Characterization of compounds derived from copper-oxamate and imidazolium by X-ray absorption and vibrational spectroscopies

Abstract In this work, compounds derived from copper-oxamate anions ( ortho , meta , and para )-phenylenebis (oxamate) and imidazolium cations (1-butyl-3-methylimidazolium) were synthesized. The compounds were characterized by Raman and FTIR spectroscopies and the band assignments were supported by DFT calculations. Strong IR bands from 1610 to 1700 cm −1 dominated the spectra of the complex and can be assigned to νC O vibrations of the [Cu(opba)] 2− anions by the comparison with the DFT data. In opposition to the FTIR spectra, the main vibrational bands in the Raman spectra are observed in the 1350–1600 cm −1 range. All bands in this region are associated to the modified benzene vibrations of the copper-phenylenebis(oxamate) anions. X-ray absorption near edge (XANES) at different energies (NK and Cu L 2,3 edges) was also used to probe the interionic interactions. XANES data show that anion–cation interaction in the Cu-oxamate–imidazolium changes the electronic structure around the Cu N sites in the oxamate anion.