Charge-Transfer Interactions in Face-to-Face Porphyrin-Fullerene Systems: Solvent-Dependent Luminescence in the Infrared Spectral Region

25th Anniversary Article: 25 Years of Fullerene Research in Electron Transfer Chemistry

“…An important variable in this work is solvent polarity. By increasing the solvent polarity the energy of the radical pair ion state is lowered without affecting the energy of the precursor state, that is, the porphyrin singlet excited states . The dependence of the back electron transfer rate on the free energy changes reveals stabilizing effects at larger ‐∆G° values – a key features of the Marcus theory .…”

“…By increasing the solvent polarity the energy of the radical pair ion state is lowered without affecting the energy of the precursor state, that is, the porphyrin singlet excited states. [ 36 ] The dependence of the back electron transfer rate on the free energy changes reveals stabilizing effects at larger −ΔG° values -a key features of the Marcus theory. [ 37 ] The latter implies that the intramolecular rate constant fi rst increases with increasing thermodynamic driving force in the "normal region" of the parabolic relationship, when the driving force reaches the same magnitude as the reorganization energy (λ) -vide infra.…”

The effect of structural changes on charge transfer states in a light-harvesting carotenoid-diaryl-porphyrin-C60 molecular triad

“…To emulate the light-absorbing property of chlorophylls, many artificial reaction centers feature porphyrins, chlorophyll derivatives, and related cyclic tetrapyrrolic molecules as the primary chromophore and excited-state electron donor. 3,12,[16][17][18]20,31,34,36,37,40,42,[44][45][46][47][48][49] Modeling natural photosynthesis led to the inclusion of quinones as the electron acceptor among some of the earliest synthesized photosynthetic mimics. 19,26,27,29,[50][51][52] Subsequently, fullerenes were found to possess ideal electron acceptor qualities in artificial photosynthetic systems due to their large electron affinity, large charge accumulation capacity, and a small reorganization energy upon electron transfer.…”

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“…111 Similarly, multiply addended [60]fullerene derivatives have fluorescence quantum yields similar to those found in mono-addended [60]fullerenes. 112 Evidence for 'Marcus-inverted' back electron transfer (BET) 113 has been produced by studying p-stacked bismethano [60]fullerene porphyrin dyads 113,114 in which both chromophores (the fullerene and porphyrin) are rigidly held at van der Waals distance in a tangential orientation. The kinetics of photoinduced electron transfer in several multicomponent arrays consisting of p-stacked bis-methano [60]fullerene porphyrin dyads and, for example, [60]fulleropyrrolidine ligands have also been probed and the lifetimes of the charge-separated states found to be markedly improved as compared with those of the starting bis-methano [60]fullerene porphyrin dyads.…”