Molecular Design using Electrostatic Interactions. Part 2: Synthesis and Properties of Flexible Dipodand Di- and Tetra-cations with Restricted Conformations. Charge, Shape and Size in Molecular Complexation

A number of dipodand dications and tetracations were synthesised with structures based on 1,2,4,5-, penta- and hexa-substituted benzene, DABCO substituents providing the positive charges. The binding of these polycations in water to a variety of polyanions was examined with respect to the effect of the ‘spectator’ counter cations on the observed association constants. The polycations precipitate ferri- and ferrocyanide, in some cases preferentially for one oxidation state, and an X-ray crystallographic analysis of the complex between the tetracation 5 and ferricyanide reveals the complexity involved even in the molecular recognition of small, charged compounds.