NEW SOLIDS AND SURFACES, VIA COORDINATION CHEMISTRY

Coordination chemistry represents an attractive means for forming well-ordered surface multilayer films and crystalline three-dimensional networks. The preferred bonding geometries of metals and ligands dictate the structures of these layered and framework solids. Ligand substitution rates of metal ions vary over some 15 orders of magnitude, and this property can be used to make bond formation irreversible (in layered films) or reversible (in framework solids, allowing 'annealing' of the lattice). The lamellar Hofmann clathrates, M(BL)M'(CN)4, where M and M' are divalent metal ions (Ru2+ and Ni2+, respectively) and BL is a bridging ligand, such as 4,4'-bipyridine, can be grown layer-by-layer on surfaces using a three-step adsorption sequence. Bulk solids that resemble 'expanded' perovskite can be grown from octahedrally coordinated ions such as Cd2+ and a bridging phenylenediamine ligand. Preliminary structural data on solids prepared from tetrahedral Cu+ cations in combination with bent bridging ligands, intended to mimic the coordination of oxygen in silicate structures, are also described.