Local structure analysis of some Cu(II) theophylline complexes

The CuT2L2. 2H(2)O complexes [T = Theophylline (1,3-dimethylxanthine); L = NH3, n-propylamine (npa), 2-aminoethanol (ae)] were prepared and investigat ed by ESR spectroscopy. Powder ESR spectrum of CuT2(NH3)(2). 2H(2)O is axia l (g(parallel to) = 2.255, g(perpendicular to) = 2.059). ESR spectrum of Cu T2(npa)(2). 2H(2)O with (g(parallel to) = 2.299, g(perpendicular to) = 2.08 1) is a superposition of one axial (g(parallel to) = 2.299, g(perpendicular to) = 2.073) and one isotropic component (g(0) approximate to 2.089), in t he same amount. The axial spectra of the former complexes are due to a stat ic Jahn-Teller effect (E-JT approximate to 2880 cm(-1)). ESR spectrum of Cu T2(ae)(2). 2H(2)O is orthorhombic (g(1)(c) = 2.199, g(2)(c) = 2.095, g(c)(3 ) = 2.037). The local symmetries around the Cu(II) ions remain unchanged by DMF solvating, by adsorbing these solutions on NaY zeolite or by lowering the temperature. (C) 1999 Elsevier Science B.V. All rights reserved.