| 1. |
- Csendes, Zita, et al.
(författare)
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Superoxide dismutase inspired immobilised Ni(II)-protected amino acid catalysts Synthesis, characterisation, and catalytic activity
- 2014
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Ingår i: Journal of Molecular Catalysis A: Chemical. - : Elsevier BV. - 1381-1169. ; 395, s. 93-99
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Tidskriftsartikel (refereegranskat)abstract
- Covalently anchored Ni(II)-C-protected amino acid (L-histidine, L-cysteine, and L-cystine) complexes inspired by the active site of the Ni-superoxide dismutase enzyme were synthesised using chloropropylated silica gel as support. The structural features of the surface complexes were studied by the Kjeldahl method and ICP-MS, mid/far IR, UV-vis diffuse reflectance, and X-ray absorption spectroscopies. The enzyme-like activities of the materials were determined in a biochemical test reaction. Covalent grafting and building the complex onto the surface of the support were successful in all cases. It was found that in many instances the structures obtained and the coordinating groups substantially varied upon changing the conditions of the syntheses. All the covalently immobilised Ni(II)-complexes displayed enzyme-like activity. They also were active in the liquid-phase oxidation of cyclohexene, providing the epoxide with high selectivity. (C) 2014 Elsevier B.V. All rights reserved.
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| 2. |
- Varga, Gabor, et al.
(författare)
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Bioinspired covalently grafted Cu(II)-C protected amino acid complexes: selective catalysts in the epoxidation of cyclohexene
- 2015
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Ingår i: Reaction Kinetics, Mechanisms and Catalysis. - : Springer Science and Business Media LLC. - 1878-5204 .- 1878-5190. ; 115:1, s. 33-43
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the syntheses of covalently grafted C-protected Cu(II)-amino acid (methylesters of l-histidine and l-cystine) uniform and mixed ligand complexes with two different amino acid esters are described using chloropropylated silica gel as the support. The conditions of the syntheses were systematically altered. The structural features of the substances obtained were studied by the Kjeldahl method, ICP-MS, X-ray absorption and mid/far infrared spectroscopies. The superoxide dismutase-like activities of the materials were determined in a biochemical test reaction and these substances were also tested as catalysts in the oxidation of cyclohexene. It was possible to prepare metal ion-amino acid complexes grafted with covalent bonds onto the supports. All the covalently anchored materials displayed superoxide dismutase-like activity and most of them were active in the oxidation of cyclohexene, providing the epoxide with high selectivity.
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| 3. |
- Szabados, Márton, et al.
(författare)
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Synthesis of high-quality, well-characterized CaAlFe-layered triple hydroxide with the combination of dry-milling and ultrasonic irradiation in aqueous solution at elevated temperature
- 2016
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Ingår i: Ultrasonics Sonochemistry. - : Elsevier BV. - 1350-4177. ; 32, s. 173-180
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Tidskriftsartikel (refereegranskat)abstract
- The combination of mechanochemical and ultrasonic treatment was applied to synthesize CaAlFe-layered triple hydroxides with carbonate or chloride anions in the interlamellar space. The optimal parameters of the preparation were explored by altering the initial ratio of the metal ions and the temperature of ultrasonic irradiation. The resulting triple hydroxides were characterized by X-ray diffractometry, infrared and X-ray absorption spectroscopies, thermogravimetric analysis and scanning electron microscopy. The products were close-to-phase-pure CaAlFe-layered triple hydroxides. Elevation of the temperature transformed the CaAlFe-Cl--layered triple hydroxide to rare oxyhalides (Ca2FeO3Cl and Ca12Al14O32Cl2).
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| 4. |
- Varga, Gábor, et al.
