Synthesis and characterization of copolyformals containing electron-rich or electron-poor porphyrin units in the main chain and their use as sensors

In this study two new porphyrin monomers, 5,15-di(pentafluorophenyl)-10,20-di(p-hydroxyphenyl)-porphyrin and 5,15-di(pentabutoxyphenyl)-10,20-di(p-hydroxyphenyl)-porphyrin, were synthesized and characterized by NMR and MALDI-TOF mass spectrometry. The chemical characteristics of these monomers are strongly influenced by their respective electronic distribution which, in turn, is determined by the phenyl ring substituents. By reaction with different amounts of 1,20-di(bisphenoxy-A)-eicosane in presence of dibromomethane, copolyformals containing porphyrin dyes at different percentages were subsequently obtained. The sensing responses of the synthesized copolymers were tested with the following analytes: acetic, trifluoroacetic and hydrochloridic acids and nitrogen dioxide. Our data indicate that porphyrin units interact with analytes in a reversible fashion, it being understood that the decabuthoxy porphyrin derivative has a greater affinity than the other one with both acids and NO2.