Alkali Metal Ion Complexes with Pyrazinetetracarboxylate: Two- and Three-Dimensional Frameworks

Three novel polymeric assemblages have been obtained from alkali metal salts of pyrazinetetracarboxylic acid (H(4)PZTC). In the complexes [Na-2(H(2)PZTC)(H2O)(2)] (1), [K(H(3)PZTC)] (2), and [Cs-2(H(2)PZTC)] (3), the cations are chelated in the O, N,O site of one (1) or two ligands (2 and 3),and further carboxylic/ate complexation results in the formation of two-(1) or three-dimensional (2 and 3) compact assemblages with alternate rows or planes of cations and ligands. The H(4-x)PZTC(x-) ligand is bound to 6, 4, and 12 cations in 1-3, respectively, with four oxygen atoms in the last case being coordinated to as many as four cesium atoms each. The crystal structure of complex 3 is particularly remarkable, with the cesium cation having a coordination number of 12 and a hexagonal prismatic environment. The Cs center dot center dot center dot Cs contacts in this compound are among the shortest reported. These compounds further illustrate the potential or H(4)PZTC for the building of metal-organic frameworks.