Zinc(II) and cadmium(II) complexes based on 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine (L): Synthesis, structure, luminescence. Double lone pair-π interactions in the structure of ZnL2Cl2

A series of zinc(II) and cadmium(II) complexes with 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl) pyrimidine (L), ZnLCl2, CdLCl2, ZnL2Cl2, CdL2Cl2, CdL2Cl2 center dot 0.5Me(2)CO center dot 1.5H(2)O and CdL2Cl2 center dot 0.5CHCl(3)center dot 0.5H(2)O, have been synthesized. The compounds ZnLCl2 and CdLCl2 were obtained in a M:L = 1:1 molar ratio in EtOH solutions, while ZnL2Cl2 and CdL2Cl2 were isolated in a M:L = 1:3 molar ratio in EtOH/Me2CO mixtures. Surprisingly, attempts to crystallize CdLCl2 from EtOH/Me2CO mixture afforded single crystals of a compound, having 1:2 metal-to-ligand stoichiometry, CdL2Cl2 center dot 0.5Me(2)CO center dot 1.5H(2)O, instead of a complex with 1:1 stoichiometry. At the same time, crystallization of CdL2Cl2 from Me2CO/CHCl3 mixture afforded CdL2Cl2 center dot 0.5CHCl(3)center dot 0.5H(2)O single crystals. According to X-ray crystal structure data, ZnLCl2, ZnL2Cl2, CdL2Cl2 center dot 0.5Me(2)CO center dot 1.5H(2)O and CdL2Cl2 center dot 0.5CHCl(3)center dot 0.5H(2)O complexes have molecular mononuclear structures. The molecules of L adopt bidentate chelating binding mode being coordinated to the metal ions through N-2 atom of the pyrazole and N-3 atom of the pyrimidine rings. The coordination core of zinc atom in ZnLCl2 complex is a distorted ZnN2Cl2 tetrahedron. The coordination cores of metal atoms in the structures of ZnL2Cl2, CdL2Cl2 center dot 0.5Me(2)CO center dot 1.5H(2)O and CdL2Cl2 center dot 0.5CHCl(3)center dot 0.5H(2)O are the distorted cis-MN4Cl2 (M = Zn, Cd) octahedra. In the structure of ZnL2Cl2 double lone pair(N(piperidine))-pi(pyrimidine) interactions were observed. The photoluminescent properties of L, ZnLCl2, CdLCl2, ZnL2Cl2 and CdL2Cl2 were studied in the solid state under the same experimental conditions. These compounds were found to display bright blue luminescence. Highest relative intensity of emission was detected for ZnL2Cl2. (C) 2011 Elsevier B. V. All rights reserved.