CU(NH3)(1-3) COMPLEXES - A MATRIX-ISOLATION ESR STUDY

The interaction between Cu atoms and ammonia molecules cocondensed in argon matrices was examined by ESR. The observed spectra revealed the formation of CU(NH3)(1-3) complexes. The g tensors and the hyperfine c oupling tensors for the Cu and N nuclei of the complexes were determin ed. All three complexes showed large, essentially isotropic Cu hyperfi ne coupling interaction corresponding to 50-60% of that observed for i solated Cu atoms. No hyperfine structures due to protons were discerne d. It is thus concluded that these complexes are formed merely by the dative interaction of the NH3 lone pair electrons with vacant Cu 4s/4p valence orbitals. The unpaired electron resides in a Cu 4s/4p-hybridi zed orbital projected away from the ligand(s). The ESR spectrum of the monoligand complex Cu(NH3) showed reversible photoconversion to the s econd spectrum in accord with the photoisomerization process Cu(NH3) < -> HCuNH2 reported in an earlier IR study. The second spectrum, though partially obscured by other signals, revealed a pattern consistent wi th the ionic character H-Cu2+(NH2)(-) where the unpaired electron resi des in the Cu 3d(z)(2) orbital.