Resolving multiple non-equivalent metal sites in magnesium-containing metal-organic frameworks by natural abundance 25Mg solid-state NMR spectroscopy

In a spin: Directly differentiating multiple Mg sites in Mg-containing MOFs by 25Mg solid-state NMR spectroscopy is very challenging at natural abundance. By performing 25Mg two-dimensional triple-quantum magic-angle spinning solid-state NMR experiments at a magnetic field of 21.1 T at natural abundance, four non-equivalent Mg sites with very similar local environments in \u3b1-Mg3(HCOO)6 were unambiguously resolved (see figure). Copyright \ua9 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Peer reviewed: YesNRC publication: Ye

Theoretical and experimental insights into applicability of solid-state 93Nb NMR in catalysis

Ab initio DFT calculations of 93Nb NMR parameters using the NMR-CASTEP code were performed for a series of over fifty individual niobates, and a good agreement has been found with experimental NMR parameters. New experimental and calculated 93Nb NMR data were obtained for several compounds, AlNbO4, VNb9O25, K 8Nb6O19 and Cs3NbO8, which are of particular interest for catalysis. Several interesting trends have been identified between 93Nb NMR parameters and the specifics of niobium site environments in niobates. These trends may serve as useful guidelines in interpreting 93Nb NMR spectra of complex niobium oxide systems, including amorphous samples and niobium-based multicomponent heterogeneous catalysts. Potential applications of 93Nb NMR to study solid polyoxoniobates are discussed. \ua9 2013 The Owner Societies.Peer reviewed: YesNRC publication: Ye

Solid state complex chemistry: Formation, structure, and properties of homoleptic tetracyanamidogermanates RbRE[Ge(CN2)4] (RE = La, Pr, Nd, Gd)

Tetracyanamidometallates with the general formula RbRE[T(CN 2)4] (RE = La, Pr, Nd, Gd; T = Si, Ge) were prepared by solid state metathesis reactions starting from stoichiometric mixtures of RECl3, A2[TF6], and Li2(CN 2). Reactions were studied by differential thermal analysis that showed ignition temperatures between 360 and 390 C for the formation of RbGd[T(CN2)4] with T = Si and Ge. The powder diffraction patterns of RbRE[Ge(CN2)4] were indexed isotypically to the already known RbRE[Si(CN2)4] compound. IR spectra of RbLa[Ge(CN2)4] were measured and compared with those of RbLa[Si(CN2)4]. 73Ge, 87Rb, and 139La solid state NMR measurements and density functional theory calculations were used to verify the novel homoleptic [Ge(CN2) 4]4- ion. Luminescence properties of Eu3+, Ce3+, and Tb3+ doped samples are reported. \ua9 2013 American Chemical Society.Peer reviewed: YesNRC publication: Ye