The 1,4,5,8-tetracations 5 and 11 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-tetracarboxyl ate and naphthalene-1,4,5,8-tetracarboxylate tetraanions in water were investigated by (1)H 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 5 gave a precipitate with ferrocyanide. The X-ray structure of the crystalline ferricyanide tetracation 14 from tetra-methylnaphthalene showed the methylDABCO cationic anus 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 14 appears to have a more intimate role in the crystal structure than does the bound water in the charge-matched ferricyanide 15 derived from 2,4,6-tris(DABCO-N-methyl)mesitylene tribromide which we reported previously. An analogy with interactions in biological receptors is made. (C) 2002 Elsevier Science Ltd. All rights reserved.
