Design,Synthesis And Mechanochromic Property Of A New Type Of Difluoroboron ?-diketonate Complexes

Mechanochromic fluorescent materials are a class of ‘‘smart'' materials,which can undergo the reversible change of fluorescence wavelength and intensity under external force stimulus.In recent years,it has attracted more and more attention because of its potential application in information storage,trademark security and micro-stress sensing.Organic boron complexes have become a class of important molecular systems in the field of stimuli response materials with their unique photochemical and photophysical properties.The tetraphenylethylene(TPE),which is a typical aggregation induced emission(AIE)material,and have the advantages of twisted conjugate structure and high solid-state luminescence efficiency.In this thesis,a series of TPE derivatives were synthesized by the addition of TPE to difluoroboron ?-diketonate complexes,different types of substituents are introduced by chemical modification.The AIE performance and force stimulus response property of these TPE derivatives were studied.The main contents of this thesis are as follows:In the first chapter the photophysical processes of excited molecules,the aggregation induced emission properties are briefly introduced.The latest progress of the application of TPE-based luminescent materials,the application of organoboron complexes and the organic luminescent change materials are reviewed.In the second chapter,we designed and synthesized a series of TPE-containing difluoroboron ?-diketonate derivatives based on halogen effect,which mainly studied the photophysical properties,AIE property and Mechanochromic properties.The results show that the target molecular has good AIE performance.The target compounds also exhibit excellent Mechanofluorochromic property,the results show that the reversible transformation of the crystalline state to the amorphous state take place in target compounds,leading to the Mechanofluorochromic phenomenon.Meanwhile,we propose that the grinding-induced emission wavelength red-shift is due to the planarization of molecular twist conformation under pressure,which increases the degree of conjugation of the molecules,and eventually leads to the widening of the absorption spectrum and the red shift of the emission spectrum.In addition,we found that compound TPEDKBF2 Br exhibit fluorescence self-recovery property,and we hypothesize that the fluorescence self-recovery property is due to the excellent crystallization performance.In the third chapter,we explored the effect of alkyl chains on the fluorescence properties of parent molecular,and studied their AIE performance and Mechanofluorochromic property.The results show that the five compounds have good AIE performance.The crystals of TPEDKBF2 OMe,TPEDKBF2OBu,and TPEDKBF2 OHe have tensile(isotropic force)induced emission blue shift and fluorescence enhancement properties,and we find that the blue shift of fluorescence emission wavelength and fluorescence enhancement are due to the fact that the tensile force destroys the originally closely packed crystals,so that some of the intermolecular interaction in the crystal are released to form a more loose microcrystals.In addition,five compound all display emission wavelength red shift under the anisotropic force.Meanwhile,the thermodynamic performance study also found that with the growth of the alkyl chain,the response of the target molecule to temperature gradually increased,so the modification of the alkyl chain could regulate the AIE molecules on the temperature response.Finally,we find that long alkyl chains make it possible to form many large cavities when arranged in a single crystal by analyzing the single crystals,so that the cultured crystals are relatively easy to covert to amorphous state under external forces.In the fourth chapter,three compounds with dimethylamino group,dibenzylamino group and carbazolyl group were synthesized.The effects of rigid nitrogen-containing groups and flexible nitrogen-containing groups on the luminescence efficiency and solid state Mechanofluorochromic property of target molecules are invested.The results show that the compound TPEDKBF2 Ca has good AIE performance and also shows the mechanical-induced fluorescence red shift property,but the wavelength red shift before and after grinding is small,indicating that the low-contrast Mechanofluorochromic property.The TPEDKBF2 DMeA has good fluorescence efficiency in solution(45.5% in toluene),but only 18.8% in the crystal state,showing the properties of aggregation induced fluorescence quenching(ACQ)effect,its Mechanofluorochromic property also poor,the emission wavelength only red shift 10 nm before and after grinding.TPEDKBF2 DBeA exhibits DSE characteristics.In the aspect of Mechanofluorochromic property,the phenomenon of griding-induced blue shift was demonstrated.It was concluded that the molecular alignment of the compound in the crystal phase was closely and the degree of conjugation was large.However,in the amorphous state,the molecular conformation is distorted,and the overall conjugation is decreased,so display fluorescence blue shift property.In addition,the crystalline of the compound is poor,and it can not be changed from an amorphous state to a crystalline state by heating or solvent fuming,and thus does not have a reversible Mechanofluorochromic property.