Sn(IV) porphyrins as NMR shift reagents and supramolecular protecting groups: Preparation of a carboxylate-catenane porphyrin complex

Coordination of a carboxylic acid diaryl crown ether to a Sn(IV) porphyrin promotes its ability to act as a template for the formation of a [2]catenan e: in the absence of the porphyrin the acid-crown yields only a tiny amount of the interlocked derivative, Once isolated the free acid-[2]catenane pre sents extremely broad resonances in its 500 MHz H-1 NMR spectrum, but compl exation to a Sn(IV) porphyrin results in dramatic resolution via a combinat ion of dynamic and dispersive effects.