Publications by authors named "Carla D Nunes"

Nanosized MoO2 can be prepared by different protocols, which yield different morphologies of the nanoparticles. Among their many properties, they can serve as catalysts for styrene oxidation (among other olefins), which is an industrially relevant transformation. In this work, we prepared MoO2 nanosized catalysts by two slightly different hydrothermal protocols using ethylenediamine and either Fe2O3 or hydroquinone.

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New complexes [Mo(η3-C3H5)X(CO)2(4-Y-BIAN)] (4-Y-BIAN = bis(4-Y-phenyl)-acenaphthenequinonediimine), with X = Br and Y = H, Me, OMe, COOH and X = Cl, Y = OMe, as well as the cation with X = NCMe and Y = OMe were synthesized, expanding the scope of this family. Two single crystal X-ray structures (X = Br, Y = Me, OMe) display a less symmetric arrangement (axial isomer), where one N donor atom is trans to the allyl group and the second to one CO. DFT studies showed similar energies for the two possible isomers of the complexes, with a very small preference for the observed axial isomer.

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Article Synopsis
  • Three new molybdenum complexes were synthesized and characterized, showing fluxional behavior and different isomers depending on the substituent R (H, Me, Ph).
  • X-ray crystal structures revealed various isomers, including equatorial and axial forms, with notable arrangements of bromine and imine nitrogen in the complex involving R = H.
  • The complexes were immobilized in MCM-41 for catalytic activity testing in olefin epoxidation, demonstrating good performance with certain substrates but no significant differences compared to traditional Mo-containing catalysts.
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  • Researchers are focusing on creating eco-friendly nanomaterials, specifically layered double hydroxide (LDH) nanoclusters, that are synthesized in safe water-based solutions.
  • The LDH nanoclusters have a high concentration (98.7 g/L), can stay mixed in solution for over two weeks, and possess unique catalytic properties with an average size of 7.8 nm.
  • These nanoclusters can be used as solid catalysts that are easy to separate from liquid mediums after reactions, making them promising for various applications in sustainable chemistry.
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Styrene oxidation mediated by a Mo-based mesoporous catalyst can yield selectively styrene oxide or benzaldehyde. Kinetic data evidenced that styrene oxide is the initial single-product formed by the catalytic Mo-mediated process. However, after some hours of reaction benzaldehyde yield rises while that of the epoxide decreases concomitantly.

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Three new mononuclear oxovanadium(IV) complexes [VO(acac)(R-BIAN)]Cl (BIAN = 1,2-bis{(R-phenyl)imino}acenaphthene, R = H, 1; CH3, 2; Cl, 3) were prepared and characterized. They promoted the catalytic oxidation of olefins such as cyclohexene, cis-cyclooctene, and styrene with both tbhp (tert-butylhydroperoxide) and H2O2, and of enantiopure olefins (S(-)- and R(+)-pinene, and S(-)- and R(+)-limonene) selectively to their epoxides, with tbhp as the oxidant. The TOFs for styrene epoxidation promoted by complex 3 with H2O2 (290 mol mol(-1)V h(-1)) and for cis-cyclooctene epoxidation by 2 with tbhp (248 mol mol(-1)V h(-1)) are particularly good.

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Several molybdenum complexes, [Mo(η(3)-C(3)H(5))X(CO)(2)(N-N)] (N-N = 1,10-phenanthroline, phen: X = CF(3)SO(3)T1, X = Br B1, X = Cl C1; N-N = 2,2'-bipyridyl, X = CF(3)SO(3)T2, X = Br B2) and [W(η(3)-C(3)H(5))Br(CO)(2)(phen)] (W1) have been synthesized and characterized. Their antitumor properties have been tested in vitro against human cancer cell lines cervical carcinoma (HeLa) and breast carcinoma (MCF-7) using a metabolic activity test (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, MTT), leading to IC(50) values ranging from 3 to 45 μM, approximately. Most complexes exhibited significant antitumoral activity.

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Article Synopsis
  • Organic-inorganic mesoporous materials like MCM-41 can be synthesized through two main methods: post-synthesis derivatization and one-pot synthesis.
  • The study evaluated samples derived from Si-based MCM-41, focusing on their local characteristics through advanced spectroscopy techniques, including DRIFT and Raman spectroscopy.
  • Findings indicate that hydrophilicity and structural integrity of these materials depend on the type of organic groups used and the synthesis method, with pressure affecting the channel structure due to low mechanical stability.
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Sertraline hydrochloride (designated as sertraline from now on) is an antidepressive drug with unpleasant effects in the gastric tract. Therefore, improved means of delivery allowing for a more controlled and efficient release were looked for. Two different porous materials, montmorillonite-K10 and MCM-41, were chosen as hosts.

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Mo K-edge XAFS spectra have been measured for ordered mesoporous silica MCM-41 grafted with the complexes [MoO2X2(thf)2] (X=Cl, Br). For grafting reactions in the absence of triethylamine, materials with 1 wt. % Mo are obtained; the Mo K-edge EXAFS results indicate the co-existence of isolated surface-fixed monomeric species [MoO2[(-O)3SiO]2(thf)(n)] and [MoO2[(-O)3SiO]X(thf)(n)].

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