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Herein, we report the synthesis of a small molecule quinoline Schiff-base "turn-on" fluorescence probe L, denoted as (2-NC9H6)C(H)=N(C6H4OCH3-p), utilizing 4-aminoanisole and quinoline-2-carboxaldehyde as precursors. The synthesized probe was comprehensively characterized through EA,1H/13C NMR, FT-IR, and ESI-MS spectral analysis. In a CH3CN/H2O solution (1/1, v/v, 0.01 M PBS buffer, pH = 7.30), probe L responded to Hg(II) with high sensitivity (LOD = 2.98 × 10−7 M) and selectivity. Upon binding to Hg(II), the fluorescence of the probe shifted from being initially off to a distinct blue emission. The probe L to Hg(II) binding ratio was 1:1 and the binding constant was 1.955 × 104 M−1. The detection mechanism of Hg(II) by probe L is due to the complex formation between the metal ion and imine nitrogen (–CH = N), thus causing chelation-enhanced fluorescence. TD-DFT studies at the B3LYP/6-31G(d) level of theory further confirmed that the complexation of L and Hg(II) occurred. Finally, probe L could reversibly identify Hg(II) upon adding EDTA, thus developing a molecular logic gate. In addition, this probe was successfully used to detect Hg(II) in actual water samples. : [ABSTRACT FROM AUTHOR]

The reactions of α-diazocarbonyls have been extensively studied and widely applied in organic synthesis acting as 1,3-dipoles, metal carbene precursors and C-nucleophiles. However, the utility of the electrophilic capability of their terminal nitrogen has been a challenging problem. Herein, a novel copper-catalyzed cascade cyclization reaction of isocyanides with α-diazocarbonyls as N-terminal electrophiles has been developed for the first time. The reaction involves a sequential intermolecular nucleophilic addition/[3+2] cycloaddition/intramolecular cyclization-ring-opening/elimination procedure and provides a new and efficient method for the construction of imidazolines and biimidazoles in a single step from readily available starting materials under very mild conditions. [ABSTRACT FROM AUTHOR]

For the first time α-diazocarbonyls have been used as highly active N-terminal electrophiles in the presence of bicyclic amidine catalysts. The CN bond-forming reactions of active methylene compounds as C nucleophiles with α-diazocarbonyls as N-terminal electrophiles proceed quickly under ambient conditions, in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), because of the formation of the reactive N-terminal electrophilic intermediates. DBU activates both the active methylene and α-diazocarbonyl. Importantly, this reaction is general for both active methylenes and α-diazocarbonyls, and the activation mode will lead to new synthetic applications of α-diazocarbonyls., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)