X-Ray crystal structures and electron spin resonance spectroscopic characterization of mixed-ligand chromium( III ) complexes with L -aspartate or pyridine-2,6-dicarboxylate and 1,10-phenanthroline or 2,2′:6′,2″-terpyridyl

The crystal and molecular structure of two newly prepared chromium(III) complexes [Cr(L-asp)(phen)(H2O)]NO3·2H2O 1[L-asp =L-aspartate(2–), phen = 1,10-phenanthroline] and [Cr(terpy)(pydca)][Cr(pydca)2]·4H2O 3(pydca = pyridine-2,6-dicarboxylate, terpy = 2,2′:6′,2′′-terpyridyl) were determined by means of X-ray diffraction. Crystals of 1 are triclinic, space group P, with a= 11.793(5), b= 10.507(5), c= 9.258(5)Å, α= 111.43(3), β= 86.44(3) and γ= 111.71(3)°. Crystals of 3 are triclinic, space group P, with a= 19.100(5), b= 12.874(5), c= 7.575(5)Å, α= 86.16(3), β= 95.10(3) and γ= 96.62(3)°. The co-ordination around the Cr atom in both 1 and 3 is distorted octahedral, the sixth position of 1 being occupied by a water molecule. Crystals of 3 are built up of two different ionic units. ESR spectra were run on magnetically dilute powders and frozen solutions, and the values of the spin-Hamiltonian parameters obtained by computer simulation. The similarity between these parameters for the chromium(III) species in powders and glasses suggests that the solution species possess the same kind of distortion found for the solid complexes.