Diaquabis(3,6-dioxaheptanoato)copper(II): crystal structure and EPR characteristics

The structure of the title compound has been determined by X-ray diffraction at 190 K. The complex has an all trans configuration with an elongated tetragonally distorted octahedral CuO6 chromophore. The elongated axis corresponding to the trans-Cu-O(ether) bonds. The ligand molecules are bidentate via the carboxyl and the 3-ether O atoms; the 6-ether O atoms are not coordinated and are remote from the Cu centres. The bond lengths to the Cu centres are Cu-O(ether) 2.355 Angstrom, Cu-O(Carboxyl) 1.933 Angstrom and Cu-OH, 1.995 Angstrom. The EPR spectrum of both the powder and frozen solution forms is typical of a rhombic system with a d(x2-y2)(1) electronic configuration. There were no significant differences in spectra recorded over the temperature range 77 K to room temperature. These results are discussed in relation to earlier published results on closely related oxa-carboxyl complexes. (C) 2001 Elsevier Science B.V. All rights reserved.