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Spectroscopic techniques are a powerful tool for structure determination, especially if single-crystal material is unavailable. 113Cd solid-state NMR is easy to measure and is a highly sensitive probe because the coordination number, the nature of coordinating groups, and the geometry around the metal ion is reflected by the isotropic chemical shift and the chemical-shift anisotropy. Here, a detailed investigation of a series of 27 cadmium coordination polymers by 113Cd solid-state NMR is reported. The results obtained demonstrate that 113Cd NMR is a very sensitive tool to characterize the cadmium environment, also in non-single-crystal materials. Furthermore, this method allows the observation of guest-induced phase transitions supporting understanding of the structural flexibility of coordination frameworks. [ABSTRACT FROM AUTHOR]

Pure component sorption isotherms of n-butane, isobutane, 1-buteneand isobuteneon the metal-organic framework (MOF) [sup 3]∞[[Cu[sub 4](μ[sub 4]-O)(μ[sub 2]-OH)[sub 2](Me[sub 2]trz-pba)[sub 4]] at various temperatures between 283 K and 343 K and pressures up to 300 kPa are presented. The isotherms show a stepwise pore filling which is typical for structurally flexible materials with broad adsorption-desorption hysteresis loops. Gate opening pressures in their endemic characteristic depend on the used hydrocarbon gases. From all investigated gases only the isotherms of 1-butene present a second step at a relative pressure above p/p[sub 0] = 0.55. As a consequence, only 1-butene can fully open the framework resulting in a pore volume of 0.54 cm[sup 3] g[sup -1]. This result is in good agreement with the value of 0.59 cm[sup 3] g[sup -1] calculated based on single crystal structure data. The isosteric heat of adsorption was calculated from the experimental isotherms for all C[sub 4]-isomers. At low loadings the isosteric heat is in a narrow region between 41 and 49 kJ mol[sup -1]. Moreover, in situ XRD measurements at different relative hydrocarbon pressures were performed at 298 K for the C[sub 4]-isomers. The differences in the pressure-depending powder diffraction patterns indicate phase transitions as a result of adsorption. Similar diffraction patterns were observed for all C[sub 4]-hydrocarbons, except 1-butene, where the second step at higher relative pressure (p/p[sub 0] > 0.55) is accompanied by an additional phase transition. This powder pattern resembles that of the as-synthesized MOF material containing solvent molecules in the pore system. The resulting structural changes of the material during guest and pressure induced external stimuli are evidenced by the new coupled XRD adsorption equipment. [ABSTRACT FROM AUTHOR]

The crystal structures of five new CoII, ZnII, and CdII coordination polymers based on pyridine-substituted triazolyl carboxylates are reported. The two isomorphous compounds ∞3[M(Me-3py-pba)2] (M = Zn, Co) possess {66} topology (dia). In order to obtain heteronuclear compounds, we synthesized CoII-substituted ZnII and CdII coordination polymers. At T = 5 K, the powder samples of the diamagnetically diluted CoII/ZnII and CoII/CdII systems [Co/(Zn,Cd) ≈ 0.01] show intense electron paramagnetic resonance spectra, which were analyzed with an effective spin of S' = ½. The g tensor as well as the 59Co hyperfine tensor ACo are strongly anisotropic. The g tensor components are used to gain information about the symmetry of the CoII coordination sphere and covalency effects. Differential thermal analysis/thermogravimetry-mass spectrometry and temperature-dependent powder X-ray diffraction studies reveal high thermal stability of the three-dimensional coordination polymers up to 390 °C. [ABSTRACT FROM AUTHOR]

