Photophysics, Photochemistry and Electrochemistry of Mixed-Ligand Platinum(II) Complexes with 2-Phenylpyridine and 2-(2′-Thienyl) pyridine as Cyclometalating Ligands

The spectroscopic and electrochemical properties of two series of some [Pt(ĈN)XY]z complexes are studied where (ĈN) is cyclometalated 2-phenyl-pyridinate, Ppy−, and 2-(2-thienyl)pyridinate, Tpy−; X and Y represent various monodentate and bidentate ligands: Cl−, CN−, CO, (Mor)3P=trismorpholinophosphine, Bpy=2,2-bipyridine, Phen=1,10-phenanthroline, En=ethylenediamine, Edp=1,2-bis(diphenylphosphino)ethane, Etdp=1,2-bis(diphenylphosphino)ethene, Edt=1,2-bis(phenylthio)ethane, Mnt2−=1,2dicyano-1,2-ethylenedithiolate. The lowest excited state in the [Pt(Ppy)XY]+ complexes with an unsaturated ligand, (NN) being Bipy and Phen, is assigned to a 3MLCT {d(Pt)−π∗(NN)} transition, while for the Tpy− complexes it corresponds to a 3{d(Pt)−π*(ĈN)} transition. The lowest excited state of the [Pt(ĈN)Mnt]− complexes is assigned to a 3{p(S)/d(Pt)−π∗Mnt)} transition. In the related complexes, in which a saturated chelating ligand replaces the unsaturated one, (NN)En, (SS)Edt, (PP) Edp, and in Pt(ĈN)(P(Mor)3)Cl, Pt(ĈN)COCl, [Pt(ĈN)(CN)2]−, [Pt(ĈN)Cl2]− the lowest excited state is assigned to a 3{d(Pt)−π∗(ĈN)} transition. When replacing the cyclometalating ligand Ppy− with Tpy− the 3MLCT {d(Pt)−π∗(ĈN)} absorption and emission bands are red shifted by ca. 3000 cm−1. The redox potentials, however, are very similar and depend only on the additional ligands X and Y showing the linear relationship relative to Lever's electrochemical parameters. The values of the calculated radiative rate constants are sensitive both to the identity of the X,Y ligands (Edp

Keywords:

• Electrochemistry
• 2-Phenylpyridine
• Pyridine
• Platinum
• Polymer chemistry
• Chemistry
• Organic chemistry
• Ligand
• mixed ligand

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