Synthesis And Properties Of Luminescent Chiral Carborane Compounds

Chiral luminescent materials have received attention due to their unique properties and have wide applications in chiroptical switches,liquid crystal displays,nonlinear optics,and fluorescent probes.Chiral luminescent materials mainly include metal complexes,polymers,small organic molecules,inorganic materials,etc.The chiroptical properties are characterized by circluar dichroism（CD）and circularly polarized luminescence（CPL）spectroscopy,etc.Two important parameters to measure the performance of CPL materials are the luminescence dissymmetry factor(g_lum)and quantum efficiency.Small organic molecules usually have high luminescence quantum yields,but their g_lumvalues are often very small.Therefore,it is important to design and synthesize chiral organic compounds with both bigger luminescence quantum yields and large g_lum.The main purpose of this work is to combine the organic chromophore anthracene or tetraphenylethylene,the chiral group tert-butylsulfinamide,and the emission regulating unit o-C₂B₁₀H₁₂（cluster compound which has 3D geometry and C/H/B vertices）to synthesize a series of chiral luminescent carborane compounds by a simple synthesis method and to investigate their structures and optical properties,especially the regulating effect of carborane on the optical property.The main research results are as follows:1.Synthesis and optical properties of bridged carborane-anthracene compoundsThe reduction of carborane Schiff base 9-anthracenylene 1-amino-o-carborane（1）led to the corresponding product 2.The carboranylanthracenylmethanol（3）was obtained by the reaction of o-carborane and 9-anthracene formaldehyde in the presence of butyllithium or tetrabutylammonium fluoride.The photophysical properties（absorption,emission,luminescence quantum yield and lifetime）and mechanochromic properties of compounds 1-3were studied.The results show that compounds 1-3 are dual-state emission luminogens both in solution and in solid state,and the tetramer structure in crystalline 2 with multipleπ…πinteractions between anthracene rings leads to the excimer emission.The luminescence of solutions and solids of 2 and 3 mainly shows the property of locally excited state of anthracene,whereas in THF/H₂O（98%water fraction）,it shows excimer emission.Compound 3 has two crystal forms,i.e.3’（dichloromethane-free）and 3（dichloromethane-bound）,both of which have vapochromic properties.After grinding or fumigation with ethyl acetate,the luminescence of 3 is red-shifted and shows the excimer emission property.The results from compounds 1-3 provides a simple strategy for studying carborane dual-state emission compounds,and fine-tuning the luminescence and stimulus response of carborane compounds.2.Synthesis and properties of chiral carborane-anthracene compoundsChiral anthracene imine compounds were obtained by the condensing 9-anthracene aldehyde and（R/S）-tert-butylsulfinamide with a sulfur chiral center,and chiral carborane-anthracene compounds 6 and 7 were obtained by the addition reaction of the imine with carboranyllithium.The photophysical properties show that both compounds are dual-state emission luminogens,and the quantum yields（6:49.21%,7:48.03%）are much higher than those of the starting imines（4:0.50%,5:0.60%）.The compounds in THF-H₂O（98%water fraction）shows the excimer emission.The circular dichroism spectra of the solutions of6 and 7 show the characteristic mirror image.Both the solution and solid of 6 exhibit CPL signals,and the g_lumvalues are+7.69×10^-4and+1.0×10^-3,respectively.3.Synthesis and properties of chiral carborane-tetraphenylethylene compoundsChiral imine compounds were obtained by condensation reaction of tetraphenylethene-based aldehydes with chiral tert-butylsulfinamide,and chiral carborane-tetraphenylethylene compounds were obtained by addition reaction with carboranyllithium.The structure and optical properties of the compounds were studied.The results show that the chiral carborane compounds have aggregation-induced emission effect,and their luminescence quantum yield（12:50.89%,13:51.90%,14:60.88%,15:57.69%）is greatly improved（8、9:2%,10、11:4%）.Compared with the solution,the intensity of CD signals of the aggregates is weakened,and the peaks are broadened and red-shifted.The g_lumof the solid of fluorinated carborane-tetraphenylethylene compound 13 is+7.0×10^-4.In this thesis,the design and synthesis of（chiral）luminescent bridged carborane compounds,the fluorescence properties of the solutions,solids and aggregates,the stimuli-responsiveness,the CD and CPL property,were studied,which provide useful information for synthesizing chiral carborane compounds and regulating the（chiral）optical properties of these functional carborane compounds.