Coreceptor Molecules. Synthesis of Metalloreceptors Containing Porphyrin Subunits and Formation of Mixed Substrate Supermolecules by Binding of Organic Substrates and of Metal Ions

Three coreceptor molecules, two macrotetracycles 1 and 2 and one macropentacycle 3, containing [18]-N₂0₄ macrocyclic and porphyrinic subunits, have been synthesized and characterized. They form metalloreceptors by complexation of transition-metal ions like Zn(II) or Cu(II) with the porphyrin groups. Binding of α,ω-diammonium cations to the [18]-N₂0₄ units occurs with substrate inclusion, yielding η²-cryptates like 27, 28, and 31, as indicated by very large upfield shifts of the CH₂ proton NMR signals of the substrates. Similarly, these organic cations also bind to the Zn(II)-containing metalloreceptors 19, 20, and 22, giving organic/inorganic mixed substrate supermolecules, such as 29, 30, and 32. In these and similar species, the simultaneous complexation of several substrates opens the way to the study of mutual interactions within supramolecular structures and of regulation effects on physical and chemical properties.