Magnetic gap and partial charge transfer in mixed donor—acceptor stacks

Abstract

The ground state charge transfer γ( z) and magnetic gap Δ E m( z) of organic donor—acceptor complexes with one dimensional⋯D +γA −γD +γA +γ⋯ stacks are computed for arbitrary ratios of z = δ/2 1 2 | t|where | t| is the charge-transfer integral and −2δ is the excitation energy for a D +A − electron—hole pair. Valence bond techniques give exact results for rings of N = 4, 6, 8, and 10 sites, which suffice to show that the neutral—ionic transition and Δ E m( z) → 0 occur at z c = 0.53 ± 0.01 with γ( z c) = 0.68 ± 0.01.