Spectroscopic characterisation of crystal violet inclusion complexes in β-cyclodextrin

In the presence of β-CD the spectra of crystal violet can be decomposed in three Gaussians centered at λ = 557, λ = 595 and λ = 607 nm. The Gaussian centered at λ = 607 nm will be a consequence of a structure with pyramidal geometry where the solvation of the carbocation takes place through the hydroxyl groups of the cyclodextrin. On the basis of the areas of the Gaussian constituents, we have obtained the complexation constants of the different ground state structures with the β-CD. The results obtained show a high complexation efficiency and are independent of the crystal violet concentration in the interval [CV] = (0.501 − 2.5) × 10−5 M.