Browsing by Author "Kukeva R."
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Item A new cu(Ii) complex of pamam dendrimer modified with 1,8-naphthalimide: Antibacterial and anticancer activity(2022-08-15) Manov H.; Staneva D.; Vasileva-Tonkova E.; Kukeva R.; Stoyanov S.; Grabchev I.; Alexandrova R.; Stoyanova R.A new fluorescent PAMAM copper complex ([Cu2 (D)(NO3 )4 ]) has been synthesized and identified. The formation of the complex has been investigated by fluorescence spectroscopy which revealed two copper ions to be bound to the dendrimer ligand. That has also been confirmed upon subjecting the solid copper complex to electron paramagnetic spectroscopy. The antimicrobial activity of the copper complex against Gram-negative bacterium Pseudomonas aeruginosa in light and the dark has been studied. The results demonstrate an increase in its activity when irradiated with daylight. This activity of the copper complex is retained even after being loaded onto a cotton cloth. The antitumor activity of the copper complex and dendrimer ligand against triple-negative breast cancer MDA-MB-231 cells has been investigated as well.Item Chemical and mechanistic modelling of green solvent extraction of metallic species with 4-acylpyrazolones(2024-12-01) Atanassova M.; Kukeva R.; Kurteva V.Solvent extraction chemistry of metals needs the use of suitable organic ligands like 4-acylpyrazolones to coordinate the studied cation, to make it soluble in an organic phase and then allow its phase transfer from the aqueous phase. The competitive solvent extraction test of almost 25 metal ions by one powerful ligand, i.e. 3-methyl-1-phenyl-4-(4-trifluoromethylbenzoyl)-pyrazol-5-one diluted in one ionic liquid ([C1Cnim+][Tf2N−]) has been conducted to get a snapshot of its efficacy. Effect of diluents on the liquid–liquid extraction of 4f-ions with a series of chelating ligands of 4-acylpyrazolones family (∼5) is presented comparing ionic liquids and typical organic diluents: 14 in number. In addition, the solvent extraction of 12 refractory metals with a series of chelating extractants is investigated in five diluents: four 4-acylpyrazolones with different radicals. The solvent extraction stoichiometry of MoO42− and Zr4+ is studied in detail using molecular and ionic diluent for comparative purposes through slope analysis method. Ethylene glycol is used to develop a non-aqueous process for Gd3+ switchable extraction, i.e. boost of two immiscible organic phases. Furthermore, EPR, NMR, IR and DTA-TG-MS spectroscopies have been used to study the extracted d- and f-species in the obtained organic extracts in ionic liquid solutions.Item Hyperbranched polymers modified with Dansyl units and their Cu(II) complexes. bioactivity studies(2020-10-02) Bosch P.; Staneva D.; Vasileva-Tonkova E.; Grozdanov P.; Nikolova I.; Kukeva R.; Stoyanova R.; Grabchev I.Two new copper complexes of hyperbranched polymers modified with dansyl units were synthesized and characterized by infrared spectroscopy (IR) and electron paramagnetic resonance (EPR) techniques. It was found that copper ions coordinate predominantly with nitrogen or oxygen atoms of the polymer molecule. The place of the formation of complexes and the number of copper ions involved depend on the chemical structure of the polymer. The antimicrobial activity of the new polymers and their Cu(II) complexes was tested against Gram-negative and Gram-positive bacterial and fungal strains. Copper complexes were found to have activity better than that of the corresponding ligands. The deposition of the modified branched polymers onto cotton fabrics prevents the formation of bacterial biofilms, which indicates that the studied polymers can find application in antibacterial textiles.Item Improvement of Gd(III) Solvent Extraction by 4-Benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one: Non-Aqueous Systems(2023-05-01) Atanassova M.; Kukeva R.The study of the liquid–liquid extraction of gadolinium (Gd(III) ion) with a chelating compound, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP), and the determination of the process parameters are presented by employing two ionic liquids, namely, ([C1Cnim+][Tf2N−], n = 4, 10) and CHCl3, as diluents. Compared to CHCl3, the