Polyoxotungstates in Molecular Boxes of Purine Bases

Abstract

Three new compounds, (GuaH)4[W10O32](H2O)4 (1), (ThbH)3(H3O)[(W10O32](H2O)7.5 (2) and (ThbH)2[W6O19](H2O)2 (3) (GuaH = guaninium, thbH = theobrominium) were synthesized in acidified acetonitrile solutions. The polyoxotungstates in all of these compounds are surrounded by an organic matrix consisting of protonated purine bases and water molecules. The distinctive structural arrangement of the aromatic organic cations around the polyoxoanions parallel to their faces is reminiscent of nanosized boxes. The results of IR spectroscopy are consistent with previously reported results for polyoxotungstates and neat organic compounds. The polyoxoanions are reduced to tungsten(IV) oxide upon heating over 400 °C in an intramolecular redox reaction.

Keywords

• polyoxometalates
• purines
• non-covalent interactions
• tungsten