Synthesis And Character Research Of Porphyrins As Sensor Materials

Four atropisomers of "picket fence" porphyrin were synthesized based on the first separation of four atropisomers of meso-tetra (o-aminophenyl) porphyrin by column chromatograph with petroleum ether and ethyl acetate, respectively. Results show that each atropisomer could be successfully synthesized by controlling the acylation temperature at 0℃. They were characterized by1H NMR, HRMS, IR, UV-vis and Langmuir-Blodgett (LB) film analyses. Although the results of HRMS, IR, UV-vis analyses indicate there is no marked difference among atropisomers, while the results of the1H NMR and the mean molecular areas obtained by LB film technique imply that atropisomers are significantly discrepant. The former shows that the chemical shifts of the methyl and amide protons of each atropisomer are distinguished obviously, while the later presents that the different atropisomer molecules can occupy the different surface areas at the air/water interface. Moreover, the corresponding interfacial behavior of the four atropisomers of PivPP was investigated by LB film balance at the air/water interface since the "picket fence" porphyrin and its atropisomers are advantageous as gas sensor materials. The solutions of four atropisomers have a tendency to be red in ethyl acetate, acetone, ether or chloroform, green in lacial acetic acid, ethanol or concentrated acid. From the consideration that glacial acetic acid, ethanol or concentrated acid contains H+, while ethyl acetate, acetone, ether or chloroform doesn't, it should be drawn a conclusion that H+can make dark purple atropisomers of PivPP green.The reason is that the N atom in the center of porphyrin ring is protonated when hydrogen ions are adsorbed onto the porphyrin ring, which makes the density of electron cloud changed and results in the color alteration.