Syntheses and structure of three 2D polyoxometalates derived from macrocation [Cr3O(COOH)6(H2O)3]+ and α-Keggin-type polyoxomolybdate anions

Three novel organic–inorganic hybrid compounds with 2D infinitely extended structure, K3[Cr3O(COOH)6(H2O)3][SiMo12O40]·8.5H2O (1), K3[Cr3O(COOH)6(H2O)3][GeMo12O40]·9H2O (2) and K2[Cr3O(COOH)6(H2O)3][PMo12O40]·10.25H2O (3), were synthesized by reaction of Keggin-type polyoxomolybdates with a macrocation of [Cr3O(COOH)6(H2O)3]+ and further characterized by elemental analyses, IR, UV–Vis spectroscopy, single crystal X-ray structural analyses, thermogravimetric and electrochemical properties, which were constructed from saturated Keggin-type polyoxomolybdates and trinuclear chromium formate macrocations. Single crystal X-ray structural analyses of 1, 2 and 3 reveal that polyoxomolybdate anions [XMo12O40]n− (X = SiIV, n = 4; X = GeIV, n = 4, X = PV, n = 3) and macrocations [Cr3O(COOH)6(H2O)3]+ are polymerized through the bridging K+ cations to form a 2D infinitely extended layer structure with honeycomb-like apertures.