Synthesis And Properties Of Ferrocenylimidazo[4,5-b]Pyridine Derivatives

Heavy metal ions do great harm to human body and environment.Using organic molecules as probes to detect heavy metal ions has been widely concerned.2-Ferrocenyl imidazole[4,5-b]pyridine derivatives can be used as an ion probe for selective identification of Hg²⁺ ions and Pb²⁺ ions.In this paper,five 2-ferrocenyl imidazole[4,5-b]pyridine derivatives beared different substituents on 5-position have been synthesized.The influence of molecular structure on the metal ion recognition performance was analyzed.2-ferrocenyl imidazole[4,5-b]pyridine derivatives 3a-3c were synthesized by ammonia-aldehyde condensation reaction with ferrocenyl formaldehyde and 2,3-diaminopyridine derivatives under the catalysis of potassium iodide and acetic acid.The yields of 3a-3c were 46-58%.New compounds 2-ferrocenyl-5-（3-pyridyl）imidazo[4,5-b] pyridine（3d）and 2-ferrocenyl-5-（4-pyridyl）imidazo[4,5-b]pyridine（3e）were prepared by tris（dibenzylideneacetone）dipalladium catalyzed Suzuki cross-coupling reaction of 2-ferrocenyl-5-bromoimidazo[4,5-b]pyridine（3b）and 3-pyridineboronicacid/4-pyridineboronic acid,with yields of 77%-85%.The structure of these compounds were characterized by NMR,MS and IR spectrum.The yields of 3a-3c were 46-58%.New compounds Compounds 3a,3d and 3e were used as ion probes,and their multichannel recognition abilities to 19 common metal ions werec studied by square wave voltammetry（SWV）,cyclic voltammetry（CV）,UV-Vis spectroscopy and fluorescence spectroscopy under optimized conditions.The results show that the probe 3a can work as Hg²⁺ ion optical probe and electrochemical probe for Al³⁺ ion.Compound 3d can be used to detect Hg²⁺ ion through fluorescence/UV-Vis/electrochemistry three channels,and detect Al³⁺ ion by electrochemical method.Probe 3e can recognize Hg²⁺,Al³⁺,Fe³⁺ and Cr³⁺ ions through fluorescence/UV-Vis channels.The analysis results showed that adding and changing recognition site can influence the selectivity of probes.