Synthesis and characterization of an unprecedented water-soluble tris-functionalized Anderson-type polyoxometalate

A water-soluble single-sided tris-functionalized Anderson-type polyoxometalate (POM) with counter ammonium cations, (NH4)2{[NH3C(CH2O)3]Cr(OH)3Mo6O18}·5H2O(1), has been synthesized by a hydrothermal reaction of parent Anderson-type POMs, [NH4]3[Cr(OH)6Mo6O18] (CrMo6) and tris ligand (HOCH2)3CNH2·HCl (Tris) in aqueous solution. Single-crystal X-ray diffraction analysis has revealed that compound 1 crystallizes in triclinic space group P-1. Each asymmetric unit contains one protonated single-side tris-functionalized Anderson-type POMs anion cluster, {[NH3C(CH2O)3]Cr(OH)3Mo6O18}2- (CrMo6-tris-NH3), and two NH4+ counter cations and five crystallized H2O solvent molecules, which can assemble into a layer-by-layer structure via hydrogen bonding interactions. Furthermore, compound 1 was characterized by elemental analysis, FT-IR, 1H NMR, UV–Vis and TGA. Such a water-soluble tris-functionalized POM with the remote amino reactive group has not been reported before and it may serve as a valuable synthon for further post-functionalization in aqueous solution.