Synthesis of a di-porphyrin molecular cage

Abstract

Porphyrins and their derivatives are highly stable macrocyclic compounds with extended 𝜋-network that play crucial roles in different life forms. Inspired by the important roles of porphyrins in nature, molecular scientists have deployed both natural and synthetic analogues of porphyrins and their metal complexes in different areas of applications including biomimetic, single molecule magnet, molecular switches, nanoreactors, photodynamic therapy and molecular information storage. This work describes synthesis of a metal-free di-porphyrin molecular cage that was designed and synthesised via triple-decker lanthanum porphyrin-phthalocyanine porphyrin intermediate. This triple-decker intermediate was assembled by previously described methods with functionalised linkers that were cross-linked by olefin metathesis using Grubbs catalyst. Attempt to demetallation this triple-decker cage using different acid-treatments to obtain the desired dimeric porphyrin molecular cage with phthalocyanine guest yielded different results. Reaction of the triple-decker cage with H2SO4 and trifluoroacetic acid respectively gave a di-porphyrin molecular cage, while treatment with acetic acid led to removal of one of the lanthanum ions. The intermediate triple-decker and the synthesised free di-porphyrin molecular cage have been characterised by 1H and 13C NMR, MALDI-ToF-MS, UV-visible absorption spectroscopy and X-ray crystallography.