The synthesis and spectral properties of an encapsulated aminoazobenzene dye

An aminoazobenzene dye rotaxane containing N,N-dimethylamino end groups in the presence of α-cyclodextrins was synthesized and its UV–visible spectral properties investigated as a function of pH. The rotaxane structure was characterized using 1H NMR and 2D COSY NMR. The azo dye rotaxane exhibited enhanced polarity and was soluble only in polar solvents, displaying good solubility in water. The formation of the rotaxane structure did not interfere with the protonation of the threaded aminoazobenzene dye. In a sol–gel film coating the azo dye rotaxane exhibited pH sensitivity under neutral to acidic conditions in a reversible and reproducible manner.