Calculations of NMR properties for sI and sII clathrate hydrates of carbon dioxide

Nuclear shielding and spin-spin coupling constants (intra- and intermolecular) have been calculated for cages forming sI and sII clathrate hydrates of carbon dioxide (for all atoms of host and guest molecules). Structures of 5(12), 5(12)6(2) and 5(12)6(4) cages have been constructed using neutronographic data and DFT/B3LYP calculations conducted with HuzIII-su3 basis set for NMR parameters determination. Based on those results it is possible to discriminate between CO2 molecules residing in each type of the cage. The analysis of NMR parameters calculated for water molecules is focused on their dependence on geometry of the molecular environment. It is possible to connect changes in NMR parameters with types of H-bond patterns present in cages of hydrates and the strength of H-bonds formed. Moreover, our results show that topologically differentiable water molecules forming cages are characterized by distinct NMR parameters, for example O-17 shielding constants for water molecules of different topologies differ by 1.6 and 2.1 ppm for cages 5(12)6(2) and 5(12)6(4), respectively. This observation could be confirmed experimentally. (C) 2014 Elsevier B.V. All rights reserved.