Proton NMR chemical shift and intrinsic acidity of hydroxyl groups. Ab initio calculations on catalytically active sites and gas-phase molecules

Dissolution mechanisms of water in depolymerized silicate melts: Constraints from 1H and 29Si NMR spectroscopy and ab initio calculations

“…Similar 1 H chemical shifts (around 1.4 to 2.3 ppm) have been reported for non-hydrogen-bonded SiOH in clusters of various sizes in the SiO 2 -H 2 O system, calculated with robust basis sets similar to that used here for shielding and with a wider range of methods for geometry optimization (e.g., Fleischer et al, 1993;Xue and Kanzaki, 1998;Casanovas et al, 1999;Civalleri et al, 1999; bonded SiOH in Si 2 O(OH) 6 dimer and Si 3 O 2 (OH) 8 linear trimer clusters are 3.14 and 2.98 Å at B3LYP/6-31ϩG(d,p), corresponding to 1 H chemical shifts of 3.3 and 3.8 ppm, respectively (see Fig. 17a and Table 5).…”

“…The 1 H chemical shifts of SiOH groups in silicates have been the subject of a number of previous ab initio MO studies using clusters of various sizes (e.g., Fleischer et al, 1993;Xue and Kanzaki, 1998;Casanovas et al, 1999;Civalleri et al, 1999;. It is now clear from both ab initio calculations and experimental 1 H-NMR data (e.g., Yesinowski and Eckert, 1987;Eckert et al, 1988;Heidemann, 1994) that the 1 H chemical shifts for acidic OH groups (e.g., SiOH, POH and SOH) and molecular H 2 O all show a general correlation with hydrogen bonding distance.…”

Study of hydrogen bonds in N-methylacetamide by DFT calculations of oxygen, nitrogen, and hydrogen solid-state NMR parameters

“…Since the employed method and basis sets of this study are proper to yield reliable NMR parameters [19,27,28], the calculated results are validated. However, as mentioned in Sect.…”

“…However, as mentioned in Sect. Computational aspects, since IGLO-II type of basis set is expected to yield more reliable NMR parameters [27,28], in the following text, these calculated results are referred.…”

“…The larger Kutzelnigg's IGLO-II [25] basis set having functions with large exponents for representation of core electrons are derived by Huzinaga's basis sets [26]. Both of 6-311++G** and IGLO-types basis sets are adapted to reproduce reliable NMR parameters [19,27,28]. Furthermore, since the sizes of both employed basis set are large, and also by the results of previous studies [29,30], basis set supper position error effects are not considered in present NMR calculations.…”