Mesoionic 1,2,3-Triazolo[1,5-a]pyridine-3-ylidenes in Phosphorescent Platinum(II) Complexes

Mesoionic carbene ligands based on 1,2,3-triazole platforms can be used in cyclometalated platinum(II) complexes to achieve an efficient phosphorescence even at room temperature. In this report, 1,2,3-triazolo[1,5-a]pyridine-3-ylidenes are employed in such molecules along with beta-diketonates with varying steric demand. For full structural characterization, NMR spectroscopy and XRD experiments were employed. The photophysical properties were studied in solid poly(methyl methacrylate) (PMMA) matrices, as well as dichloromethane solutions. In PMMA, the synthesized complexes show quantum yields of 47-54 % with emission bands in the yellow region of the visible spectrum. Cyclic voltammetry measurements along with DFT calculations helped to assign the nature of the observed emissions.