SPECTROSCOPIC AND ELECTROCHEMICAL PROPERTIES OF SOME MIXED-LIGAND CYCLOMETALATED PLATINUM(II) COMPLEXES DERIVED FROM 2-PHENYLPYRIDINE

The spectroscopic and electrochemical properties of some new cyclometalated Pt(II) complexes, [Pt(ppy)(N-N)]X, are reported. The 2-phenylpyridinate anion, ppy, acts as the cyclometalating ligand while (N-N) represents alpha,alpha'-diimines such as 2,2-bipyridine (bpy) and 1,10-phenanthroline (phen) or a saturated chelating ligand, 1,2-diaminoethane (en). The anion X(-) is Cl-, ClO4- or CH3COO-. The complexes show luminescence in fluid solutions. The photophysical and electrochemical behaviour of the complexes is found to be related to the presence of vacant pi(*) orbitals on the nitrogen chelating ligands. On the basis of the electrochemical and spectroscopic data the low-energy absorption and emission spectra of [Pt(ppy)en](+) are essentially due to the (3)MLCT (d(pt)-pi*(ppy)) transition while for the diimine complexes these spectra correspond to the (3)MLCT (d(pt)-pi*(diimine)) transition. Contrary to [Pt(ppy)en]ClO4 the emission spectra of [Pt(ppy)en]Cl and especially of [Pt(ppy)(alpha,alpha'-diimine)]X show solid state effects.