Understanding the solvation process and solute-solvent interactions of imidazole compounds in three different solvents through solution calorimetry and 1 H NMR Filiberto Herrera-Castro ⁎, Luis Alfonso Torres Centro de Investigación y de Estudios Avanzados, Departamento de Química, Av. I.P.N. 2508, San Pedro Zacatenco, 07360 Ciudad de México, Mexico abstract article info Article history: Received 7 February 2019 Received in revised form 27 March 2019 Accepted 1 April 2019 Available online 05 April 2019 The enthalpies of solvation of imidazole, 2-methyl-, 2-ethyl- and 2-isopropyl-imidazole in water, methanol and acetonitrile were determined through thermochemical measurements of the corresponding enthalpies of subli- mation and solution. The Pierotti equation, which incorporates the enthalpy of cavity formation and the solvent reorganization for each solute in each solvent, was used to obtain the corresponding enthalpies of interaction. Ad- ditionally, the 1 H NMR spectra of all solutes, in the corresponding deuterated solvents, were also obtained. The discussion of the solvation process and enthalpies of interaction of the imidazole compounds is based on the spe- cific intermolecular interactions, like hydrogen bonds, H − π and non-specific interactions from London forces nature, supported by the features of the 1 H NMR spectra of each solute in each solvent. © 2019 Elsevier B.V. All rights reserved. Keywords: Solvation process Molecular interactions Imidazole NMR Solution calorimetry Enthalpy of solution Enthalpy of sublimation Enthalpy of sublimation of 2- isopropylimidazole Enthalpy of solvation Enthalpy of interaction 1. Introduction The solvation process has been treated in various theoretical [1–6] and experimental [7–12] works. At a molecular level, the solvation pro- cess can be considered to be performed in different stages: (a) the for- mation of a cavity inside the solvent core, with the suitable size and form, to receive a solute molecule; (b) the establishment of specific or anisotropic molecular interactions between solute and solvent, such as hydrogen bonds; (c) the reorganization of the solute and solvent mole- cules, through non-specific or isotropic interactions between them and (d) the establishment of isotropic interactions, like dispersion and the solvent reorganization. The solvation process is significantly important in the supramolecu- lar chemistry, which is the study of the assembly of molecules to form discrete molecular units [13,14]. The assembly of molecules through non-covalent interactions, like those considered in this study, implies a decrease in the degrees of freedom of the interacting molecules. In the same way, the solvation process is directly related to the intermo- lecular interactions [15,16]. These interactions are of electrostatic nature and must consequently affect the electronic environment of the atoms in the solute molecule. The enthalpy of interaction, a more comprehensive parameter that accounts the possible intermolecular interactions during solvation, is obtained when the enthalpy of solvation is corrected by the enthalpy value of the cavity formation and solvent reorganization. This concept has been proposed and treated in [10,17,18]. The influence of molecular interactions in solutions can be detected by the effect in the chemical shifts through the nuclear magnetic reso- nance (NMR) spectroscopy of the different solutes in different solvents. In the same sense, chemical shifts values have been correlated to pK a of hydrogen atoms acidity in organic compounds and proteins [19–21]. In this context, the aim of this work includes the determination of the enthalpy of solvation for imidazole molecules in water, methanol and acetonitrile by measurement of the corresponding enthalpies of sublimation and solution. Then, the magnitude and trend of the en- thalpy of interaction is elucidated in terms of the chemical structure of the solutes, the chemical nature of the different solvents used, as well as the nature of the intermolecular interactions between them. The magnitude and variations of the chemical shifts in the 1 H NMR spectra of the solutes are taken as a molecular insight for the nature of molecu- lar interaction and provide evidence about how the magnitude of the Journal of Molecular Liquids 284 (2019) 232–240 ⁎ Corresponding author. E-mail address: fherrerac@cinvestav.mx (F. Herrera-Castro). https://doi.org/10.1016/j.molliq.2019.04.002 0167-7322/© 2019 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq