BCSJ : Vol. 78 (2005) , No. 7 pp.1270-1278

Observation of a Large Current on the Cyclic Voltammetry of Acylaminoferrocenes in the Solid State: An Efficient Electron-Transfer Pathway through Continuous NH···O=C Hydrogen-Bond Chains and π-Conjugation

Taka-aki Okamura¹⁾, Keiko Sakauye¹⁾, Mototsugu Doi¹⁾, Hitoshi Yamamoto¹⁾, Norikazu Ueyama¹⁾ and Akira Nakamura²⁾

1) Department of Macromolecular Science, Graduate School of Science, Osaka University
2) OM Research

(Received December 14, 2004)

A series of crystal structures of acylaminoferrocenes, [(C₅H₅)Fe(C₅H₄NHCOR)] (R = CH₃ (1), CH₂CH₃ (2), t-Bu (3), and CF₃ (4)) revealed an unusually delicate dependence of the alkyl substituent structure on electron transfer through NH···O=C bonding and π-conjugation. The presence of strong intermolecular NH···O=C hydrogen bonds in the crystal was established by X-ray, IR, and CRAMPS. Compounds 1 and 2 are without steric or electrostatic hindrance, and both exhibit continuous and strong hydrogen-bond chains, or an effective π-electrons system. However, the hydrogen-bond chains in 3 and 4 are weak, or broken, by the bulkiness of t-Bu or the electrostatic repulsion of CF₃. Solid-state cyclic voltammograms of 1–4 have revealed the electrochemical processes, which are critically dependent on the array and the strength of the hydrogen bonds. Although both 3 and 4 show typical reversible cyclic voltammograms, 1 and 2 exhibit irreversible redox behaviors and remarkably large current values, which indicate the presence of an effective electron transfer through the continuous hydrogen-bond chains.