Azobenzenes and heteroaromatic nitrogen cyclopalladated complexes for advanced applications

The five-membered "(C,N)Pd" metallacycle is a structural feature common to a number of stable photoactive molecular materials. This review is centred on the connection among molecular geometries, types of ligand and photophysical, optical, thermal and electrooptical properties of several series of dinuclear and mononuclear cyclopalladated species, based on HC,N ligands (HC,N = azobenzenes or nitrogen containing heteroaromatic ligands). In the discussion, some representative examples of complexes featuring an useful set of physical properties, were selected and divided into different classes, depending on the nature of the ancillary ligands bonded to the "(C,N)Pd" fragment.