Dinuclear Gold(I) Isocyanide Complexes with Luminescent Properties, and Displaying Thermotropic Liquid Crystalline Behavior

Dinuclear gold(I) complexes [μ-(4,4‘-CN-R-NC){Au(C6F4OC4H9)}2] [R = 1,4-phenylene, n = 8; R = 4,4‘-biphenylene,
2,2‘-dichloro-4,4‘-biphenylene, 2,2‘-dimethyl-4,4‘-biphenylene, n = 4,6,8,10] have been prepared and their liquid
crystal behavior and optical properties studied. Although the free ligands are not mesomorphic, all the gold(I)
derivatives described, except the phenylisonitrilegold(I) derivative [μ-(1,4-CN-C6H4-NC){Au(C6F4OC8H17)}2], display
liquid crystal behavior, giving rise to a nematic mesophase. The transition temperatures decrease in the order
4-4‘-biphenylene > 2,2‘-dichloro-4-4‘-biphenylene > 2,2‘dimethyl-4-4‘-biphenylene. All compounds show photoluminescence in the solid state and in solution. The single-crystal X-ray diffraction structures of [μ-(4,4‘-CN-R-NC){Au(C6F4OCnH2n+1)}2] (R = 4-4‘-biphenylene and 2,2‘-dichloro-4-4‘-biphenylene) have been determined confirming
the rodlike structure of the molecule, with a linear coordination around the gold atoms. There are Au···Au interactions
in the 2,2‘-dichlorobiphenyl derivative but not in the 4-4‘-biphenyl compound.