A series of metal-organic complexes constructed from in situ generated organic amines

A series of hydrothermal reactions of metallic salts (CoCl₂, CdSO₄ and ZnCl₂), carboxylates (oxalic acid and 1,4-H ₂BDC) and organic amines (o-PD, Him) have been investigated. Five coordination complexes, [Zn₂(bim)₄]_n (1), Cd(H₂bbim)₂SO₄·1/3(H₂O) (2), [Co₂(H₂bbim)₄(bbim)]Cl₂ (3), [Co(Hbim)(Him)(C₂O₄)]_n (4) and [Zn(H ₂bbim)(1,4-BDC)]_n (5) (o-PD = o-phenylenediamine, Hbim = benzimidazole, H₂bbim = 2,2′-bisbenzimidazole, Him = imidazole, 1,4-H₂BDC = 1,4-benzenedicarboxylic acid), were prepared and characterized by elemental analyses, IR, single-crystal X-ray diffraction, fluorescence and magnetic analyses. Interestingly, two different ligands Hbim and H₂bbim were generated via hydrothermal in situ reactions of o-PD and oxalic acid during the formation processes of these compounds. In 1, bim ligands bridge each pair of Zn atoms into a single-stranded helical chain through metal-ligand interactions to generate a 2-D grid-like structure. Complex 2 features a mononuclear structure due to the large steric hinderance of H ₂bbim ligand. Through N-H⋯Cl hydrogen bonds, the dinuclear units of 3 are alternately arranged to afford a unique 1-D helical chain. Complex 4 exhibits a 1-D zig-zag chain which consists of [Co(Hbim)(Him)] ²⁺ units bridged by oxalate ligands, and 5 displays a 1-D chain structure consisting of Zn(H₂bbim)²⁺ units linked by 1,4-BDC ligands.