Syntheses and mesomorphic properties of gold(I)-carbene complexes

Article abstract of DOI:10.1021/om9606202

The liquid-crystalline gold(I)-carbene complexes ClAu=C(YC_mH_2m+1)(NHC₆H₄CO ₂C₆H₄-OC_nH_2n+1), Y = O and NH, have been prepared by reactions of gold(I)-isonitrile complexes [ClAU{CNC₆H₄CO₂C₆H ₄OC_nH_2n+1}] with alcohols and amines, respectively. The gold(I)-(alkoxy)(amino)carbene complexes show stable enantiotropic smectic A phases over the range of around 15 °C. The partial double-bond character of the C-N bond in the carbene complex gives rise to two geometrical isomers (E:Z = ca. 3:1). Their molecular structures were spectroscopically characterized, and the E-isomer was confirmed by an X-ray structural analysis. The phase behaviors of E- and Z-isomers which were isolated by repeated recrystallization from CHCl₃/Et₂O or CH₂Cl₂/C₆H₁₄ were examined. In the gold(I)-diaminocarbene complexes, a novel dinuclear gold-carbene complex, [ClAu{C(NHC₆H₄-CO₂C₆H ₄OC_nH_2n+1)}](NCH₃C_mH _2mNCH₃)[ClAu{C(NHC₆H₄CO ₂C₆H₄OC_nH_2n+1)}], was synthesized by the reaction with a secondary diamine. This dinuclear complex generated a smectic mesophase although it decomposed at temperatures below its clearing temperature.