Selective colorimetric and fluorometric sensing of Cu(ii) by iminocoumarin derivative in aqueous buffer
作者:B. Nisar Ahamed、Pradyut Ghosh
DOI:10.1039/c1dt10177c
日期:——
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.
以吡啶基和苯并噻唑基官能团为基础,合成了一种新的亚氨基香豆素受体 L (C27H26N4OS)。L 的合成非常容易,且分离率高。与 Li+、Na+、Ca2+、Mg2+、Cr2+、Mn2+、Fe2+、Co2+、Ni2+、Cu2+、Zn2+、Cd2+、Pb2+ 和 Ag+ 相比,L 在 Cu2+ 的作用下显示出选择性和明显的颜色变化,从黄色变为橙色。Cu2+ 的肉眼检测限为 2 μM,而发射实验显示的检测限较低,为 200 nM。通过发射实验对存在 50 个等量的其他离子时 L 的选择性研究表明,对 1 个等量的 Cu2+ 的检测没有干扰。在不同大小和形状的反阴离子(Cl-、ClO4-、NO3-、CF3SO3-、SO42- 和 BF4-)的 Cu2+ 盐存在下进行的紫外可见光和荧光研究表明,无论反阴离子的性质如何,缓冲介质中的光谱输出几乎是相似的。详细的紫外可见光和荧光滴定实验表明,存在 1 :1 和 2 :1 : 1 和 2 : 2(L : Cu2+)的络合比例,而 EPR 研究则显示了络合物中 Cu(II)中心的 dx2-y2 基态。此外,单晶 X 射线结构研究证实了[Cu(L)(CH3CN)].2ClO4 单核复合物的形成以及 L 在固态下的柔性构象。