title: Selective colorimetric and fluorometric sensing of Cu(II) by iminocoumarin derivative in aqueous buffer.
abstract: A new iminocoumarin based receptor L (C(27)H(26)N(4)OS) 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 Cu(2+) over Li(+), Na(+), Ca(2+), Mg(2+), Cr(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Pb(2+), and Ag(+) whereas a slight change in color is also observed in the case of Hg(2+) but L shows selective fluorescent quenching only in the presence of Cu(2+) in aqueous HEPES buffer (pH 7.0). The naked eye detection limit of Cu(2+) 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 Cu(2+). Both UV-Vis and fluorescence studies in the presence of Cu(2+)-salts of different counter anions with various sizes and shapes (Cl(-), ClO(4)(-), NO(3)(-), CF(3)SO(3)(-), SO(4)(2-) and BF(4)(-)) 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:Cu(2+)) complexation stoichiometry and EPR study shows d(x(2)-y(2)) ground state of the Cu(II) centre in the complex. Furthermore the formation of a mononuclear [Cu(L)(CH(3)CN)].2ClO(4) complex and the flexible conformation of L in the solid state are confirmed by the single-crystal X-ray structural study.
authors.affiliation: Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata, 700 032, India.
authors.forename: B Nisar
authors.initials: BN
authors.lastname: Ahamed
authors.forename: Pradyut
authors.initials: P
authors.lastname: Ghosh
mesh_terms: D003124:Colorimetry / Q000379:methods*; D003300:Copper / Q000032:analysis*; D003374:Coumarins / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005456:Fluorescent Dyes / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007097:Imines / Q000138:chemical synthesis / Q000737:chemistry*; D008968:Molecular Conformation; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D014867:Water / Q000737:chemistry
chemical_list: D003374:Coumarins; D005456:Fluorescent Dyes; D007097:Imines; D014867:Water; D003300:Copper; C030123:coumarin