New synthetic route of polyoxometalate-based hybrids in choline chloride/urea eutectic media

The deep eutectic solvents synthetic method was initially explored as a facile synthesis route to prepare new polyoxometalate (POM)-based hybrids. Such a method can not only avoid poor solubility, lower yields and the potential explosion, but also act as a new type of noxious, convenient and environmental friendly organic reagents. Using the choline chloride/urea eutectic mixture as the deep eutectic solvents, two new compounds, [(CH3)3N(CH2)2OH]4[β-Mo8O26] (1) and {(N2H5CO)[(CH3)3N(CH2)2OH]2}[CrMo6O24H6]·4H2O (2), were successfully obtained at room temperature. Both compounds were fully characterized by elemental analyses, IR, UV–Vis, TG analyses, cyclic voltammetry and single-crystal X-ray diffraction. The crystal structures of both compounds exhibit 3-D supramolecular assembly based on the extensive hydrogen bonding interactions between organic cations and polyoxoanions. Compounds 1 and 2 represent the first POM-based hybrids prepared by the deep eutectic solvents synthetic method.