Theoretical Study On Nonlinear Optical Properties Of Inorganic-Organic Hybrid Molecules Containing (Metalla) Carborane

Carboranes and metallacarboranes are a class of inorganic clusters with special molecular architecture and unconventional bonding through covalent bonds.Because of their rich variety,unique cage structure and high thermal and chemical stability,they have been widely used in many fields,such as biomedicine,environmental science,industrial production,photoelectric materials,etc.As always,in order to introduce their physicochemical characteristics into organic molecules and form the inorganic-organic hybrid functional derivatives with novel structures and excellent properties,the functional modification of?metalla?carborane?like,electrophilic and nucleophilic reaction at the B-and C-site,as well as coordination the metal center?has received a great deal of attention.In addition,due to their unique electron delocalization structure,high optical and thermal stability,easy functionalization,and good transparency in the ultraviolet region?the absorption wavelength of carborane is generally less than 200nm?,they have great potential to become a new type of inorganic-organic hybrid NLO material.To develop highly efficient and stable novel NLO materials,however,it not only need to seek the new breakthrough on the molecular structure design,but should also take a systematically study at the micro level for revealing the relationship between the structure and NLO properties.Therefore,the study of based on the quantum chemistry theory is especially importantIn this paper,the density functional theory?DFT?method,combined with analytical derivative,finite field?FF?and sum-over-states?SOS?approaches,are performed to present a systematic theoretical study of various carborane and metallacarborane derivatives.Calculations of geometric and electronic structure,absorption spectrum,electronic transition characteristic and hyperpolarizability density performed herein with the aim of rationalizing microscopic mechanism of NLO response at the molecular level and providing sufficient theoretical basis for designing efficient novel inorganic-organic hybrid NLO materials.The main obtained results of this work include:?1?A series of BODIPY/carborane/diketopyrrolopyrrole multi-component hybrid chromophores have been systematically studied by DFT and TD-DFT calculations.The second-order NLO response can be rationally optimized by the linear combination of basic functional modules,changing one-/two-dimensional geometric structure and carborane's different substituted position.And the relationship between the structure and NLO properties of such compounds was clarified.?2?A series of Pt?II?zwitterionic complexes containing closo-CB₁₁H₁₂ was studied.The difference of the second-order NLO properties between linear and V-shaped structures was explored.Furthermore,the effect of electron-donating and electron-withdrawing groups at the carborane cage on the first hyperpolarizabilities was examined.?3?We explore a novel design strategy which repeating the small individual sandwich unit?Et₂C₂B₄H₄?Fe??⁶-C₆H₆?through“series connection”mode for forming the multinuclear“staircase”oligomers.By changing the number of sandwich units in the molecule,the second order NLO response can be quantitatively regulated.In addition,the redox reaction give a significant influence on the relevant first hyperpolarizabilities,and further present a high-efficiency redox-triggered NLO switches.?4?A comparative investigation on the electronic structures and third-order NLO properties was performed between the 2D planar octagonal tetranuclear cobaltacarborane[??⁵-C₅Me₅?Co?2,3-Et₂C₂B₄H₃-5-C?C-7-C?C?]₄ and its 1D linear rod-like mono-/di-nuclear building blocks.Furthermore,because of the multipath of redox process,related molecules can also be used as efficient multistate controlled cubic NLO switches.