Amorphous iron nanoparticles were synthesized using an aqueous reduction in iron(II) sulfate with sodium borohydride and sodium citrate. Various radio frequency (rf) exposure times were investigated in order to determine trends in nonclassical crystallization. RF times from 15 to 300 s revealed an increase in crystallite size from 5 to 60 nm, as determined by powder x-ray diffraction. Also, solvent optimization revealed that ethanol produced the largest trends for increasing crystallite size without total oxidation of the samples. Magnetic characterization by room temperature vibrating sample magnetometry and high resolution transmission microscopy was performed to verify magnetic properties and particle morphology.
Influence of the metal center on hydrolysis of organometallic anticancer complexes containing an N-phenyl-2-pyridinecarbothioamide (PCA) ligand, [M(η6-p-cymene)(N-phenyl-2-pyridinecarbothioamide)Cl] + (M = RuII, 1A, and OsII, 2A), as well as their N-fluorophenyl derivatives [M(η6-p-cymene)(N-fluorophenyl-2-pyridinecarbothioamide)Cl] + (M = RuII, 1B, and OsII, 2B) have been investigated using the DFT method in aqueous medium. The activation energy barriers for the hydrolysis of 1A (21.5 kcal/mol) and 1B (20.7 kcal/mol) are found to be significantly lower than those of their corresponding osmium analogs 2A (28.6 kcal/mol) and 2B (27.5 kcal/mol). DFT evaluated results reveal the inertness of Os(II)–PCA complex toward the hydrolysis that rationalizes the experimental observations. However, the incorporation of fluoride substituent slightly decreases the activation energy for the hydrolysis of Ru(II)– and Os(II)–PCA. In addition, the interaction of hydrolyzed Ru(II)–PCAs (1AH and 1BH) and Os(II)–PCAs (2AH and 2BH) complexes with the histidine (Hist) have also been investigated. The aquated 1BH and 2BH show an enhanced propensity toward the interaction with histidine, and their activation Gibbs free energies are calculated to be 15.9 and 18.9 kcal/mol, respectively. ONIOM (QM/MM) study of the resulting aquated complexes inside histone protein shows the maximum stability of the 2BH complex having a binding energy of −43.6 kcal/mol.
Umpolung-based organocatalysis has made a remarkable breakthrough in the field of synthetic organic chemistry. Among a plethora of umpolung catalysts, bis(amino)cyclopropenylidenes (BACs) have emerged as efficient organocatalysts with potential applications in synthesizing numerous essential organic moieties. In this study, a plausible mechanism for bis(diethylamino)cyclopropenylidene (Et-BAC)-catalyzed synthesis of α,α′-diarylated ketones has been established using the density functional theory (DFT) method. The proposed catalytic cycle of the studied reaction initiates with the nucleophilic interaction of Et-BAC with p-chlorobenzaldehyde to form a zwitterionic intermediate, which is then transformed to a reactive Breslow intermediate. The Breslow intermediate further undergoes a chemoselective and stereoselective 1,6-conjugate addition reaction with p-quinone methide to form a new C–C bond connection. Finally, the generated adduct undergoes a proton shift reaction with the assistance of both 8-diazabicyclo(5.4.0)undec-7-ene (DBU) and protonated DBU to yield the desired product. Conceptual DFT-derived reactivity indices and frontier molecular orbital theory analysis have been successfully utilized to unravel the role of Et-BAC in this studied reaction. In addition to Et-BAC, DBU and protonated DBU also play a very important role in lowering the activation energy barrier of proton transfer steps. This investigation will help in the rational designing of simple nonheterocyclic carbene-mediated novel organic transformations.
A comprehensive hydrolysis mechanism of the promising class of Au(III) anticancer drugs [Au(DMDT)Cl 2 ] (DMDT = N,N-dimethyldithiocarbamate) (R) and [Au(damp)Cl 2 ] (damp = 2-[(dimethylamino)methyl]phenyl) (R′) was done by means of density functional theory (DFT) in combination with the CPCM solvation model to explore the solution behavior and stability under physiological conditions. The activation free energies (ΔG) for the second hydrolysis, R (13.7 kcal/mol) and R′ (10.0 kcal/mol) are found to be relatively lower in comparison to the first hydrolysis, and their rate constant values are computed to be 5.62 × 10 2 and 2.90 × 10 5 s −1 , respectively. Besides these, the interaction mechanisms of aquated R and R′ with the potential protein-binding sites cysteine (Cys) and selenocysteine (Sec) were also investigated in detail. The kinetic study and activation Gibbs free energy profiles reveal that the aquated complexes of R and R′ bind more effectively to the Se site of Sec than to the S site of Cys. Intra-and intermolecular hydrogen bonding play a pivotal role in stabilizing the intermediates and transition states involved in the ligand substitution reactions of R and R′. Natural population analysis (NPA) was done to determine the charge distributions on important atoms during the hydrolysis and ligand substitution reactions.
Density functional theory (DFT) has been utilized to understand the mechanism for N-heterocyclic carbene (NHC) catalyzed synthesis of 1-(4-methoxyphenyl)-2,4-diphenylbutane-1,4-dione from p-methoxybenzaldehyde and E-chalcone. Quantum chemical simulations suggest that the catalytic cycle for the formation of α,δ-diketone commences with nucleophilic interaction of in situ generated active catalyst NHC and p-methoxybenzaldehyde to form a tetrahedral zwitterionic intermediate, which on subsequent proton transfer reactions result the Breslow intermediate. 1,4-umpolung addition of Breslow intermediate to E-chalcone followed by a proton shift facilitates the release of NHC from the catalytic cycle along with the generation of enolic form of the product. Enolic form finally transforms into the desired product under the assistance of both protonated and free 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). Furthermore, conceptual DFT and frontier molecular orbital analyses help to unravel the role NHC in this catalytic cycle. Apart from NHC, protonated and free DBU, existence of advantageous π-π stacking interaction is also very effective in lowering the activation energy barrier efficiently.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.