Triple-decker assemblies based on strapped di-porphyrins

Abstract

Over the last few decades, remarkable attention has been focused on the study of multidecker sandwich type complexes. Porphyrins and/or phthalocyanines (Pcs) are heterocycle-containing macrocycle compounds that can be used as building blocks to form multidecker complexes. These complexes have potential applications in imaging technology and information storage. Owing to their unique properties in material science, mixed porphyrins and /or phthalocyanines were investigated by our group to synthesise triple decker complexes. As a result, a number of complexes have been prepared by our group. The ultimate goal of this study was to extend the strategy to threaded systems (catenanes and rotaxanes). Our model system is designed to demonstrate this strategy by synthesizing the triple decker complex based on the clipping strategy followed by removal of metals. Initially, the current work focused on the synthesis of trans porphyrins as key building blocks for our model system. Their synthesis proved challenging due to the formation of scrambled products, but within the project's later stages we solved this by employing removable blocking bromide substituents. As the cis porphyrin was obtained as a side product from trans porphyrin reactions, it was used in this thesis. A triple decker (TD) complex from a cis 5,10 double bridged porphyrin was designed and synthesised using a clipping strategy. The triple decker complex from trans 5,15-double bridged porphyrin was synthesised via an uncontrolled strategy due to the poor solubility of trans porphyrin dyad intermediate that was initially targeted. These novel TDs have been successfully characterized using spectroscopic tools including NMR, MALDI-tof MS, UV and unambiguously through X-ray crystallography. Treatment of the TD with TFA resulted in the removal of both the metals and the sandwiched Pc, as expected for this particular Pc.