great detail and to tune the properties of the photocatalyst by alterations of the molecular framework. Herein we focus on both possibilities in studying the photocatalytic reduction of protons by derivatives of the well-known photocatalyst [(tbbpy)(2)Ru(tpphz)PdCl2](PF6)(2) [4,4'-di-tert-butyl-2,2'-bipyridine (tbbpy), tetrapyrido[3,2-a:2',3'-c:3 '',2 ''-h:2'", 3'"-j]phenazine (tpphz)]. We report on a modified photocatalyst where the crucial bridging ligand tpphz is substituted by bromine and investigate the effect of the structural variation on the catalytic properties of the complex and its ultrafast intramolecular charge transfer behavior. It is found that structural modification stabilizes the phenanthroline-centered metal-to-ligand charge-transfer state on the tpphz moiety, thereby reducing the electron transfer gradient across the entire electron-relaying bridging ligand and at the same time accelerating nanosecond ground-state recovery. The same structural modifications cause an overall reduction of the catalytic activity of the complex. Thus, the results highlight the potential of small structural variations in the molecular framework of supramolecular catalysts in understanding the photoinduced charge-transfer processes and optimizing their catalytic performance. (Less)
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author
; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
hydrogen, photocatalysis, photochemistry, supramolecular chemistry, time-resolved spectroscopy
in
ChemPhysChem
volume
12
issue
11
pages
2101 - 2109
publisher
John Wiley and Sons
external identifiers
  • wos:000293385400009
  • scopus:79960773147
ISSN
1439-7641
DOI
10.1002/cphc.201100245
language
English
LU publication?
yes
additional info
The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Chemical Physics (S) (011001060)
id
eb170b7c-abe9-4e0e-ba6f-538bf33649b8 (old id 2071647)
date added to LUP
2016-04-01 10:33:46
date last changed
2021-10-06 01:15:23
@article{eb170b7c-abe9-4e0e-ba6f-538bf33649b8,
  abstract     = {Artificial photosynthesis based on supramolecular photocatalysts offers the unique possibility to study the molecular processes underlying catalytic conversion of photons into chemical fuels in great detail and to tune the properties of the photocatalyst by alterations of the molecular framework. Herein we focus on both possibilities in studying the photocatalytic reduction of protons by derivatives of the well-known photocatalyst [(tbbpy)(2)Ru(tpphz)PdCl2](PF6)(2) [4,4'-di-tert-butyl-2,2'-bipyridine (tbbpy), tetrapyrido[3,2-a:2',3'-c:3 '',2 ''-h:2'", 3'"-j]phenazine (tpphz)]. We report on a modified photocatalyst where the crucial bridging ligand tpphz is substituted by bromine and investigate the effect of the structural variation on the catalytic properties of the complex and its ultrafast intramolecular charge transfer behavior. It is found that structural modification stabilizes the phenanthroline-centered metal-to-ligand charge-transfer state on the tpphz moiety, thereby reducing the electron transfer gradient across the entire electron-relaying bridging ligand and at the same time accelerating nanosecond ground-state recovery. The same structural modifications cause an overall reduction of the catalytic activity of the complex. Thus, the results highlight the potential of small structural variations in the molecular framework of supramolecular catalysts in understanding the photoinduced charge-transfer processes and optimizing their catalytic performance.},
  author       = {Karnahl, Michael and Kuhnt, Christian and Ma, Fei and Yartsev, Arkady and Schmitt, Michael and Dietzek, Benjamin and Rau, Sven and Popp, Juergen},
  issn         = {1439-7641},
  language     = {eng},
  number       = {11},
  pages        = {2101--2109},
  publisher    = {John Wiley and Sons},
  series       = {ChemPhysChem},
  title        = {Tuning of Photocatalytic Hydrogen Production and Photoinduced Intramolecular Electron Transfer Rates by Regioselective Bridging Ligand Substitution},
  url          = {http://dx.doi.org/10.1002/cphc.201100245},
  doi          = {10.1002/cphc.201100245},
  volume       = {12},
  year         = {2011},
}