Correlating the Structural and Photo­physical Features of Pincer Luminophores and Monodentate Ancillary Ligands in Pt II Phosphors (Eur. J. Inorg. Chem. 36/2015)

Abstract

Phosphorescent PtII complexes featuring pincer luminophores of 2,6-bis(1,2,4-triazolyl)pyridine (H2L1) and 2,6-bis(pyrazolyl)pyridine (H2L3) with a bulky adamantyl or tolyl substituent (H2L4) are systematically compared, and their structural features are correlated with their photophys. properties. The combination with 4-amylpyridine (Py), triphenylphosphine (P) or benzimidazol-2-ylidene (N-heterocyclic carbene, NHC) donors as monodentate ancillary ligands gave highly luminescent triplet emitters with variable aggregation properties. The mol. structures of four of these complexes, namely, Pt-L1-P, Pt-L1-NHC, Pt-L3-P, and Pt-L4-P were garnered from single-crystal x-ray diffraction anal. The coordination complexes displayed green phosphorescence in soln. and in the solid state. In doped poly(Me methacrylate) (PMMA) matrixes, most of the complexes exhibited high phosphorescence quantum yields, which reached 59% for Pt-L3-P. A comparative anal. between the spectroscopic data and the computed parameters derived from time-dependent d. functional theory (TD-DFT) calcns. suggests that the emission originates from metal-perturbed ligand-centered excited triplet states (3MP-LC). The radiationless deactivation rate consts. of the emissive states can be correlated with the aggregation properties derived from the substitution pattern at the tridentate luminophores and the ancillary ligands, whereas the radiative rate consts. are detd. by the electronic structures of the complexes. PtII complexes contg. pyrazolate donors showed an enhanced charge-transfer character in the excited state, whereas bulky adamantyl moieties and triphenylphosphine ancillary ligands suppress bimol. aggregation and quenching phenomena. [on SciFinder(R)]