ESR spectra of copper(II) complexes in the solids

The ESR spectra of Cu(sal)2 • 4H 20, Cu(sal)2(2-pycar)2 and Cu(sal)2(3-pycar)2 (sal = salicylate ion; pycar = pyridinemethanol) at 77 К were stud­ ied. The spin Hamiltonian parameters indicate that the unpaired electron is in the antibonding y/b]g molecular orbital. The ESR spectra of pentacoordinated Cu(II) complexes of the [Cu(phen)2X]C104 (phen = 1,10-phenanthroline; X = CI, Br) exhibit axial symmetry. The compressed trigonal-bipyramidal (TBP) configuration with D3// symmetry points (|z 2 > ground electronic state) is consistent with the spin Hamiltonian parameters of the ESR spectra. The ESR spectra of the pentacoordinated complex of [Co(l,3-diaminopropane)3] [CuCl5]-3H20 have been studied in the temperature range 100—290 K. At higher temperature (T> 160K) the ESR spectra change their symmetry into the orthorhombic one, the square pyramidal (SP) structure of [CuCl5] ~ polyhedrons is violated and a dynamical tran­ sition between the SP and TBP structures takes place.