Sulfate-Bridged, Octanuclear Chromic and Ferric Wheels.

Two new amine-templated transition metal-based sulfates, [(CH3)2NH2]17.4 [SO4]0.7 [MIII8(µ2-OH)8(µ2-SO4)16] where M = Cr and Fe, have been synthesized via mild solvothermal synthesis. The compounds are isostructural and were refined in the monoclinic space group P21/n. They feature the rare sulfate-bridged inorganic molecular wheels [CrIII8(OH)8(SO4)16]16- and [FeIII8(OH)8(SO4)16]16-. In both the octanuclear chromic (J = -2.4 cm-1 based on Hex = -J Sî · Sĵ convention) and ferric wheels (J = -38.3 cm-1), the coupling between the adjacent metal ions is antiferromagnetic giving spin-singlet ground states. The variation in the magnitude of the exchange coupling constants is due to the differences in the superexchange mechanisms, namely, a π-pathway for the Cr- and a σ-pathway for the Fe-wheel cluster.

A large spin, magnetically anisotropic, octanuclear vanadium(iii) wheel.

A large spin, magnetically anisotropic, octanuclear vanadium(iii) wheel-like cluster has been synthesized. The coupling between adjacent VIII ions is ferromagnetic giving a ground state of St = 8, the largest known for a vanadium-based complex.

Nb2O2F3: a reduced niobium (III/IV) oxyfluoride with a complex structural, magnetic, and electronic phase transition.

A new niobium oxyfluoride, Nb2O2F3, synthesized through the reaction of Nb, SnO, and SnF2 in Sn flux, within welded Nb containers, crystallizes in a monoclinic structure (space group: I2/a; a = 5.7048(1)Å, b = 5.1610(1)Å, c = 12.2285(2)Å, ß = 95.751(1)°). It features [Nb2X10] units (X = O, F), with short (2.5739(1) Å) Nb-Nb bonds, that are linked through shared O/F vertices to form a 3D structure configurationally isotypic to ζ-Nb2O5. Nb2O2F3 undergoes a structural transition at ∼90 K to a triclinic structure (space group: P1̅; a = 5.1791(5)Å, b = 5.7043(6)Å, c = 6.8911(7)Å, α = 108.669(3)°, ß = 109.922(2)°, γ = 90.332(3)°). The transition is described as a disproportionation or charge ordering of [Nb2](7+) dimers: (2[Nb2](7+) → [Nb2](6+) + [Nb2](8+)), resulting in doubly (2.5000(9) Å) and singly bonded (2.6560(9) Å) Nb2 dimers. The structural transition is accompanied by an unusual field-independent "spin-gap-like" magnetic transition.

Photocatalytic degradation of paraquat using nano-sized Cu-TiO2/SBA-15 under UV and visible light.

Photocatalytic degradation of paraquat using mesoporous-assembled Cu-TiO2/SBA15 under UV and visible light was investigated. The catalyst was synthesized by impregnation of Cu-TiO2 colloids onto SBA-15. The colloids of Cu-TiO2 were prepared via sol-gel method while the mesoporous support was prepared using hydrothermal technique. The catalyst was characterized using X-ray diffraction, nitrogen adsorption-desorption, transmission electron microscopy, UV diffuse reflectance spectroscopy, Zeta potential and X-ray adsorption spectroscopy. Results from characterizations showed that Cu doped TiO2 had a small crystalline size and was well-dispersed on SBA-15. The inclusion of SBA-15 significantly enhanced the photocatalytic activity of the catalyst. Among the three types of undoped catalyst in this study (P25, TiO2, TiO2/SBA-15), TiO2/SBA-15 yielded the highest degradation of paraquat for all pH under UV illumination. Meanwhile 2 wt.% Cu-TiO2/SBA-15 yielded the highest activity under visible light.