Isocyano-triphenylene complexes of gold, copper, silver and platinum. Coordination features and mesomorphic behavior

Abstract

Stable organometallic complexes [AuX(CN-TriPh)] [X = Cl, C6F5, C6F4O-C10H21), C6F4O- (R)-2-octyl)], [(-4,4’-C6F4C6F4){Au(CN-TriPh)}2], [AuX(CN-TriPh)], [CuCl(CN-TriPh)], trans-[PtI2(CN-TriPh)2] and [Ag(CN-TriPh)2]BF4, bearing the previously unreported triphenylene-isocyanide ligand 1-isocyano-2,3,6,7,10,11-hexadodecyloxytriphenylene (CNTriPh), have been synthesized. The coordination features of the metal ion determine their thermal behavior. The free isocyanide ligand and all of the monomeric gold derivatives display enantiotropic mesomorphic behavior over a wide range of temperature (from 5 to 220 ºC), while the copper complex, with the same stoichiometry but not isostructural with the gold complexes, melts directly to an isotropic liquid. The bis-isocyanide platinum and silver complexes also melt directly to an isotropic liquid at low temperatures. In this case, the two trans coordinated isocyanide ligands, connected by a too short linker, cannot become coplanar, which prevents the formation of a mesogenic structure. On the contrary, in the dinuclear gold complex the two isocyanide trans ligands are, due to the long Au-C6F4-C6F4-Au bridge, sufficiently separated to become coplanar and this complex gives rise to a mesophase. The structures of the mesophases were determined by small-angle X-ray scattering. All materials prepared show a fluorescent emission centered on the triphenylene core