The Theoretical Study Of The Electronic Structures And Nonlinear Optical Properties Of Compounds Containing (Metallo) Carborane

Boron cluster compounds represent distinctive covalent species with a uniquemolecular architecture, nonconventional cluster bonding, and unusual chemistry. Dueto the rich variety, unique electronic structure, and excellent chemical stability,potential applications of this species are enormous, such as solvent extraction ofradionuclides, electrolyte, homogeneous catalysts, medicine, and so on. Addition ofhigh thermal stability, transparency in UV region, high delocalization and polarizableelectron, the boron cluster can be the candidate of nonlinear optical (NLO) materials.Especially, the NLO properties of polyhedral borane, heterborane andmetalloheterborane have been concerned and studied experimentally and theoretically.However, this respect is few and still in early stage. Importantly, one of core issues ofNLO materials is searching good methods to enhance the molecular second-orderNLO response and physical performance. With the development of multi-function ofNLO materials, the switchable effect becomes a research focus. For the boron cluster,especially the metalloheterborane, the electrochemical characters determine theirpotential ability on switchable NLO materials controlled by redox. Because the valueof hyperpolarizability is the criterion of measuring the NLO materials, rationalcomputational techniques and functionals are important for evaluating thehyperpolarizability. Based on the electronic properties and unique bonding of thepolyhedral carboranes and metallocarboranes, we will investigate the electronicstructures and NLO properties of this species to have an insight into the mechanism ofNLO responses. This work should provide rational theoretical reasons for optimizingthe NLO responses and further selecting the excellent multi-functional NLO materials,and guide the experimental synthesis.In the present thesis, designing and evaluating the NLO molecules containingcarborane or metallocarborane by employing density functional theory (DFT) andtime-dependent DFT (TDDFT) combined with finite field (FF) or analytic derivatemethods. The purpose of this thesis is that:(1) to understand the electronic structuresand properties of polyhedral carboranes and metallocarboranes.(2) to explore rationalDFT functionals to calculate the NLO responses of polyhedral carboranes andmetallocarboranes.(3) to obtain the switchable NLO molecules based on the experiment methods.The first part of this thesis is a review of skeleton structure, electronic structure,and related potential applications for boron cluster compounds, addition of theprinciple, experimental and theoretical studies of NLO property. The second part is anbrief introduction of computational methods calculating NLO coefficients, and somequestions needing attention on theoretical design of NLO materials. Subsequent partis the main body of this thesis, and it includes the following four sections:(1) We have designed a series of pull-push Cp*CoEt2C2B4H3-expanded(metallo)porphyrins compounds and employed DFT and TDDFT methods to calculatethe NLO properties. Due to the reversible redox of expanded (metallo)porphyrins, wehave also the NLO responses of reduced forms. To determine the rational functionalfor evaluating NLO coefficients, pure DFT, hybrid DFT, long-range (LC) DFTfunctionals and ab initio were used.(2) Two-dimensional (2D) NLO materials possess more excellent performancethan one-dimensional NLO materials. We thus designed a series of2D NLOmolecules containing sandwich metallocarborane Cp2Co2C2B3H5with D-?-A-?-D orA-?-D-?-A model. According to the positions of acceptor and donor, we named thestudied molecules as ?-and W-shaped and discussed their NLO responses.(3) Using DFT and TDDFT methods, we have theoretically investigated the NLOproperties of sandwich metallocarboranes [Ni(C2B9H11)2]. The rotation ofconfigurations of this species can be controlled by redox or photon excitation, andthus we studied the switchable effect on NLO response. To obtain a remarkableswitchable effect, we also explored the NLO responses of C, B-functionalizedderivates based on experimental synthesis.(4) A series of novel hybrid have been designed by organoimido bridging the(car)borane and hexamolybdate clusters. The electronic effects of the carboranylgroup depend on the position of the substituent in the carborane cage. We employedthe RESPONSE model in ADF program to calculate the second-order NLO responsesof studied compounds. The NLO properties of the hybrids were compared with that ofhexamolybdate-organoimido, and the differences between C-carboranyl andB-carboranyl on NLO responses were also discussed.