Aleksandar Tot

DFT study of 1-butyl-3-methylimidazolium salicylate: a third-generation ionic liquid

A detailed theoretical investigation of the third-generation ionic liquid (IL) 1-butyl-3-methylimidazolium salicylate ([BMIM][Sal]), performed within the framework of density functional theory (DFT), is presented in this paper. The B3LYP-D3, M06-2X, and M06-2X-D3 functionals were used to obtain the equilibrium geometries of the two ions [BMIM]+ and [Sal]–. It is shown that the equilibrium ion geometries obtained with the dispersion-corrected B3LYP functional are very close to the ion geometries obtained with the M06-2X and M06-2X-D3 functionals. Global reactivity was assessed using molecular orbital theory and quantum molecular descriptors. Molecular electrostatic potential (MEP) surfaces and average local ionization energy (ALIE) surfaces were created in order to elucidate the charge distribution and reactivity of the investigated IL. Ion-pair binding energies were calculated with all three functionals, and the results confirmed the presence of a strong electrostatic interaction between the ions, while further insight into the interactions between the two ions was obtained by analyzing noncovalent interactions based on the reduced density gradient (RDG) surface, which revealed a total of nine interactions between the ions. Finally, the aromaticity of each ion was investigated by calculating the nucleus-independent chemical shift (NICS) parameter, which indicated that significant changes in the charge delocalization on each ion occur when the two ions interact.

The effect of imidazolium based ionic liquids on wheat and barley germination and growth: Influence of length and oxygen functionalization of alkyl side chain

In this work five different imidazolium based ionic liquids, namely: 1-(2-oxybutyl)-3-methylimidazolium chloride, [C2OC2mIm][Cl]; 1-(2-oxypropyl)-3-methylimidazolium chloride, [C1OC2mIm][Cl]; 1-(3-hydroxypropyl)-3-ethylimidazolium chloride, [OHC3eIm][Cl]; 1-(3-hydroxypropyl)-3-methylimidazolium chloride, [OHC3mIm][Cl]; 1-(2-hydroxyethyl)-3-methylimidazolium chloride, [OHC2mIm][Cl], together with commercial 1-butyl-3-methylimidazolium chloride, [bmim][Cl] and synthesized protic imidazolium chloride, [Im][Cl], were prepared and their toxicity examined towards wheat and barley germination and growth. Introduction of the polar groups (in the form of hydroxyde and/or ether group) in the alkyl side chain of the imidazolium cation and their influence on the reduction of the ionic liquids toxicity is demonstrated. The results indicate that toxicity of oxygen functionalized ILs is significantly lower against wheat comparing to non-functionalized analogues. In the case of barley, influence on germination follow the same trend as in the case of wheat, but for seedlings growth different trend is observed with more pronounced toxicity of ether functionalized ILs. From these results it was also shown that alkylation in the position N-3 atom of the imidazole significantly reduces toxicity of cation.

Evaluation of the impact of different alkyl length and type of substituent in imidazolium ionic liquids on cucumber germination, growth and oxidative stress

In this work, the effect on cucumber growth of seven different imidazolium-based ionic liquids, namely 1-(2-oxybutyl)-3-methylimidazolium chloride, [C2OC2mIm][Cl]; 1-(2-oxypropyl)-3-methylimidazolium chloride, [C1OC2mIm][Cl]; 1-(3-hydroxypropyl)-3-ethylimidazolium chloride, [OHC3eIm][Cl]; 1-(3-hydroxypropyl)-3-methylimidazolium chloride, [OHC3mIm][Cl]; 1-(2-hydroxyethyl)-3-methylimidazolium chloride, [OHC2mIm][Cl], 1-butyl-3-methylimidazolium chloride, [bmim][Cl] and imidazolium chloride, [Im][Cl], were examined. The influence of polarity of the alkyl side chain of the imidazolium cation on the reduction of the ionic liquid’s toxicity is investigated. For all investigated seedlings, significant reduction of biomass was noted, with the incoherent influence of the ionic liquid (IL) concentration. The total inhibition of germination was shown at the highest used concentration for some of the used ionic liquids. Although investigated ILs affected root and shoot growth of cucumber, the effect on stress marker (MDA) as well as biosynthesis of chlorophyll and carotenoids was negligible. The data collected in this research suggest that tuning of the lipophilicity of imidazolium cations by the introduction of polar groups in the side alkyl chain does not have pronounced effect on cucumber, as it was shown for other plant species.

Biological evaluation of selected 3,4-dihydro-2(1H)-quinoxalinones and 3,4-dihydro-1,4-benzoxazin-2-ones: Molecular docking study

In order to investigate new potential therapeutically active agents, we investigated the biological properties of two small libraries of quinoxalinones and 1,4‐benzoxazin‐2‐ones. The results obtained showed that compounds 5, 9–11 have good cytotoxic activity against HeLa cells where the lowest IC50 value (10.46 ± 0.82 μM/mL) was measured for compound 10. Additionally, the most active compounds (5, 9–11) showed much better selectivity for MRC‐5 cells (up to 17.4) compared to cisplatin. In vitro evaluation of the inhibition of the enzyme α‐glucosidase showed that compounds 10 and 11 exert significant inhibition of the enzyme at 52.54 ± 0.09 and 40.09 ± 0.49 μM, respectively. Competitive experiments with ethidium bromide (EB) indicated that all tested compounds have affinity to displace EB from the EB‐DNA complex through intercalation, suggesting good competition with EB (Ksv = (3.1 ± 0.2), (5.1 ± 0.1), (5.6 ± 0.2), and (6.3 ± 0.2) × 103 M−1). A molecular docking study was also performed to better understand the binding modes and to conclude the structure–activity relationships of the synthesized compounds.

Experimental and computational study of guanidinoacetic acid self-aggregation in aqueous solution

In this work for the first time the physicochemical and thermal properties of guanidinoacetic acid (GAA) and its aqueous solutions have been performed to test for its viability as a potential dietary supplement. Thermal stability, viscosity, solubility and experimental density are determined. From measured densities the volumetric properties were estimated and discussed in the scope of GAA self-aggregation in aqueous solutions using experimental and computational results. Based on thermal stability and solubility measurements, it is found that GAA is more thermally stable but less soluble comparing to creatine due to a self-aggregation process that occurs at GAA concentrations higher than 0.013mol·dm-3. Existence of self-aggregation influences the macroscopic properties of aqueous GAA solutions, but also its bioavailability.