Solution state structure determination of silicate oligomers by 29SI NMR spectroscopy and molecular modeling |
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Authors: | Cho Herman Felmy Andrew R Craciun Raluca Keenum J Patrick Shah Neil Dixon David A |
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Institution: | Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA. hm.cho@pnl.gov |
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Abstract: | Evidence for nine new solution state silicate oligomers has been discovered by (29)Si NMR homonuclear correlation experiments of (29)Si-enriched samples. In addition to enhancing signal sensitivity, the isotopic enrichment increases the probability of the (29)Si-(29)Si two-bond scalar couplings that are necessary for the observation of internuclear correlations in 2-D experiments. The proposed assignments are validated by comparisons of experimental and simulated cross-peaks obtained with high digital resolution. The internuclear connectivity indicated by the NMR data suggests that several of these oligomers can have multiple stereoisomers, including conformers and/or diastereomers. The stabilities of these oligomers and their possible stereoisomers have been investigated by electronic structure calculations. |
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