Synthesis And Structure Study Of A Series Of Phenoxy Carboxylic Acid Complexes

The carboxyl group?-COOH?can bond with metal through a variety of coordination modes,and has good electron-donating ability due to two oxygen atoms thus allow its strong coordinational capability.The carboxylic acid complexes have been widely used in the fields of gas storage material,magnetic material,biomedical material,catalyst and so on.Phenoxyacetic acid not only contains a carboxyl group,but also possess flexibility owing to the presence of a-OCH₂-spacer between the phenyl ring and carboxylate moiety,thus allow phenoxyacetic acid an excellent functional ligand.In the past few decades,alkaline earth metal with versatile coordination number and geometric configuration catches a lot of attention due to the excellent water-solubility,low cost and biocompatibility.But alkaline earth metal has large volume and small electrical charge,which make it difficult to coordinate with ligands.Therefore,alkaline earth metal monocrystalline can't be cultivated by the conventional methods,for example,solvent evaporation method and hydrothermal method.In this thesis six phenoxyacetic acid ligands with similar chemical structure?o-HCPA?m-HCPA?p-HCPA?HMCPA?HDCPA and HTCPA based on the oxygen position on benzene ring?were selected.And we have successfully synthesized fourteen crystals of alkaline earth metal and teen crystals of rare earth metal with phenoxyacetic acids based on solvent evaporation method,hydrothermal method and microwave method using these selected ligands.The structural formulas are as follows:[Mg?o-CPA?₂?H₂O?₄] 1;[Mg?H₂O?₆]·?MCPA?₂2;[Mg?DCPA??H₂O?₅]·?DCPA?₃;[Mg?TCPA?₂?H₂O?₄]·2H₂O 4;[Ca?CPA??H₂O?₄]·?CPA?₅;[Ca?MCPA?₂?H₂O?₂]·H₂O 6;[Ca?TCPA?₂?H₂O?₃]·2H₂O 7;[Sr(o-CPA 2?H₂O?₄]·?C₈H₆O₃Cl?8;[Sr?m-CPA?₂?H₂O?₄]·?m-CPA?9;[Sr?p-CPA?₂?H₂O?] 10;[Ba?o-CPA?₂?H₂O?]·H₂O 11;[Ba?m-CPA?₂?H₂O?₄]2·H₂O 12;[Ba?p-CPA?₂?H₂O?] 13;[Ba?TCPA?₂?H₂O?₄] 14;[Dy?o-CPA?₃?H₂O?]·H₂O 15;[Ho?o-CPA?₃?H₂O?]·H₂O 16;2[Er?m-CPA?₃?H₂O?]·3H₂O 17;2[Gd?m-CPA?₃?H₂O?]·3H₂O 18;[Ce2?m-CPA?₆?H₂O?₃]·2H₂O 19;[Er2?p-CPA?₆?H₂O?₆] 20;[Ho2?p-CPA?₆?H₂O?₆] 21;[Sm?p-CPA?₃?H₂O?] 22;[Pr?p-CPA?₃?H₂O?]·3H₂O 23;[Ce?p-CPA?₃?H₂O?₂]·2H₂O 24.These complexes were characterized by elemental analysis,infrared spectroscopic analysis and thermogravimetric analysis.The structures were characterized by single crystal X-ray?coordination environment,coordination polyhedron,1D chain,2D layer,3D network?.The hydrogen bond structures of complexes?1-4?were detailed studied.The influences of chlorine substituent group position in phenoxyacetic acid on complex property?5-7?have also been discussed.The main conclusion of this article as follows:The results of structure study could be concluded as follows: For alkaline earth metal complex,the coordination number of Mg?II?was 6 with a slightly distorted octahedron structure.The coordination number of Ca?II?was 8 with a slightly distorted bicapped trigonal prism coordination geometry.The coordination number of Sr?II?was 8 or 9 with a slightly distorted bicapped trigonal prism coordination geometry and tricapped triangular prism coordination geometry.The coordination number of Ba?II?was 9 with a slightly distorted tricapped triangular prism coordination geometry.In the rare earth metals complexes,the coordination number was 9 or 10,and the coordination geometry become more complexity with a slightly distorted tricapped trigonal prism coordination geometry and bicapped dodecahedron coordination geometry.The existence of ortho hydrogen atom,make the formation of O-H-Cl bond easier,and the more complex hydrogen bond,the more stable structure,which corroborate with thermal weight test;Among the obtained 24 single crystalline,the carboxyl group shows six kinds of coordination modes:?2-?¹: ?²,?2-?¹: ?¹,?3-?²: ?²,?1-?¹: ?¹,?1-?0: ?¹,?3-?¹: ?².The oxygen of phenoxy group also participated in coordination;The ligands which posses o-position substituted chlorine?o-HCPA,HDCPA,HTCPA?can easily form O-H···Cl hydrogen-bond with metal ions,while the m-position?m-HCPA?and p-position substituted chlorine?p-HCPA,HMCPA?are difficult to form the O-H···Cl hydrogen-bond with metal ions;Most of the complexes based on phenoxyacetic acids were synthesized by microwave method,solvent evaporation method and solvent diffusion method.Complexes and the crystals could also be achieved by the microwave method,which is much more greener and efficient compared to traditional method.And it is used in the area of complexes synthesis for the first time;Thermalanalysis has shown that complexes 1-24 have two mass-loss steps.The first mass-loss is the release of water molecules including all the coordinated water molecules as well as lattice water molecules,the next mass-losses corresponds to the continuous collapse of the frameworks,the final residue could be assigned to the corresponding oxide;Besides the coordinate bond,supramolecular interactions?hydrogen bond and ?-?stacking interaction as well as C-H-? interaction?also play an important role in forming the1 D,2D,even 3D structures for the complexes.