Solvent-controlled novel Cu+ and Cu+/2+ fluorescent turn-ON probing

Abstract

Anovel Schiff base probe, carbamoyl salicylimine benzothiazole hydrazine, was prepared and measured for its probing ability. High sensitivity was shown for Cu+and Cu2+. When solvent polarity was regulated through a combination of H2O and acetonitrile, selective sensing ofCu+or the total amount of Cu+andCu2+ was possible. In addition, a linear hypsochromic fluorescent shift of about 30 nm was shown. A binding stoichiometry of 1:1 exists at low concentration. Time-dependent emission measurement showed an exponential decay curve (τ1 = 2.99 × 103s, 10 equiv of Cu+) and a linear decay line (slope = -0.0216, 5 equiv of Cu+). Interference experiments in 50% acetonitrile inH2Oshowed that the emission produced by Cu+and Cu2+ was not disturbed by other metal ions or by acidity or basicity. Peroxynitrite changed the emission trends; Cu+emission decreased (78%) and Cu2+ fluorescence increased (28-fold). Biothiols, L-cysteine, DL-homocysteine, reduced glutathione, and N-acetyl-L-cysteine affected the complete reversibility of Cu+-induced emission in 50% (v/v) acetonitrile in H2O, relative to partial reversibility of Cu2+ emission. Thus, by regulating the ratio between acetonitrile and H2O, Cu+and Cu+/2+ can be probed selectively. © 2015 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim