Gold, silver and copper luminescent molecular materials with mesomorphic properties

Abstract

Cyclic trinuclear complexes of the gold group are unique molecular materials that contain a planar or nearly planar nine-membered metallacycle. Increasing interest has been taken in them owing to their chemical and luminescent properties. Their emission spectra depends on the arrangement of the molecules in the solid state, which can involve intermolecular metallophilic interactions, and these can be easily influenced by external factors such as temperature, ions, solvents, and so forth. All these studies have opened new perspectives for the development of new stimuli responsive luminescent materials for sensors, organic electronics or biomedicine. We report herein the synthesis and characterization of novel gold, silver and copper cyclic trinuclear pyrazolate complexes able to self-assemble in columnar phases. In particular, gold and silver complexes display thermotropic columnar liquid crystal phases at high temperatures which have been characterized by POM, DSC and XRD. The luminescent properties have been studied by luminescence spectroscopy. Gold and copper compounds show phosphorescence in the visible-near IR region at room temperature. It has been observed that luminescent behavior is temperature sensitive with unique color changes (thermochromism), and chemically sensitive, leading to new stimuli-responsive materials.