- Metal isotope and density functional study of the tetracarboxylatodicopper(II) core vibrations
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Vibrational spectra of tetrakis(acetato)diaquadicopper(II) complex have been deeply examined in order to provide a detailed description of dynamics of [Cu2O8C4] core being a typical structural unit of most copper(II) carboxylates. Low frequency bands related to significant motions of metal atoms were detected by metal isotope substitution. Observed spectra and isotope shifts were reproduced in DFT calculations. For clear presentation of computed normal vibrations, a D4h symmetry approximation was successfully applied. Basing on observed isotope shifts and calculation results, all skeletal vibrations have been analyzed including normal mode with the largest Cu...Cu stretching amplitude assigned to Raman band at 178 cm-1.
- Drozdzewski, Piotr,Brozyna, Anna
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- Effect of a tridentate ligand on the structure, electronic structure, and reactivity of the copper(I) nitrite complex: Role of the conserved three-histidine ligand environment of the type-2 copper site in copper-containing nitrite reductases
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It is postulated that the copper(I) nitrite complex is a key reaction intermediate of copper containing nitrite reductases (Cu-NiRs), which catalyze the reduction of nitrite to nitric oxide (NO) gas in bacterial denitrification. To investigate the structure-function relationship of Cu-NiR, we prepared five new copper(I) nitrite complexes with sterically hindered tris(4-imidazolyl) carbinols [Et-TIC = tris(1-methyl-2-ethyl-4-imidazolyl)carbinol and iPr-TIC = tris(1-methyl-2-isopropyl-4-imidazolyl)carbinol] ortris(1-pyrazolyl)methanes [Me-TPM = tris(3,5-dimethyl-1-pyrazolyl)methane; Et-TPM = tris(3,5-diethyl-1- pyrazolyl)methane; and iPr-TPM = tris(3,5-diisopropyl-1-pyrazolyl)methane]. The X-ray crystal structures of all of these copper(I) nitrite complexes were mononuclear η1-N-bound nitrite complexes with a distorted tetrahedral geometry. The electronic structures of the complexes were investigated by absorption, magnetic circular dichroism (MCD), NMR, and vibrational spectroscopy. All of these complexes are good functional models of Cu-NiR that form NO and copper(II) acetate complexes well from reactions with acetic acid under anaerobic conditions. A comparison of the reactivity of these complexes, including previously reported (iPr-TACN)Cu(NO2) [iPr-TACN = 1,4,7-triisopropyl-1,4,7-triazacyclononane], clearly shows the drastic effects of the tridentate ligand on Cu-NiR activity. The copper(I) nitrite complex with the Et-TIC ligand, which is similar to the highly conserved three-histidine ((His)3) ligand environment in the catalytic site of Cu-NiR, had the highest Cu-NiR activity. This result suggests that the (His)3 ligand environment is essential for acceleration of the Cu-NiR reaction. The highest Cu-NiR activity for the Et-TIC complex can be explained by the structural and spectroscopic characterizations and the molecular orbital calculations presented in this paper. Based on these results, the functional role of the (His) 3 ligand environment in Cu-NiR is discussed.
- Kujime, Masato,Izumi, Chiemi,Tomura, Masaaki,Hada, Masahiko,Fujii, Hiroshi
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- Copper(II) acetates with aliphatic/heterocyclic amines: Coupled TG-DTA-EGA study, IR characterization and structure correlation
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Three copper acetate complex compounds, namely Cu(CH3COO) 2(en)2?2H2O (I), Cu(CH3COO) 2(tn)2(II) and Cu2(CH3COO) 4(pyz) (III) (en=ethylenediamine, tn=1,3-diaminopropane, pyz=pyrazine), were prepared and characterized during heating in argon by thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA) using mass spectrometry (MS). The results of infrared spectroscopy (IR) were evaluated to be used as a spectroscopic criterion for the determination of the carboxylate binding mode in the compounds.
- Zeleoak,Vargova,Gyoeryova, Katalin,Vecernikova,Balek
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- Mg storage properties of hollow copper selenide nanocubes
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Rechargeable Mg batteries are thought to be suitable for scalable energy-storage applications because of their high safety and low cost. However, the bivalent Mg2+cations suffer from sluggish solid-state diffusion kinetics. Herein, a hollow morphological approach is introduced to design copper selenide cathodes for rechargeable Mg batteries. Hollow Cu2?xSe nanocubes are fabricatedviaa solution reaction and their Mg-storage properties are investigated in comparison to simple nanoparticles. The hollow structures accommodate the volume change during magnesiation/demagnesiation and maintain material integrity, and thus a remarkable cycling stability of over 200 cycles is achieved. A kinetic study demonstrates that a hollow structure favors solid-phase Mg2+diffusion, and therefore the hollow Cu2?xSe nanocubes exhibit a high capacity of 250 mA h g?1at 100 mA g?1as well as a superior rate capability. Mechanism investigation indicates that Cu2?xSe experiences a structure conversion during which a phase transformation occurs. This work develops a facile method for the preparation of hollow copper selenides and highlights the advantages of hollow structures in the design of high-performance Mg-storage materials.
- Cao, Shun-An,Chen, Dong,Li, Ting,Luo, Wei,Shen, Jingwei,Xu, Fei
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p. 13253 - 13261
(2020/10/13)
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- Designing a biomimetic catalyst for phenoxazinone synthase activity using a mesoporous Schiff base copper complex with a novel double-helix morphology
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The condensation reaction of 3-aminopropyltrimethoxysilane with o-hydroxyacetophenone and subsequent complexation with Cu(CH3COO)2·H2O afforded a Schiff base copper complex with a silane moiety. Covalent functionalisation of MCM-41 with the Schiff base copper complex yielded a heterogenised copper complex which mimics the "CuN2O2" coordination site that resembles the galactose oxidase enzyme. The synthesized materials were characterized by UV-DRS, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) studies along with high resolution transmission electron microscopy (HR-TEM) to confirm successful functionalisation. Low-angle X-ray diffraction (LA-XRD) and nitrogen sorption analyses not only revealed the conservation of the textural properties of the support but also the permeability of the copper Schiff base complex into the channel system despite simultaneous decreases in surface area, pore volume and pore size. Electron paramagnetic resonance (EPR) studies confirmed the presence of copper Schiff base in MCM-41 even after dimerisation with o-aminophenol. The catalytic reaction was carried out with tert-butyl hydroperoxide (TBHP) and aqueous peroxide for MCM-41 and heterogenised copper complex under the mild reaction conditions.
- Muthusami, Rubiga,Moorthy, Malathy,Irena, Kostova,Govindaraj, Anbarasu,Manickam, Chozhanathmisra,Rangappan, Rajavel
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p. 18608 - 18620
(2018/11/27)
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