Synthesis of New Electron Donor ClMe₃-TTP: Structures and Properties of (ClMe₃-TTP)₃X (X = PF₆ and AsF₆)

Abstract

In this study, we synthesized 2-(4-Chloro-5-methyl-1,3-dithiol-2-ylidene)-5-(4,5-dimethyl-1,3-dithiol-2-ylidene)-1,3,4,6-tetrathiapentalene (ClMe₃-TTP). Results show that the cation radical salts of ClMe₃-TTP with PF₆⁻ and AsF₆⁻ anions show high conductivities (10¹ S cm⁻¹) at room temperature and semiconducting behavior with low activation energy (24–27 meV). A crystal structure analysis of the PF₆⁻ and AsF₆⁻ salts reveals a 3:1 donor–anion ratio of these salts. The ClMe₃-TTP molecules form one-dimensional columns along the a axis, and tape-structures, connected by the side-by-side S⋯S interactions, also form along the a axis. The calculated intra-column and intra-tape overlap integrals are relatively large; however, the overlap integrals between the one-dimensional columns and the tapes are approximately 1/2–1/5 the value of the intra-column and intra-tape overlap integrals. The band calculations suggest that they have one-dimensional electronic structures, indicating that they would comprise a Mott insulator.