ionic liquid offers increased distribution ratios in an aqueous medium. A step forward, enhanced solvent extraction, and improved separation upon the addition of ethylene glycol are demonstrated, i.e., a boost of two immiscible organic phases, compared to traditional aqueous solutions. However, this is noticeable when using CHCl3, but unfortunately not with ionic liquid combination, [C1C10im+][Tf2N−]. Several conclusions are given, highlighting the role of the ionic diluent in complexation processes and selectivity with an employment of the chelating agent HP for various metal s-, p-, d-, and f-cations, i.e., nearly 25 metals. A detailed evaluation of the selectivity between these metals was made when changing both the aqueous phase completely with ethylene glycol or partially with glycerol (1:1). Electron paramagnetic resonance (EPR) spectroscopy has been used to study the established chemical species in the obtained organic extracts, such as Gd3+, Fe3+, Cu2+, and Cr3+, with unpaired electrons.Item New Poly(Propylene Imine) dendrimer modified with acridine and its Cu(II) complex: Synthesis, characterization and antimicrobial activity(2019-09-01) Bosch P.; Staneva D.; Vasileva-Tonkova E.; Grozdanov P.; Nikolova I.; Kukeva R.; Stoyanova R.; Grabchev I.A second-generation poly(propylene imine) dendrimer modified with acridine and its Cu(II) complex have been synthesized for the first time. It has been found that two copper ions form complexes with the nitrogen atoms of the dendrimeric core by coordinate bonds. The new compounds have been characterized by nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), fourier-transform infrared spectroscopy (FTIR) and fluorescence spectroscopy. The spectral characteristics of the modified dendrimer have been measured in different organic solvents, and a negative fluorescence solvatochromism has been observed. The antimicrobial activity of the dendrimers has been tested against model pathogenic microorganisms in agar and by broth dilution method. The cotton fabric treated with both dendrimers has been evaluated towards pathogenic microorganisms. The obtained modified cotton fabrics have been shown to hamper bacterial growth and to prevent biofilm formation. Dendrimer cytotoxicity has been investigated in vitro in the model HEp-2 cell line.Item New Sustainable Solvent Extraction Pathways for Rare Earth Metals via Oximes Molecules(2023-11-01) Atanassova M.; Kukeva R.; Kurteva V.A study on the synergistic extraction of Eu(III) ions with a series of chelating ligands and determination of the process parameters is presented by employing ionic liquids and typical organic diluents. The investigations of the liquid–liquid extraction, commonly applied in the separation science of 4f and 5f-ions acidic chelating compounds, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP), 4-benzoyl-3-phenyl-5-isoxazolone (HPBI), and 2-thenoyltrifluoroacetone (HTTA) alone and in combination with two synergistic agents, meso-hexamethylpropyleneamine oxime (S2: HM-PAO) and its bis-imine precursor (S1: pre-HM-PAO), are presented. The interaction between the two extractants (acidic/neutral) in deuterochloroform was studied using 1H, 13C, and 1H-1H NOESY experiments. Several conclusions are given highlighting the role of the ionic diluent in complexation processes and selectivity with an employment of the two synergistic agents for various metal s-, p-, d-, and f-cations in the Periodic table, with almost 25 metal ions. The objective was to optimize a system for 4f-ions solvent extraction based on the new oxime molecules with β-diketone/isoxazolone/pyrazolone partnership. As detailed above, slight enhancements of extraction efficiencies were obtained either by using basic synergistic agents such as HM-PAO and/or using pre-HM-PAO. A competitive solvent extraction test of nearly 18 f-ions by various ligands (HTTA, S1, S2, and HPBI) and the two mixtures HTTA−S1 and HTTA−S2 diluted in ILs or organic diluents was also conducted in order to evaluate the switchable diluent impact. Additionally, electron paramagnetic resonance (EPR) spectroscopy was used to study the established chemical species with Cu2+ cations in the obtained organic extracts involving the two synergistic molecules.