| Abstract [eng] |
Bioactive room temperature ionic liquids (b-RTILs) are room temperature-molten salts compatible with living organisms. RTILs are becoming more popular in the scientific community due to the high number of ion combinations and tunability. Specifically, b-RTILs are applied in the medical field in drug delivery systems and to increase non-soluble drug solubility in water. One of the important parameters of ILs is diffusion because it gives us information about the size or structure of molecules and how molecules interact with each other due to the change in concentration. The main objective is to investigate diffusion of choline type ionic liquids (choline glycinate [Cho][Gly], choline lysinate [Cho][Lys] and choline tryptophanate [Cho][Trp]) in the water mixtures. Besides medicine, these ionic liquids could be used in CO2 absorption, biofilm growth regulation, seed germination and elongation. DOSY (Diffusion-Ordered Spectroscopy) is a powerful NMR (Nuclear Magnetic Resonance) method. The gradient of a magnetic field is applied to the sample. Due to magnetic field inhomogeneity, the magnetic spin orientation of protons across the sample differs. Also, due to the constant movement of molecules, the intensity of the spectra is lower than with a homogenous magnetic field across the sample. The change in the intensity also depends on the size of the molecule. Using Stejskal-Tanner equation, diffusion coefficient of a specific proton can be approximated from 1H NMR spectral intensity dependency from magnetic field gradient. Using the DOSY method, it was found that the diffusion coefficient of water molecule is larger than the diffusion coefficient of ions in all b-RTIL water mixtures. Also, there are two diffusion regimes present in b-RTILS water mixtures: H2O in IL and IL in H2O. The breaking points in [Cho][Gly], [Cho][Lys] and [Cho][Trp] water mixtures are observed at χ_RTIL=0.16 mol. frac., χ_RTIL=0.11 mol. frac. and χ_RTIL=0.14 mol. frac. respectively. The only difference is that in [Cho][Trp], the breaking point in water diffusion coefficient dependency is not observed clearly. The occurrence of two separate regimes is due strong hydrogen and Coulombic bonds between choline and glycine anion and water’s ability to break those bonds and themselves forming hydrogen bonds with those ions. In addition, fast and slow diffusion of H2O and NH can be observed in [Cho][Trp] water mixture. Also, the diffusion coefficient values of [Trp] anion’s ring and chain parts differ. |
