meso Myths: What Drives Assembly of Helical versus meso-

Both a triple helix as well as a meso complex are formed by the Ga(III) and Al(III) complexes with a bis-bidentate bis-hydroxypyridinone ligand H(2)L. The two forms are in equilibrium in solution, though formation of the helical structure in the presence of water, which as guest molecule finds sufficient space in the cavity of the helix, is favored (the structure of the helical H(2)O subset[Al(2)L(3)] complex is shown).

Self-Assembly of a Three-Dimensional

A near trigonal antiprism with metal-metal distances in the nanometer regime is formed by the six metal ions in the crystalline, homochiral [Ga(6)(L(2))(6)] (see structure). This metal-ligand "cylinder" is based on a threefold symmetric, beta-diketone ligand, and represents a new geometry for metal-ligand clusters.