Premium
Control of Electron Transfer in a Conjugated Porphyrin Dimer by Selective Excitation of Planar and Perpendicular Conformers
Author(s) -
Winters Mikael U.,
Kärnbratt Joakim,
Blades Holly E.,
Wilson Craig J.,
Frampton Michael J.,
Anderson Harry L.,
Albinsson Bo
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200700434
Subject(s) - chemistry , porphyrin , conformational isomerism , electron transfer , dimer , excitation , photochemistry , acceptor , electron acceptor , ground state , crystallography , molecular physics , atomic physics , molecule , condensed matter physics , physics , organic chemistry , electrical engineering , engineering
A donor–acceptor system is presented in which the electron‐transfer rates can be sensitively controlled by means of excitation wavelength and temperature. The electron donor is a butadiyne‐linked zinc porphyrin dimer that is connected to a C 60 electron acceptor. The broad distribution of conformations allowed by the butadiyne linker makes it possible to selectively excite perpendicular or planar donor conformers and thereby prepare separate initial states with driving forces for electron transfer that differ by almost 0.2 eV. This, as well as significant differences in electronic coupling, leads to distinctly different rate constants for electron transfer, which in consequence can be controlled by changing excitation wavelength. By extending the system with a secondary donor (ferrocene), a second, long‐range charge‐separated state can be formed. This system has been used to test the influence of conformational heterogeneity on electron transfer mediated by the porphyrin dimer in the ground state. It was found that if the dimer is forced to a planar conformation by means of a bidentate ligand, the charge recombination rate increased by an order of magnitude relative to the unconstrained system. This illustrates how control of conformation of a molecular wire can affect its behaviour.