Variable band filling in organic conductor with proton donor/acceptor H nTNBP (2− n)− (TNBP: 3,3′,5,5′-tetranitro-4,4′-biphenyldiol)

Abstract

H 2TNBP (3,3′,5,5′-tetranitro-4,4′-biphenyldiol) is known as a proton donor forming monoanion HTNBP 1− and dianion TNBP 2−. We have studied radical salts of TTF-series with TNBP 2− as counter anion, and found two kinds of ET (BEDT-TTF) salts, namely 4:1 and 2:1. In the 2:1 salt, it is strongly suggested that the formula is represented as (ET 0.5+) 2(HTNBP 1−) by the optical data and relatively high conductivity. The chemical species of anion part is determined by the chemical shift of 13 C -CP/MAS NMR in the solid state. Coexistence of TNBP 2− and HTNBP 1− is observed in 3:1 BO salt and 2:1 TMTSF salt, though only TNBP 2− exists in 4:1 ET salt. The 2:1 TMTSF salt exhibited optical transitions at ca. 2500 and 7500 cm −1 simultaneously in the reflection spectrum, however, the intensity ratio differs from crystal to crystal. It suggests that the charge of TMTSF varies between +0.5 and +1.0, and the formula is represented as ( TMTSF (1−x/2)+) 2( TNBP 2−) 1−x( HTNBP 1−) x (0<x<1) .