Photoluminescence And Mechanical Propertiesof β-cyanostilbene Single Crystals

In recent decades,organic solid emission materials have been applied in organic light-emitting diodes,organic solid-state lasers bio-imaging,sensors,and so on for their advantages on synthesis and cost.Besides raising emission yield of the materials,developing their special characters outside emission is a key direction in optimization of organic solid emission materials.As one of such material,organic flexible emission crystals have aroused major attention from researchers for their compensation of the disadvantage that traditional organic crystals are usually brittle and potential application on flexible device.In this thesis,two simple organic small molecules were designed and their crystals whose relations between macroscopic character and microscopic structure were investigated by a series of test such as three-point bending test,spectrum and single crystal X-ray diffraction were synthesized.The investigation provided new ideas for designation of organic emission materials possessing certain property.Furthermore,investigation on their waveguide and polarized emission property was also carried out.In the second chapter,started with 2,5-dimethoxyterephthalaldehyde,2Z,2’Z)-3,3’-(2,5-dimethoxy-1,4-phenylene)bis(2-(3-(trifluoromethyl)phenyl)acrylonit rile),DPBTFPA,was successfully synthesized and by recrystallization rod-like crystals which possessed elastic bending and plastic twisting property simultaneously were obtained.Single crystal XRD data indicates crystal possesses layer structure which grows along b axis by π…π stacking and F…F interaction and connects each other by C-H…F interaction.Differences between the strength of intralayer and interlayer interaction and natural distinction between bearing stress and shearing stress contribute the difference of recoverable ability between bending and twisting.In addition,the flexible waveguide ability and polarized emission property were also studied.The properties rendered the crystal potentially useful in flexible optical device.In the third chapter,DPBTFPA analogue(2Z,2’Z)-3,3’-(2,5-dimethoxy-1,4-phenylene)bis(2-(3-nitrophenyl)acrylonitrile),DPBNPA,was successfully synthesized and red long rod-like crystals R and orange plate-like crystals O were obtained by controlling recrystallization condition.The two crystals were proven to be polymorphs by hydrogen nuclear magnetic resonance spectroscopy.With diameter being over 100μm,crystal R still possesses good elastic bending property.Single crystal XRD data show that crystal R has similar structure with that of DPBTFPA crystal but with more abundant intermolecular interaction which explained its better elasticity.Single crystal XRD data of crystal O show that molecules are less planar and layer structure formed by π…π interaction is absent in crystals,which explained differences in morphology,thermodynamic stability,optical and mechanical property between crystals of two polymorphs.In addition,both crystals possess polarized emission property and crystal R can conduct flexible waveguide.The properties rendered the crystal potentially useful in polarized emission device.In conclusion,we successfully synthesized two organic molecules with highly efficient emission and prepared their flexible crystals.We investigated flexible deformation and polymorphism of the crystals and illustrated the relation between microscopic structure and macroscopic property by characterization of crystal structure.Our research would provide new idea and strategies for the designation of organic small molecular materials with certain function.