Raman spectroscopy is a convenient technique for the efficient evaluation of cyclodextrin inclusion molecular complexes of azo-dye colorants and largely polarisable guest molecules
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Raman spectroscopy has been successfully employed in order to investigate the formation of β-cyclodextrin host–guest inclusion molecular complexes with several different azo-dye structures. The Raman pattern of the carbohydrate framework results negligible when neared to the magnificent intensity of the highly polarisable guest systems and a complete and feasible comparison of the spectral features between the free and the complexed situation of the guest molecule is allowed. In general, with respect to the free guest state, it was found within the complex that a hampering of Raman intensity displays, accompanied by a levelling directed variation of the relative peak intensities, and peculiar Raman peak broadening with shifts occur, relatable to the host–guest settling of inclusive intermolecular interactions. Supportively to the other commonly established characterising methods, or in valid alternative, Raman technique has proved astoundingly useful under the perspective of the diagnostic evaluation of cyclodextrin host–guest molecular inclusion for azo-dyes and, more generally, for a highly polarisable guest structure. It features sample non-destructivity, handiness, fastness and sensitive reproducibility, occasionally providing useful suggestions about the complexation topology.
Keywordsβ-Cyclodextrin Azo-dyes Host–guest inclusion phenomena Raman spectroscopy
Signature A. A. indebted acknowledges Professor Pier Luigi Stanghellini (University of Eastern Piedmont, Italy) for nearing him to Raman spectroscopy. Authors appreciated the valuable comments provided by two anonymous Reviewers. Wacker-Chemie Ltd. is thankfully acknowledged for the kind supply of a β-cyclodextrin sample. Work was gratefully funded by public Fondo Ricerca Locale of the Italian Ministero dell’Istruzione, dell’Università e della Ricerca (M.I.U.R).
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