Cation-Controlled Assembly of Polyoxotungstate-Based Coordination Networks

The Preyssler polyoxoanion, [NaP5W30O110](14-)({P5W30}), is used as a platform for evaluating the role of nonbridging cations in the formation of transition-metal-bridged polyoxometalate (POM) coordination frameworks. Specifically, the assembly architecture of Co2+-bridged frameworks is shown to be dependent on the identity and amount of alkali- or alkaline-earth cations present during crystallization. The inclusion of Li+, Na+, K+, Mg2+, or Ca(2+)in the framework synthesis is used to selectively synthesize five different Co2+-bridged {P5W30} structures. The influence of the competition between K(+)and Co(2+)for binding to {P5W30} in dictating framework assembly is evaluated. The role of ion pairing on framework assembly structure and available void volume is discussed. Overall, these results provide insight into factors governing the ability to achieve controlled assembly of POM-based coordination networks.