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Most luminophores often suffer from the problem of aggregation-caused quenching (ACQ) or fluorescence disappearance in dilute solution. It is significant to bridge the gap between ACQ and AIE. In this work, a facile but effective strategy was proposed for the fabrication of always-on luminophores based on the excited state intramolecular proton transfer (ESIPT) mechanism, and six luminophores emitting bright fluorescence in solution, aggregation and solid states were synthesized from 5-tert-butyl-2-hydroxyisophthalaldehyde. All these ESIPT systems show only keto emission owing to their congested structures which block the breakage of intramolecular hydrogen bond (O-H⋯N) by solvation, and subsequently make enol emission impossible. Three of these luminophores are prone to convert into the corresponding phenolate anions emitting blue-shifted emission, which enable them to sense pH variation in the weakly basic range. Furthermore, white-light emission was achieved by combining two of them which show complementary-color fluorescence, and one of them was utilized for bioimaging of living Hela cells and the high-resolution image was obtained., (© 2024 IOP Publishing Ltd.)

The excimer emission based on discrete π-stacked dimers of polycyclic π-systems has generated significant interest in the structure-luminescence relationship of excimers owing to their ultra-large Stokes shift. Herein, a series of excimer emissive luminogens were obtained by conjugating different polycyclic aromatic aldehydes (anthraldehyde, pyrenealdehyde and perylenealdehyde) with triphenylmethylamine. In crystalline states, all the molecules were arranged in the form of π-stacked arene dimers which were spatially isolated from each other by the bulky triphenylmethyl groups, and thus emitted bright excimer emission. The anthracene and pyrene derivatives showed fluorescence enhancement responses to grinding and the enhanced fluorescence could recover to the original state upon heating. The aggregation-induced emission (AIE) properties of them were dependent on the shapes and sizes of the polycyclic aromatic groups. The pyrene derivative showed the most excellent excimer-based AIE behavior among them. All of them were more apt to exhibit the excimer emission when formed nanoparticles with pluronic F-127 than that without pluronic F-127. Furthermore, PETP was utilized for bioimaging of living Hela cells and the high-resolution image was observed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A series of 3-aroylbenzocoumarin-based luminogens have been synthesized for investigating their aggregation-induced emission (AIE) and solid-state fluorescence. The single crystal X-ray diffraction analysis of one of them showed that the molecules are arranged in the form of π-dimers which may lead to excimer emission. The large Stokes shifts and the broad-band emission of these 3-aroylbenzocoumarins in solid/aggregation state demonstrated the probable formation of excimers. The shapes of benzocoumarin units have a great effect on the AIE behaviors. The linear benzocoumarin derivatives show larger Stokes shifts, while the bent-benzocoumarin derivatives exhibit better AIE performances. All of them show aggregation-enhanced excimer emission which is supported by the large Stokes shifts. The electronic effect of 3-aroyl groups also has a certain effect on their fluorescence properties. The polymorphism phenomenon was observed for one of the benzoyl-containing derivatives. Additionally, two of the derivatives containing methoxy group were successfully used for cell imaging., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

AIE-active compounds have lately attracted considerable attention owing to their versatile applications, especially in OLED and bioimaging. Herein, a series of coumarin-3-formylhydrazone derivatives (CFH-1, 2, 3 and 4) were developed for investigating their AIE and solid-state luminescence behaviors. All the obtained compounds emit varying degrees of solid-state fluorescence. CFH-1 and 2 show the typical AIE characteristics, while CFH-3 and 4 exhibit stronger solution fluorescence than their aggregation-induced emission. The single crystal X-ray diffraction analysis of CFH-1 and CFH-3 showed that both of them adopt planar conformation and the CH···O hydrogen bonding plays a crucial role in their crystal packing. Meanwhile, there is a notable difference between them. Successive π-π stacking interaction was observed in the crystal packing of CFH-1, while the crystals of CFH-3 contain dimeric π-π stacking interaction. Their distinct crystal packing interactions result in their different fluorescence properties. Moreover, both CFH-1 and CFH-2 displayed excellent bioimaging performances in living cells., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

