SELF-ASSEMBLY VIA HYDROGEN BONDING AND METALLATION REACTIONS Paul R. Raithby, Department of Chemistry, Cambridge University, U.K.

Our studies on multi-functional organic molecules have shown that they may self-aggregate via hydrogen bonding or the assembly may be induced via metallation reactions involving the intermediacy of neutral Lewis base molecules. Both types of interaction have been confirmed by X-ray crystallographic studies on the reaction products.

Our work has been concerned with alkali or alkaline earth metallation of multi-functional organic molecules which contain acidic groups such as NH, NH₂ or OH along with heteroatoms such as S, O or N or with functional groups such as C=O or SO₂. Metallation produces highly polar anionic organic residues in conjunction with the metal cations. It is electrostatically inevitable that such species will aggregate, the negative centres and the heteroatoms within the organic anion will interact with as many metal atoms as possible. The extent of the aggregation depends largely upon the steric constraints of the organic ligand and upon those of the neutral Lewis base usually present during metallation. The Lewis bases normally stabilise the metal cation in the metallated organic product by complexing with it, and often block metal coordination sites limiting the extent of the aggregation. However, we have found recently that having such Lewis bases in the system can prevent metallation of the organic acid. Instead, these Lewis bases form adducts with the intact organic molecules. The adducts assemble using hydrogen bonds, the cumulative strength of which appears to be sufficient to block metallation.

I. Cragg-Hine, M.G. Davidson, A.J. Edwards, E. Lamb, P.R. Raithby and R. Snaith, Chem. Commun, 1996, 153.

M.G. Davidson, C. Lambert, I. Lopez-Solera, P.R. Raithby and R. Snaith, Inorg. Chem., 1995, 34, 3765.