Abstract
The ESR spectra of the polycrystalline [Cu(phen)
2
X]ClO
4
and [Cu(bipy)
2
I]ClO
4
complexes (phen 1,10-phenanthroline, bipy 2,2'-bipyridyl, X = Cl, Br, I) were studied. The values of the optimized parameters of the spin Hamiltonian of the experimental ESR spectra indicate that the CuN
4
X chromophor has the shape of a compressed trigonal bipyramid with the
D
3h
symmetry, and its structure involves the
z
2
> ground electronic state of the unpaired electron of the Cu(II) ion.