Synthesis and complexation properties of an oligooxaethylene-spacered porphyrin dimer - Toward the construction of a new switchable porphyrin array

A new linear switchable diporphyrin array has been synthesized in good yiel d by a Williamson coupling of 5-(4'-hydroxyphenyl)-10,15,20-triphenylporphy rin with tetraethylene glycol ditosylate. H-1-NMR binding studies reveal th at the title receptor binds to Na+ and K+ salts to give a supramolecular co mplex with stability constants (K) of 30 and 160 M-1, respectively (CD3CN/C DCl3, 1:1). The formation of the host-guest complexes promotes a change of the geometry of the system toward a topology in which the two tetrapyrrolic macrocycles tend to face together. UV/Vis and fluorescence spectroscopy gi ve indications of the actual geometry of the assembly. The system reported represents an important step toward the construction of a supramolecular mo del of relevant biological systems.