Sanja J. Armaković

Influence of electron acceptors on the kinetics of metoprolol photocatalytic degradation in TiO2 suspension. A combined experimental and theoretical study

Metoprolol (MET) belongs to a group of frequently used β1-blockers, which often occur in waste waters. The objective of this work was to employ liquid chromatography (LC) and total organic carbon methods to study the photocatalytic degradation of MET in UV irradiated aqueous suspensions of TiO2 (Wackherrs “Oxyde de titane standard” and Degussa P25), in the presence of different electron acceptors such as molecular oxygen, hydrogen peroxide, potassium bromate, and ammonium persulfate. The degradation rates were found to be strongly influenced by the kind of electron acceptor and the type of catalyst. The optimal amount of hydrogen peroxide and potassium bromate was investigated as well. MET photocatalytic degradation was the fastest in the presence of O2 and potassium bromate with TiO2 Degussa P25, while mineralization was most efficient in the presence of molecular oxygen alone. In all investigated cases, degradation followed a pseudo-first order kinetics. Reaction intermediates of MET degradation in the presence of different electron acceptors with both catalysts were studied in detail and a number of them were indentified using LC-ESI-MS/MS. The interactions with MET of reactive radical species relevant to this study (O2˙−, ˙OH, BrO2˙, and SO4˙−) were theoretically investigated by means of density functional theory (DFT) computations.

Toxicity assessment of metoprolol and its photodegradation mixtures obtained by using different type of TiO2 catalysts in the mammalian cell lines

Toxicity of metoprolol (MET) alone and in mixtures with its photocatalytic degradation intermediates obtained by using TiO2 Wackherr and Degussa P25 under UV irradiation in the presence of O2 was evaluated in vitro in a panel of three histologically different cell lines: rat hepatoma (H-4-II-E), human colon adenocarcinoma (HT-29) and human fetal lung (MRC-5). Both catalysts promoted a time-dependent increase in the toxicity of the photodegradation products, and those obtained using Degussa P25 photocatalyst were more toxic. The most pronounced and selective toxic action of MET and products of its photodegradation was observed in the hepatic cell line. The higher toxicity of the mixtures obtained using Degussa P25 catalyst could be explained by a different mechanism of MET degradation, i.e. by the presence or higher concentrations of some intermediates. Although the concentrations of intermediates obtained using TiO2 Wackherr catalyst were higher, they did not affect significantly the growth of the examined cell lines, indicating their lower toxicity. This suggests that a treatment aiming at complete mineralization should be performed bearing in mind that the type of catalyst, the concentration of target molecule, and the duration of the process are significant factors that determine the nature and toxicity of the resulting mixtures. Although the EC50 values of MET obtained in mammalian cell lines were higher compared to the bioassays for lower trophic levels, the time-dependent promotion of toxicity of degradation mixtures should be attributed to the higher sensitivity of mammalian cell bioassays.

Theoretical investigation of loratadine reactivity in order to understand its degradation properties: DFT and MD study

Antihistamines are frequently used pharmaceuticals that treat the symptoms of allergic reactions. Loratadine (LOR) is an active component of the second generation of selective antihistaminic pharmaceutical usually known as Claritin. Frequent usage of this type of pharmaceuticals imposes the need for understanding their fundamental reactive properties. In this study we have theoretically investigated reactive properties of LOR using both density functional theory (DFT) calculations and molecular dynamics (MD) simulations. DFT study is used for collecting information related to the molecule stability, structure, frontier molecular orbitals, quantum molecular descriptors, charge distribution, molecular electrostatic potential surfaces, charge polarization, and local reactivity properties according to average local ionization energy surfaces. Based on these results, N24 atom of pyridine ring and oxygen atom O1 were identified with nucleophilic nature. In order to collect the information necessary for the proposition of degradation compounds we also calculated bond dissociation energies (BDE) for hydrogen abstraction and single acyclic bonds as well. According to BDE, the oxidation is likely to occur in the piperidine and cycloheptane rings. MD simulations were used in order to understand the interactions with water through radial distribution functions (RDF). Based on RDFs the most important interactions with solvent are determined for carbon atom C5, chlorine atom Cl15, and oxygen atom O1. Collected results based on DFT calculations and MD simulations provided information important for suggestion of possible degradation compounds. Covalent and noncovalent interactions between LOR and •OH have also been investigated.

