The intriguing effect of thiolates as co-ligands in platinum(II) complexes bearing a cyclometalated 1,3-di(2-pyridyl)benzene.

[Display omitted] • A novel complex, [Pt(5-mesityl-1,3-di(2-pyridyl)benzene)(thioacetate)], has been prepared and fully characterised. • The luminescence quantum yield of [Pt(5-mesityl-1,3-di(2-pyridyl)benzene)(thioacetate)] is lower than that of related complexes with chloride or 1-phenyl-1 H -tetrazole-5-thiolate but higher than that with arylthionates. • In Pt(II) complexes bearing a cyclometalated 1,3-di(2-pyridyl)benzene, the effect of thiolates co-ligands is really intriguing and merits further investigations. Substitution of the chlorido ligand of the fascinating cyclometalated complex [Pt(5-mesityl-1,3-di(2-pyridyl)benzene)Cl] by thioacetate leads to the related thiolato complex [Pt(5-mesityl-1,3-di(2-pyridyl)benzene)(thioacetate)], which has been fully characterised. Its photophysical properties were determined in degassed dichloromethane solution, as blend in Poly(MethylMethAcrylate) (PMMA) thin films, and as powders, at room temperature. Both in solution and in thin films, an increase of the concentration of the complex leads to a red shift of the phosphorescence spectra and to a decrease of lifetime decays and quantum yield. It appears that tuning of emission spectra depends on the competition between monomeric and aggregate emissive states. No clear evidence of excimer formation has been detected. In powders, an aggregate emission spectrum is red-shifted at 602 nm, reaching a very low phosphorescence quantum yield of 1 %. [ABSTRACT FROM AUTHOR]