Magnetic-Resonance Studies on Copper(II) Complex Ions in Solution. II. Oxygen−17 NMR and Copper(II) EPR in Aqueous Solutions of Cu(en)(H2O)42+ and Cu(en)2(H2O)22+

Abstract

The temperature dependences of the 17 0 NMR and CU(Il) EPR spectra of solutions of the ethylenediamine complex ions Cu(en) (H20) ,2+ and Cu(en),(H20)22+ are analyzed in terms of an octahedrally coordinated structure with tetragonal distortion. It is found that the 17 0 NMR spectrum is broadened and shifted by Cu(en) (H20).2+ through scalar hyperfine interaction with the copper (II) electron spin, while Cu(en)2(H20j.2+ has no effect. The Cu(II) EPR spectra of both species have linewidth contributions from spin-rotational relaxation, from tumbling of an ionic complex having an anisotropic g factor and an anisotropic hyperfine coupling constant, and from 63CU isotropic hyperfine and 14N isotropic extrahyperfine splitting. The results are discussed in terms of the antibonding molecular-orbital model for the Blg ground state of Cu(II) and compared with the previous study on Cu(H20)a2+.

Spectroscopic studies on the anticancer antibiotic Altromycin H and the interaction with copper(II) ions

“…The values of the EPR parameters (g i = 2.427, A i = 118 G and g^= 2.085) at pH = 3.82 (Fig. 6) suggest that the only species present in the solution are the Cu(II) hexaqua ions [24][25][26]. This fact confirms the observation from the CD spectra, that under these pH conditions no complexation takes place.…”

“…The hydroxy-anthraquinone moiety causes a strong field around the copper ion and the g i and A i values, which are usually taken as an indication of the field strength in Cu(II) compounds, are more reminiscent of nitrogen-containing Cu(II) chromophores than tetra-oxo Cu(II) ligand [27,28]. Indeed, the relation g i = 2.306 > g^= 2.07 > g e (=2.00023) is typical for axially symmetric complexes in which the coordination geometry is at least approximately square planar and the unpaired electron is in the d x 2 Ày 2 orbital of copper ion [25,26,29,30]. Furthermore, as nitrogen hyperfine structure in the g^region is not observed, the participation of the N atom of the Altromycin H disaccharide moiety in the coordination sphere of the Cu(II) ion is excluded [26].…”

“…Indeed, the relation g i = 2.306 > g^= 2.07 > g e (=2.00023) is typical for axially symmetric complexes in which the coordination geometry is at least approximately square planar and the unpaired electron is in the d x 2 Ày 2 orbital of copper ion [25,26,29,30]. Furthermore, as nitrogen hyperfine structure in the g^region is not observed, the participation of the N atom of the Altromycin H disaccharide moiety in the coordination sphere of the Cu(II) ion is excluded [26].…”

“…and CD spectra at the same conditions do not supply any indication for the oxidation of the ligand (Altromycin H). At last it is important to say that neither precipitation of Cu(OH) 2 nor formation of [Cu(OH) 4 ] 2À is observed (the formation of [Cu(OH) 4 ] 2À leads to a typical EPR spectra [26]). …”

Synthesis and structural studies of some first row transition metal complexes of acetone nicotinoyl hydrazone

“…The spectral data indicate gll > gl > free-spin (2.002 3), which shows that the unpaired electron is in the dx2_y2 orbital of the Cu II atom(2S). The gn and gl values depart considerably from the free-spin value and are close to those reported for distorted octahedral structure of Cu II complexes ( 26,27). The e.s.r, data thus support the conclusion drawn earlier from the electronic spectrum regarding the geometry of the above complex.…”