Unusual EPR Spectra with Inverse Axial g values of Chlorosalicylate-Cu(II)-2,6-Pyridinedimethanol Complex in Frozen Water-Methanol Solution

Copper(II) complex systems containing 3,5-di, 4-, or 5-chlorosalicylic acids (X-ClsalH) and different copper(II) salts (copper acetate (Cu(ac)(2)) or copper sulphate (CuSO4)), with varying 2,6-pyridinedimethanol (pydime) concentration, [Cu(ac)(2)(aq) or CuSO4(aq) + 2 (X-ClsalH(solv)) + x pydime(solv)], where X = 3,5-di, 4-, or 5- and x = 0, 1, 2, 4, or 8, were prepared. The effects of two copper(II) salts (containing anions of different basicity) and N-donor ligand (pydime) with varying ligand-to-metal ratio (x) on the formation of resulting complexes were studied by electron paramagnetic resonance (EPR) spectroscopy in frozen water/methanol (1:3 v/v) solutions. For x a parts per thousand yen 2, unusual Cu(II) EPR spectra with inverse axial g values of (g (aSyen) > g (ayen) > 2.0023) were observed, which can indicate the compressed octahedral geometry of the central copper atom with the unpaired electron/hole localized on the orbital. However, for x = 1, composite Cu(II) EPR spectra with both usual and inverse axial g values were detected. Finally, for x = 0 (ligand not present) Cu(II) EPR spectra only with the 'usual' axial g values of g (ayen) > g (aSyen) > 2.0023 were collected, which can indicate the elongated octahedral geometry of the central copper atom with the unpaired electron/hole localized on orbital. The above described observations are independent of the usage of different copper(II) salts and X-chlorosalicylic acids.