Chiral Phenomena in Multinuclear and Metallosupramolecular Coordination Systems Derived from Metalloligands with Thiol-Containing Amino Acids

In this account, we focus on the stereochemical and chiral behavior of S-bridged multinuclear and metallosupramolecular coordination compounds that are derived from mononuclear metal complexes with cysteine (H(2)cys) or penicillamine (H(2)pen). The mononuclear complexes act as versatile metalloligands with amine and/or carboxyl groups, in addition to the thiol groups, as donor sites, allowing them to form a large variety of coordination compounds in combination with additional metal ions. Several chiral elements, such as chiral metal centers, asymmetric bridging sulfur atoms, and molecular and supramolecular helicity, in addition to asymmetric carbon atoms, are created in the resulting molecular and crystal structures, and their absolute configurations are often controlled to produce a single kind of homochiral species. In addition, this metalloligand approach leads to several unique chiral phenomena, such as stimulus-responsive chiral switching/inversion based on geometrical changes in metal centers, highly efficient chiral recognition between multinuclear complex cations and anions, and unusual spontaneous resolution behavior, in the resulting coordination systems.