Riccardo F. Carina

CYCLOMETALLATED FRAGMENTS AS BUILDING BLOCKS FOR SELF-ASSEMBLY REACTIONS

Abstract Organometallic complexes have not hitherto been employed as building blocks in supramolecular chemistry, but they offer a number of interesting possibilities. Palladium(II) acetate reacts with derivatives of 1,3-bis-(benzimidazol-2-yl)-benzene ( 1 ) to give Pd( 1 -H)(OAc) which self-assembles to a molecular tricorn, but which may also undergo a second cyclometallation to give [Pd 2 ( 1 -2H)(OAc) 2 ]. This species may be cleaved by acid to give [Pd 2 ( 1 -2H)X 2 ] (X = Br, TsO); the latter species react with hydroxyacetate to give [Pd 2 ( 1 -2H)HOCH 2 CO 2 ) 2 ] 2 . The crystal structure of this compound shows two Pd 2 ( 1 -2H) fragments clipped together by four bridging hydroxyacetate ligands.

Modulation of iron reduction potential by deprotonation at a remote site

Remote site deprotonation of a coordinated imidazole ligand switches the reduction potential of coordinated iron over a narrow pH range from +0.920 to –0.460 V.

Following the Self-Assembly Process in Solution

Two aspects of the self-assembly of complex structures around labile metal ions are discussed. Some experimental methods, including ion-spray mass spectroscopy, spectroscopic titrations, and nmr probes, which allow one to study the self-assembly in solution are presented. The types of chemical information carried by the components and the conditions used for the synthesis are illustrated by examples, particularly in the field of double- and triple-helical complexes.