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.