Use of spectra resolution methodology to investigate surfactant/β-cyclodextrin mixed systems

A study of the spectral behavior of crystal violet in mixed systems formed by hexadecyltrimethylammonium chloride (CTACl) and beta-cyclodextrin (beta-CD) has been carried out. The spectra resolution methodology was used to decompose the absorption spectra of crystal violet in the sum of constituent sub-bands centered at 17 953, 16 807, and 16 474 cm(-1). The sub-bands centered at upsilon = 17 953 and 16 807 cm(-1) correspond to planar and pyramidal isomers of the dye in water and the same isomers associated with the cyclodextrin and micelle. The sub-band centered at upsilon = 16 474 cm(-1) is due to the formation of an inclusion complex between the dye and the cyclodextrin, where solvation of the carbocation takes place through the hydroxyl groups of the cyclodextrin and the association of the crystal violet to micelles of CTACl through the formation of ion pairs in the Stern layer. The results obtained in the mixed systems are compatible with the results obtained in the previously studied simple systems, thus supporting the situation where interactions do not exist between cyclodextrins and micelles once these have formed.