Imidazolio joninių skysčių struktūros ir BMR spektrų modeliavimas /

Ionic liquids are compounds that are made entirely of ions and have a melting point below 100°C. In the last two decades, ionic liquids became a major scientific area on account of applications in organic chemistry, solar energy, and pharmaceutical manufacturing where it is used in many chemical reactions as solvents, catalysts, reagents, or combinations of these. Experimental, theoretical, and molecular modeling research methods must be applied to describe the application of ionic liquids for specific applications. The aim of this work was to evaluate the accuracy of modeling the 1H NMR spectra of ionic liquids [C4mim][BF4] and [C4mim][NO3] by the integral method, which combines classical molecural dynamics simulations and combined QM/MM methods, in comparison with experimental data. The parameters of the force field potential, which were taken from B. Doherty’s research article, were determined, and ionic liquids were modeled using ’’GaussView’’ software before running the simulations. Thereafter, the MD simulations were carried out in an NPT ensemble where the density of the simulated ionic liquid was registered until its fluctuation became negligible. Afterwards, the simulations were run in an NVT ensemble where the trajectories of molecules were noted. Radial distribution functions were calculated between cations’ C10 atoms as well as between cations’ imidazolium rings’ H2, H4, H5, and anions’ B and N atoms. The coordination numbers were also calculated between the pairs mentioned. Prior to the QM/MM calculations, a basis set analysis was performed to select an appropriate basis set for the quantum mechanically described part to model the system accurately and efficiently and it was decided that the def2-TZVP basis would be used for the central cation for the final QM/MM calculations, and the 3-21G basis would be used for the additional included ions. The PBE0 functional was applied to the quantum mechanically described part and calculations of shielding constants and chemical shifts were carried out using the QM/MM method, firstly by including only the central cation in the quantum-mechanically described part and afterwards additional ions. It was found that the theoretical values of the chemical shift correspond most closely to the experimental values in the case when additional ions are included near the central cation. The chosen model of QM/MM calculations allows to model the 1H NMR spectrum of ionic liquids with sufficient accuracy and to determine the chemical shifts of all hydrogen protons, except H2, within the error limits.

Grantor dc:publisher

Institutional Repository of Vilnius University

Year dc:date

2024

Author dc:creator

• Ropė, Gvidas,

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

lit

Repository record dc:identifier

https://repository.vu.lt/VU:ELABAETD210578346&prefLang=en_US

OAI identifier oai:identifier

oai:vu.lt:elaba:210578346