Trans-membrane controlling of an amphiphilic metalloporphyrin

In order to perform a transfer process of the porphyrin moiety across membrane media, an amphiphilic porphyrin 5,10,15-tri(4-hydroxyphenyl)-20-(4-hexadecyloxy-phenyl) porphyrin (P₁) and its metalloporphyrin (P₁Zn) were selected to be solubilized in cetyltrimethyl ammonium bromide (CTAB) micellar solutions. By taking advantage of the microenvironment sensitivity of their Sorer band, UV-Vis spectra were used to study the dependence of location of the porphyrins in CTAB micellar media on the bulk pH value or the salt concentration of bulk solutions. The red shift of the Soret band, the decrease of its absorbance and the increase of the full width at half-maximum (FWHM) of P₁Zn and P₁ with pH titration process from neutral to weak basicity were attributed to the transfer process of the porphyrin moiety from the inner core to the outer surface of the micelles. In the pH sensitive area of the Soret band of P₁Zn and P₁, the blue shift of the Soret band, the increase of its absorbance and decrease of FWHM were observed on decreasing the bulk pH value or increasing the salt bulk solution concentration, indicating that the porphyrin moiety was pushed into the inner core again. Therefore, we can control the trans-membrane transfer process of porphyrin moiety by changing the pH value or the salt concentration of the bulk solutions.