Poster

Computer Simulation Study of the Solvation of Inorganic Salts in N,N-Dimethylformamide

Helga Tóth Ugyonka, Viktor Szilágyi, Ákos György Juhász, Abdenacer Idrissi, Angela Jedlovszky-Hajdú, and Pál Jedlovszky*
1. Department of Chemistry, Eszterházy Károly Catholic University
2. Center for Natural Sciences, University of Pannonia
3. Department of Biophysics and Radiation Biology, Semmelweis University
4. Unità di Ingegneria Tissutale, ISBReMIT, Fondazione IRCCS Casa Sollievo della Sofferenza
5. University of Lille, CNRS UMR 8516 -LASIRe - Laboratoire Avancé de Spectroscopie pour les Interactions la Réactivité et l'environnement
jedlovszky.pal@uni-eszterhazy.hu

Abstract

N,N-dimethylformamide (DMF) is one of the most widely used aprotic dipolar solvents in both synthetic chemistry and the chemical industry. It is applied in numerous organic syntheses, the processing of cellulosic biomass, and the production of various plastics, acrylic fibers, resins, adhesives, synthetic leathers, and pesticides, as well as in electrochemistry, nanoparticle synthesis, and electrospinning. The effect of inorganic salts on the local structure of DMF, which is crucial for processes such as electrospinning, is studied using molecular dynamics simulations. Four salts: LiCl, LiBr, MgCl2, and CaCl2 are examined at different concentrations across their full solubility ranges.

The molecular dynamics simulations of solutions of four inorganic salts, along with neat DMF as a reference, were performed in the N,p,T ensemble at 298 K and 1 bar. The DMF molecules have been described by the HIJ1 model. The performance of several interaction models of the salts was assessed. With appropriate charge scaling, all models reasonably reproduced the experimental properties. The only exception in this respect is the solubility of the salts: as only the AMBER model is found to be able to simultaneously reproduce the good solubility of all the four salts considered, this is the model of our choice in this study.

Our results revealed that the structure of these solutions is primarily determined by the strong interaction between the cations and the solvation shell DMF molecules. This strong interaction destroys the weak, CH-donated H-bonding structure of neat DMF.

The average lifetime of cation-DMF contacts is found to be in the order of 1 ns for Li+ and Ca2+ while, for Mg2+, it turns out to be several orders of magnitude longer than the entire length of our simulated equilibrium trajectories of 50 ns. Further, the interaction energy of contact Mg2+-DMF pairs falls in the order of covalent chemical bonds, the coordination number is resulted in exactly 6.00 in every case, and the first solvation shell itself is exceptionally well ordered. All these findings strongly suggest (yet do not prove) the formation of the [Mg(DMF)6]2+ hexa-complex by a Mg2+ ion and its six first shell DMF neighbors.

References

[1] B. Honti, A. Idrissi, and P. Jedlovszky, J. Phys. Chem. B, 125, 4819–4830 (2021).