Research On The Synthesis Process And Structure-activity Relationship Of One Kind Of Nonlinear Optical Crystal

1-(5-Bromothiophen-2-yl)-3-(4-nitrophenyl) prop-2-en-1-one(BTNP) has high melting point and thermal stability, which make them a new kind of nonlinear optical(NLO) organic material for wide applications in the fields of optical communication.However, there is little published articles about optimal synthesis process, HPLC analysis methods of BTNP and relationship between crystal structure and optical performance. Therefore, synthesis process and structure-activity relationship of BTNP was investigated in this work.Firstly, to optimize the synthesis process and improve the purity of the product,the synthetic process of BTNP was monitored in situ by Raman spectroscopy to find out the mechanism of main reaction and possible side reactions. The possible side reactions were proposed based on Raman spectroscopy data. The effect of reaction conditions, including dosage of sodium hydroxide and reaction temperature, was investigated and analyzed by using the proposed side reaction scheme and HPLC analysis data.Then, we discovered and identified two crystal forms and three kinds of co-crystals of BTNP. The single crystal of two crystal forms of BTNP was prepared to analyze and compare the difference between them in molecule and crystal structure.The SHG conversion efficiency of two crystal forms and three kinds of co-crystal of BTNP was measured by powder technique. Meanwhile, the UV-Visible absorption spectrum, refractive index, the tensor of nonlinear optical coefficients and hardness of two crystal forms was determined by UV–Visible spectrophotometer, Brewster's angle method,marker fringer method and Vicker's microhardness tester, respectively.The molecular hyperpolarizabilities ? and the tensor of nonlinear optical coefficients dij of two crystal forms was investigated theoretically by computational approach of quantum chemistry. The highest occupied molecular orbital(HOMO) and lowest unoccupied molecular orbital(LUMO) of two crystal forms were calculated with cam-b3lyp/6-31 method to explain how the molecular hyperpolarizabilities ?change with molecules. The calculated largest values of dij agree well with measured ones.The investigations on the side reactions mechanism, optimal synthesis process,crystal polymorphism, co-crystals and structure-activity relationship of BTNP was not found from literature.