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Quantitative analysis of specifically deuterated compounds can be achieved by a number of conventional methods, such as mass spectroscopy, or by quantifying the residual 1H NMR signals compared to signals from internal standards. However, site specific quantification using these methods becomes challenging when dealing with non-specifically or randomly deuterated compounds that are produced by metal catalyzed hydrothermal reactions in D2O, one of the most convenient deuteration methods. In this study, deuterium-induced NMR isotope shifts of quaternary 13C resonances neighboring deuterated sites have been utilized to quantify the degree of isotope labeling of molecular sites in non-specifically deuterated molecules. By probing 13C NMR signals while decoupling both proton and deuterium nuclei, it is possible to resolve 13C resonances of the different isotopologues based on the isotopic shifts and the degree of deuteration of the carbon atoms. We demonstrate that in different isotopologues, the same quaternary carbon, neighboring partially deuterated carbon atoms, are affected to an equal extent by relaxation. Decoupling both nuclei (1H, 2H) resolves closely separated quaternary 13C signals of the different isotopologues, and allows their accurate integration and quantification under short relaxation delays (D1 = 1 s) and hence fast accumulative spectral acquisition. We have performed a number of approaches to quantify the deuterium content at different specific sites to demonstrate a convenient and generic analysis method for use in randomly deuterated molecules, or in cases of specifically deuterated molecules where back-exchange processes may take place during work up. 相似文献
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Wiebke Unkrig Fu Zhe Razan Tamim Friederike Oesten Dr. Daniel Kratzert Prof. Dr. Ingo Krossing 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(2):758-765
The syntheses of the homoleptic bis(arene) niobium cations [Nb(arene)2]+ (arene = C6H3Me3, C6H5Me) with 16 valence electrons and heteroleptic arene-carbonyl cations [(CO)Nb(arene)2]+ (arene = C6H3Me3, C6H5Me) and [(arene)M(CO)4]+ (arene = C6H3Me3, C6H6) obeying 18 valence electrons are described. Stabilization of these complexes was achieved by using the weakly coordinating anions [Al(ORF)4]− or [F{Al(ORF)3}2]− (RF = C(CF3)3). The limits of two synthesis routes starting from neutral Nb(arene)2 (arene = C6H3Me3, C6H5Me) or [NEt4][M(CO)6] (M = Nb, Ta) were investigated. All compounds were analyzed by single crystal X-ray determination, vibrational and NMR spectroscopy. DFT calculations were executed to support the experimental data. 相似文献
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Interpenetration as a Mechanism for Negative Thermal Expansion in the Metal–Organic Framework Cu3(btb)2 (MOF‐14) 下载免费PDF全文
Yue Wu Dr. Vanessa K. Peterson Emily Luks Dr. Tamim A. Darwish Prof. Cameron J. Kepert 《Angewandte Chemie (International ed. in English)》2014,53(20):5175-5178
Metal–organic framework materials (MOFs) have recently been shown in some cases to exhibit strong negative thermal expansion (NTE) behavior, while framework interpenetration has been found to reduce NTE in many materials. Using powder and single‐crystal diffraction methods we investigate the thermal expansion behavior of interpenetrated Cu3(btb)2 (MOF‐14) and find that it exhibits an anomalously large NTE effect. Temperature‐dependent structural analysis shows that, contrary to other interpenetrated materials, in MOF‐14 the large positive thermal expansion of weak interactions that hold the interpenetrating networks together results in a low‐energy contractive distortion of the overall framework structure, demonstrating a new mechanism for NTE. 相似文献
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