Construction,Structure And Properties Of Complexes Based On Zwitterionic Dicarboxylic Acid Ligands

Recently,coordination supramolecules(CSs)have attracted wide attention because of their rich structures,and,especially,tuned and modified structure nature.Just based on the tunability and modifiability of structure,CSs have shown broad application prospects in adsorption/storage and separation,ion exchange/recognition,heterogeneous catalysis,optical materials and other aspects,which attracts the attention of chemists and relevant research is blooming.CSs are mainly composed of metal ions/clusters and ligands.The selectivity of two building components plays an important role in the final structure and properties of CSs.Currently,there are mainly two kinds of organic ligands,N-heterocyclic ring and carboxylic acids-containing ligands.Carboxylic acid ligands are widely used in the construction of supramolecules due to their negative charge,strong coordination ability and various coordination modes.Carboxyl imidazolium/pyridinium ligands,essentially the functional products of imidazole or pyridine ligands,are zwitterionic ligands.The CSs based on these two kinds of zwitterionic ligands have good host-guest interactions because of their permanently charged organic skeletons,and have potential applications in molecular/ion recognition,proton conduction and other aspects.On the other hand,charged organic ligands can be regarded as organic Lewis acids,which make CSs potentially can act as Lewis acid catalysts.In this thesis,we design and synthesize two semirigid imidazolium ligands:1,3-bis(4-carboxybenzyl)-2-methylimidazolium(BBMI)and 1,3-bis(4-carboxybenzyl)-2-ethylimidazolium(BBEI)and one pyridinium ligand:3-carboxy-1-(4-carboxybenzyl)pyridinium(CCBP),and using them to react with Mn(?),Co(?),Cu(?),Zn(II),Cd(?)and Pb(?)metal salts,ten CSs were successfully prepared.We further investigate the effect of reaction conditions on the final structures,and study their structures and properties.The following is the specific content of this paper:1.By using BBMI ligand and auxiliary malonic acid to react with d10 Zn(?),Cd(II)salts,respectively,two CSs formulated with[Zn(BBMI)2]·11H2O(1)and[Cd(BBMI)2]·6H2O(2)were synthesized by solvent thermal method.By comparison,by using only BBMI ligand to react with Cd(II),Cu(II)and Pb(II)salts,respectively,three CSs,namely[Cd(BBMI)2]·10.61H2O(3),[Cu2(BBMI)(CH3CN)(OH)2]·(C1O4)·0.31H2O(4)and[Pb2(BBMI)4]·15H2O(5),were obtained.The structure analysis reveals that malonic acid ligands do not take part in coordination,meaning that malonic acid may only serve as acidity regulator.CSs 1 and 2 both have 6-fold interpenetrating dia network structures,in which Zn(?)and Cd(?)ions act as 4-connected tetrahedral nodes and cis,trans-configurational BBMI ligands serve as 2-connected linear nodes.Compared with 2,3 exhibits a 1D beaded chain architecture,which are packed in a parallel mode to form a 3D structure.4 is a 2D sandwich inorganic-organic hybrid layer composed of 2D[Cu2(OH)2]+inorganic layer and two organic layers consisting of bridged BBMI ligands.In contrast to the polymerization structures of complex 1-4,5 is a M2L4 metalloid ring.Moreover,1 has strong fluorescence and can act as Fe3+,Al3+and acetone sensors.On the other hand,three CSs,[Zn(BBEI)2]·DMF·7H2O(6),[Cd(BBEI)2]·DMF-7H2o(7)and[Mn(BBEI)(COOH)1.5(H2O)]·Cl·2.5H2O(8),were prepared by the reaction of BBEI ligands and corresponding metal salts.CSs 6 and 7 are isostructural with 1 and 2,displaying a 3D 6-fold interpenetrating dia network.These results indicate that the substituents on the imidazole ring have no effect on the final structures of CSs.8 shows a 1D loop-and-chain structure,which take…ABAB… parallel arrangement to generate a 3D structure.2.In this chapter,two CSs with formula[Co(CCBP)2(H2O)4]·2H2O(9)and[Cd(CCBP)2(H2O)]·3H2O(10)have been obtained by reactions of CCBP ligands and Co(?)and Cd(?)salts via solvent thermal and diffusion methods.Crystal structure analysis shows that 9 is a neutral mononuclear complex.Whereas,considering its abundant hydrogen bonds and ?-? interactions components,it can serve as supramolecular synthons.As anticipated,mononuclear[Cd(CCBP)2(H2O)]motifs are first connected via hydrogen bonds to form a channel-structured 2D layer,which are further linked via ?-? stacks in an interdigitation fashion to generate a 3D porous framework.10 is a ID zigzag chain,which are joined together via ?-? interactions between pedent CCBP ligands,giving rise to the formation of 1D ladder chain.Above 1D ladder chains are further combined into wavy 2D network via ?-?interactions between two adjacent sides of ID ladder chains.Finally,the 2D layers interpenetrate each other to form a 2D?3D frame structure.From another point of view based on 1D chains,the dense packing mode of 10 can be described as the plywood-like arrangement.In addition,the fluorescence property of 10 at room temperature were also studied.The experimental results showed that the 10 has strong ultraviolet fluorescence emission.By comparing the fluorescence of ligands,the fluorescence of comples 10 could be ascribed as MLCT mechanism.