| In recent years,organic semiconductor materials have been deepening,and remarkable achievements have been made in the fields of organic electroluminescence,organic solar cells,organic field effect transistors,organic memory,sensors and so on.Organic luminescent materials have attracted more and more attention from scientists,due to their unique electronic structures and optical properties.Among them,organic multi-stimuli responsive luminescent materials possess important significance,owing to their structural adjustability and wide application prospects.These materials can be applied in various fields,such as,photoelectric devices,sensors,optical switches,storage and so on.Since organic luminescent molecular crystals have specific conformation and packing mode,an intuitive model based on the crystal structures can be provided to accurately study the relationship between the aggregation states and their luminescent properties.In this paper,distyrylanthracene was used as the basic framework,and pyridine group was introduced to it,obtaining a new material.The effects of different aggregation states on the photophysical properties of materials and the multi-stimuli fluorescent switching properties were studied.And the application of this kind of multi-stimuli smart material was preliminarily explored.In addition,carbazole substituted by benzophenone was used as the basic framework.By introducing different groups,novel room temperature phosphorescent materials were obtained and the photophysical properties of the materials with different aggregation states were studied.And the main research contents are as follows:1.Based on the research about the multi-stimuli responsive properties of 9,10-bis((E)-2-(pyridin-3-yl)vinyl)anthracene(BP3VA)11b in our group,we designed and synthesized a novel molecule 9,10-bis-((E)-4-(pyridin-3-yl)styryl)anthracene(BP3SA)by introducing benzyl groups into BP3 VA,in order to increase the conjunction degree,regulate the emission color and the response to pressure.Two polymorphs(G-phase and O-phase)based on BP3 SA were obtained by using solvent evaporation method.Piezochromic properties,structural transitions,together with the protonation-deprotonation effect were investigated for the two polymorphs.G-phase with J-type aggregation possesses high photoluminescent quantum yield(PLQY),0.98,while O-phase with H-type aggregation presents 0.48 for PLQY.Upon grinding,the ground samples show red-shifted emissions.Upon further heating,the ground samples can partly recover their initial emissive colors.According to PXRD and DSC data,a structural transition from O-phase to G-phase appears during grinding and further heating processes.In order to further understand the piezochromic behaviour of the two crystals,the effect of hydrostatic pressure on the luminescence of BP3 SA was investigated.Less various intermolecular interactions in O-phase are beneficial to a higher sensitivity to the hydrostatic pressure.The protonation-deprotonation effect of the two crystalline phases is investigated,due to the existence of pyridyl groups which can be response to acid.The result reveals that destruction of various C-H···N bonds in G-phase results in more distinct luminescent switching of G-phase than that of O-phase under acid and alkali stimuli.2.Two carbazole derivatives,CMTPM and CFMTPM,were synthesized by molecular design.CFMTPM is a typical D-A structure molecule.Due to the introduction of the trifluoromethyl group,the charge distribution in the molecular orbital of the material were different,which reduces the energy between singlet and triplet states in CFMTPM.Crystals of two materials were successfully obtained.From the photoluminescent spectra,we can see that both materials were fluorescent-phosphorescent dual-channel emission.The difference was that CMTPM crystals showed strong phosphorescent emission and weak fluorescent emission,while CFMTPM crystals possessed strong fluorescent emission and weak phosphorescent emission,which was caused by the introduction of trifluoromethyl groups.The phosphorescent lifetime of CMTPM crystal was 404 ms,and that of CFMTPM crystal was 830 ms.Crystal structure analysis showed that there was strong ?···? interactions between adjacent molecules in CMTPM crystal and there is no ?···? interaction between adjacent molecules in CFMTPM crystal,but there was molecular coupling between carbonyl group and benzene ring in carbazole.In addition,due to the introduction of trifluoromethyl,there were more abundant weak interactions between adjacent molecules in CFMTPM crystals,which made CFMTPM crystals have a longer phosphorescent lifetime,830 ms.Temperature was one of the factors affecting the emission intensity of room temperature phosphorescence.The results shown that the molecular movements were restricted at low temperature,which reduced the non-radiative transition channels,leading to the increasement of the emission intensity and lifetime of room temperature phosphorescence. |
PDF Full Text Request