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

Abstract 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, [(CH 3 ) 3 N(CH 2 ) 2 OH] 4 [β-Mo 8 O 26 ] ( 1 ) and {(N 2 H 5 CO)[(CH 3 ) 3 N(CH 2 ) 2 OH] 2 }[CrMo 6 O 24 H 6 ]·4H 2 O ( 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.