Rational Design of a Coordination Cage with a Trigonal-Bipyramidal Shape Constructed from 33 Building Units

摘要

The rapidly growing field of supramolecular coordination chemistry can be divided into two classes according to the products formed. The polymers are already well-studied because of possible applications as new materials, heterogeneous catalysts, and ion-exchange materials.[1] The other class of supramolecular entities, discrete cage molecules, are conceived by rational design and prepared from a set of molecular building blocks that fit together such that the stoichiometry and symmetry elements of the product are predestined by the starting compounds.[2] In most of the coordination cages formed by this method the corners correspond to the metal centers, which are linked by twofold bridging ligands.[2]-[6] The use of building blocks that cover the faces of the cage is not as common. Triangular subunits were used to form tetrahedral, octahedral, and adamantanoid coordination cages.[2]-[6] Cages with lower symmetry and triangular faces have been synthesized only in the past few years.[6]-[10] Here we report the rational design of a coordination cage with the outer shape of a trigonal bipyramid. The characterization of an intermediate gives insight into the reaction mechanism.