Synthesis,Structures And Properties Of Coordination Polymers Based On Benzimidazole Carboxylic Acid Ligands

Coordination polymers（CPs）have been an attractive research field due to intriguing architectures and their potential applications in magnetism,catalysis,luminescence and absorption.As is known to all,the polycarboxylate ligands as well as the imidazol derivatives are two kinds of most widely used organic ligands due to their strong coordination abilities and diverse coordination modes.Up to now,many CPs with versatile structures have been constructed from the above-mentioned two kinds of organic ligands.However,there are relatively few studies on bifunctional organic ligands containing carboxyl groups and benzimidazoles.We hope to broaden research in this area.In this paper,we choose two similar ligands:2-（2-methyl–benzimidazole-1-yl）benzoic acid（HL）and 2-（benzimidazol-1-yl）terephthalic acid（H₂bitp）with six different auxililiary pyridine ligands:1,2-bis（4-pyridyl）ethylene（bpe）,1,2-bis（4-pyridyl）ethylane（bpa）,4,4’-bipyridine（4,4’-bpy）,2,2’-bipyridine（2,2’-bpy）,2,2’-dipyridylamine（bipyam）and1,10’-Phenanthroline（phen）to obtain CPs.Fortunately,twelve CPs were synthesized by hydrothermal method:[CdL₂]_n（1）,[Zn L₂]_n（2）,{[Ni₂（bitp）₂（bpe）（H₂O）₄]·（bpe）}_n（3）,{[Ni₂（bitp）₂（bpa）（H₂O）₄]·（bpa）}_n（4）,{[Ni（bitp）（4,4’-bpy）_0.5（H₂O）]·3H₂O}_n（5）,{[Ni_1.5（bitp）（Hbitp）（2,2’-bpy）（H₂O）·3H₂O]}_n（6）,[Ni（bitp）（bipyam）]_n（7）,{[Co₂（bitp）₂]·DMF}_n（8）,{[Zn₂（bitp）₂]·DMF}_n（9）,{[Cu₂（bitp）₂]·DMF}_n（10）,[Mn₂（bitp）₂（H₂O）₃]_n（11）and[Cd（bitp）（phen）]_n（12）.1 and 2 based on HL ligand are similar 1D looped chain,which can be used as potential and highly selective luminescent sensors for Fe³⁺ions.Isostructural 3 and 4 feature 3D layered-pillared frameworks with one-dimensional（1D）channels housed by free bpe and bpa.But different from 3 and 4,complex 5 is a wavelike 2D stacked layer despite they employ similar bridging ligands.Moreover,when terminal ligands is used to replace bridging ligands,2D wavelike layer 6,1D ladder chain 7 and 2D wavelike layer 12 are obtained.Notably,3-7 exhibits outstanding thermal and chemical stability.Furthermore,gas adsorption studies for 3 and 4show high selective adsorption of CO₂.8-10 exhibit isomorphic 3D paddle-wheel,and 11 is a 3D densely packed structure.On the basis of their individual characteristic,the fluorescence,magnetism and adsorption properties have been investigated.There are four chapters in this paper:Chapter 1 presents the concept,development and application of coordination polymers,as well as the coordination polymers based on benzimidazol-carboxylate ligands,and the basis and significance of dissertation.Chapter 2 introduces two coordination polymers based on the HL ligand,which can be used as potential and highly selective luminescent sensors for Fe³⁺ions.Chapter 3 offers the structural comparison of five novel Ni（II）-CPs,which are synthesized by H₂bitp and five different pyridine auxililiary ligands under same hydrothermal conditions.The adsorption of complex 3 and 4 is measured and the chemical stabilities,magnetism and catalyze properties of five CPs is tested and analysized as well.In Chapter 4,five novel coordination polymers is constructed from H₂bitp and phen ligands,and the magnetism and luminescent properties are discussed.