Mesomorphic Mixtures of Metal Isocyanide Complexes, Including Smectic C Mesophases at Room Temperature and Liquid Crystalline "Molecular Alloys"

The thermotropic behavior and phase diagrams of binary mixtures of copper and gold complexes of the type [MX(CNR)] (X = anionic ligand, R = palkoxyaryl group) have been studied. The systems examined are mixtures of the pairs of complexes such that new compounds cannot be formed in the mixture by ligand rearrangement. These include pairs differing in just one structural parameter, where rearrangements would not give rise to new complexes: (i) complexes [AuCl(C(identical)NC6H4C6H4OCnH2n+1)] changing the alkoxy length (n = 4 and n =12); (ii) complexes [AuCl(C(identical)N(C6H4) mOC12H25)] with different numbers of aromatic rings (m = 1 and m = 2); and (iii) complexes differing in the metal, namely the derivative [CuCl(C (identical)NC6H4OC12H25)] (which is not liquid crystal) and the mesomorphic [AuCl(CNC6H4C6H4OCnH2n+1)]; also (iv) complexes [Au(C6F4OC10H21) (CNC6H4C6H4OC6H13)] and [Au(C6F4OC6H13)(C(identical)NC6H4C6H4OC10H21)], in which a study proves that rearrangement does not occur. All the mixtures studied display liquid crystal behavior with improved properties with respect to the pure components. Smectic C mesophases from room temperature to ca. 200 C have been obtained. Upon cooling and crystallization, segregation occurs and separate nets of the starting complexes are observed, except for mixture (iv), which gives a solid solution.