Sumanene and its adsorption properties towards CO, CO 2 and NH 3 molecules

AbstractDensity functional theory calculations were used in the theoretical investigation of the adsorption properties of sumanene towards molecules considered as common air pollutants: CO, CO2 and NH3. The insignificant perturbation of sumanene after adsorption and the adsorption energies obtained indicate a physisorption mechanism. It was shown that, contrary to carbon nanotubes, sumanene is able to adsorb CO molecules, and that adsorption of CO2 by sumanene is stronger than adsorption of CO2 by C60. To better understand the adsorption characteristics of sumanene, density of states and natural bond order analyses were performed, which showed that chemical interactions exist and that these are more important mostly on the convex side. Better adsorption properties were obtained for the concave side as adsorption is dictated by physisorption mechanisms due to the specific bowl-shaped geometry of sumanene, because of which more negative charge is located precisely on the concave side. Molecular electrostatic potential surfaces were also used in order to better locate the adsorption sites and gain additional details about adsorption. FigureSumanene and its adsorption properties towards CO, CO2 and NH3 molecules; adsorption properties are better from the concave side

Spectroscopic, single crystal XRD structure, DFT and molecular dynamics investigation of 1-(3-chloro-4-fluorophenyl)-3-[3-(trifluoromethyl)phenyl]thiourea

The title compound 1-(3-chloro-4-fluorophenyl)-3-[3-(trifluoromethyl) phenyl]thiourea (ANF-2) was synthesized and structurally characterized by single crystal XRD. The optimized molecular structure, vibrational frequencies, and corresponding vibrational assignments of ANF-2 have been investigated experimentally and theoretically using Gaussian 09 and Schrodinger Materials Science Suite software packages. The stability of the molecule arising from hyper-conjugative interaction and charge delocalization has been analyzed using NBO analysis. The HOMO and LUMO analysis is used to determine the charge transfer within the molecule. Gauge-including atomic orbital NMR chemical shifts calculations were carried out and compared with experimental data, while the first hyperpolarizability is 48 times that of the standard NLO material. The maximum negative region is localized over the CS group and 1,3-disubstituted phenyl ring, while the maximum positive region is localized on NH groups indicating a possible site for nucleophilic attack. Average local ionization energies have been mapped to the electron density surface in order to detect molecule sites where electrons are least tightly bound. Other possible reactive centers of the title molecule have been detected by calculation of Fukui functions. In order to investigate the possibility for autoxidation and hydrolysis of the investigated molecule, we have calculated bond dissociation energies and radial distribution functions. Charge hopping properties have been assessed using the Marcus semi-empiric approach and the results were compared with urea and thiourea molecules. The docked ligand forms a stable complex with prostaglandin E synthase and has a binding affinity value of −6.5 kcal mol−1 and the title compound can be a lead compound for developing new analgesic drugs.

Specificities of boron disubstituted sumanenes

In this article we focused on computational research of sumanenes disubstituted by boron where the two carbon atoms are substituted by two boron atoms. Disubstitution of rim carbon atoms with boron atoms significantly affected the geometry of the bowl. The main stability factors were used to determine the stability of isomers. The most stable, the shallowest and the deepest isomers were subjected to further study of NMR parameters, chemical shielding and NICS, aromaticity, bowl to bowl inversion barrier and NBO/NPA analysis. The introduction of boron atoms significantly affected the above parameters, changing the aromatic nature of rings, reducing bowl to bowl inversion barrier and produced charge transfer. The NICS are correlated with bowl depth having the result that the function of the fourth degree of bowl depth does not only correlate well to the bowl to bowl inversion barrier with bowl depth, but also finely correlates the change of the NICS and NICSzz with bowl depth.

