Linearly Extended π-Conjugated Dithiafulvene Polymer Formed Soluble Charge-Transfer Complex with 7,7,8,8-Tetracyanoquinodimethane

Abstract

A soluble charge-transfer (CT) complex of π-conjugated donor polymer with 7,7,8,8-tetracyano-quinodimethane (TCNQ) was formed when TCNQ was added to a dimethyl sulfoxide (DMSO) solution of a π-conjugated poly(dithiafulvene) (2). In DMSO, 2 reacted with TCNQ to produce a dark green solution. After the precipitated TCNQ was filtered, the filtrate was evaporated to obtain a dark green powder. The resulting CT complex was soluble in acetonitrile, DMSO, N, N-dimethylformamide (DMF), acetone, and MeOH, and partially soluble in tetrahydrofuran (THF). The UV-Vis absorption spectra suggested a formation of the CT complex containing about 1:1 ratio of dithiafulvene unit to TCNQ. The UV-Vis absorption and FT-IR analyses indicated that the anion radical of TCNQ was initially formed by the charge-transfer reaction when TCNQ was added to the solution of 2, and the remaining TCNQ was interacted with 2 as a partially charge-transferred form. In the 1H NMR spectra, the broad peak attributed to the benzylidene proton of 2 was shifted to a lower magnetic field proportional to the TCNQ feed ratio against the dithiafulvene unit of 2. The CT complex has a conductivity of 2×10-4 S cm-1, three orders of magnitude greater than the uncomplexed polymer.