A novel class of Cd(II), Hg(II) turn-on and Cu(II), Zn(II) turn-off Schiff base fluorescent probes

• Published in: Dalton transactions : an international journal of inorganic chemistry 2010-12, Vol.39 (47), p.11344-11352
• Main Authors: Hu, Yuan, Li, Qian-qian, Li, Hua, Guo, Qian-ni, Lu, Yun-guo, Li, Zao-ying
• Format: Article
• Language: English
• Subjects: Cadmium - chemistry; Crystallography, X-Ray; Fluorescent Dyes - chemistry; Mercury - chemistry; Molecular Conformation; Quinoxalines - chemical synthesis; Quinoxalines - chemistry; Schiff Bases - chemical synthesis; Schiff Bases - chemistry; Spectrometry, Fluorescence; Zinc - chemistry
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c0dt00737d

N,N'-((5,5'-(quinoxaline-2,3-diyl)bis(1H-pyrrole-5,2-diyl))bis(methanylylidene))bis(4-methoxyaniline) 4 and N,N'-((5,5'-(quinoxaline-2,3-diyl)-bis(1H-pyrrole-5,2-diyl))bis(methanylylidene))dianiline 5 have been prepared and structurally characterized. The X-ray crystal structures of compounds 4 and 4a have been determined. These compounds displayed good sensitivity toward transition metal ions with Cd(II), Zn(II) turn-on and Cu(II), Hg(II) turn-off in fluorescence. It is an elegant example of on/off behavior like a lamp. When Cd(II) or Zn(II) is added into compounds 4 or 5, the lamp will switch on, and then when Cu(II) or Hg(II) is added into the mixture, the lamp will switch off. The binding properties of 4 and 5 for cations were examined by fluorescence spectroscopy. The fluorescence data and crystal structure indicate that a 1:1 stoichiometry complex is formed between compound 4 (or 5) and metal ions, and the binding affinity is very high. The recognition mechanism between compound 4 (or 5) and metal ion was discussed based on the their chemical constructions and the CHEF/CHEQ effect when they interacted with each other.