Supramolecular organization in copper(I) isocyanide complexes:: copper(I) liquid crystals from a simple molecular structure

The synthesis, characterization and mesomorphic properties of five series of copper(i) isocyanide complexes [CuCl(CNR)] [R = C6H4C6H4OCnH2n + 1 (L-A), C6H4OOCC6H4OCnH2n + 1 (L-B), C6H4COOC6H4OCnH2n + 1 (L-C), C6H3{3,4-(OCnH2n + 1)(2)} (L-D), C6H2{3,4,5-(OCnH2n + 1)(3)} (L-E); n = 4, 6, 8, 10, 12] are described. Although some of the free isocyanides used are not liquid crystals, all the copper isocyanide complexes prepared, except four, are mesogens. The copper derivatives Cu-L-A show smectic A (S-A) and smectic C (S-C) mesophases, the complexes Cu-L-B and Cu-L-C display only S-A phases and the di- and tri-alkoxyphenylisocyanide copper complexes, Cu-L-D and Cu-L-E, display hexagonal columnar mesophases, some of them at room temperature. These copper isocyanide complexes are compared with the similar gold(i) isocyanide complexes [AuClCNR] and the influence of the metallic atom on the mesogenic behaviour for representative complexes is discussed.