Synthesis properties and applications of modified porphyrins

Abstract

Porphyrins are naturally occurring dye molecules containing four pyrroles connected through methine bridges. They function as one of the fundamental classes of enzymes in nature and act as the pigments in natural photosynthesis process to convert sun light in to energy. Because of their photoactive and redox active nature, porphyrins have been synthetically targeted for several studies such as models for enzyme catalysis as well as electron and energy transfer processes. Currently, porphyrins are widely considered as high-potential photosensitizers in photodynamic therapy of cancer, photoinactivation of bacteria and environmental remediation research due to their ability to generate singlet oxygen upon external light stimuli.An ideal photosensitizer should first of all be easily accessible through synthesis and exhibit high quantum yield of singlet oxygen besides being cheap, selective, non-toxic and photostable. The work presented in this thesis aims to address these issues through chemical modification of the porphyrin and#960;-ring framework. Several modifications have been effected such as the addition of heavy bromine atoms in the and#946; position, core metallation with tin(IV) or Zn(II) ion, variation of the axial ligands and dimerization. Effect of these changes on the electronic properties, singlet oxygen generation ability, photostability and aggregation of the porphyrin macrocycle has been studied in detail along with their application potential. In the first part, tin(IV) porphyrins containing bromine atoms at 2,3,12,13 and#946;-pyrrole positions were synthesized using four different bis-axial ligands namely, chloro, hydroxo, phenolato and 4-nitrophenolato. The compounds were characterized using 1H NMR, ESI-MS spectroscopies and elemental analysis. newline