The synthesis and structural characterization of N-(ferrocenyl)2 and N-(ferrocenoyl)2 cystine dimethyl ester derivatives: Potential anion sensing agents

Standard peptide coupling reactions were use to prepare the N-(ferrocenyl)2 and N-(ferrocenoyl)2 cystine dimethyl ester derivatives 4–11. The ferrocene carboxylic acids 1 and 3 were treated with 1-hydroxybenzotriazole (HOBt), N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC), l-cystine methyl ester hydrochloride and triethylamine in dichloromethane at 0 °C to furnish compounds 4–9. The preparation of compounds 10 and 11 employed the dipeptide derivatives (glycine)2-l-cystine dimethyl ester and (β-alanine)2-l-cystine dimethyl ester respectively. The N-(ferrocenyl)2 and N-(ferrocenoyl)2 cystine dimethyl ester derivatives 4–11, which are potential anion sensing agents, were spectroscopically characterized by a combination of 1H NMR, 13C NMR, IR, UV, DEPT-135 and 1H–13C COSY (HMQC) spectroscopy, mass spectrometry and cyclic voltammetry.The electrochemical detection of dihydrogen phosphate and adenosine nucleotide anions in aqueous electrolyte by monolayers of {N-(ferrocenoyl)-β-alanine}2-l-cystine dimethyl ester 11 immobilized on gold electrodes using cyclic voltammetry is described. Immobilization of this receptor on a gold electrode surface enabled the recognition process to be detected in aqueous media. The recognition process is as a result of electrostatic interactions between the ferricenium cation and the anion, and hydrogen bonding interactions between the peptide amide bonds and the anion. The complexation process was amperometrically sensed via a reduction in the peak current of the ferrocene/ferricenium redox couple. A linear relationship (R2 = c. 0.99) was observed between anion concentration and change in peak current in both cases.

Graphical abstractThe N-(ferrocenyl)2 and N-(ferrocenoyl)2 cystine dimethyl ester derivatives which are potential anion sensing agents, were prepared and spectroscopically characterized. The electrochemical detection of dihydrogen phosphate and adenosine nucleotide anions in aqueous electrolyte by monolayers of {N-(ferrocenoyl)-β-alanine}2-l-cystine dimethyl ester immobilized on gold electrodes using cyclic voltammetry is described. Immobilization of this receptor on a gold electrode surface enabled the recognition process to be detected in aqueous media.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Potential ferrocene anion sensing agents were prepared. ► Electrochemical detection of dihydrogen phosphate and ATP anions was performed. ► Monolayers of the ferrocene peptide conjugates were formed. ► A linear response of the monolayers to anions was observed.