Hydrogen bonding guest-water interactions in pinacolone, tert-butyl amine, and tert-butylmethyl ether: a theoretical study on energetics, structure, and topological + .

CONTEXT

In guest-host interactions, guest molecules used for hydrogen bonding potential of clathrate hydrate cages are involved as "promoters" for hydrogen or methane storage. Among the promoter molecules, there are pinacolone and tert-butylmethyl ether containing oxygen atom, and tert-butyl amine among those containing nitrogen atom. The dimer and trimer interactions of these molecules with the water clusters were investigated. The cooperativity effect, which is a measure of the hydrogen bonding of these oxygen and nitrogen-containing complexes, was calculated and these complexes were analyzed. Moreover, molecular electrostatic potential (MEP) analysis was performed to determine intermolecular interactions. Clusters of several molecules may seem like a non-significant state of matter; however, in systematic studies with small clusters, important results can be obtained. Therefore, it is very useful to work with clusters to understand the properties of the dense phase, and this study aimed to examine the properties of structures, energies, infrared vibration frequencies, and topological parameters, which develop as a result of the interaction of structures in different clusters with water molecules.

METHODS

The MP2 level was performed using aug-cc-pVDZ basis set calculations for this study. Tight converting criteria were used in the optimization step. Harmonic vibrational modes were calculated at the MP2/aug-cc-pVDZ level. Each minima obtained from the MP2 level was subjected to single-point energy calculations using CCSD(T) levels with the aug-cc-pVDZ basis set by the Gaussian16 package program suite. The topological analyses were performed with non-covalent interaction (NCI). MEP surface of the complex was also composed by Gaussian program using the optimized geometry at a MP2/aug-cc-pvdz level.