Browsing by Author "Trofymchuk, Oleksandra S."

Now showing 1 - 5 of 5
  • No Thumbnail Available
    Item
    Aminoquinoline derivative nickel phosphine complex for ethylene dimerization: A computational and experimental approach
    (2025) Trofymchuk, Oleksandra S.; Ortega, Daniela E.; Alan Raúl, Cabrera Caballero; Daniliuc, Constantin G.; Rojas, René S.
    In this study, we report the synthesis and characterization of a novel nickel complex derived from an aminoquinoline derivative formed during its reaction with Ni(PPh₃)₂ClPh in the presence of potassium hydride under heating. Notably, the resulting nickel complex (precatalyst 2) exhibits catalytic activity toward ethylene activation in the presence of five equivalents of B(C₆F₅)₃, promoting ethylene oligomerization. This study highlights the potential of this new nickel system for selective olefin transformations. Density Functional Theory (DFT) calculations indicate that β-hydride elimination is kinetically favored, but 1-butene decoordination is highly endergonic (ΔG ◦ = 21.6 kcal/mol), making it slow under catalytic conditions. However, in the presence of ethylene significantly lowers this energy to 4.1 kcal/mol, facilitating product release. In contrast, 2-butene decoordination is significantly less endergonic (ΔG ◦ = 4.5 kcal/mol), implying a higher selectivity for 2-butene formation. Despite this, the catalytic cycle for 1-butene formation exhibits significantly higher activity (δG = 22.4 kcal/mol, TOF = 2.5 × 10⁻⁴ s⁻¹) compared to the 2-butene cycle (δG = 36.8 kcal/mol, TOF = 6.3 × 10⁻¹⁵ s⁻¹). Here, δG represents the energetic span of the catalytic cycle, which accounts for the difference between the highest energy transition state and the most stable intermediate within the cycle, directly correlating with the turnover frequency (TOF). The lower δG value for 1-butene formation indicates a kinetically more favorable pathway, while the higher δG for 2-butene formation suggests a slower overall rate despite its thermodynamic preference. These findings provide valuable insights into the reactivity and selectivity of nickel-mediated olefin oligomerization, offering a deeper mechanistic understanding of transition-metal-catalyzed transformations.
  • Thumbnail Image
    Item
    Approach to Circular Chemistry Preparing New Polyesters from Olive Oil
    (2023) Werlinger, Francisca; Caprile, Renato; Cardenas-Toledo, Valentino; Tarraff, Bastian; Mesias-Salazar, Angela; Rojas, Rene S.; Martinez, Javier; Trofymchuk, Oleksandra S.; Flores, Mario E.
    The transformation of cooking oils and their waste intopolyestersis a challenge for circular chemistry. Herein, we have used epoxidizedolive oil (EOO), obtained from cooking olive oil (COO), and variouscyclic anhydrides (such as phthalic anhydride PA, maleic anhydrideMA, and succinic anhydride SA) as raw materials for the preparationof new bio-based polyesters. For the synthesis of these materials,we have used the bis(guanidine) organocatalyst 1 andtetrabutylammonium iodide (Bu4NI) as cocatalyst. The optimalreaction conditions for the preparation of poly(EOO-co-PA) and poly(EOO-co-MA) were 80 degrees C for 5 husing toluene as solvent; however, the synthesis of poly(EOO-co-SA) required more extreme reaction conditions. Furthermore,we have exclusively succeeded in obtaining the trans isomer for MA-polyester.The obtained biopolyesters were characterized by NMR, Fourier transforminfrared, thermogravimetric analysis, and scanning electron microscopyanalyses. Since there are few examples of functionalized and definedcompounds based on olive oil, it is innovative and challenging totransform these natural-based compounds into products with high addedvalue.
