Luminescence properties of some monomeric and dimeric cycloplatinated(ii) complexes containing biphosphine ligands

Abstract

The starting complexes [PtCl(C^N)(dmso)], in which C^N is either ppy = 2-phenylpyridinate, 1a, or bhq = 7,8-benzo[h]quinolinate, 2a, were prepared by a known method using the reaction of [PtCl₂(dmso)₂] with ppyH or bhqH, respectively, in toluene under reflux conditions. The reaction of [PtCl(C^N)(dmso)], 1a or 2a, with 1 equiv. of a number of biphosphine ligands, P^P, gave the cationic monomeric complexes [Pt(ppy)(P^P)]Cl, for which P^P is either 1,2-bis(diphenylphosphino)ethane (dppe), 3a, 1,3-bis(diphenylphosphino)propane (dppp), 3c, or bis(diphenylphosphino)methane (dppm), 3d; the bhq analogous complex [Pt(bhq)(dppe)]Cl, 4a, was prepared similarly. However, the complex [Pt(ppy)(dfppe)]Cl, 3b, in which dfppe is 1,2-bis(dipentafluorophenylphosphino)ethane, was prepared by the reaction of 1a with excess amount of dfppe. When each of the starting complexes [PtCl(C^N)(dmso)], 1a or 2a, were reacted with 0.5 equiv. of any of the P^P ligands, the dimeric complexes [Pt₂Cl₂(ppy)₂(μ-P^P)], 5a–5d, or [Pt₂Cl₂(bhq)₂(μ-P^P)], 6a–6b, were formed. The complexes were fully characterized using multinuclear (¹H and ³¹P) NMR spectroscopy and elemental analysis. The structures of typical complexes 3a, 3c, 5b, and 5d were also confirmed by X-ray crystallography. The effect of ligands on the luminescent properties of the complexes was investigated and DFT calculations were performed to confirm the assignments.