Structural Design, Synthesis And Properties Of Benzothiazole-based Organic Nonlinear Optical Crystals

2-(4-(dimethylamino)styryl)-benzothiazole(DMASBT)is a new type of organic nonlinear optical(NLO)crystal with potential research value.As a single molecular crystal,DMASBT has a special arrangement of chromophores in the adjacent molecular layers,which can effectively suppress the dipole-dipole coupling between chromophores and improve the polarization efficiency,compared with the ionic crystals with complex structure of anion and cation layers.Therefore,its NLO performance is better than that of ordinary crystals.The second harmonic generation efficiency of the crystal is 9.8 times higher than that of the standard KDP.In this work,DMASBT crystal materials were synthesized and grown by slow cooling method.DMASBT crystals with different sizes were grown from different solvents.The crystal was characterized by thermal,optical and electrical properties.At the same time,the growth mechanism,optimum growth conditions and intermolecular interaction were studied.In addition,in view of the stronger electron obtaining ability of benzothiazole acceptor,based on the donor-?conjugated-acceptor(D-?-A)type organic NLO crystal structure,the ionic type OHB-T,OHB-TMS and OHB-BS crystal materials were synthesized by changing the functional groups based on 2-methylbenzothiazole electron acceptor.OHB-T crystal with the maximum size of 10×4×4 mm~3 and OHB-BS crystal with the maximum size of 8×4×7 mm~3 were grown by slow cooling method.The extinction coefficient,transmittance and band gap are calculated and compared.On the basis of OHB-T crystal,OH5CB-T crystal was synthesized by molecular modification based on 5-chloro-2-methylbenzothiazole electron acceptor.The preliminary test and analysis showed that the second harmonic signal intensity of OH5CB-T powder was about 2.2 times that of KDP.At the same time,the thermal and electrical properties of the crystal were characterized.