Metal ion-purine base interactions. Zinc(II) and cadmium(II) complexes of 8-methylthiotheophylline. X-ray crystal structure and solution structure of bis(8-methylthiotheophyllinato)diaquazinc(II)

Abstract

Abstract The complexes [M(H2O)2)(L)2], (where M = Zn2+ or Cd2+ and L is the 8-methylthiotheophyllinato anion) have been prepared and characterized by means of IR and 1H and 13C NMR spectral studies. The crystal structure of [Zn(H2O)2(L)2] has been determined by single-crystal x-ray methods. The complex crystallizes in the monoclinic system, space group C2/c, with a = 14.6615(6), b = 8.664(3), c = 17.253(1) A, β = 94.22(1)°, Z = 4, and R = 0.043. The zinc(II) atom is coordinated at N7 of two monodentate L anions and two water molecules, giving rise to a ZnN2O2 environment with appropriate local C2v symmetry. The molecules of the complex are held together by intermolecular hydrogen bonds and base-base stacking interactions where the interbase stacking distance is 3.40 A.