UV-visible spectral analysis on the aggregation forms of an amphiphilic porphyrin

Aim To study the effects of the concentrations of 5, 10, 15-tri(p-hydrox- ylphenyl)-20-(p-hexadecyloxyphenyl)-porphyrin (a synthesis amphiphilic porphyrin) , as well as solvent polarity on the aggregation forms of this porphyrin. Methods The information of interaction between the phorphyrins was obtained by the shifts and FWHHs of the Soret band according to UV-vis spectra of the amphiphilic porphyrin in aqueous, chloroform and cyclohexane solutions at various concentrations. Results and Conclusion In aqueous solutions at lower concentrations, the amphiphilic porphyrins exist as monomers. When its concentration is higher than 3. 50×10^-6 mol · L ^-1, it does not follow Beer's law, indicating that the aggregations are formed. With continuously increasing its concentration, a blue shift of the Soret band from 428 nm to 410 nm takes place, which means that H-type aggregates are formed by the self-assembled action of porphyrin moiety. In cyclohexane solutions,.the porphyrins are monomeric in a wide concentration range. In chloroform solutions with solvent polarity located between water and cyclohexane, the self-assembled action of the- porphyrin moiety results in the formation of face to face dimers or H-type aggregates when the concentration is higher than 4. 00×10^-6 mol · L^-1.