(författare)
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Cu(II)-amino acid–CaAl-layered double hydroxide complexes, recyclable, efficient catalysts in various oxidative transformations
- 2016
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Ingår i: Journal of Molecular Catalysis A: Chemical. - : Elsevier BV. - 1381-1169. ; 423, s. 49-60
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Tidskriftsartikel (refereegranskat)abstract
- Intercalated composite materials were prepared with CaAl-layered double hydroxide as host and Cu(II)-amino acid (L-cysteine, L-histidine and L-tyrosine) complex anions as guests. Two methods (intercalation of the ligand first followed by constructing the complex; preforming the complex first, then introducing it among the layers of the host) and optimization of the synthesis conditions were performed to obtain composites having the complex exclusively among the layers. The composite materials were structurally characterized by powder X-ray diffractometry, mid infrared (IR) spectroscopy with ATR (attenuated total reflectance) or photoacoustic detections, transmission and scanning electron microscopies and X-ray photoelectron spectroscopy. Structural features of the intercalant (coordination number, coordination sites) were elucidated by classical chemical and energy dispersive X-ray analyses, EPR (electron paramagnetic spectroscopy), X-ray absorption and far IR spectroscopies. Structural models based on these methods are also given. Catalytic activities, selectivities and recycling abilities of the substances were studied in the oxidation reactions of cyclohexene with peracetic acid and in situ formed iodosylbenzene as oxidants in the liquid phase. The catalysts were active in the Ullmann coupling reaction as well. The intercalated substances were found to be efficient and highly selective catalysts with very good recycling abilities.
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| 5. |
- Varga, Gabor, et al.
(författare)
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Fe-amino acid complexes immobilized on silica gel as active and highly selective catalysts in cyclohexene epoxidation
- 2015
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Ingår i: Research on Chemical Intermediates. - : Springer Science and Business Media LLC. - 0922-6168 .- 1568-5675. ; 41:12, s. 9155-9169
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the syntheses, structure, superoxide dismutase (SOD) activity, and the catalytic use in the oxidative transformations of cyclohexene of covalently grafted Fe(III)-complexes formed with various or various combinations of C-protected amino acid (l-histidine, l-tyrosine, l-cysteine and l-cystine) ligands are presented. The structural features of the surface complexes were studied by XANES/EXAFS and mid/far-IR spectroscopies. The compositions of the complexes were determined by ICP-MS and the Kjeldahl method. The SOD activities of the materials were evaluated in a biochemical test reaction. The obtained materials were used as catalysts for the oxidation of cyclohexene with peracetic acid in acetone. Both covalent grafting and building the complex onto the surface of the chloropropylated silica gel were successful in most cases. In many instances, the obtained structures and the coordinating groups were found to substantially vary upon changing the conditions of the syntheses. All the covalently immobilized Fe(III)-complexes displayed SOD activities, and most of them were found to be capable of catalyzing the oxidation of cyclohexene with appreciably high activities and outstanding epoxide selectivities.
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| 6. |
- Varga, Gábor, et al.
(författare)
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Mn(II)-amino acid complexes intercalated in CaAl-layered double hydroxide - Well-characterized, highly efficient, recyclable oxidation catalysts
- 2016
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Ingår i: Journal of Catalysis. - : Elsevier BV. - 0021-9517. ; 335, s. 125-134
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Tidskriftsartikel (refereegranskat)abstract
- Intercalated composite materials were prepared with CaAl-layered double hydroxide as the host and Mn(II)-amino acid (l-cysteine, l-histidine and l-tyrosine) complex anions as the guest. Two methods (intercalation of the ligand first followed by constructing the complex; preforming the complex first, then introducing it among the layers of the host) and optimization of the auxiliary conditions were performed to arrive at composites having the complex exclusively among the layers. The obtained substances were structurally characterized by powder X-ray diffractometry, mid IR spectroscopy in diffuse reflectance mode and with ATR or photoacoustic detections, and scanning electron microscopy. The structural features of the intercalant (coordination number, coordination sites) were elucidated by classical chemical and energy dispersive X-ray analyses, EPR, X-ray absorption and far IR spectroscopies. Structural models are also given. The catalytic activities, selectivities and recycling abilities of the substances were studied in the oxidation reactions of cyclohexene with peracetic acid and in situ formed iodosylbenzene as oxidants and allylic alcohol with peracetic acid, in the liquid phase. The intercalated substances proved to be efficient and highly selective (with peracetic acid: outstanding epoxide, with iodosylbenzene superior diol selectivities) catalysts with very good recycling abilities.
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