Infrared study of intercomponent interactions in a switchable hydrogen-bonded rotaxane.
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 double bond 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 nu(CO) frequencies of the C double bond O groups of the succinamide and the reduced naphthalimide stations. The macrocycle was found to shield the encapsulated station from the solvent: wavenumbers of nu(CO) bands of the C double bond O groups residing inside the macrocycle cavity remain unaffected by the solvent polarity.
Jagesar
Dhiredj C
DC
Van 't Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 129, 1018 WS Amsterdam, The Netherlands.
Hartl
Frantisek
F
Buma
Wybren Jan
WJ
Brouwer
Albert M
AM