An incisively designed notable aggregation-induced emission enhancement (AIEE) active fluorescence probe, 1-(2hydroxynaphthylmethylene)-2-(3-methoxy-2-hydroxybenzylidene) hydrazine (L), was synthesized via straightforward reaction from inexpensive reagents. It exhibited rapid response, superb selectivity, and swift sensitivity toward Zn 2+ based on its promising CHEF/AIEE feature. L not only can sense Zn 2+ through sharp colorimetric and selective turn-on fluorescence responses in DMF/H 2 O (9:1, v/v) medium, but also can distinguish between its significant AIEE activity in high water ratio and Zn 2+ triggered AIEE activity through individual emission signals. Intriguingly, the AIEE properties of L may improve its impact. The molecules of L are aggregated into ordered one-dimensional rod-shaped microcrystals that show an obvious optical waveguide effect. Job's plot from UV−vis absorption revealed the formation of L-Zn 2+ complex with 1:1 stoichiometry. When bound with Zn 2+ in 1:1 mode, enhanced turn-on emission was observed via chelation enhanced fluorescence through sensor complex (L-Zn) formation and excess addition of Zn 2+ , a vivid enhancement of fluorescence intensity over manifold through aggregate formation was observed. The entire process takes ∼5 s, i.e., faster response time. The probe can detect Zn 2+ as low as 1.1 × 10 −7 M. The AIEE mechanism of L and Zn 2+ triggered AIEE mechanism were well established from fluorescence anisotropy, DLS, SEM, optical fluorescence microscope, time-resolved photoluminescence, and fluorescence reversibility study by adding Zn 2+ and EDTA sequentially. Furthermore, the proposed analytical system with clear AIEE mechanism demonstrates a potential outlook for the on-site practical applications.

A pyrene based fluorescent probe, 3-methoxy-2-((pyren-2yl-imino)methyl)phenol (HL), was synthesized via simple one-pot reaction from inexpensive reagents. It exhibited high sensitivity and selectivity toward Al(3+) over other relevant metal ions and also displayed novel aggregation-induced emission enhancement (AIEE) characteristics in its aggregate/solid state. When bound with Al(3+) in 1:1 mode, a significant fluorescence enhancement with a turn-on ratio of over ∼200-fold was triggered via chelation-enhanced fluorescence through sensor complex (Al-L) formation, and amusingly excess addition of Al(3+), dramatic enhancement of fluorescence intensity over manifold through aggregate formation was observed. The 1:1 stoichiometry of the sensor complex (Al-L) was calculated from Job's plot based on UV-vis absorption titration. In addition, the binding site of sensor complex (Al-L) was well-established from the (1)H NMR titrations and also supported by the fluorescence reversibility by adding Al(3+) and EDTA sequentially. Intriguingly, the AIEE properties of HL may improve its impact and studied in CH3CN-H2O mixtures at high water content. To gain insight into the AIEE mechanism of the HL, the size and growth process of particles in different volume percentage of water and acetonitrile mixture were studied using time-resolved photoluminescence, dynamic light scattering, optical microscope, and scanning electron microscope. The molecules of HL are aggregated into ordered one-dimensional rod-shaped microcrystals that show obvious optical waveguide effect.

Two new azide bound cobalt(III) complexes, [Co(L(1))(N3)3] (fac-1) and [Co(L(2))(N3)3] (mer-2), where L(1) is bis(2-pyridylmethyl)amine and L(2) is (2-pyridylmethyl)(2-pyridylethyl)amine, derived from tridentate reduced Schiff-base ligands have been reported. Interestingly, a methylene bridge regulated preferential coordination mode of ligands is noticed in their crystal structures: it is found in a facial arrangement in fac-1 and has a meridional disposition in mer-2. Both complexes show phenoxazinone synthase-like activity and the role of the structural factor on the catalytic activity is also explored. Moreover, the easily reducible cobalt(III) center in mer-2 favors the oxidation of o-aminophenol. The ESI-MS positive spectra together with UV-vis spectroscopy clearly suggest the formation of a catalyst-substrate adduct by substitution of the coordinated azide ions in the catalytic cycle.

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