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Photophysical Properties and Conformational Effects on the Circular Dichroism of an Azobenzene–Cyclodextrin [1]Rotaxane and Its Molecular Components
Author(s) -
Di Motta Simone,
Avellini Tommaso,
Silvi Serena,
Venturi Margherita,
Ma Xiang,
Tian He,
Credi Alberto,
Negri Fabrizia
Publication year - 2013
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201203676
Subject(s) - rotaxane , moiety , azobenzene , conformational isomerism , circular dichroism , chemistry , fluorescence , covalent bond , molecular dynamics , cyclodextrin , crystallography , photochemistry , molecule , materials science , computational chemistry , stereochemistry , supramolecular chemistry , organic chemistry , optics , physics
The photophysical properties of a multicomponent [1]rotaxane bearing a β‐cyclodextrin ring covalently connected to an axle comprising an azobenzene photoisomerisable moiety and a naphthalimide‐type fluorescent stopper are investigated by a combined experimental and computational study. The absorption and fluorescence spectra, and particularly the induced circular dichroism (ICD) signal, are determined. The latter shows a sign relation that cannot be rationalised in terms of the simple general rules commonly employed to analyse the ICD spectra of achiral guests encircled by chiral hosts. To assist the interpretation of experimental results, DFT and time‐dependent (TD) DFT calculations are performed to explore the availability of low‐energy conformations and to model their spectroscopic response. Molecular dynamics simulations performed in water show the interconversion of a number of conformers, the contribution of which to the ICD signal is in agreement with the observation.