Two new extended frameworks constructed from the sandwiching polytungstoarsenate clusters

Two new extended frameworks based on two different sandwich-type polytungstoarsenates have been synthesized under routine conditions. The reaction of Na9[AsIIIW9O33]·19.5H2O, MnSO4·H2O and citric acid in a weak acidic aqueous solution at pH = 4.23 led to the isolation of a new extended sandwich-type compound {K3Na8[{MnII(H2O)}2.5{(WO)(H2O)}0.5(AsW9O33)2]·12.5H2O}n (1). In compound 1, each sandwiching polyoxoanion [{MnII(H2O)}2.5{(WO)(H2O)}0.5(AsW9O33)2]11− acts as a quadridentate ligand to connect with four neighbors via the mode of {W–O–Mn}, finally leading to an interesting 2D network. The reaction of Na8[HAsW9O34]·11H2O, CeCl3·7H2O and hexamethylenetetramine in an aqueous solution with pH = 5.07 resulted in the obtainment of a polytungstoarsenate-based extended compound [HMTA–CH3]2[HMTA]K2Na7[Ce(AsW11O39)2]·19H2O(2) (HMTA–CH3 = methyl-hexamethylenetetraamine; HMTA = hexamethylenetetraamine). In 2, the polyoxoanions [Ce(AsW11O39)2]11− construct a new extended structure through coordinating to the {KO5(H2O)[HMTA–CH3]} and {KO4(H2O)2[HMTA]} units. The two compounds are characterized by elemental analyses, IR, the diffuse reflectance UV–Vis spectra, PXRD and TG analyses. The electrochemical and electrocatalytical properties of 1 and 2, as well as the fluorescent property of 2 were also investigated.

Graphical abstractTwo new extended frameworks constructed from two different sandwiching polytungstoarsenate aggregates have been successfully synthesized at various pH values and structurally characterized, which are new members in the family of POM-based extended structures. They exhibit electrocatalytic activities for nitrite reduction.Figure optionsDownload full-size imageDownload as PowerPoint slide