Trimethyltetrathiafulvalene Bearing anN-Methylpyridinium Substituent: Synthesis, Crystal Structures, and Charge Transfer Properties

Abstract

The synthesis of 4,4′,5-trimethyl-5′-(4-pyridyl)tetrathiafulvalene (3), has been accomplished by reaction of the stannylated precursor 2 with 4-bromopyridine. Alkylation of 3 affords the N-methylpyridinium salt 4 which displays intramolecular charge transfer properties in solution as deduced from UV/Vis spectra, cyclic voltammetric data, and semiempirical quantum mechanical calculations. The X-ray crystal structures of neutral molecule 3, the salt (4+)I− and the charge transfer salt (4+)2(TCNQ3)2−· are reported. The positive charge in (4+)I− and (4+)2(TCNQ3)2−· is predominantly confined on the pyridinium ring. The structure of (4+)2(TCNQ3)2−· comprises segregated stacks of cations and TCNQ radical anions, with the anions overlapping in the usual ring-over-bond fashion. This salt is a semiconductor (σrt = 10−2 S cm−1).