The UV-Vis and Fluorescence Spectra of the Amphiphilic Porphyrins Sensitive to the Micellar Microenvironments

Electronic absorption, fluorescence emission and fluorescence excitation spectra of amphiphilic porphyrins in THF (tetrahydrofuran) solutions and CTAB (cetyltrimethylammonium bromide) micellar solutions are acquired and studied. Tetra (4-hydroxylphenyl) porphyrin (P₀) and its analogs with one (P₁), two (P₂) and three hexadecyl chains (P₃) exist as the monomers in homogeneous THF, and their similar spectral characteristics indicate that the effects of the substituted hexadecyl groups on the electronic states of porphyrins are negligible in the homogeneous phase of non-polar THF solutions. While the absorption spectral characteristics of amphiphilic porphyrins in neutral CTAB micellar solutions are different in the peak positions and FWHH of the Soret bands. P₀ is proposed to be solubilized in the inner core of CTAB micelles, P₁ is probably solubilized near the interface of CTAB micelles. P₂ has a certain aggregating ability, P₃ is the easiest to aggregate according to the FWHH(41. 6 nm) of the Soret band. The substituted hexadecyl chains of the amphiphilic porphyrins also affect the pH-dependent fluorescence emission spectra on the relative intensity of Q bands. The fluorescences are quenched at different extents to nearly zero with increasing pH values.