Progress Towards A Facile Synthesis of a Gadolinium (III) Octabrominated Porphyrin

Towards preparing porphyrin complexes that combine contrast agent and photodynamic therapy capabilities at tumor sites, the Gd(III) porphyrin derivative of the octabrominated meso-tetrakis(N-methyl-4-pyridyl)porphyrin, GdTMPyPBr8 5+ was synthesized by refluxing Gd(III) ion with H3TMPyPBr8 5+ at pH 7. The metallocomplex was characterized by UV-visible spectroscopy and showed a Soret band shift from 503 nm to 463 nm at pH 7, suggesting that metal insertion of Gd(III) into the core of porphyrin ligand had occurred. However, synthesis of the Gd(III) complex required high temperatures and long reaction times. To circumvent these harsh conditions, the lithium porphyrin derivative was first prepared and subsequently combined with Gd(III) ion to yield the desired product at room temperature