The DFT Study On The NLO Properties Of The O-carborane Ternary System With Two-Dimensional Structure

Nonlinear optical?NLO?materials have attracted much attention due to their wide application in information processing,laser technology,photoelectric conversion,and optical communication.Nearly twenty years,although the practical NLO materials are mostly inorganic compounds,due to the delocalization of?electrons in some organic compounds which produce large second-order NLO response and attract many technicians attention.Carboranes and derivatives have good properties such as unique physical and chemical properties,high chemical and thermal stability.It has always been a topic of great interest to researchers,experiment and theoretical research on such substances are endless.At the same time,the study found that carborane and its derivatives have significant NLO responses and will be expected to be an NLO alternative material.In this paper,quantum chemical calculation method is used to calculate the properties of the two-dimensional structure of the o-carborane ternary systems.The main work includes:1.The NLO properties of the D-A-D?D'?o-carborane triads were calculated by density functional theory?DFT?method.The results show that the electron donating ability of the compound substituent Ar group has little influence on the geometric configuration.With the electron donating ability of Ar group for compounds?D-A-D/D-A-D'?increasing,the larger value of the first hyperpolarizability(?_tot)are aquired of the corresponding compounds.The direction of charge transfer from the ground state to the excited state of compounds is from the Ar group to the carborane.As the donating ability of the Ar group increasing,the compounds are red-shifted.When introducing the strong electron-donating substituents N,N-dimethylbenzene and methoxybenzene into the compounds,the obvious charge transfer and a small transition energy can be observed.Hence,the studied compounds have good NLO response.2.The NLO properties of the two-dimensional structure of carborane derivatives were calculated and analyzed by DFT method.The results show that changing compound substituents and increasing the length of the conjugated bridge have little effect on compound configuration.The polarizability value of the compound is proportional to the value of the electronic space range.As the length of the conjugated bridge increasing,the absorption spectrum will red-shift and the corresponding?_totot will enhance,which provide an effective way to get good NLO materials.When the electron-donating group?-CH₃,-OCH₃?were introduced on compounds,the?_totot values of the compounds are increase.The absorption spectrum of the compounds will red-shift.However,when the electron withdrawing group?-CF₃?was introduced into the compound,the?_totot values of the compound is reduced,and the absorption spectrum of the compound is blue-shifted.The system after increasing the conjugate bridge has a large?_totot value and is expected to be an alternative system for NLO materials.