6533b7d6fe1ef96bd1265a1a

RESEARCH PRODUCT

Biferrocene Amino Acid, a Ferrocenylogoue of Ferrocene Amino Acid: Synthesis, Cross-Linking, and Redox Chemistry

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Access of the novel biferrocene amino acid 7 is provided by two different routes, namely, via desymmetrization of a biferrocene and via palladium-catalyzed cross-coupling of two substituted ferrocenes. The dissymmetric biferrocene 7 is head−head coupled to ureylene-bridged bis(biferrocene) 9 and also head−tail coupled to amide-bridged bis(biferrocene) 14. The monomer 7 and the dimers 9 and 14 are oxidized to mixed-valent cations 7+, 9+, 92+, and 142+. The valencies are trapped in the solid state as shown by Mossbauer and EPR spectroscopy and by X-ray diffraction analysis of [7](I3). Paramagnetic NMR shift studies (7 → 7+) suggest that the hole is localized at the N-substituted ferrocene unit [BocNH-{III}-{II}-COOMe]+. According to DFT calculations and individual redox potentials, the dications 92+ and 142+ are best described as [MeOOC-{II}-{III}-NHCONH-{III}-{II}-COOMe]2+ and [BocNH-{III}-{II}-CONH-{III}-{II}-COOMe]2+ valence isomers, respectively. The interaction between neighboring ferrocene/ferrocenium...