Multi-stimuli responsive fluorescence switching of D-A tetraphenylethylene functionalized cyanopyridine isomers

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.

Photoinduced E to Z isomerization of tetraphenylethylene derivatives within organometallic supramolecular assemblies

Isolation of E-1,2-bis(4-bromophenyl)-1,2-diphenyl-ethylene from the E/Z isomer mixture obtained by a McMurry coupling reaction and reaction of this isomer with imidazole followed by N-alkylation with nBuBr and anion exchange yielded the bisimidazolium tetraphenylethylene (TPE) derivative H2-E-1(PF6)2. The reaction of H2-E-1(PF6)2 with Ag2O yielded the di-nuclear metallarectangle [Ag2(E-1)2](PF6)2 where the two bis-NHC donors E-1 bridge two silver atoms. Irradiation of [Ag2(E-1)2](PF6)2 leads to E/Z isomerization of the di-NHC ligand and formation of Z-1 in the mononuclear complex [Ag(Z-1)]PF6. Demetallation of the di-NHC ligand with NH4Cl/NH4PF6 yielded bisimidazolium salt H2-Z-1(PF6)2. The unique isomerization of the E-TPE derivative into its Z-isomer via metal complex formation/irradiation/demetallation cannot be achieved by irradiation of the individual imidazolium salt. The emissive properties of the TPE complexes [Ag2(E-1)2](PF6)2 and [Ag(Z-1)]PF6 have been investigated.

Palladium-Catalyzed Direct Mono- and Diarylation of Diphenydithienylethenes: A Useful Method for Enhancing Fluorescence Intensity and Aggregation-Induced Emission

In this study we report efficient method for the syntheses of mono- and diarylated diphenyldithienylethene (DPDTE) via a palladium-catalyzed C–H arylation reaction. These new derivatives showed amplified luminescent properties thanks to a change in polarity, particularly in the presence of an electron-withdrawing groups (EWG). Moreover, the arylated DPDTEs showed dual-emissive phenomena, including fluorescence in organic solvents and aggregation-induced emission.

D–A type luminophores with a twisted molecular conformation constructed by phenoxazine and diphenylsulfone showing high contrast mechanofluorochromism

Two new stimulus-response luminescence materials PXZ-DPS and BPXZ-DPS possessing the twisted molecular conformation exhibit a unique ICT effect, effective solid-state fluorescence, and high-contrast and reversible mechanofluorochromism.