摘要:
A series of ferrocene amide cystamine derivatives was prepared from 1'-methoxycarbonylferrocene-1-carboxylic acid in a step-wise fashion, via amide bond formation with a series of Boc-protected diamines, followed by coupling to cystamine. The length of the diamine linker was varied systematically from 2 to 10 methylene groups. All products were characterized spectroscopically. In solution, all ferrocene compounds displayed a quasi-reversible ferrocene/ferrocenium redox couple between 258 and 320 mV versus external Fc/Fc(+). The Boc-protected ethylene diamine ferrocene conjugate 7 was characterized by single crystal X-ray crystallography. Intermolecular hydrogen bonding exists between amide groups of adjacent molecules. The presence of the disulfide group allows chemisorption of Fc-conjugates 18-22 onto gold surfaces. Electrochemical measurements allow an evaluation of the electron transfer kinetics using the Butler-Volmer formalism. Electron transfer rate constants were determined to be in the range of 1.871(67)-2.105(258) s(-1). (C) 2012 Elsevier B.V. All rights reserved.