Synthesis of a hierarchy of zinc oxalate structures from amine oxalates

A hierarchy of novel zinc oxalates including monomers and dimers has been p repared by reaction of amine oxalates with zinc ions, the amine oxalates ha ving been characterized for the first time. In most of the amine oxalates o ne of the carboxyl groups transfers a proton to the amino nitrogen, leaving the other carboxyl group free to form hydrogen bonds. The zinc oxalates ob tained are composed of a network of ZnO6 octahedra and oxalate units, and p ossess zero-, one-, two- and three-dimensional structures. The monomer, dim er, and chain zinc oxalates are the first members of the hierarchy of struc tures. Relationships amongst these various oxalate structures are noteworth y and give indications as to the manner in which these structures are forme d. Thus, the three-dimensional structure can be formed by the linking of la yers, and the layer structure by condensation of linear chains. The isolati on and characterization of a hierarchy of zinc oxalates of differing dimens ionalities assumes significance in the light of the recent finding that low -dimensional structures transform to higher, more complex structures in the phosphate family.