Study On Synthesis And Properties Of Azobenzene Carboxylic Acid Complexes

The carboxyl group has strong coordination ability and diverse coordination modes,which provides a variety of options and feasible directions for the structural design and orientation synthesis of functional coordination compounds.The photoisomerization of azobenzene group makes it potential value in the fields of light control switch,information storage,nonlinear optical materials and so on.Therefore,the introduction of azobenzene group into carboxylic acid molecular system,then synthesis of azobenzene functional carboxylic acid molecules and complexes have very important research value and significance.In this paper,three azobenzene-functionalized carboxylic acid compounds,4-amino-2-(p-carboxylidene-anilino)-azobenzene(Hacaa,for short and the same as below),2,4-(dicarboxylidene-anilino)-azobenzene(H2dcaa)and p-carboxylidene-anilino azobenzene(Hcaa),were designed and synthesized through the condensation reactions between amino group and aldehyde group of those raw materials 2,4-diaminazobenzene hydrochloride(Ketine,DAAB),p-aminoazobenzene(AAB)and 4-carboxybenzaldehyde(CBA).The metal ions(Cd2+,Co2+,etc.)were coordinated with these carboxylic acid compounds,as molecular ligand,to obtain corresponding complexes.The photoisomerization and fluorescence properties of them were studied.The main contents are as follows:(1)Three compounds were synthesized by condensation reactions between amino group and aldehyde group in flux,and were characterized by EA,UV-vis,FT-IR and so on.The experimental conditions of slow evaporation,diffusion and solvothermal,three methods were discussed and optimized.The single crystals of Hacaa suitable for single crystal XRD were obtained by slow evaporation method.It was red cuboid with the size 0.5×0.3×0.2 mm,monoclinic system,space group C2/c,the unit cell parameters:a=12.82 A,b=7.81 A,c=19.83 A,?=90.00 deg,?=90.26 deg,?=90.00 deg.The structure of Hacaa consists of "wave"molecular chains along the axis z with the help of intermolecular hydrogen bonds.The results showed that the compound UV absorbtion,thermal stability,etc.was closely related to the degree of conjugation of molecules.(2)The metal(Cd2+,Co2+,etc.)complexes were synthesized by coordinated by above obtained compounds,and characterized by EA,UV-vis,FT-IR,TG-DTA and so on.The experimental conditions and factors of solvothermal and diffusion methods were discussed and optimized.The results show that the solvent molecules in the complex are involved in the coordination,and the stability of the complex is closely related to the degree of conjugation of the molecule.The larger the degree of conjugation is,the more stable the complex is.(3)The photoisomerization and fluorescence properties of compounds and their metal complexes were studied.UV absorption spectroscopy and fluorescence emission spectroscopy showed that it occurred configuration change from trans-to cis-,accompanied by color change,under UV irradiation.The isomerization conversion rate and the conversion rate showed that the photoisomerization reaction of azobenzene group is affected by substituents,steric hindrance,degree of conjugation and other factors.The higher degree of conjugation,the faster conversion rate,the stronger fluorescence intensity,and shift to the long wavelength direction.