Multistimuli-Responsive Fluorescent Switching Of Anthracene-Substituted Diamide Derivatives

Organic fluorescent materials have extensively researched and applied in mechanical,temperature,gas sensors,bioimaging,optical information storage and other fields due to their unique tunable and efficient luminescence properties.The obvious changes in physical and chemical properties of these materials can be caused by the stimulation of outside environment.Thus,stimuli-responsive organic fluorescent materials have always been a hot topic for researchers.In this thesis,the anthracene-substituted diamide derivative（4-ENS and 3,4-ENS）have been designed and synthesized,and their liquid crystalline properties,organogel as well as light,force and thermal stimulus-responsive properties have been studied in detail.1.A novel 4-（4-（dodecyl））phenyl-2-anthracylamide derivative（4-ENS）with a dodecyloxy substitution was designed and synthesized.4-ENS exhibits mechanofluorochromism and liquid crystalline properties.4-ENS emits blue light and the luminescence color of ground sample changed into bluish-green.The luminescence color emission could be recovered to the orginal color by annealing or heating.The SEM of 4-ENS exhibited sheet morphology.In contrast,the ground sample showed irregular nature.The FT-IR spectra showed that theν_N-H andν_c=o=o became obviously widen after grinding,which indicated that the intermolecular hydrogen bonding weakened obviously after grinding.The XRD results displayed well-ordered crystal structure of the original sample,and the diffraction peaks were almost completely disappeared of the ground sample indicated the amorphous nature.DSC result also showed that the obviously disordered structure after grinding.Thus,the transition from well-ordered crystals to metastable disordered aggregations is the possible main reason for the mechanofluorochromism.Moreover,The results of DSC,POM,XRD indicated that 4-ENS exhibited monotropic SmA with focal conic fan-like texture on first cooling.2.4-（3,4-（dodecyl））phenyl-2-anthracylamide（3,4-ENS）with two dodecyloxy substitution was designed and synthesized.3,4-ENS can form stable organogels in DMSO,cyclohexane,1,2-dichloroethane et al.The DMSO organogel emitted weak blue fluorescence whereas the cyclohexane and 1,2-dichloroethane organogels emitted bright pale blue fluorescence,and the cyclohexane and 1,2-dichloroethane organogels exhibited gelation-induced enhanced fluorescence emission.The XRD patterns and UV-Vis absorption can further show that the different fluorescences in different organogels are induced by molecular self-assembly structures.The1,2-dichloroethane organogel can change into solution and the fluorescence quenched under photo-irradiation.The ¹H NMR and mass spectra showed that photo-responsive behaviors is due to the anthracene rings photocycloaddition upon visible light irradiation,destroyed the main driving force of gel formation,resulting in gel collapse and fluorescence quenching.3.The DMSO xerogel of the 3,4-ENS exhibits machanofluorochromism,and thermochromism.Upon grinding the DMSO xerogel,the fluorescent emission changed from blue to yellowish-green.The absorption spectra after grinding indicated that the overlap of anthracene groups andπ-πinteraction was stronger than that in the xerogel.The XRD pattern of the DMSO xerogel displayed some strong sharp diffraction,indicating the ordered structure.For ground sample,the diffraction peaks were almost completely disappeared,indicating the amorphous nature after grinding.Thus,the transition from well-ordered crystals to metastable disordered aggregation is the main reason for the mechanofluorochromism.When the DMSO xerogel was heated at 110℃for 1min,the fluorescent emission changed from blue to yellowish-green.The FT-IR spectra of heated sample exhibited that part ofν_C=O=O bands shifted to higher wavenumber and theν_N-H bands widened and weakened,which indicated that the intermolecular hydrogen bonding interaction weakened upon heating.The XRD pattern of the DMSO xerogel showed several sharp strong diffraction peaks,indicated a well-ordered structure.For heated sample,only one strong diffraction peak appeared.Thus,the aggregated structure changed from the ordered crystalline state to the relatively poor ordered state is the possible reason for the thermochromism features.