Single-crystal polarized electronic and electron spin resonance spectra of the trigonal-bipyramidal complex aquobis(1,10-phenanthroline)copper(II) nitrate

The single-crystal polarized electronic and electron spin resonance spectra of the trigonal-bipyramidal complex aquobis( 1,lO-phenanthroline)copper(II) nitrate have been recorded. The crystals are monoclinic, and the copper atom possesses Cz site symmetry. By recording four couples of electronic spectra, on different crystal faces, we were able to determine the directions of maximum polarization in the ac plane, yielding both the principal directions and values of the c tensor, The order of the electronic transitions was found to conform to ligand field predictions, in contrast with previous findings in similar chromophores. Angular overlap calculations reproduced nicely the energies of the electronic transitions and the directions and values of the magnetic tensor, but the values of the parameters were found to be at variance from those expected on the basis of chemical considerations.