Triphenylamine-based small molecules with aggregation-induced emission and mechanochromic luminescence properties for OLED application

Investigation of Mechanochromic Luminescence of Pyrene-based Aggregation-Induced Emission Luminogens: Correlation between Molecular Packing and Luminescence Behavior

To better understand the correlation between molecular structure and optical properties such as aggregation-induced emission (AIE) and mechanochromic luminescence (MCL) emission, two new pyrene-based derivatives with substitutions at the 4- and 5-positions (1HH) and at the 4-, 5-, 9-, and 10-positions (2HH) were designed and synthesized. Cyano groups were introduced at the periphery of the synthesized compounds (1HCN, 1OCN, 1BCN, 2HCN, 2OCN, and 2BCN) to investigate the influence of these groups on the emission properties of the pyrene derivatives both in solution and in the solid state. The fluorescence emission performance of these compounds in water/acetone mixtures was simultaneously studied, revealing outstanding aggregation-induced emission properties. The typical shift in emission maxima to higher values was attributed to J-aggregate formation in the aggregate state. Careful investigation of the crystal structures demonstrated abundant and intense intermolecular interactions, such as C-H…π and C-H…N hydrogen bonds, contributing to the remarkable mechanochromic luminescence performance of these compounds. The MCL properties of all the compounds were investigated using powder X-ray diffraction, and the remarkable mechanochromic properties were attributed to J-aggregate phenomena in the solid state. These results provide valuable insights into the structure-property relationship of organic MCL materials, guiding the design of efficient organic MCL materials.

Synthesis and Performance of Imide-Based Small Molecules Containing Carbazole Groups with AIE Properties

Here, two novel naphthalimide derivatives SNI-Cz and SNI-DCz with AIE were designed and synthesized. The correctness of the two structures was characterized by NMR and HRMS. Their crystal structures, photophysical properties, electrochemical properties, thermal stabilities, fluorescence lifetime and yields have been characterized. Photoluminescence experiments revealed that SNI-DCz had superior properties due to the D-π-A-π-D structure and sliding away stacking of molecules. SNI-DCz exhibited weak fluorescence in pure DMF, with a significant AIE effect observed in the 40% water mixture and a sharp increase in fluorescence intensity was also observed. Cyclic voltammetry and thermogravimetric analysis indicated that SNI-DCz had good electron affinity and thermal stability. The excellent properties of SNI-DCz made it a promising emitter for optoelectronics.

Tuning Photophysical Properties via Positional Isomerization of the Pyridine Ring in Donor-Acceptor-Structured Aggregation-Induced Emission Luminogens Based on Phenylmethylene Pyridineacetonitrile Derivatives

A series of aggregation-induced emission (AIE)-featured phenylmethylene pyridineacetonitrile derivatives named o-DBCNPy ((Z)-3-(4-(di-p-tolylamino)phenyl)-2-(pyridin-2-yl)acrylonitrile), m-DBCNPy ((Z)-3-(4-(di-p-tolylamino)phenyl)-2-(pyridin-3-yl)acrylonitrile), and p-DBCNPy ((Z)-3-(4-(di-p-tolylamino)phenyl)-2-(pyridin-4-yl)acrylonitrile) have been synthesized by tuning the substitution position of the pyridine ring. The linkage manner of the pyridine ring had influences on the molecular configuration and conjugation, thus leading to different photophysical properties. The absorption and fluorescence emission peak showed a bathochromic shift when the linking position of the pyridine ring changed from the meta to the ortho and para position. Meanwhile, o-DBCNPy exhibited the highest fluorescence quantum yield of 0.81 and the longest fluorescence lifetime of 7.96 ns as a neat film among all three isomers. Moreover, non-doped organic light-emitting diodes (OLEDs) were assembled in which the molecules acted as the light-emitting layer. Due to the relatively prominent emission properties, the electroluminescence (EL) performance of the o-DBCNPy-based OLED was superior to those of the devices based on the other two isomers with an external quantum efficiency (EQE) of 4.31%. The results indicate that delicate molecular modulation of AIE molecules could endow them with improved photophysical properties, making them potential candidates for organic photoelectronic devices.

AIEE compounds based on 9, 10-dithienylanthracene-substituted triphenylamine: design, synthesis, and applications in cell imaging

Four new 9, 10-dithienylanthracene-based triphenylamine derivatives (TPA-DTAs) were designed and synthesized by adjusting the linkage model of phenylacetonitrile group with different substituents. They all displayed aggregation-induced emission enhancement (AIEE) features...