Liquid-crystalline, polycatenar complexes of silver(I): dependence of the mesomorphism on the ligand and the anion

We have synthesised several series of poly(alkoxy)stilbazole ligands, and i nvestigated the thermal behaviour of their complexes with some silver salts . Most of the complexes, with the general formula [AgL2] [X], where X = dod ecyl sulfate (DOS) or trifluoromethanesulfonate (OTf), and L = poly(alkoxy) stilbazole, were found to be liquid-crystalline over a wide-temperature ran ge, the vast majority of them being low-melting. The mesomorphic properties were mainly dominated by the formation of hexagonal columnar (Col(h)) phas es and to a lesser extent, of bicontinuous Ia (3) over bar d cubic phases; monotropic nematic and smectic C phases were also seen for one structural t ype of compound only. The mesophases were assigned on the basis of their op tical textures under polarised optical microscope (POM) prior to being iden tified by X-ray diffraction (XRD). The temperatures and enthalpies of the t ransitions were determined by differential scanning calorimetry (DSC). The mesomorphism was found to be strongly dependent on the substitution pattern of the ligand, that is on the number, position and length of alkoxy chains , as well as on the type of the counter anion. We explain the mesomorphism in terms of ionic interactions and in terms of mean interfacial curvature b etween the hydrophobic, aliphatic chains and the rigid, aromatic, central c ore, by analogy to lyotropic systems.