Preparation, crystal and molecular structure of aquadichlorocaffeinecopper(II)

Abstract Preparation, crystal and molecular structure of aquadichlorocaffeinecopper(II), determined by three-dimensional X-ray data, are reported. The darkish green crystals are orthorhombic, space group P 2 1 2 1 2 1 with cell dimensions: a = 16.370(9), b = 13.432(7), c = 5.814(6) A and Z = 4. The structure was solved by the heavy-atom method from 1221 reflections collected by counter, and refined by least-squares method to R = 0.028. The geometry around copper is tetragonal pyramidal distorted towards trigonal bipyramidal, the C 2V symmetry being maintained. The caffeine imidazole nitrogen atom (Cuz.sbnd;N 1.98 A ), oxygen atom from water (Cuz.sbnd;O 1.96 A ) and trans chlorine atoms (CuCl(1) 2.32, Cuz.sbnd;Cl(2) 2.25 A ) lie at the corners of an approximate square as closest ligands to the copper. Through a screw-axis parallel to c , Cl(1) atom is placed at the apex of the pyramidal configuration (Cuz.sbnd;Cl(1)′ 2.79 A ); since only one chlorine atom forms a bridge between successive symmetry related copper atoms a polynuclear chain with alternating short and long CuCl distances is formed. The single chain is further strengthened by Cl- - -HOH hydrogen bonds; moreover, symmetry-related chains are held together by O- - -HOH hydrogen bonds.