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

The spectroscopic and electrochemical properties of some new cyclometa lated Pt(II) complexes, [Pt(ppy)(N-N)]X, are reported. The 2-phenylpyr idinate anion, ppy, acts as the cyclometalating ligand while (N-N) rep resents alpha,alpha'-diimines such as 2,2-bipyridine (bpy) and 1,10-ph enanthroline (phen) or a saturated chelating ligand, 1,2-diaminoethane (en). The anion X(-) is Cl-, ClO4- or CH3COO-. The complexes show lum inescence in fluid solutions. The photophysical and electrochemical be haviour of the complexes is found to be related to the presence of vac ant pi() orbitals on the nitrogen chelating ligands. On the basis of the electrochemical and spectroscopic data the low-energy absorption a nd emission spectra of [Pt(ppy)en](+) are essentially due to the (3)ML CT (d(pt)-pi(ppy)) transition while for the diimine complexes these s pectra correspond to the (3)MLCT (d(pt)-pi(diimine)) transition. Cont rary to [Pt(ppy)en]ClO4 the emission spectra of [Pt(ppy)en]Cl and espe cially of [Pt(ppy)(alpha,alpha'-diimine)]X show solid state effects.