Discotic Liquid Crystals of Transition Metal Complexes 121: The Effect of the Alkoxy Chain Length on the Mesomorphism of Bis[1,2-di(3′,4′-di-n-alkoxyphenyl)ethane-1,2-dithiolene]nickel Complexes

A series of disk-like complexes, bis[1,2-di(3′,4′-di-n-alkoxyphenyl)ethane-1,2-dithiolene]nickel (abbreviated as [(CnO)4DPD]2Ni, n = 1 ∼ 12) have been synthesized in focusing our interest on the effect of the alkoxy chain length on the discotic mesomorphism. It was found that the [(CnO)4DPD]2Ni (n = 2 ∼ 4) complexes have a monotropic discophase, and that the [(CnO)4DPD]2Ni (n = 5 ∼ 12) complexes have an enantiotropic discophase (Dhd). The half-wave potentials for reduction of the [(CnO)4DPD]2Ni (n = 1 ∼ 12) complexes are -0.05 ∼ -0.06V (vs. SCE in dichloromethane solution). It is noteworthy that the π-acceptor discotic columnar liquid crystals can be obtained without impairment of the π-acceptor ability by introduction of the long alkoxy chains to the bis(dithiolene)nickel complex.