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 yield by a Williamson coupling of 5-(4′-hydroxyphenyl)-10,15,20-triphenylporphyrin with tetraethylene glycol ditosylate. 1H-NMR binding studies reveal that the title receptor binds to Na+ and K+ salts to give a supramolecular complex with stability constants (K) of 30 and 160 M–1, respectively (CD3CN/CDCl3, 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 give indications of the actual geometry of the assembly. The system reported represents an important step toward the construction of a supramolecular model of relevant biological systems.