Author(s)

Sa’ib J. Khouri, Volker Buss

.
Department of Chemistry, American University of Madaba, Madaba, Jordan.

Different structures are proposed for the complexes formed from the interaction between the cationic cyanine dye 1, 1’-diethyl-2, 2’-carbocyanine chloride (Pinacyanol chloride) and the anionic surfactant sodium bis (2-ethylhexyl) sul- fosuccinate (Aerosol-OT) in ethanol-water solutions. UV/vis and electronic circular dichroism (CD) spectra provide tools to study the concentration and solvent dependence of this interaction. The aggregation spectra of the dye are dominated by a strongly blue-shifted, sharp and single visible band, which appears at concentrations much below the critical micelle concentration (cmc) of Aerosol-OT. Above the cmc, the spectra in pure aqueous solution indicate disso- ciation into monomer and dimer species, and the system becomes completely empty of chirality. Two different CD spectra with a distinct isosbestic point are observed for complexes with different surfactant to dye ratios. Both the addi- tion of ethanol (more than 7.5%) and increasing the temperature retards the metachromatic process between the dye and Aerosol-OT. By using the peakFit program, the two overlapping excitonic absorption bands together with the optically inactive absorption band for one spectrum (the most optimal one) at a specific Aerosol-OT concentration were sepa- rated.

Cyanine Dye; Pinacyanol; Surfactant; Aerosol-OT; Aggregation; Circular Dichroism; Derivative Spectra

S. Khouri and V. Buss, "Circular Dichroism and Derivative Spectra Study of the Excitonic Aggregation of Pinacyanol by Aerosol-OT," Open Journal of Physical Chemistry, Vol. 2 No. 1, 2012, pp. 34-40. doi: 10.4236/ojpc.2012.21005.