Solvent- and Temperature-Tuned Orientation of Ferrocenyl Azide Inside β-Cyclodextrin

An induced circular dichroism (ICD) solution study on the
orientation of ferrocenyl azide within the β-cyclodextrin
cavity is described. In DMSO, ferrocenyl azide prefers an
axial inclusion, whereas in ethylene glycol and DMSO/H2O
= 50/50 an equatorial alignment dominates. As shown by
temperature-dependent ICD spectra, at lower temperatures
ferrocenyl azide adopts preferentially an equatorial arrangement, whereas at higher temperatures an axial one is favored.
Temperature and solvent effects on the co-conformation of
ferrocene noncovalently bound to cyclodextrin have never
been observed before.