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A newly developed acylhydrazone derivative (compound 1) displayed solvatochromic fluorescence effect with dominant fluorescence from its keto form in most solvents, fluorescence from its phenolic anion in DMF, and concentration-dependent emission intensities for both enol and keto forms in toluene. The aggregation-induced emission enhancement (AIEE) properties of 1 were observed in THF − H2O and DMF − H2O. Red fluorescence in the root cells of paulownia sprouts was observed for application of 1 as a fluorescence marker. Notably, strong fluorescence centered at 602 nm with a large stokes shift (232 nm) and an absolute quantum yield of 22% for 1 was obtained in crystals. X-ray analysis indicates that the fluorescence of crystal 1 is caused by intramolecular hydrogen bonding-induced limitation in C = N isomerization and weak intermolecular interactions. Furthermore, compound 1 exhibited good colorimetric/ratiometric sensing properties for quantitative detection of acetate and dihydrogen phosphate anions with detection limits of 250 nM and 170 nM, respectively, and blue-shifted amplified fluorescence response with detection limits of 45 nM and 62 nM, respectively. Based on 1H NMR analyses, intermolecular hydrogen bonding/deprotonation interactions of 1 with these anions and inhibiting ESIPT process were proposed for anions sensing. [ABSTRACT FROM AUTHOR]

A new bis-spirocyclic rhodamine B derivative was developed as a near-infrared colorimetric and "turn-on" fluorometric chemodosimeter (1) with a large Stokes shift (70 nm) for Cu2+. In response to Cu2+, the solution of 1 displayed major absorption at 700 nm, from colorless to blue within ten seconds. At the same time, emissions at 580 nm (excitation at 520 nm) and at 770 nm (excitation at 650 nm) were turned on. Good linear relationships between absorbance at 700 nm, fluorescence at 580 and 770 nm and concentration of Cu2+ in wide ranges were obtained in both colorimetric and fluorometric analyses, with the detection limits of 0.57 μM, 9 nM and 28 nM, respectively. Irreversible ring-opening processes of 1 coordinated with Cu2+, followed by hydrolysis as well as acylated reaction were proposed. Furthermore, 1 was applied to image Cu2+ in HepG2 living cells and within the mitochondria of the cells in the roots of paulownia sprouts. [ABSTRACT FROM AUTHOR]

Fluorescent single crystals that respond to multiple external stimuli are of great interest in molecular machines, sensors, and displays. The integration of photo‐ or acid‐induced fluorescence enhancement and bending in one organic crystal, however, has not been reported yet. Herein, we report the interesting plastic photomechanical bending and switching on of the fluorescence of an azine crystal in a single‐crystal transformation, due to extended π‐conjugation and molecular slippage. Moreover, the fluorescent plastic bending driven by multiple volatile acid vapors was firstly observed, and attributed to the synergistic effect of push–pull electronic structure and hydrogen bonding. The single crystal also shows high elasticity under external force. In addition, reversible fluorescence switching can be triggered by grinding and solvent fuming, as well as by the adsorption and desorption of HCl vapor. The integration of plastic, elastic bending and switch‐on fluorescence into one single crystal provides a new strategy for next‐generation smart materials. [ABSTRACT FROM AUTHOR]

Research has been conducted on bis-ethylenediamine- and tetraammine-bipyridineruthenium(II) complexes. The authors have investigated the metal-to-ligand charge-transfer emission spectra of these complexes, and present the results.