Dimethylformamide clusters: non-covalent bondings, structures and temperature-dependence

Abstract

Thermodynamics properties as well as infrared spectra of liquids can be determined using the quantum cluster equilibrium (QCE) theory. The QCE theory requires the knowledge of the structures of the clusters formed by the solvent molecules. In prelude to this determination, in this work, we studied the non-covalent bondings, the structures and the temperature-dependence of the clusters of dimethylformamide (DMF) from dimer to tetramer. To perform this study, we used classical molecular dynamics to sample initial geometries of DMF clusters. Then, optimisation of the geometries is carried out at the MP2/aug-cc-pVDZ level of theory. Besides, we carried out a quantum theory of atoms in molecule analysis. The results show that the structures of the DMF dimer exhibit a stacking configuration, and mainly stabilised by CH··· O hydrogen bondings. For the DMF trimer and DMF tetramer, the structures exhibit an amorphous behaviour. Moreover, it has been found that the CH··· O hydrogen bondings are the main non-covalent bondings in DMF clusters. CH··· C, CH··· N, N··· O, N··· C, C··· O and H··· H bonding interactions are also located in the studied DMF clusters. In addition, the temperature-dependence study shows that only isomers with relative energy within ∼ 1.0 kcal/mol have meaningful contribution to the population of DMF clusters.

GRAPHICAL ABSTRACT

Keywords:

• Dimethylformamide clusters
• non-covalent interactions
• relative energies
• temperature effects

Acknowledgments

The authors are grateful to the Center for High Performance Computing (CHPC) in South Africa for granting them access to their clusters and computational resources. The Norwegian Supercomputing Program (UNINETT Sigma2, Grant No. NN9684K) is acknowledged for computer time. We would also like to thank the Central Research Fund of the University of the Free State.

Disclosure statement

There are no conflicts of interest to declare.

Supplementary material

Optimised Cartesian coordinates of the investigated structures, QTAIM analysis data, and all the isomers of the DMF tetramer as well as their relative energies.

Additional information

Funding

This work was supported by Universiteit van die Vrystaat. The Norwegian Supercomputing Program, UNINETT Sigma2 [grant no. NN9684K].