Synthesis And Properties Of Mechanochromic Materials Accompanied By Aggregation-Induced Emission Phenomenon

Organic fluorescent materials have been extensively investigated as an important class of photoelectric materials and have been utilized in fields of OLEDs,OLEFET,organic solid-state lasers and organic fluorescent sensors.In these organic photoelectric devices,luminophors are usually used in aggregated or solid state like thin films and nano structures.Moreover,the complicated photophysical properties of the luminophors in condensed or solid state can hardly be explained with the theories based on isolated molecular spectrum due to packing modes,configuration and intramolecular interaction.There still exists aggregation-caused quenching problem,which caused by the dipole-dipole interaction in the π-π overlap.How to solve the high fluorescence quantum efficiency under the state of aggregation and long fluorescent life is a difficult point of solid organic luminescent material.This paper focuses on discussing the high fluorescence quantum efficiency and long-time fluoscent life of mechanochromic material.Part 1: Design and synthesize TPAN-C2 and TPAN-C3 with TPAN unit for nuclear,another structure unit is carbazole（rigid plane structure）.After grinding,their colors changed from sky-blue to light green,45 nm and 38 nm reshift,respectively.Ground powers can restore to its original color by fuming with ethol or heating under 100°C.TPAN-C2 and TPAN-C3 showed typical aggregation-induced fluorescence enhanced properties.As-prepared powders fluorescence quantum efficiency reached 0.78 and 0.97;Part 2: a twisting donor-acceptor（D-A）molecule with triphenylamine（TPA,as a donor）and diphenylacrylonitrile（DiCN,as an acceptor）were reported.Under the static pressure（0-10GPa）,its color changed from blue（508nm）to blood-red（654nm）,146 nm reshift.Ground powders color can restore to its original color by fuming with ethol or heating under 120°C.As-prepared powders fluorescence quantum efficiency reached 0.826 and its fluoscent life reached 25.7ns.Part 3: X-shaped D-A molecule DCF₃-TPA was designed and synthesized.Results show that DCF₃-TPA has significant piezochromic properties.After grinding,its colors changed from orange yellow（601nm）to red（634nm）,33 nm reshift.Ground powders color can restore to its original color by fuming with ethol or heating under 120°C.WXRD experiments show that the phase transformation in the process of grinding,namely from order crystal to disorder amorphous.