  • No Thumbnail Available
    Item
    Natural and Synthetic Naphthoquinones as Potential Anti-Infective Agents
    (2021) Ortiz Perez, Eyra; Rivera, Gildardo; Salas Sánchez, Cristián Osvaldo; Zarate Ramos, Juan J.; Trofymchuk, Oleksandra S.; Hernandez Soberanis, Lucio; Perales Flores, Juanita D.; Vazquez, Karina
    Background: Naphthoquinones are a class of aromatic compounds relevant for their chemical characteristics, structural properties, and biological activity. These compounds are found in nature with a wide range of effects, highlighting their antibacterial, antifungal, and antiprotozoal properties. Additionally, naphthoquinones are used as a scaffold to obtain new derivatives with pharmacological potential, mainly compounds against parasitic diseases. Objective: The purpose of this work was to carry out a comprehensive review of naphthoquinones and their derivatives obtained from both natural and synthetic sources, also, to analyze their biological activity against Leishmania spp. (Leishmaniasis), Trypanosoma cruzi (Chagas disease), Plasmodium falciparum (Malaria), Toxoplasma gondii (Toxoplasmosis), and Toxocara canis (Toxocariasis). All of these agents are responsible for relevant diseases worldwide. Results: Natural naphthoquinones, such as plumbagin, diospyrin, burmanin, lapachol, lawsone and psychorubrin, show an antiprotozoal activity similar or enhanced antiprotozoal activity to reference drugs. Some naphthoquinones obtained by synthesis or semi-synthesis showed better biological activity or less toxic effects than natural compounds. Conclusion: In this review, natural and synthetic naphthoquinones showed antiparasitic activity, in most cases, with improved results than current drugs currently used in clinical trials. A modification of their structure with different functional groups can enhance their biological effects, improve solubility, and reduce undesirable side effects. Therefore, naphthoquinones are important molecules in the development of new chemotherapeutic agents against parasitic diseases.
  • No Thumbnail Available
    Item
    Neutral and cationic methallyl nickel complexes in alkene activation: a combined DFT, ESI-MS and chemometric approach
    (2021) Trofymchuk, Oleksandra S.; Ortega, Daniela E.; Cortes-Arriagada, Diego; Pereira, Alfredo; Daniliuc, Constantin G.; Klitzke, Clecio F.; Santos, Leonardo S.; Rojas, Rene S.
    Herein, we report a comparative study of ethylene activation and 1-hexene isomerization carried out with isomeric neutral and cationic methallyl nickel complexes L1Ni(eta(3)-C3H5) and [L1Ni(eta(3)-C3H5)][B(Ar-F)(4)] in the presence of borane co-catalysts. To understand the reactivity of the nickel complexes with NacNac ligands, we used chemometric methods to classify different catalysts reported to date. The mechanism of the interaction of [L1Ni(eta(3)-C3H5)][B(Ar-F)(4)]/B(C6F5)(3) with 1-hexene was studied by ESI-MS which allowed the detection of cationic species formed in situ. Moreover, there is a very small difference in reactivities from combination of nickel complexes and borane co-catalysts used for alkene isomerization, while the reactivity with ethylene of both systems is very different; [L1Ni(eta(3)-C3H5)][B(Ar-F)(4)]/B(C6F5)(3) produces butene, while L1Ni(eta(3)-C3H5)/B(C6F5)(3) forms polyethylene. Furthermore, DFT studies revealed that the origin of the catalytic activity in the cationic and neutral methallyl nickel complexes co-activated by B(C6F5)(3) is mainly from direct steric effects of the ligand-nickel center where the conformation of the chelate ring is affected by the catalyst symmetry. This work demonstrates how the cationic or neutral nature of the same system affects its catalytic and structural properties.
  • No Thumbnail Available
    Item
    Synthesis and structures of N-arylcyano-β-diketiminate zinc complexes and adducts and their application in ring-opening polymerization of L-lactide
    (2015) Trofymchuk, Oleksandra S.; Daniliuc, Constantin G.; Kehr, Gerald; Erker, Gerhard; Rojas, Rene S.
    Zinc amide complexes ZnL1N( SiMe3) 2, ZnL2N( SiMe3) 2 ( 1 and 2), their tris( pentafluorophenyl) borane adducts ZnL1N( SiMe3) 2$ B( C6F5) 3 ( 3), ZnL2N( SiMe3) 2$ 2B( C6F5) 3 ( 4), pentafluorophenyl zinc complex ZnL1C6F5 ( 5) and its adduct ZnL1C6F5$ B( C6F5) ( 6) supported by N- arylcyano- b- diketiminate ligands, as well as bis- ligated Zn( L2) 2 ( 7) were synthesized and characterized by NMR, IR, elemental analysis and X- ray diffraction. Zinc crystal structures of 1, 4, and 7 showed mononuclear complexes, while 2 and 5 were dimmers. ROP of L- lactide with zinc complexes and their B( C6F5) 3 adducts leads to generation of poly( L- LA) with high molecular weight and relatively narrow molecular weight distribution. The monomer conversion reached completion in 40 min only for zinc amide complex 1, while for other compounds it was necessary to use at least 5 hours to achieve significant polymerization yields. Coordination of the B( C6F5) 3 molecule close to the metal center blocks L- lactide insertion and thus decreases the activity of respective adducts in comparison with borane- free zinc complexes.