In situ synthesis and characterization of a series of new pyridyl containing complexes based on 3d metals: from oligomer to 3D framework

Abstract

Five coordination compounds assembled from the pyridyl based ligand, Ni(PBN)4(N3)2, 1; {[Co(PPT)2·(H2O)2]·2H2O}n, 2; [Cu(PPT)]n, 3; {[Zn2(PPT)3(OH)]·2H2O}n, 4, and [Cd(PPT)2]n, 5 (PPT ​= ​5-(3-pyridylphenyl)tetrazole and PBN ​= ​4-(3-pyridyl)benzonitrile) have been solvothermally synthesized and characterized by single-crystal X-ray diffraction, powder XRD, elemental analysis, IR spectroscopy, solid state fluorescence and TG analysis. The PPT ligand in the complexes is generated via the in situ [2 ​+ ​3] cycloaddition in the reaction of the cyano groups of the organonitrile and sodium azide. Single-crystal X-ray diffraction analyses reveal compound 1 is an oligomer of 6-coordinated Ni(II) compound where the 6 coordination sites are occupied by six nitrogen atoms from four distinct PBN ligands and two azide ions, respectively. Compound 2 exhibits a 1D chain structure where the 6-coordinated cobalt centers are double connected by two upside down μ2-PPT ligands. Both compound 3 and compound 4 present the 2D sheet structures constructed by μ2-tetrazole-linked copper(I) dimmer and μ2-hydroxy-connected zinc(II) dimmer, respectively, with both centers of 4-coordinated fashions. Compound 5 is a dense 3D framework with the PPT ligand of a μ3-bridging mode. Structural analyses indicate the structural varieties of the dimensionalities in these compounds result from the coordination diversity of the PPT ligands. In addition, compound 3 represents a rare example of copper(II) that is experienced the self-reduction process during the in situ [2 ​+ ​3] cycloaddition and exhibits a blue emission at room temperature. Thermal stability analyses indicate the compounds 4 and 5 are stable up to 300 ​°C and the temperature dependent PXRD reveal the residues of compounds 4 and 5 are ZnO and CdCO3, respectively.