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Bernasconi L Belanzoni P Baerends EJ 《Physical chemistry chemical physics : PCCP》2011,13(33):15272-15282
We study the generation of a dinuclear Fe(IV)oxo species, [EDTAH·FeO·OFe·EDTAH](2-), in aqueous solution at room temperature using Density Functional Theory (DFT) and Ab Initio Molecular Dynamics (AIMD). This species has been postulated as an intermediate in the multi-step mechanism of autoxidation of Fe(II) to Fe(III) in the presence of atmospheric O(2) and EDTA ligand in water. We examine the formation of [EDTAH·FeO·OFe·EDTAH](2-) by direct cleavage of O(2), and the effects of solvation on the spin state and O-O cleavage barrier. We also study the reactivity of the resulting dinuclear Fe(IV)oxo system in CH(4) hydroxylation, and its tendency to decompose to mononuclear Fe(IV)oxo species. The presence of the solvent is shown to play a crucial role, determining important changes in all these processes compared to the gas phase. We show that, in water solution, [EDTAH·FeO·OFe·EDTAH](2-) (as well as its precursor [EDTAH·Fe·O(2)·Fe·EDTAH](2-)) exists as stable species in a S = 4 ground spin state when hydrogen-bonded to a single water molecule. Its structure comprises two facing Fe(IV)oxo groups, in an arrangement similar to the one evinced for the active centre of intermediate Q of soluble Methane Monooxygenase (sMMO). The inclusion of the water molecule in the complex decreases the overall symmetry of the system, and brings about important changes in the energy and spatial distribution of orbitals of the Fe(IV)oxo groups relative to the gas phase. In particular, the virtual 3σ* orbital of one of the Fe(IV)oxo groups experiences much reduced repulsive orbital interactions from ligand orbitals, and its consequent stabilisation dramatically enhances the electrophilic character of the complex, compared to the symmetrical non-hydrated species, and its ability to act as an acceptor of a H atom from the CH(4) substrate. The computed free energy barrier for H abstraction is 28.2 kJ mol(-1) (at the BLYP level of DFT), considerably below the gas phase value for monomeric [FeO·EDTAH](-), and much below the solution value for the prototype hydrated ferryl ion [FeO(H(2)O)(5)](2+). 相似文献
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Bartmeyer Petra Maria Bocanegra Silvana Oliveira Aurelio Ribeiro Leite 《Numerical Algorithms》2021,86(1):397-424
Numerical Algorithms - In general, interior point methods are successful in solving large-scale linear programming problems. Their effectiveness is determined by how fast they calculate each... 相似文献
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Lopez Kenneth Pinheiro Silvana Zamora William J. 《Journal of computer-aided molecular design》2021,35(8):923-931
Journal of Computer-Aided Molecular Design - A multiple linear regression model called MLR-3 is used for predicting the experimental n-octanol/water partition coefficient (log PN) of 22... 相似文献
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Gabriel Rezende Ximenez Mirelli Bianchin Joo Marcos Parolo Carmona Silvana Maria de Oliveira Osvaldo Ferrarese-Filho Lindamir Hernandez Pastorini 《Molecules (Basel, Switzerland)》2022,27(17)
Weeds pose a problem, infesting areas and imposing competition and harvesting difficulties in agricultural systems. Studies that provide the use of alternative methods for weed control, in order to minimize negative impacts on the environment, have intensified. Native flora represents a source of unexplored metabolites with multiple applications, such as bioherbicides. Therefore, we aimed to carry out a preliminary phytochemical analysis of crude extracts and fractions of Miconia auricoma and M. ligustroides and to evaluate these and the isolated metabolites phytotoxicity on the growth of the target species. The growth bioassays were conducted with Petri dishes with lettuce, morning glory, and sourgrass seeds incubated in germination chambers. Phytochemical analysis revealed the presence of flavonoids, isolated myricetin, and a mixture of quercetin and myricetin. The results showed that seedling growth was affected in a dose-dependent manner, with the root most affected and the seedlings of the lettuce, morning glory, and sourgrass as the most sensitive species, respectively. Chloroform fractions and myricetin were the most inhibitory bioassays evaluated. The seedlings showed structural changes, such as yellowing, nonexpanded cotyledons, and less branched roots. These results indicate the phytotoxic potential of Miconia allelochemicals, since there was the appearance of abnormal seedlings and growth reduction. 相似文献
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Slobodanka Stankovi Duan Lazar Ljubica Medi‐Mija
evi Katarina Penov‐Gai Marija Saka
Silvana Andri Bruvo Milenko 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(3):o172-o173
The title molecule, C26H30O3, shows a novel chemical rearrangement of the substituents at position 17, i.e. an α‐orientation of the hydroxy group and a β‐orientation of the bulky benzyl moiety. The packing arrangement consists of coils formed by O2?O3 hydrogen bonds along the c axis. The compound shows complete loss of oestrogenic activity, and neither does it exhibit an antagonistic effect. 相似文献
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