New AB3-type porphyrins with piperidine and morpholine motifs; synthesis and photo-physicochemical and biological properties

Abstract

In this study, new unsymmetrical meso-tetraaryl AB₃-type porphyrins 1 and 2 were successfully synthesized by the reaction of p-bromobenzaldehyde and p-hydroxybenzaldehyde with pyrrole in propionic acid. AB₃-type porphyrin building blocks with hydroxyl functionality (1 and 2) were further used to generate both covalently linked metal free and Zn(II) porphyrins 3–6 having piperidine and morpholine heterocyclic units. These novel compounds were characterized by using ¹H NMR, ¹³C NMR, FT-IR and MALDI-TOF spectrophotometry. The photophysical and photochemical properties of compounds 1–6 were investigated by employing UV–vis absorption and fluorescence emission spectroscopy in tetrahydrofuran (THF). From the view of biological properties, the antioxidant capacities of porphyrins were determined by using DPPH radical scavenging activity and 2 was determined as the most potent porphyrin analog with a value of 98.42% at 200 mg L⁻¹. All the targeted compounds displayed significant DNA nuclease activity. In addition, the antimicrobial potential of compounds 1–6 was also investigated by a micro-dilution process and 2 was found to be the most effective candidate against the tested microbial strains. The newly synthesized porphyrins also showed 100% microbial cell viability inhibition against E. coli at all examined concentrations. In terms of biofilm inhibition activity, the best results for the maximum photodynamic antimicrobial biofilm inhibition of S. aureus and P. aeruginosa were obtained by compound 2 with the values of 99.75% and 93.39%, respectively.