Synthesis And Properties Of Luminescent Materials Contanining Acrylamide Derivatives

Organic solid state luminescent materials have attracted more and more attentions due to excellent photoelectric properties and extensive application prospect. In addition, earlier studies suggested that there were important relationships between molecular packing modes and luminous properties. For example, morst Organic solid state luminescent materials with H-aggregate dramatically decreased the luminescence quantum yield in the solid state(films and crystal). Because the inter dipole interaction along their long axis induced the nonradiative decay of exciton. Recently, knowledge of the role of molecular packing in controlling luminous properties of Organic solid state luminescent materials have been utilized for exploring stimuli-responsive material, where the fine-tune molecular packing modes were achieved by an external stimulus including pressure, heat and solvent vapor. At present, however, the number of organic dyes exhibiting piezofluorochromism was still limited, due to lack of full understanding of the piezochromic mechanisms at the molecular-level. Thus, It was of great significance and challenge to investgate the molecular packing modes and intermolecular interactions for obtaining the practical stimuli-responsive material. A series of novel organic Organic solid state luminescent materials containing aromatic amine were desighed and synthesized. Then the relationship among external factor(heating, pressure and solvent vapor), molecular packing modes and luminescent properties was systematically investigated.In Chapter 2, three structural-simple o-MPCPA, m-MPCPA and p-MPCPA were synthesized. Among structural isomer, the m-MPCPA and p-MPCPA samples with a blue fluorescence exhibited remarkable MCF properties. Its fluorescence was changed into green under the grinding treatments. Upon fuming processing with the solvent vapours such as the CH2Cl2 and ethyl acetate, the luminescence recovered its original state. For the o-MPCPA, the phase transition also underwent an obviously change upon grinding, but the MCF behaviour was not observed. To further investigate the MCF behaviours, differential scanning calorimetry(DSC) and powder wide-angle X-ray diffraction patterns(PXRD) of MPCPA(o-, m-, p-) powders in various states were performed. They could be attributed to the transformation from the crystalline phase to the amorphous phase. What were the reasons causing the “abnormal” phenomenon? In the crystalline state and The experiment of time-resolved ?uorescence further verified the proposal. The interplanar distance was effectively reduced upon grinding, which had been demonstrated in other MCF molecules. However, the decrease in distance did not lead to the enhancing of π-π interactions. In sharp contrast, as for m-MPCPA and p-MPCPA with the head-to-head packing, the intermolecular interaction between the adjacent aromatic rings was enhanced result from the excitonic coupling. And such strong π-π interactions of the neighbouring molecules blocked the decay of the excited species through radiative pathways. So there was an obvious spectral shift upon grinding.In Chapter 3, the 3,4-MPCPA sample exhibited more remarkable MCF properties. The emission spectrum of the 3,4-MPCPA powder(λmax = 487 nm) shows blue fluorescence. Once the powder has been ground using a pestle and mortar, a significant red-shift(λmax = 503 nm) occurs. To further investigate the MCF behaviours, differential scanning calorimetry(DSC) and powder wide-angle X-ray diffraction patterns(PXRD) of 3,4-MPCPA powders in various states were performed. They could be attributed to the transformation from the crystalline phase to the amorphous phase. The results indicated that the π-π interaction was further enhanced, which blocked the radiative deactivation pathways. the intermolecular interaction between the adjacent aromatic rings was enhanced as a result of the excitonic coupling. Such strong π-π interactions between the neighbouring molecules blocked the decay of the excited species through radiative pathways, resulting in the altering of the excited state as well as the weak Φf of 3,4-MPCPA. After being fumed by acetic acid(CH3COOH) or hydrochloride(HCl) vapor, the powder exhibits a yellow emission and the peak is shifted to 520 nm under 365 nm UV illumination. After being fumed with DMF vapor, the original green light exhibited by the powder was recovered. According to the theory of frontier molecular orbits, the delocalization of the electron cloud is beneficial for stabilizing the molecular excited state, resulting in a decreased band gap. Consequently, the delocalization of the LUMO stabilizes the excited molecule at a lower band gap, leading to red-shifts in the emission and absorption of the 3,4-MPCPA samples.Finally, single crystals of MPCPA-B(ΦF = 24 %)and MPCPA-G(ΦF = 15 %)were obtained by slow evaporation of ethanol/n-hexane mixtures and ethanol, respectively. To further investigate the MCF behaviours, powder wide-angle X-ray diffraction patterns(PXRD) of MPCPA-B(ΦF = 24 %)and MPCPA-G(ΦF = 15 %)single crystals in various states were performed. The crystals of MPCPA-G emitted green light(λmax = 468 nm) under the UV lights, which was changed into blue(λmax = 489 nm) under the grinding treatments. Its fluorescent the same the MPCPA-B. Upon fuming processing with the solvent vapours such as the DMF, the luminescence recovered its original state. The “abnormal” phenomenon remains to be proved.