Aromaticity, response, and nonlinear optical properties of sumanene modified with boron and nitrogen atoms

AbstractWe investigated the effects of substitution on the sumanene benzylic CH2 groups with BH and NH groups using density functional theory computations. Our study shows that various properties of sumanene could be finely tuned for the application in the areas closely related to the materials science. Structural properties are significantly altered with such modifications and other properties as well. Charge distributions were evaluated through natural population analysis (NPA), while stability of investigated structures was investigated using quantum molecular descriptors. Using molecular orbital analysis further insight into the effects of substitution was obtained. Potential of sumanene as a candidate for application in the field of organic electronics is assessed through calculations of exciton binding energy. Non-linear optical properties of investigated structures were investigated using the first hyperpolarizability tensor. Special attention was paid to the aromaticity of sumanene. This property was evaluated employing NICS parameter while for detailed study of obtained results we used NBO and NBOdel analysis. Graphical AbstractSumanene modified with boron and nitrogen atomsᅟ

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.

Coordination compounds of a hydrazone derivative with Co(III), Ni(II), Cu(II) and Zn(II): Synthesis, characterization, reactivity assessment and biological evaluation

A new hydrazone-type ligand with a five N-donor set and its coordination compounds with Co(III), Ni(II), Cu(II) and Zn(II) metal centres were synthesized. The crystal and molecular structure of the Co(III) complex was determined by X-ray structural analysis. All the compounds were characterized by elemental analysis, molar conductivity and FT-IR spectral data. The cobalt(III) compound is a neutral binuclear complex formed by coordination of two, doubly deprotonated ligand anions as bridges between the Co(III) centres. The metal centres are additionally connected by a peroxido bridge, which was observed for the first time in Co(III) complexes with similar ligands. The other coordination compounds are mononuclear complexes wherein only one doubly deprotonated ligand is coordinated to the central ion in a tetradentate fashion. The structures were theoretically investigated employing density functional theory (DFT) calculations with B3LYP exchange–correlation functional and LACV3P+(d,p) basis sets for the coordination compounds and 6-31+G(d,p) basis set for the ligand. Molecular electrostatic potential (MEP) and average local ionization energy (ALIE) surfaces were calculated to study the reactive properties of the compounds. The thermal behaviour of the compounds was determined by simultaneous thermogravimetric-differential scanning calorimetric (TG-DSC) measurements and the results were correlated to the proposed structures and to calculated MEP/ALIE surfaces. The compounds were tested in vitro for antiproliferative effects on parental (L5178Y) mouse T-cell lymphoma cells, on L5178Y transfected with pHa ABCB1/A retrovirus and for reversal of multidrug resistance (MDR) in tumor cells by flow cytometry. The preliminary measurements showed that the cobalt(III) compound was an effective inhibitor of the ABC transporter PGP drug efflux pump. The ligand was somewhat less effective, the zinc complex had a moderate inhibition activity, whereas the nickel(II) and copper(II) compounds were inactive.

Investigation of 1,2,3-trialkylimidazolium ionic liquids: experiment and density functional theory calculations

Physico-chemical properties, thermal stability and bonding in 1,2,3-trialkylimidazolium based ionic liquids (ILs) were investigated by viscosity and density measurements together with thermogravimetric analysis (TGA) and IR spectroscopy. The obtained results were compared to those obtained for the corresponding 1,3-dialkylimidazolium based ILs. To obtain more insight into the influence of the methylation at position C-2 of the imidazolium ion, IR spectra were calculated with the help of density functional theory (DFT) calculations. The reduction in bonding intensity between ions was confirmed as a consequence of chain reduction and methylation. In this regard, DFT calculations indicated a much higher influence of methylation and these results were explained through the analysis of inter-molecular non-covalent interactions (NCIs). Intra-molecular NCIs together with quantum molecular descriptors were also applied for the explanation of thermal stability of the investigated ILs.