Redox Control of Rotary Motions in Ferrocene-Based Elemental Ball Bearings
摘要:
Rotational motions of ferrocene-based carousels have been achieved by electron transfer centered on pi-dimerizable 4,4'-bipyridinium substituents introduced on both cyclopentadienyl rings through covalent linkers of different size, geometry, and flexibility. Detailed spectroscopic, electrochemical, and theoretical analyses demonstrate that rigid and fully conjugated linkers allow the quantitative formation of intrarnolecular pi-dimers resulting from optimized orbital overlaps within the HOMO of the electrochemically generated bis-radical species. The tetra-cationic "charge-repelled" conformers, the selfassembled, pi-dimers, and their electron triggered interconversions have been investigated by UV-vis, NMR, and ESR spectroscopy, electrochemistry, X-ray diffraction analysis, and theoretical calculations. These studies support the conclusion that the rotation of both cyclopentadienyl rings in ferrocene can be controlled electrochemically using noncovalent reversible interactions arising from pi-radical coupling processes.
Substantial yield increases have been noted in the use of a di-SmI2 binding ligand for the pinacol coupling of alkyl aldehydes compared to 1∶1 complexes of SmI2 and tetraglyme. High diastereoselectivities of ca. 10∶1 are also observed for α-substituted alkyl aldehydes in favour of the (±)-isomers.
A new synthesis and electrochemistry of 1,1′-bis(β-hydroxyethyl)ferrocene
作者:Kevin P. Barry、Chip Nataro
DOI:10.1016/j.ica.2008.09.017
日期:2009.4
The preparation of 1,1'-bis(beta-hydroxyethyl)ferrocene (1) by oxidation of 1,1'-divinylferrocene is described. Compound 1 has been characterized by H-1 and C-13H-1} NMR, and cyclic voltammetry. The electrochemical data are compared to ferrocene and the closely related 2-ferrocenylethanol, 2. (C) 2008 Elsevier B.V. All rights reserved.