Luminescence and photochemistry of transition metal complexes. I. Studies of temperature dependence of tervalent chromium complexes with oxygen-, nitrogen-, and carbon-coordinated ligands

Experimental investigations of the luminescence exhibited by a range of tervalent chromium complexes are reported. The effects of the coordinated ligand on the temperature dependence of phosphorescence are examined and rationalized in terms of the 4T2-2E energy interval. In the case of hexaureachromium complexes which emit both phosphorescence and fluorescence the varying emission intensities observed for compounds with a variety of anions are interpreted in terms of competition between the non-radiative thermal repopulation process 2E ~~→ 4T2 and the radiative processes 2E → 4A2, 4T2 → 4A2.