Luminescence Properties of Two New Pt(II)-2-Phenylpyridine Complexes; The Influence of Metal-Carbon Bonds

Preparations and characterizations of two novel Pt(II) organometallic complexes, each containing the ortho-metalating ligand 2-phenylpyridine (ppy^-) are reported. One of the complexes, [Pt(ppy) (Cl)₂]^1-, is anionic. A second complex, [Pt(ppy) (H-ppy)Cl], is neutral and contains one ortho-metalated 2-phenylpyridine and one N-coordinated monodentate 2-phenylpyridine ligand and (H-ppy). These two complexes were characterized by both ¹H and ¹³C NMR. Photophysical investigations reveal that the lowest energy excited states of both complexes are metal-to-ligand charge-transfer states. The anionic Pt(II) complex is luminescent at room temperature as a solid, although no luminescence is detected at room temperature in fluid solution. In addition, a low energy transition is observed in the excitation spectra of this solid and the transition is indicative of a bandgap type absorption. The neutral Pt(II) complex luminesces in fluid solution at room temperature from a long-lived excited state. The magnitude of the luminescence lifetime for this complex is solvent dependent with observed room temperature lifetime ranging from 677 ns in ethanol to 5.9 μs in dichloromethane.