Synthesis and Properties of Mesogenic π-Donors Precursors of Mesomorphic Organic Conductors

Abstract In sequence with previous work on 4-(2,6 diphenyl 4-H pyran-4 ylidene-2,6 diphenyl) and their sulfur analogs, useful precursors of organic conductors, we now report on the synthesis and properties of parent heterocyclic compounds, 1, in which the phenyls have long chain substituents. Introduction of four alkyl or alkoxy side chains in the para position of phenyl leads to compounds, 2, which exhibit disk-like mesophases. All new donors 2 give stables 1: 1 charge transfer complexes, 3, with TCNQ. Disk-like donors lead to mesomorphic conducting complexes. For example the TCNQ complex of 2b, × = S, R = C12H25 exhibits a SA phase between 120-154°C. The electrical conductivity at room temperature of a single crystal is 0.7 (Ωcm)−1.