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Charge-transfer emission of compact porphyrin–fullerene dyad analyzed by Marcus theory of electron-transfer

2001; Elsevier BV; Volume: 57; Issue: 11 Linguagem: Inglês

10.1016/s1386-1425(01)00496-6

1873-3557

Visa Vehmanen, Nikolai V. Tkachenko, Hiroshi Imahori, Shunichi Fukuzumi, Helge Lemmetyinen,

Photochemistry and Electron Transfer Studies

A porphyrin–fullerene dyad, which is characterized by a close proximity of the porphyrin donor and the fullerene acceptor, was found to undergo a photoinduced electron transfer both in solutions and in solid films. Near-infrared charge-transfer (CT) emission was observed and analyzed in frame of the semi-classical Marcus electron-transfer theory yielding values for the reaction free energy, −ΔG°=1.75 eV, the internal reorganization energy, λv=0.05 eV, and the donor–acceptor vibrational energy, hvv=0.14 eV, both in solution and in solid film. The influence of the environment on the CT properties of the dyad is described by a single parameter, the outer-sphere reorganization energy, λs, which varies from 0.05 eV in non-polar solvents and films to 0.13 eV in solvents of moderate polarity. At low temperatures (T<200 K), the CT emission consists of distinct bands shifted from each other by value hvv. This is the first direct observation of the vibrational frequencies of a porphyrin–fullerene donor–acceptor system.