A series of new mixed-ligand complexes based on 3,6-bis(imidazol-1-yl)pyridazine: syntheses, structures, and catalytic activities

Abstract

Seven new mixed-ligand complexes based on L [L = 3,6-bis(imidazol-1-yl)pyridazine], namely, [Ni(L)2(SCN)2]n (1), [Cu5(L)(1,2-BDC)4(μ3-OH)2]n (2), {[Cu4(L)2(1,3-HBDC)(1,3-BDC)(μ3-OH)4]·ClO4·2.6H2O}n (3), {[Ni(L)(1,4-BDC)H2O]·0.25H2O}n (4), [Co(L)(1,3,5-H2BTC)2H2O]n (5), {[Cu2(L)(2,6-PYDC)2(H2O)2]·4.4H2O}n (6), and {[Co(L)(4,4′-OBA)]·3.725H2O}n (7) [1,2-benzenedicarboxylic acid (1,2-H2BDC), 1,3-benzenedicarboxylic acid (1,3-H2BDC), 1,4-benzenedicarboxylic acid (1,4-H2BDC), 1,3,5-benzenetricarboxylic acid (1,3,5-H3BTC), 2,6-pyridine dicarboxylic acid (2,6-H2PYDC), and 4,4′-oxydibenzoic acid (4,4′-H2OBA)], have been synthesized by solvothermal reactions. Complexes 1 and 2 possess a two-dimensional (2D) layered structure, and the 2D framework of complex 1 can be rationalized to be a four-connected {44·62} topological sql network, while 2 exhibits a similar topological network with pentanuclear [Cu5(μ3-OH)2(μ2-COO−)6]2+ secondary building units (SBUs). Complex 3 presents an 8-connected sqc3 3D framework based on a chair-shaped [Cu4(μ3-OH)4]4+ SBU with a Schlafli symbol of {424·64}. Complex 4 displays a 3D framework with diamondoid topology, which includes L/Ni(II)/L helical chains. Complex 5 features a 1D chain structure formed by L ligands. Complex 6 shows a dinuclear structure, which is arranged into a 1D supramolecular chain by hydrogen-bonding interactions. The 3D framework of 7 presents a 4-connected porous architecture with a Schlafli symbol of {66}, the same as that of complex 4. The powder X-ray diffraction spectra, IR spectra, UV-vis absorption spectra and thermal stabilities of 1–7 have been investigated. Moreover, in the complex-catalyzed homocoupling reaction of 4-substituted aryl iodides, the catalytic activities of 1–7 have also been studied and discussed.