Abstract: For two series of isostructural, heteronuclear 3D coordination polymers containing Co and Zn, i.e., [CoxZn1−x(tdc)(bipy)] and [CoxZn1−x(Me2trz–pba)2], with nCo/nZn-ratios from 0.00 to 1.00, the epoxidation of cyclooctene with tert-butyl hydroperoxide in liquid toluene at 348K was studied. In dependence of the Co-content in the material, the catalytic activity steadily increases with the Co-free materials being inactive and the Zn-free materials showing the highest catalytic activity (cyclooctene conversion of 32% and epoxide selectivity of 50%). Although the catalytic conversion occurs at the outer crystallite surface, the results prove that a sensitive tuning of the catalytic properties of coordination polymers and metal-organic frameworks can be achieved by isomorphous substitution with redox active elements. [Copyright &y& Elsevier]

Spectroscopic techniques are a powerful tool for structure determination, especially if single-crystal material is unavailable. (113)Cd solid-state NMR is easy to measure and is a highly sensitive probe because the coordination number, the nature of coordinating groups, and the geometry around the metal ion is reflected by the isotropic chemical shift and the chemical-shift anisotropy. Here, a detailed investigation of a series of 27 cadmium coordination polymers by (113)Cd solid-state NMR is reported. The results obtained demonstrate that (113)Cd NMR is a very sensitive tool to characterize the cadmium environment, also in non-single-crystal materials. Furthermore, this method allows the observation of guest-induced phase transitions supporting understanding of the structural flexibility of coordination frameworks., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Synthesis and solid-state NMR characterization of two isomorphous series of zinc and cobalt coordination networks with 1,2,4-triazolyl benzoate ligands are reported. Both series consist of 3D diamondoid networks with four-fold interpenetration. Solid-state NMR identifies the metal coordination of the ligands, and assignment of all (1)H and (13)C shifts was enabled by the combination of (13)C editing, FSLG-HETCOR spectra, and 2D (1)H-(1)H back-to-back (BABA) spectra with results from NMR-CASTEP calculations. The incorporation of Co(2+) replacing Zn(2+) ions in the MOF over the full range of concentrations has significant influences on the NMR spectra. A uniform distribution of metal ions is documented based on the analysis of (1)H T1 relaxation time measurements.

The newly synthesized Zn(4)O-based MOF (3)(∞)[Zn(4)(μ(4)-O){(Metrz-pba)(2)mPh}(3)]·8 DMF (1·8 DMF) of rare tungsten carbide (acs) topology exhibits a porosity of 43% and remarkably high thermal stability up to 430 °C. Single crystal X-ray structure analyses could be performed using as-synthesized as well as desolvated crystals. Besides the solvothermal synthesis of single crystals a scalable synthesis of microcrystalline material of the MOF is reported. Combined TG-MS and solid state NMR measurements reveal the presence of mobile DMF molecules in the pore system of the framework. Adsorption measurements confirm that the pore structure is fully accessible for nitrogen molecules at 77 K. The adsorptive pore volume of 0.41 cm(3) g(-1) correlates well with the pore volume of 0.43 cm(3) g(-1) estimated from the single crystal structure.

The crystal structures of five new Co(II), Zn(II), and Cd(II) coordination polymers based on pyridine-substituted triazolyl carboxylates are reported. The two isomorphous compounds (∞)³[M(Me-3py-pba)₂] (M = Zn, Co) possess {6⁶} topology (dia). In order to obtain heteronuclear compounds, we synthesized Co(II)-substituted Zn(II) and Cd(II) coordination polymers. At T = 5 K, the powder samples of the diamagnetically diluted Co(II)/Zn(II) and Co(II)/Cd(II) systems [Co/(Zn,Cd) ≈ 0.01] show intense electron paramagnetic resonance spectra, which were analyzed with an effective spin of S' = ½. The g tensor as well as the ⁵⁹Co hyperfine tensor A(Co) are strongly anisotropic. The g tensor components are used to gain information about the symmetry of the Co(II) coordination sphere and covalency effects. Differential thermal analysis/thermogravimetry-mass spectrometry and temperature-dependent powder X-ray diffraction studies reveal high thermal stability of the three-dimensional coordination polymers up to 390 °C.