Fluorescent Zinc(II) Complex Exhibiting 鈥?i>On-Off-On鈥?Switching Toward Cu2+ and Ag+ Ions

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• 作者：Rampal Pandey ; Prashant Kumar ; Ashish Kumar Singh ; Mohammad Shahid ; Pei-zhou Li ; Sanjay Kumar Singh ; Qiang Xu ; Arvind Misra ; Daya Shankar Pandey
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：April 18, 2011
• 年：2011
• 卷：50
• 期：8
• 页码：3189-3197
• 全文大小：1022K
• 年卷期：v.50,no.8(April 18, 2011)
• ISSN：1520-510X

文摘

Binuclear zinc(II) and copper(II) complexes based on a new Schiff base ligand N,N鈥?bis(2-hydroxybenzilidene)-2,4,6-trimethylbenzene-1,3-diamine (H₂L) have been synthesized. The ligand H₂L and complexes under investigation have been characterized by elemental analyses, spectral (FT-IR, ¹H, ¹³C NMR, ESI-MS, electronic absorption, emission), and electrochemical studies. The structures of H₂L and complexes [{Zn(C₂₃H₁₈N₂O₂)}₂] (1) and [{Cu(C₂₃H₁₈N₂O₂)}₂]路H₂O (2) have been determined crystallographically. Selective 鈥?i>On-Off-On鈥?switching behavior of the fluorescent complex 1 has been studied. The fluorescence intensity of 1 quenches (turns-off) upon addition of Cu²⁺, while enhances (turns-on) in the presence of Ag⁺ ions. The mechanisms of 鈥?i>On-Off-On鈥?signaling have been supported by ¹H NMR, ESI-MS, electronic absorption, and emission spectral studies. Job鈥檚 plot analysis supported 1:1 and 1:2 stoichiometries for Cu²⁺ and Ag⁺ ions, respectively. Association and quenching constants have been estimated by the Benesi鈭扝ildebrand method and Stern鈭扸olmer plot. Moreover, 1 mimics a molecular keypad lock that follows correct chemical input order to give maximum output signal.