Infrared study of intercomponent interactions in a switchable hydrogen-bonded rotaxane
Jagesar, D.C., Hartl, F., Buma, W.J. and Brouwer, A.M. (2008) Infrared study of intercomponent interactions in a switchable hydrogen-bonded rotaxane. Chemistry- A European Journal, 14 (6). pp. 1935-1946. ISSN 0947-6539
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To link to this article DOI: 10.1002/chem.200701531
The macrocycle in rotaxane 1 is preferentially hydrogen bonded to the succinamide station in the neutral form, but can be moved to the naphthalimide station by one-electron reduction of the latter. The hydrogen bonding between the amide NH groups of the macrocycle and the C=O groups in the binding stations in the thread was studied with IR spectroscopy in different solvents in both states. In addition, the solvent effect on the vibrational frequencies was analyzed; a correlation with the solvent acceptor number (AN) was observed. The conformational switching upon reduction could be detected by monitoring the hydrogen-bond-induced shifts of the v(CO) frequencies of the C=O groups of the succinamide and the reduced naphthalimide stations. The macrocycle was found to shield the encapsulated station from the solvent: wavenumbers of v(CO) bands of the C=O groups residing inside the macrocycle cavity remain unaffected by the solvent polarity.