Molecular design using electrostatic interactions. Part 4: Synthesis and properties of flexible tetrapodand tetracations derived from naphthalene. Role of structured water in the electrostatic binding of polyanion guests: a model for interactions in biolo

The 1,4,5,8-tetracations and have been prepared from 1,4,5,8-tetrakis(bromomethyl)naphthalene and 1,4,5,8-tetrakis(bromomethyl)-2,3,6,7-tetramethylnaphthalene, respectively by treatment with DABCO in acetonitrile. Their interactions with the benzene-1,2,4,5-tetracarboxylate and naphthalene-1,4,5,8-tetracarboxylate tetraanions in water were investigated by 1H NMR titration and both tetracations were found to have greater binding affinity to the benzene tetracarboxylate. Both also gave precipitates with ferricyanide but only the naphthalene tetracation gave a precipitate with ferrocyanide. The X-ray structure of the crystalline ferricyanide tetracation from tetramethylnaphthalene showed the methylDABCO cationic arms to be alternately above and below the naphthalene ring, which was itself distorted from the plane. The bound water in the non-charge-matched complex appears to have a more intimate role in the crystal structure than does the bound water in the charge-matched ferricyanide derived from 2,4,6-tris(DABCO-N-methyl)mesitylene tribromide which we reported previously. An analogy with interactions in biological receptors is made.