Synthesis and investigation of donor-porphyrin-acceptor triads with long-lived photo-induced charge-separate states
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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 C, as a better electron-acceptor than triptycenenaphthoquinone (TNQ). The C-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.
Kelber , J B , Panjwani , N A , Wu , D , Gómez-Bombarelli , R , Lovett , B W , Morton , J J L & Anderson , H L 2015 , ' Synthesis and investigation of donor-porphyrin-acceptor triads with long-lived photo-induced charge-separate states ' Chemical Science , vol 6 , no. 11 , pp. 6468-6481 . DOI: 10.1039/c5sc01830g
Copyright 2015 the Authors. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence (http://creativecommons.org/licenses/by/3.0/).
The authors thank the EPSRC for funding (grants EP/I035536/1 and EP/J015067/1). B. W. L. and R. G. B. acknowledge the DARPA QuBE program for financial support.