AIE-active dyes have lately received considerable attention due to their versatile applications, especially in bioimaging and theranostics. Herein, 6-methoxy-2-naphthaldehyde was used to construct fluorophores through Knoevenagel condensation with various active methylene compounds. All the obtained compounds showed varying degrees of AIE characteristics. It was worth mentioning that the condensation product of 6-methoxy-2-naphthaldehyde and malononitrile (MOP-e) exhibited a large redshift and a large Stokes shift when forming aggregates. Furthermore, it showed an ultra-wide AIE band which enabled it to be utilized for dual-channel bioimaging. The single crystal X-ray diffraction analysis showed that two different molecular arrangement modes, the monomolecular stacking and the discrete π-π dimeric stacking, existed in the aggregates of MOP-e. The discrete dimeric stacking leads to excimer-induced enhanced emission, which results in its unique AIE behavior. Moreover, MOP-e displayed an excellent bioimaging performance in living cells in green channel and in red channel respectively., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Cellular pH homeostasis is essential for many physiological and pathological processes. pH monitoring is helpful for the diagnosis, treatment and prevention of disorders and diseases. Herein, we developed a ratiometric fluorescent pH probe (TCC) based on a coumarin derivative containing a highly active lactone ring. TCC exhibited a typical AIE effect and emitted blue fluorescence under weak acidic condition. When under weak basic condition, the active lactone moiety underwent a hydrolysis reaction to afford a water-soluble product, which gave red-shifted emission. The emission color change from blue through cyan and then to yellow within pH 6.5-9.0 which is approximate to the biological pH range. And the fluorescence color change along with pH value is reversible. Furthermore, TCC was successfully utilized in the detection of the intracellular pH change of live HeLa cells, which indicated that TCC had practical potential in biomedical research., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Two coumarin derivatives, 7-diethylamino-3-(4-nitrophenyl)coumarin (DNC) and 7-hydroxy-3-(4-nitrophenyl)coumarin (HNC), were synthesized via Knoevenagel condensation of salicylaldehyde derivatives with 4-nitrophenylacetonitrile and then cyclization reaction. Both of them were characterized by single-crystal X-ray diffraction. The molecules of DNC are stacked via π-π interaction, while the hydrogen bond interactions instead of π-π interaction were observed in the crystal packing of HNC. Both of DNC and HNC showed solvatochromic properties and aggregation-induced emission (AIE) activities, but the AIE characteristics of them were entirely different. HNC exhibited an AIE phenomenon as the result of the restriction of twisted intramolecular charge transfer (TICT), while DNC emitted peculiar dual fluorescence which was assigned to the emission based on the inhibition of TICT state formation and the emission from the TICT state respectively., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Selection signature provides an efficient tool to explore genes related to traits of interest. In this study, 176 ewes from one Chinese uniparous breed and three Kazakhstan multiparous breeds are genotyped using Affymetrix 600K HD single nucleotide polymorphism (SNP) arrays, F-statistics (Fst), and a Cross Population Extend Haplotype Homozygosity Test (XPEHH). These are conducted to identify genomic regions that might be under selection in three population pairs comprised the one multiparous breed and the uniparous breed. A total of 177 and 3072 common selective signatures were identified by Fst and XPEHH test, respectively. Nearly half of the common signatures detected by Fst were also captured by XPEHH test. In addition, 1337 positive and 1735 common negative signatures were observed by XPEHH in three Kazakhstan multiparous breeds. In total, 242 and 798 genes were identified in selective regions and positive selective regions identified by Fst and XPEHH, respectively. These genes were further clustered in 50 gene ontology (GO) functional terms and 66 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways in enrichment analysis. The GO terms and pathways were relevant with reproductive processes, e.g., oxytocin signaling pathway, thyroid hormone synthesis and GnRH signaling pathway, vascular smooth muscle contraction and lipid metabolism (alpha-Linolenic acid metabolism and Linoleic acid metabolism), etc. Based on the findings, six potential candidate genes ESR1 , OXTR , MAPK1 , RYR1 , PDIA4 , and CYP19A1 , under positive selection related to characteristics of multiparous sheep breeds were revealed. Our results improve our understanding of the mechanisms of selection that underlies the prolificacy trait in sheep, and provide essential references for future sheep breeding.