Synthesis and characterization of Cu(II), Co(II) and Ni(II) coordination polymers containing bis(imidazolyl) ligands

Two structurally related flexible imidazolyl ligands, bis(N-imidazolyl)methane (L1) and 1,4-bis(N-imidazolyl)butane (L2), were reacted with Cu(II), Co(II) and Ni(II) salts of aliphatic/aromatic dicarboxylic acids resulting in the formation of a number of novel metal–organic coordination architectures, [CuB2(ox)2(L1)2(H2O)2] · 4H2O (1) (ox = oxalate), [Cu(pdc)(L2)1.5] · 4H2O (2, pdc = pyridine-2,6-dicarboxylate), [Co(L)2(H2O)2](tp) · 4H2O (3, tp = terephthalate), [Ni(L1)2(H2O)2](ip) · 5H2O (4, ip = isophthalate), [Cu2(L1)4(H2O)4](tp)2 · 7H2O (5), [Co(mal)(L1)(H2O)] · 0.5MeOH (6, mal = malonate), [Co(pdc)(L1)(H2O)] (7). All the complexes have been structurally characterized by X-ray diffraction analysis. The different coordination modes of the dicarboxylate anions, due to their chain length, rigidity and diimidazolyl functionality, lead to a wide range of different coordination structures. The coordination polymers exhibit 1D single chain, ladder, 2D sheet and 2D network structures. The aliphatic and aromatic dicarboxylates can adopt chelating μ2 and chelating-bridging μ3 coordination modes, or act as uncoordinated counter anions. The central metal ions are coordinated in N2O4, N4O2, N2O3 and N3O3 fashions, depending on the ancillary ligands. The topology of 1 gives rise to macrocycles which are connected through hydrogen bonds to form 1D chains, whereas compound 2 exhibits a 1D polymeric ladder in which the carboxylate acts as a pincer ligand. Compounds 3–5 show doubly bridged 1D chains, and the dicarboxylate groups are not coordinated but form 2D corrugated sheets with water molecules intercalated between the cationic layers. Compound 6 has a 2D network sheet structure in which each metal ion links three neighboring Co atoms by the bis(N-imidazolyl)methane ligand. The cobalt compound 7, with a 2D polymeric double sheet structure, is built from pincer carboxylate (pdc) and 1,4-bis(N-imidazolyl)methane ligands.

A series of novel coordination polymers with different structures have been synthesized by reacting Cu(II), Co(II) and Ni(II) salts of aliphatic/aromatic dicarboxylic acids with flexible bisimidazole derivatives. The dicarboxylates can adopt chelating μ2, bridging μ2 and chelating-bridging μ3 coordination modes, or act as uncoordinated counter anions. The coordination polymers exhibit 1D single chain, ladder, 2D sheet and 3D network structures.Figure optionsDownload as PowerPoint slide