A Mesoionic Carbene as Neutral Ligand for Phosphorescent Cationic Ir(III) Complexes

Two phosphorescent Ir(III) complexes bearing a mesoionic carbene ligand based on 1,2,3-triazolylidene are obtained for the first time. A silver-iridium transmetalation of the in situ-generated mesoionic carbene affords the cationic dichloro complex [Ir(trizpy)(2)Cl-2](+) (3, trizpy = 1-benzyl-3-methyl-4-(pyridin-2-yl)-1H-1,2,3-triazolylidene) that reacts with a bis-tetrazolate (b-trz) dianionic ligand to give [Ir(trizpy)(2)(b-trz)(+) (5). The new compounds are fully characterized by NMR spectroscopy and mass spectrometry, and the X-ray structure of 3 is determined. The electrochemical behavior is somewhat different compared to most standard cationic iridium complexes. The first oxidation process is shifted to substantially higher potential in both 3 and 5, due to peculiar and different two cases, which stabilize the highest occupied molecular orbital; reduction processes are center ligands. Both compounds exhibit a mostly ligand-centered luminescence band in the blue-green stronger in the case of 5 versus 3, both in CH3CN solution and in poly(methyl methacrylate) Optimized geometries, orbital energies, spin densities, and electronic transitions are determined calculations, which support a full rationalization of the electrochemical and photophysical behavior the development of Ir-based emitters with neutral mesoionic carbene ligands and anionic ancillary area of cationic Ir(III) complexes.