Synthesis and luminescence properties of [Pt{4-(o-MeC6H4)-pzbipy)CI]SbF6 [pzbipy=6-2"-pyrazinyl)-2,2′-bipyridine]

The synthesis and characterisation of the 4-(o-R-C6H4)pzbipy [R = H, CH3 or CF3; pzbipy = 6-(2 ''-pyraziryl)-2,2'-bipyridyl] ligands are described. Reaction of the 4-(o-MeC6H4)pzbipy ligand with [Pt(PhCN)(2)Cl-2] in the presence of AgSbF6 affords [Pt{4-(o-MeC6H4)pzbipy}Cl]SbF6 as a maroon-colourcd microcrystalline solid. The [Pt{4-(o-MeC6H4)pzbipy}Cl](+) cation exhibits low intensity photoluminescence in dichloromethane that maximises at 543 nm and which is assigned to a (MLCT)-M-3 excited state (tau = 20 ns). The emission spectrum of the cation was also recorded in a frozen DME {1:5:5 (v/v) DMF / MeOH / EtOH} glass; a highly structured band is observed with vibrational spacings of ca. 1400 cm(-1), indicating emission from an intraligand (3)pi-pi* state (tau = 11 mu s). Variable temperature solid emission spectra show maxima that occur at significantly lower energies than is observed in fluid solution and that shift to the red when the temperature is lowered; specifically, lambda(em)(max) is 674 nm at 280 K (tau = 80 ns) and 723 nm at 80 K (tau = 1.3 mu s). Emission behaviour of this type is typical of emission from a metal-metal-ligand charge transfer (MMLCT) excited state that has its origins in d(z2)(Pt)-d(z2)(Pt) orbital interactions in the crystal.