Synthesis Of Novel Ferrocene-based Compounds And Their Applications In Anion Recognition

Anions exist and play critical roles in various biological systems, environmental pollution, and chemical processes. To simply and quickly detect the anions is of importance both in biological chemistry and environmental protection. Ferrocene based compounds are considered to be ideal anion sensing materials due to their stability, favourable electrochemical property, and reaction activity. In this paper, we designed and synthesized seven kinds of novel ferrocene based compounds, and studied their electrochemical property intensively. Cycilc voltammotric(CV), NMR, UV-Vis, and FT-IR were employed to study the anion recognition property of these compounds.Two kinds of dentritic compounds containing ester groups have been prepared. We studied their electrochemical properties in solution, and found that in CH₂Cl₂ solution, these compounds exhibit diffusion controlled irreversible CV behavior. CV was adopted to study the anion recognition properties, and it was found that these compounds exhibit different electrochemical response behavior to different anion, the first generation dendrimer shows a selective recognition for H₂PO₄^- over other anions, and the dendrimer shows its advantage over hyperbranched polymers on anion recognition property when the redox behavior is concerned. ¹H-NMR and UV-Vis techniques were employed to study the binding mode between the dendrimer and H₂PO₄^-, and it was found that the main interaction is the hydrogen bonds between the ester group and hydrogen atoms of the anion.Three kinds of amide containing ferrocene-based compounds have been prepared. We studied their electrochemical properties in solution, and found that in CH₂Cl₂ solution, these compounds exhibit reversible and quasi-reversible CV behavior at low scan rates and high scan rates respectively. CV was employed to investigate the anion recognition properties, and it was found that the compound containing both amide and amine group undergoes remarkable electrochemical response to H₂PO₄^- and F^-, whereas the compounds containing only amide group undergo response only to H₂PO₄^-. ¹HNMR technique was utilized to study the anion recognition properties of two compounds, and it was observed that the chemical shift of the amide and amine protons change upon addition of H₂PO₄^-, and HSO₄^- can make similar changes to the protons of the compound. As to amide and imine containing compound, it was observed that the imine proton shifts to downfield by adding H₂PO₄^-. UV-Vis investigation on anion recognition properties showed that all the three compounds exhibit response to H₂PO₄^- to some extent.So far, anion recognition in aqueous media remains a challenging task. We synthesized a kind of water-soluble ferrocene-based cyclic amine through [1+1] condensation reaction, and studied its electrochemical behavior in CH₂Cl₂, CH₃CN, and CH₃CN/H₂O mixture solution. It was found thatthe compound show reversible redox wave in CH₂Cl₂ and CH₃CN, whereas the redox wave becomes unconspicuous with the increasingly content of water in CH₃CN/H₂O mixture solution. The data obtained with electrochemical and NMR indicated that the compound can detect tetrahedral anions such as H₂PO₄^- and HSO₄^- in CH₂Cl₂, CH₃CN, and CH₃CN/H₂O mixture solution containing water less than 20%. UV-Vis titration experiments showed that, the binding strength between the receptor and anion decrease with the increasingly polarity of the solution, and the receptor show similar selectivity to anions in different solution. However, the receptor can only recognize HSO₄^- in pure aqueous media, which may be due to the dimensional complement between the cave of the macrocycle and HSO₄^- anion.Two methods were adopted to prepare ferrocene derivatives based electrochemical sensor: co-deposit of ferrocene carboxylic acid pyrene ester(FcPE) and multi-walled carbon nanotubes(CNTs) on glassy carbon electrode, and modification of carbon paste electrode by N,N',N',N'-tetraferrocene diethylene triamine. It was found that the introduction of carbon nanotubes improves the stability of the modified electrode. A film modified electrode with good electrochemical property can be prepared under the optimum conditions: FcPE : CNTs= 5:1. The anion recognition property of FcPE-CNTs modified electrode was better than that of the FcPE modified electrode. The composition of materials had remarkable influence on property of the carbon paste electrode. A carbon paste electrode with good electrochemical property can be prepared under the optimum conditions: carbon paste : paraffin=9:5, and the content of ferrocene derivative is 16%. The prepared carbon paste can selectively detect H₂PO₄^-. In ethanol solution, H₂PO₄^- induced a 25% enhancement on peak current whereas the other anions induced hardly any changes on peak current.