Issue 30, 2015

Fast photo-driven electron spin coherence transfer: the effect of electron-nuclear hyperfine coupling on coherence dephasing

Abstract

Selective photoexcitation of the donor in an electron donor–acceptor1–acceptor2 (D–A1–A2) molecule, in which D = perylene and both A1 and A2 = naphthalene-1,8:4,5-bis(dicarboximide), results in sub-nanosecond formation of a spin-correlated singlet radical pair 1(D+˙–A1˙–A2) having a large electron spin–spin exchange interaction, 2J, which precludes its observation by transient EPR spectroscopy. Subsequent selective photoexcitation of A1˙ rapidly produces 1(D+˙–A1–A2˙), resulting in a dramatic decrease in 2J, which allows coherent spin evolution to mix the singlet (S) radical pair state 1(D+˙–A1–A2˙) with the T0 triplet sublevel of 3(D+˙–A1–A2˙) in an applied magnetic field, where B ≫ 2J. A spin-polarized transient EPR spectrum characteristic of the spin-correlated radical pair D+˙–A1–A2˙ is then observed. The time delay between the two laser pulses was incremented to measure the rate of decoherence in 1(D+˙–A1˙–A2) in toluene at 295 K, which was found to be 8.1 × 107 s−1. Deuteration of the perylene donor or the toluene solvent decreases the decoherence rate constant of 1(D+˙–A1˙–A2) to 4.3 × 107 s−1 and 4.6 × 107 s−1, respectively, while deuteration of both the perylene donor and the toluene solvent reduced the decoherence rate constant by more than half to 3.4 × 107 s−1. The data show that decreasing electron-nuclear hyperfine interactions significantly increases the zero quantum coherence lifetime of the spin-correlated radical pair.

Graphical abstract: Fast photo-driven electron spin coherence transfer: the effect of electron-nuclear hyperfine coupling on coherence dephasing

Supplementary files

Article information

Article type
Paper
Submitted
21 May 2015
Accepted
18 Jun 2015
First published
30 Jun 2015

J. Mater. Chem. C, 2015,3, 7962-7967

Fast photo-driven electron spin coherence transfer: the effect of electron-nuclear hyperfine coupling on coherence dephasing

M. D. Krzyaniak, L. Kobr, B. K. Rugg, B. T. Phelan, E. A. Margulies, J. N. Nelson, R. M. Young and M. R. Wasielewski, J. Mater. Chem. C, 2015, 3, 7962 DOI: 10.1039/C5TC01446H

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