Selective colorimetric and fluorometric sensing of Cu(II) by iminocoumarin derivative in aqueous buffer

Ahamed, B. Nisar ; Ghosh, Pradyut (2011) Selective colorimetric and fluorometric sensing of Cu(II) by iminocoumarin derivative in aqueous buffer Dalton Transactions, 40 (24). pp. 6411-6419. ISSN 1477-9226

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Official URL: http://pubs.rsc.org/en/Content/ArticleLanding/2011...

Related URL: http://dx.doi.org/10.1039/C1DT10177C

Abstract

A new iminocoumarin based receptor L (C27H26N4OS) is synthesized with pyridyl and benzothiazolyl functionality. Synthesis of L is easy and it is isolated in good yield. L shows a selective and distinct color change from yellow to orange with Cu2+ over Li+, Na+, Ca2+, Mg2+, Cr2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+, and Ag+ whereas a slight change in color is also observed in the case of Hg2+ but L shows selective fluorescent quenching only in the presence of Cu2+ in aqueous HEPES buffer (pH 7.0). The naked eye detection limit of Cu2+ is determined at 2 μM whereas an emission experiment shows a lower detection limit at 200 nM. Selectivity studies of L in presence of 50 equivalents of other ion(s) by emission experiment show no interference toward the detection of 1 equivalent of Cu2+. Both UV-Vis and fluorescence studies in the presence of Cu2+-salts of different counter anions with various sizes and shapes (Cl, ClO4, NO3, CF3SO3, SO42− and BF4) show almost similar spectral output in buffer media irrespective of the nature of the counter anions. The detailed UV-Vis and fluorescence titration experiments suggest the existence of both 1 : 1 and 2 : 1 (L : Cu2+) complexation stoichiometry and EPR study shows dx2-y2 ground state of the Cu(II) centre in the complex. Furthermore the formation of a mononuclear [Cu(L)(CH3CN)].2ClO4 complex and the flexible conformation of L in the solid state are confirmed by the single-crystal X-ray structural study.

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