Spectroscopic and electrochemical studies on oxaporphyrins and oxathiaporphyrins

The synthesis and characterization of oxaporphyrins (OTPP and O₂TPP) containing one and two furan rings in place of pyrrole and a mixed oxathiaporphyrin (OSTPP) is reported. Spectroscopic and electrochemical studies reveal that oxaporphyrins exhibit optical and emission characteristics closer to the parent H₂TPP, while their electrochemical behaviour parallels that reported for mono and dithiaporphyrins. However the characteristics of the mixed oxathia derivative resemble that of monothiaporphyrin. Protonation studies reveal weaker resonance interaction between the β-hydrogens and meso-phenyl substituents in sharp contrast to thiaporphyrins. The reduction potentials for OSTPP and O₂TPP indicate stabilization and destabilization of their LUMOs relative to the parent H₂TPP in the ground and excited states, respectively.