Synthesis and phase behaviour of mesomorphic transition-metal complexes of alkoxydithiobenzoates: Crystal and molecular structure of three metal alkoxydithiobenzoates

Reaction of 4-alkoxydithiobenzoates (n-odtb, where n refers to the number of carbon atoms in the alkoxy chain) with divalent salts of nickel, palladium and zinc leads to complexes of the formula [M(n-odtb)₂] where M = Ni, Pd and [Zn₂(n-odtb)₄] which are mesomorphic. The shortest-chain homologues of the Ni and Pd complexes show a nematic phase while at longer chain lengths, an S_c phase is observed. Most homologues of the zinc complexes show a nematic phase with an S_c phase appearing only for the longest homologues. The gold(III) complexes [AuX₂(n-odtb)] are also mesomorphic and show the S_A phase. Single-crystal X-ray structure determinations have been carried out for [Pd(8-odtb)₂], [Zn₂(4-odtb)₄] and [Zn₂(8-odtb)₄], showing the first to be planar and the last two dinuclear with pseudo five-co-ordinate zinc atoms.