Design, Synthesis And Properties Of Asymmetric Organic Boron Complexes And Their Ligands

Mechanochromic materials are a rapidly growing class of materials.As a stimulus-responsive material,mechanochromic materials have attracted increasing attention in recent years owing to their promising potential for applications in mechano-sensors,nondestructive detection,memory chips and data storage.AIE luminogens have become an important source of mechanochromic materials.Polymorphisms are conducive to the multifunctionalization of chromophores.Further,polymorphism provides a high-efficient and low-cost method to realize multicolor conversion.Manipulating crystalline states to achieve polymorphisms to obtain mechanochromic materials is a top priority.The main design of this thesis is to synthesize asymmetric ?-diketones and organoboron complexes,and studied the multicolor conversion and internal mechanism through crystal culture.The main tasks are as follows:1.Tradition ?-diketones are rarely used as fluorescent emitters and mechanochromic materials.Here,TPED2 F and TPED2 T with tiny structural differences(Furan unit and thiophene unit)and asymmetric ?-diketones were designed and synthesized.Both of them show abnormal solvatochromism,water-sensitive fluorescence emission,marked aggregation-induced enhanced emission(AIEE)activity and high-contrast mechanochromism.In addition,ground TPED2 F show reversible mechanochromism by heating.The abnormal solvatochromism and water-sensitive fluorescence emission are attributed to enol-keto tautomerism and solvent polarity induced conformation changes of excited states,while heavy atom effect and wide band gap respectively lead to inferior quantum efficiency and hypsochromic-shift emission for crystal TPED2 T compared with TPED2 F.Moreover,excellent crystallization ability and close melting point before/after grinding endow TPED2 F with thermal reversible mechanochromism.2.Based on the basis of the previous chapter,we successfully constructed two highly distorted conformational agents,TPE-BF and TPE-BT,by introducing benzyl bromide to TPED2 F and TPED2 T.They also exhibit abnormal solvent discoloration,water-sensitive fluorescence emission,AIE activity,and force-chromic properties.The abnormal solvent discoloration does not have the enol-ketone tautomerism,which is attributed to ? substitution that inhibits the enol-ketone tautomerism and results in more molecularly distorted configurations.Here,we tend to attribute the abnormal solvent discoloration to the complex interaction between solute and solvent.In TPE-BT crystals,ethyl acetate is selectively embedded,which highly distorted molecular configuration facilitates molecular recognition and solvent purification.In the TPE-BT crystal,one ethyl acetate molecule and two TPE-BT molecules form C–H ? C(2.388? and 2.779?)and C ? C(3.313?)intermolecular hydrogen bonds and weak interactions.3.In order to obtain polychromatic conversion materials and explore the inherent mechanism of polymorphism,this chapter designs and synthesizes six difluoroboron ?-diketone compounds based on molecular isomerism and AIE theory.Although TPEB2 F and TPEB3 F have similar solvent-induced discoloration and AIE characteristics,they exhibit high-contrast polymorphism and mechanochromism.In the same solvent environment,only one crystal 2R of TPEB2 F was obtained,but four different crystals 3S,3R,3N,and 3F of TPEB3 F were obtained.Similarly,we obtained crystals of TPEB2T(2O)and TPEB3T(3Y and 3O).However,crystal analysis,hypothesis construction and theoretical calculations show that the main factors for the formation of polymorphic states depend on the dipole moments of the stacked molecular pairs and the culture solvent.