Electron paramagnetic resonance studies of transitionmetal oxalates and their photochemistry in single crystals. I. K3[Cr(C2O4)3] · 3H2O in K3[Al(C2O4)3] · 3H2O

The spin-Hamiltonian parameters and axis directions of two inequivalent Cr(C2O4)33− complexes in single K3Al(C2O4)3 · 3H2O crystals have been determined by EPR, and a search for EPR evidence of photochemical reactions in the crystals has been made. The complexes and their environments are asymmetric. The Cr(C2O4)33− orientations in the crystal have been obtained from the axis directions. The Cr(C2O4)33− substitutions, structure, and orientations are compared with the available crystallographic information. The existence of two inequivalent Cr(C2O4)33− complexes is related to the degree of hydration of the crystal. No Cr(C2O4)33− photochemical reactions in the crystals are observed, and the maximum quantum yields consistent with these observations are very small.