Water‐soluble donor–acceptor‐type fluorophore 15Nap‐Cl having two trifluoromethyl groups and a Cl group on a 1,5‐aminonaphthyridine framework was prepared. Fluorophore 15Nap‐Cl showed strong solvatochromic fluorescence, and, as the solvent polarity increased, a bathochromic shift was observed accompanied by an increase in the fluorescence quantum yield. In addition, in the presence of amines such as ethylamine, diethylamine, and aniline, further considerable bathochromic shifts in the fluorescence were observed. Density functional calculations identified the source of the fluorescence behavior as exciplex formation between 15‐Nap‐Cl and the corresponding amine. The fluorescence behavior was exploited to fabricate a sensor that can identify various primary, secondary, and tertiary amines.

Push-pull type fluorescent amino-quinoline derivatives (TFMAQ) bearing phenyl aromatic groups in the 8-position (TFMAQ-8Ar series) were synthesized via palladium-catalyzed C-H activation reaction in short steps. The N-arylation or C-H activation reactions were selectively controlled with high yield by combinations of palladium and phosphine ligands. The TFMAQ-8Ar analogues exhibited fluorescent solvatochromism in non-polar and polar solvents. In non-polar solvent, the absolute fluorescence quantum yield was high, wheareas the fluorescence was almost quenched in polar solvent. The TFMAQ-8Ar derivatives also showed high fluorescence emission at solid state owing to the planar structure between the quinoline ring and phenyl ring at the 7-amino group, as demonstrated by X-ray crystal structure analysis. The fluorescence imaging of 3T3-L1 cell using TFMAQ-8Ar derivatives was performed by confocal laser microscopy. Strong and specific emissions at lipid droplets were observed owing to the accumulation of TFMAQ-8Ar derivatives. Therefore, we propose that the TFMAQ-8Ar derivatives should become a versatile fluorescence probe for the live imaging of lipid droplets.

Emissive push–pull‐type bisnaphthyridylamine derivatives (BNA‐X: X=Me, Et, Bzl, Ph, BuBr, and BuTEMPO) aggregate in aqueous methanol. Furthermore, a two‐step emission and aggregation process is controllable by varying the methanol‐to‐water ratio. At 2:3 MeOH/H2O, crystallization‐induced emission enhancement (CIEE) occurs via formation of an emissive crystal phase, whereas, at 1:9 MeOH/H2O, aggregation‐induced emission enhancement (AIEE) occurs, induced by emissive supramolecular nanoparticles (NPs). For BNA‐Ph, the emission quantum yield was 25 times higher in aqueous methanol than that in pure methanol. Despite the high hydrophobicity of BNA‐X (C log P=6.1–8.0), the spherical NPs were monodisperse (polydispersity indices <0.2). Moreover, the emissive NPs exhibited fluorescence resonance energy transfer (FRET) with pyrene; however, for BNA‐X bearing the TEMPO radical (BNA‐BuTEMPO), no FRET was observed because of quenching. In particular, the BNA‐BuTEMPO NPs have a slow rotational correlation time (1.3 ns), suggesting applications as magnetic resonance imaging contrast agents with large relaxivity.

Pyridocarbazole moieties are present in many natural products, such as olivacine and ellipticine, and their derivatives are well-known anticancer agents. To develop functional therapeutic and diagnostic compounds, three emissive pyrido[3,2-c]carbazole derivatives, PC-X,c ontaining secondary or tertiary amine groups, were synthesized from an aminoquinoline derivative using ap alladium complex as the catalyst. X-ray diffraction analyses revealed that PC-X showed highly planar structures between the pyridine ring and the carbazole framework, exhibiting high fluorescence intensities along with solvatochromic behavior.I magingo f HeLa cells treated with PC-X showed no specific accumulation into the organelles;h owever,acomparative examina-tion showedt hat the accumulation in mitochondriaw as the highest as comparedt on uclei and lysosomes. Cytotoxicity analysisu sing HeLa cellss howed that PC-H, containing a secondary amine group showed the highest cytotoxicity (IC 50 % 20 mm)a sc omparedt oa nother PC-X having at ertiary amine group. Colocalizationw ith MitoTracker,atypical mitochondrial staining dye, showed apoptosis-like behavior with remarkable appearance of blebbing during irradiation with near UV light (403 nm), suggesting that the PC-H may not only behave as af luorescencep robe for the imagingo rganelles, but also as at herapeutic agent fori nducing apoptosis in HeLa cells, thereby functioning as atheranostic agent.Supporting information and the ORCID identification number(s)for the author(s)ofthis article can be found under: https://doi.

An organic solution with a push–pull‐type fluorophore, which resembles the shape of a dragon in the cover image, exhibits aggregation‐induced emission enhancement upon water addition. The cover tells the story of one dragon who strayed into the mythical world. The dragon found water, which was poured by Ganymēdēs; he showered and drank the water. He then flew away swiftly, shining like the star sign Aquarius. Upon increasing the water content of the aqueous solutions, transformations from the monomer to the crystals and the crystals to the nanoparticles were observed, accompanied by emission enhancement. More information can be found in the Full Paper by S. Karasawa et al. on page 3039.