Luminescent Cyclometalated Chromium(III) Complexes

Tris(cyclometalated) chromium(III) complexes fac-Cr(C∧X)3 with dimethylamine (X = NMe2, fac-1) and diphenylphosphane (X = PPh2, fac-2) donors were fully characterized by single crystal X-ray structure analyses, cyclic voltammetry, and absorption/emission spectroscopy. Both complexes are luminescent in the near-infrared spectral region in the solid state or in frozen solution. The phosphane complex fac-2 is hemilabile and forms a weakly emissive, five-coordinate complex with a dangling PPh2 donor in fluid solution. Spectroscopic assignments are aided by quantum chemical calculations at the DFT and CASSCF/NEVPT2 levels of theory. fac-1 and fac-2 complement the cyclometalated pyridine complex fac-Cr(ppy)3 (ppy– = deprotonated 2-phenylpyridine) and allow establishment of a nephelauxetic series of aryl, pyridine, phosphane, and amine donors.