Synthesis, Structures And Properties Of Series Of Methoxyphenyl Substituted Imidazole Dicarboxylate-based Metal-organic Frameworks

Recently, the design and synthesis of new coordination polymers (CPs) have become a hottopic in the fields of coordination chemistry and material chemistry. People have focused on theselection of a useful modified organic ligand to obtain the desired polymers, especially themodified imidazole dicarboxylate ligands. In this paper, we adopted two kinds of newlydesigned ligands:2-(3-methoxyphenyl)-1H-imidazole-4,5-dicarboxylic acid (m-H3MOPhIDC)and2-(3,4-dimethoxyphenyl)-1H-imidazole-4,5-dicarboxylic acid (3,4-H3DMOPhIDC), andinvestigated their coordination abilities and properties of the corresponding CP.Firstly, the optimized geometries and natural bond orbital (NBO) charge distributions of thefree m-H3MOPhIDC and3,4-H3DMOPhIDC ligands were calculated by theB3LYP/6-311++G(d, p) level, and explored their coordination abilities. Secondly, bycontrolling the reaction temperature and time, pH value of solvent, and so on, fifteen polymerswith unique structures were synthesized. Polymers1-10have obtained by m-H3MOPhIDC, andpolymers11-15have constructed from H3DMOPhIDC.[Sr(m-H2MOPhIDC)2]n(1) exhibits a3D network with1D-hexagonal channels.{[Mn3(m-MOPhIDC)2(H2O)6]4H2O}n(2) is awindmill-shape3D structure bearing [Mn6(m-MOPhIDC)6] cages.{[Zn3(m-MOPhIDC)2(H2O)6]4H2O}n(3) is stacked in an...AAA... fashion to develop a3-Dsupramolecule.[Sr(m-HMOPhIDC)(H2O)]n(4) exhibits a2D framework containing the left-and right-hand double helixs.[Cd1.5(m-H2MOPhIDC)(m-HMOPhIDC)(H2O)]n(5) is a sheetstructure.[Cu(m-HMOPhIDC)(phen)]n(6) is a linear chain structure.{[Cu2(m-HMOPhIDC)(4,4’-bipy)]}n(7) shows a1D wave chain.[Cd2(m-HMOPhIDC)2(phen)2]n(8) and [Cd2(m-HMOPhIDC)2(2,2′-bipy)2]n(9) are very similarchain structures.[Co(m-HMOPhIDC)(H2O)2]n(10) is a chain structure.[Sr(3,4-H2DMOPhIDC)2]n(11) is a3D super-molecule.[Cd2(3,4-HDMOPhIDC)2(H2O)4]n(12)and [Ni2(3,4-HDMOPhIDC)2(H2O)4]n(13) are wave chains.[Zn(3,4-HDMOPhIDC)(phen)]n(14)and [Co(3,4-HDMOPhIDC)(phen)]n(15) are interpenetrating3-D networks supported by π…πand H-bond interactions. The two imidazole dicarboxylate ligands show various coordinationmodes and strong coordination ability, which is consistent with theoretical predictions.Finally, the thermogravimetric analyses and fluorescence measurements of the polymerswere investigated. The results indicate some polymers have strong stability, which do notdecompose below300°C. The solid-state fluorescent determinations show that the polymersshow luminescence emission except the polymers bearing quenching Mn2+, Cu2+and Co2+ions.