Synthesis and characterization of a thermoresponsive polyoxometalate-polymer hybrid.

We report the synthesis of the first organo-POM with thermoresponsive properties. Our concept will provide chemists with a new tool to design POMs whose solubility is reversibly controllable through an external stimulus. POM-polymer TBA(7)[POM]-poly(N,N-diethylacrylamide) (POM-PDEAAm), was prepared by grafting PDEAAm-NH(2) (obtained by RAFT polymerization) onto the activated Dawson acyl-POM, α(2)-[P(2)W(17)O(61)SnCH(2)CH(2)C(=O)](6-). Extensive MS analysis was used to monitor the chain-functionalization steps and to confirm the formation of the hybrid. Aqueous solutions of the (NH(4))(7)[POM-PDEAAm] exhibited a LCST of 38 °C. Thus, the solubility/aggregation of the hybrid was reversibly controlled by changing the temperature. Above 38 °C, the solution became cloudy, and cleared again upon cooling. Dynamic light scattering (DLS) revealed the formation of small aggregates in the range 100 nm. We assumed that the charged POM head units prevented the formation of the larger-scattering aggregates that are usually observed for PDEAAm, and promoted the formation of micelle-like structures. The conjugate exhibited a temperature transition, which was different from that of the polymer and depended on the counterions associated with the POM. This result demonstrates the potential for merging organic (in this case, polymer) and inorganic structures to afford materials that exhibit new properties.

Porous metal-organic truncated octahedron constructed from paddle-wheel squares and terthiophene links.

A metal-organic truncated octahedron (termed MOP-28) has been constructed from six rigid square-shaped Cu2(CO2)4 paddle-wheel building units and twelve 2,2':5',2' '-terthiophene-5,5' '-dicarboxylate (TTDC) linkers. TTDC linker in the cis,cis conformation provides the critical 90 degrees linkage for this unique construction. The porous structure of MOP-28 is maintained even after the removal of guest species, as evidenced by this compound's nitrogen sorption isotherm of Type I characteristics and unprecedented surface area (Langmuir surface area 1100 m2/g, BET surface area 914 m2/g) among materials composed of discrete molecules.