Two Tetra-CdII-Substituted Vanadogermanate Frameworks

Two new tetra-Cd-11-substituted vanadogermanate frameworks {(CdX)(4)Ge(8)V(iv)oO(46)(H2O)[V-III((HO)-O-2)(2)],(GeO2)(4)}.8H(2)O (X = ethylenediamine (en, 1) and 1,2-diaminopropane (dap, 2)) were hydrothermally prepared and characterized by IR spectra, elemental analysis, powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Xray single-crystal diffraction. Both are isomorphic, and their 3-D frameworks are made up of tetra-Cdli-substituted {(CdX)(4)(Ge8VO46)-O-IV10(H2O)}(12-) fundamental building units interconnected through planar tetra-V' [(V4O2)-O-III(H2O)(8)](8-) clusters and tetrahedral GeO4 bridges. In the unique {(CdX)(4)(Ge8VO46)-O-IV10(H2O)}(12-) cage, four [Ge2O7] dimers and four CdO4N2 trigonal prisms are alternately concatenated by mu(3)-O bridges to create a round {Ge8Cd4O28(X)(4)}(16-) fragment, five VO5 groups are linked by sharing edges to generate a pentanuclear [V5O17] subunit, and then the {Ge8Cd4O28(X)(4)}(16-) fragment is sandwiched by two V5O17 subunits via sharing O-atoms producing a D-4h-symmetric {(CdX)(4)(Ge8V10O46)-O-IV(H2O}(12-) cage with a free water molecule located at the center. As we know, both display unprecedented 3-D organic inorganic hybrid frameworks built up from the largest number of transition-metal-substituted vanadogermanate {(CdX)(4)(Ge8V10O46)-O-IV}(12-) cluster shells linked by both GeO4 tetrahedra and rare [(V4O2)-O-III(H2O)(8)](8-) clusters. Magnetic measurements reveal the antiferromagnetic couplings within the magnetic vanadium centers.