Control of electronic state in the 2D hydrogen-bonded system: β″-(CnDT-EDO-TTF) 2(PF 6) x ( n = 5, 6, 7, 8)

Abstract

A new series of CnDT-EDO-TTF [ n=5, 6, 7, 8; ( cis-1,2-cycloalkylene-1,2-dithio)ethylenedioxytetrathiafulvalene] donors containing cycloalkylene and ethylenedioxy groups as a source of intermolecular hydrogen bonds and the steric hindrance has been synthesized. The charge transfer (CT) salts, β″-(CnDT-EDO-TTF) 2(PF 6) x ( n=5, 6, 7, 8), have the similar β″-type donor arrangements owing to the intermolecular hydrogen-bonded network (CH⋯O) in the two-dimensional (2D) plane. The steric hindrance of cycloalkylene groups enlarges the intermolecular distance in the order from n=5, 6, 7, to 8 salt. The calculated bandwidth, however, decreases in the different order from n=8, 5, 7, to 6 salt in consideration of the 2D interactions. All salts, β″-(CnDT-EDO-TTF) 2(PF 6) x , show a metallic feature down to 1.5 K, and the temperature dependences indicate the negative chemical pressure effect from n=8, 5, 7, to 6 salt in the same order of the calculated bandwidth.