Interactions of imidazole with water molecules

Understanding the interactions of imidazole and water molecules is essential for several chemical and biological activities. Literature mining shows that investigations of hydrated imidazole are rare. In this work, interactions between imidazole and explicit water molecules are investigated. The structures of the complexes formed by imidazole and water molecules are used to estimate imidazole's hydration enthalpy and free energy. QTAIM investigation shows that imidazole accepts two strong hydrogen bondings while donating one. In addition, it also interacts with water molecules through weaker bonding interactions. The results reported in this work reproduce previous experimental observations and molecular dynamics simulations.

The investigation started by generating initial configurations through global optimizations using classical potential energy. Then, a suitable functional of density functional theory (DFT) is selected between 20 functionals, including dispersion corrections, by benchmarking to the DLPNO-CCSD(T1)/CBS. The M06L-D3 functional is found to be the most accurate. The structures of the imidazole-water clusters, $\text{IMZ}{\left({\text{H}}_2\text{O}\right)}_n$ , $n=1-12,64$ , are then optimized at the M06L-D3/def2-TZVPP level of theory. Hydration free energy and enthalpy are estimated using the cluster continuum solvation model. Calculations are performed using Gaussian 16 and ORCA suite of programs. Quantum theory of atoms in molecules (QTAIM) is performed using the AIMAll program.