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 (LA), C6H4OOCC6H4OCnH2n + 1 (LB), C6H4COOC6H4OCnH2n + 1 (LC), C6H3{3,4-(OCnH2n + 1)2} (LD), C6H2{3,4,5-(OCnH2n + 1)3} (LE); 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–LA show smectic A (SA) and smectic C (SC) mesophases, the complexes Cu–LB and Cu–LC display only SA phases and the di- and tri-alkoxyphenylisocyanide copper complexes, Cu–LD and Cu–LE, 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.