| 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. |
- Varga, Gábor, et al.
(författare)
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Ni-Amino Acid–CaAl-Layered Double Hydroxide Composites : Construction, Characterization and Catalytic Properties in Oxidative Transformations
- 2017
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Ingår i: Topics in Catalysis. - : Springer Science and Business Media LLC. - 1022-5528 .- 1572-9028. ; 60:17-18, s. 1429-1438
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Tidskriftsartikel (refereegranskat)abstract
- Host–guest composite materials were prepared applying the anionic forms of Ni(II)-amino acid (l-histidine, l-cysteine, and l-tyrosine) as the guests and CaAl-layered double hydroxide (CaAl-LDH) as the host. The syntheses were performed either by introducing the amino acid anions first and then constructing the metal ion–amino acid complexes or intercalating the pre-prepared complexes in anionic forms. The pristine as well as the composite LDH samples were structurally characterized by X-ray diffractometry, mid IR spectroscopy and scanning electron microscopy. The structural features of the interlayer complexes were studied by UV–Vis, inductively coupled plasma optical emission, mid and far IR and X-ray absorption spectroscopies as well as energy-dispersed X-ray analysis. On the basis of the acquired data, structural models were constructed. The composites were applied as catalysts in the liquid-phase oxidation of cyclohexene applying peracetic acid and the in situ formed iodosyl benzene as oxidants. Using peracetic acid afforded epoxide, while applying iodosyl benzene provided cis diol as the major or exclusive oxidation product. The catalysts displayed good recycling properties.
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| 4. |
- Varga, Gábor, et al.
(författare)
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Syntheses, characterization and catalytic activities of CaAl-layered double hydroxide intercalated Fe(III)-amino acid complexes
- 2018
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Ingår i: Catalysis Today. - : Elsevier BV. - 0920-5861. ; 306, s. 42-50
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis of intercalated composites were carried out using CaAl-LDH (layered double hydroxide) as host and the anionic form of Fe(III)-amino acid complexes as guest materials. Intercalation was attempted with two methods either introducing the preformed complexes or constructing the complex among the layers of the LDH. After optimization of the synthesis parameters, structural characterization was performed by X-ray diffractometry, scanning electron microscopy as well as mid and far infrared spectroscopies. Quantitative data about the intercalated complexes were collected by chemical analysis and X-ray absorption spectroscopy investigating the near edge region as well as the extended fine structure. Structural models based on characterization measurements 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-type etherification 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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