Synthons and design in metal phosphates and oxalates with open architectures

We briefly describe the structures of open-framework metal phosphates with different dimensionalities, such as the one-dimensional linear-chain and la dder structures, two-dimensional layer structures and three-dimensional str uctures with channels. We demonstrate the role of the zero-dimensional four -membered ring monomer and of the one-dimensional ladder structure as the s tarting building units or synthons involved in the formation of the complex architectures. Thus, we show how the one-dimensional ladder structure tran sforms to two- and three-dimensional structures under mild conditions. The two-dimensional layer structures also transform to three-dimensional struct ures, while the zero-dimensional monomer transforms to layered and three-di mensional structures under ordinary reaction conditions. These transformati ons provide an insight into the possible pathways involved in the building up of the complex structures of metal phosphates. The isolation of amine ph osphates during the hydrothermal synthesis of metal phosphates and also the facile reactions between amine phosphates and metal ions to yield a variet y of open-framework materials have thrown light on the mechanism of formati on and design of these structures. The existence of a hierarchy of open-fra mework metal oxalates and their ready formation by employing amine oxalates as intermediates provides additional support to the observations made earl ier with regard to the phosphates.