EXAFS study of tetramethylethylenediamine copper(II) complexes with Cl and Br as secondary ligands

Extended X-ray absorption fine structure (EXAFS) have been recorded at the K-edge of copper in binuclear copper(II) complex [Cu(tmen)Cl2] (1) and its analogous complex [Cu(tmen)Br2] (2) (where tmen = tetramethylethylenediamine), using the dispersive EXAFS beamline at 2 GeV Indus-2 synchrotron source at RRCAT, Indore, India. Theoretical model has been generated for 1 using its available crystallographic data [1] and then fitted to the experimental EXAFS data of 1 to obtain its structural parameters, which include bond-lengths, coordination numbers and thermal disorders. The results obtained have been found to be comparable with the crystallographic results. As complex 2 is analogous to complex 1, the same theoretical model, which was generated for 1, has been fitted to the experimental EXAFS data of 2. The structural parameters, thus determined for 2 have been reported. The coordination geometry around the copper center in both the complexes has been depicted showing the bond-lengths obtained in the present study. It has been demonstrated that if crystal structure is available for a complex from X-ray crystallographic studies, the structural parameters can be determined for an analogous complex from EXAFS studies. Further, the values of the chemical shifts suggest that copper is in +2 oxidation state in these complexes.