The Synthesis, Properties And Applications Of Chromic Crystal Materials Based On Viologens

Chromatic materials refers to the materials that will occur with color changes obviously when exposed to external stimulation,such as light,electricity,heat,pressure and X-ray and so on.This kind of materials have a wide range of applications in sensing and detection,which is due to the recognition of the detected material by the visible color of the naked eye or by varying degrees of fluorescence quenching.In this paper,the synthesis of inorganic-organic hybrid hybrid crystalline materials with viologen and transitions are studied,and their properties and applications are also studied.The work is carried out from the following three aspects:（1）The function and the properties of the organic ligand can affect the properties of the synthetic compound,so we first synthesized a kind of the viologen ligand,and the color change and the fluorescence property of the ligand were studied;（2）We design and synthesize the viologen chromatic and detecting material for the multiple-stimulation response by considering of the properties of synthesized viologen ligands and introducing a new electron donor and properties of synthetic viologen ligands;（3）Viologen chromatic materials with strong photo-stability and thermal-stability were synthesized and their detection properties were characterized and studied.The research results of this paper are as follows:1.For the first time,we synthesized the viologen compound 1,1-bis（3-carboxylphenyl）-4,4-bipyridine dichloride（H₂bcbpy·2Cl）and the response of the ligand to light and heat.It carried out the investigation of the fluorescence properties and obtained its corresponding crystalline compound 1 by culturing,named Hbcbpy·ClO₄.2.The three dimensional metal cadmium coordination polymer 2 was synthesized by solvothermal synthesis of using H₂bcbpy·2Cl,p-phthalic acid（PTA）and CdCl₂·2H₂O and named[Cd（bcbpy）_0.5（PTA）（H₂O）].The photo and thermal response ability of compound 2have been tested by us.As we expected,compound 2 shows good photochromism,thermochromism and potential application as optical switch because of the good performance of viologen ligand H₂bcbpy·2Cl.3.Two new one-dimensional coordination polymers 3 and 4 were synthesized by H₂bcbpy·2Cl,Cd（NO₃）₂·4H₂O and different kali salt（KBr and KSCN）,named[Cd（bcbpy）Br₂]·（H₂O）₂ and[Cd（bcbpy）（SCN）₂],respectively.These two compounds have rare multiple-coloration properties.Compound 3 and compound 4 have both photochromism and thermochromism.At the same time,these two compounds also have the properties of light-controlled fluorescence and thermal-controlled fluorescence.In addition,compounds 3and 4 show the ability to recognize and detect ammonia because the nitrogen atomic of bcbpy units have good electron deficiency and can be regarded as Lewis acid sites.we analyzed the different properties of the two compounds from the structural relationship through the influence of different anions on the structure.4.We selected a rigid one-sided ligand 1-（3-carboxybenzyl）-4,4-bipyridine chloride（m-Hbcbpy·Cl）and synthesize the first transition metal crystal compound through solvothermal.Compound 5 is named[Cd（bcbpy）Cl₂]·H₂O.Compound 5 has reversible photochromism and can absorb and detect harmful blue light in the wavelength range of 400-440 nm.We have obtained its photochromic crystal structure,which is rare in viologen crystal compounds,which indirectly proves the stability of the two-dimensional framework.At the same time,five kinds of organic amines and six kinds of benzene free substances were detected on the solid state,and these organic molecules were recognized by the change of color and fluorescence intensity.In addition,compound 5 was immersed in hydrochloric acid aqueous solution of different pH,and the structure stability was maintained in the range of pH1-7.The water vapor adsorption of compound 5 was tested and the results show that compound 5 can adsorb water vapor at low pressure.UV solid diffusion reflection,electron parammagnetic resonance and Gaussian 09 calculation software have been used to analyze the chromic mechanism of this multifunctional compound.