The mesomorphic properties of three types of gold(I) acetylide complex
es, [(ArNC)Au-C drop CAr, (ArNC)Au-C drop CR and (RNC)Au-C drop CAr, w
here R and Ar represent alkyl and aryl groups, respectively] were syst
ematically examined and it was found that of the three, (RNC)Au-C drop
CAr (complex C) is the choice for liquid-crystalline materials, and t
hat introduction of an appropriate lateral group on the isonitrile and
/or acetylene ligands led to the formation of nematic and smectic A ph
ases without any decomposition of the complexes. The linear geometry a
round the central gold atom was confirmed by X-ray crystallographic an
alysis of complex C-5b. The relation between the thermal behaviour and
the molecular structure of the complexes is discussed.