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

• Published in: Applied magnetic resonance 2013-05, Vol.44 (5), p.571-582
• Main Authors: Husáriková, L., Repická, Z., Moncol, J., Valigura, D., Valko, M., Mazúr, M.
• Format: Article
• Language: English
• Subjects: Acids; Atoms and Molecules in Strong Fields; Basicity; Complex systems; Copper; Copper acetate; Copper sulfate; Electron paramagnetic resonance; Laser Matter Interaction; Ligands; Methanol; Organic Chemistry; Physical Chemistry; Physics; Physics and Astronomy; Solid State Physics; Spectra; Spectroscopy/Spectrometry
• ISSN: 0937-9347; 1613-7507
• DOI: 10.1007/s00723-012-0431-9

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 (CuSO 4 )), with varying 2,6-pyridinedimethanol (pydime) concentration, [Cu(ac) 2 (aq) or CuSO 4 (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  ≥ 2, unusual Cu(II) EPR spectra with "inverse" axial g values of ( g ⊥  >  g ∥  > 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 ∥  >  g ⊥  > 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.