Synthesis and investigation of donor–porphyrin–acceptor triads with long-lived photo-induced charge-separate states?

Chemical Science Pub Date: 2015-07-31 DOI: 10.1039/C5SC01830G

Abstract

Two donor–porphyrin–acceptor triads have been synthesized using a versatile Suzuki-coupling route. This synthetic strategy allows the powerful donor tetraalkylphenylenediamine (TAPD) to be introduced into tetraarylporphyrin-based triads without protection. The thermodynamics and kinetics of electron transfer in the new triads are compared with a previously reported octaalkyldiphenyl-porphyrin triad exhibiting a long-lived spin-polarized charge separate state (CSS), from theoretical and experimental perspectives, in both fluid solution and in a frozen solvent glass. We show that the less favorable oxidation potential of the tetraaryl-porphyrin core can be offset by using C60, as a better electron-acceptor than triptycenenaphthoquinone (TNQ). The C60–porphyrin–TAPD triad gives a spin-polarized charge-separated state that can be observed by EPR-spectroscopy, with a mean lifetime of 16 ms at 10 K, which is longer than in the previously reported TNQ–porphyrin–TAPD triad, following the predicted trend from calculated charge-recombination rates.

Graphical abstract: Synthesis and investigation of donor–porphyrin–acceptor triads with long-lived photo-induced charge-separate states
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