ROD-LIKE LIQUID-CRYSTALS OF ORGANIC TRANSITION-METAL COMPLEXES .1. REVERSIBLE TRANSFORMATION BETWEEN BLUE SMECTOGEN AND RED NEMATOGEN

Two novel types of transition-metal-containing liquid crystals, bis(p-n-koxydithiobenzoato)nickel(II) (abbreviated as (Cn O-DTB)2Ni), and (p-n-alkoxydithiobenzoato)(p-n-alkoxyperthiobenzoato)nickel(II) (abbreviated as (C nO-DTB)(C n O-PTB)Ni), were synthesized. It was found that the (Cn O-DTB)2Ni complex for n = 8 has smectic H and C mesophases, and that the (C n O-DTB)2Ni complexes for n =4 and 8 easily transform into the corresponding monoperthio complexes, n O-PTB)Ni, by heating at temperatures between 230°C and 285°C. It was confirmed that the transformation originates from an intermolecular between the (C n O-DTB)2Ni complexes at hightemperatures, and that the origin of the extra sulphurs in the resulting (C n O-DTB)(C nO-PTB)Ni complexes is the neighbouring (C n O-DTB)2Ni complexes. Interestingly, each of the(C n O-DTB)(C n O-PTB)Ni complexes (n= 4 and 8), has nematic mesophase and exhibits a unique double melting behaviour via the nematic phase, which is the first example in liquid crystals. The reversible transformation between the blue smectic rod-like (Cn O-DTB)2Ni complex and the red nematic Λ-like (C n O-DTB)(C n O-PTB)Ni complex is possible. © 1990 Taylor & Francis Group, LLC.