Excited state redox properties of phthalocyanines: influence of the axial ligand on the rates of relaxation and electron-transfer quenching of the lowest3ππ* excited state
- 1 January 1984
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 10,p. 2137-2140
- https://doi.org/10.1039/dt9840002137
Abstract
Laser flash excitations at 640 nm have been used to generate the transient spectra of the lowest-lying 3ππ* state of phthalocyaninatoruthenium(II) complexes. The properties of this excited state such as the positions of the maxima, λmax.= 500 ± 30 nm, and lifetimes, t½= 70–4 500 ns, exhibit a large dependence on the electron-accepting and electron-withdrawing tendencies of the axial ligands. A similar influence was observed upon the rate of electron-transfer quenching of the 3ππ* state. Values between 106 and 107 dm3 mol–1 s–1 for the self-exchange rate constant have been obtained, according to Marcus–Hush theoretical treatments, for [Ru(pc˙)LL′]+/(3ππ*)[Ru(pc)LL′][L and L′= neutral axial ligands; pc = phthalocyaninate(2–)] and isoelectronic cobalt(III) and rhodium(III) couples. The redox properties of the ground and excited states are correlated with axial ligand-induced perturbations of the electronic structure.Keywords
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