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| 2. |
- Buvailo, Halyna I., et al.
(författare)
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Copper-containing hybrid compounds based on extremely rare [V2Mo6O26]6- POM as water oxidation catalysts
- 2019
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Ingår i: Inorganic Chemistry Frontiers. - : Royal Society of Chemistry (RSC). - 2052-1545 .- 2052-1553. ; 6:7, s. 1813-1823
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we report two approaches to the synthesis of heterometallic complexes (NH4)(2n)(H(2)en)(n){[Cu(en)(2)][alpha-V2Mo6O26]}center dot 4nH(2)O (1), (NH4)(2){[Cu(dien)(H2O)](2)[alpha-V2Mo6O26]}center dot 5H(2)O (2) and (NH4)(2){[Cu(dien)(H2O)](2)[alpha-V2Mo6O26]}center dot 8H(2)O (3) that have been employed in homogeneous photochemical oxidation of water to dioxygen. In these hybrid metalorganic-inorganic compounds, copper-containing complex fragments are covalently bound to the rare vanadium-disubstituted alpha-octamolybdate cluster. They exhibit variable catalytic activity controlled by the local coordination environment of copper reaching a notably high turnover frequency of 0.24 s(-1) for 3 in combination with a relatively low water oxidation overpotential. The complexes have been also used as precursors for the preparation of mixed oxide phases that have proven to be active heterogeneous water oxidation catalysts.
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| 3. |
- Buvailo, Halyna I., et al.
(författare)
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Hybrid compound based on diethylenetriaminecopper(ii) cations and scarce V-monosubstituted β-octamolybdate as water oxidation catalyst
- 2021
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Ingår i: RSC Advances. - Cambridge : Royal Society of Chemistry. - 2046-2069. ; 11:51, s. 32119-32125
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Tidskriftsartikel (refereegranskat)abstract
- Herein, we report on a new hybrid compound (NH4){[Cu(dien)(H2O)2]2[β-VMo7O26]}·1.5H2O (1), where dien = diethylenetriamine, containing an extremely rare mixed-metal pseudo-octamolybdate cluster. An ex situ EPR spectroscopy provided insights into the formation of paramagnetic species in reaction mixture and in solution of 1. The magneto-structural correlations revealed weak antiferromagnetic exchange interactions between the [Cu(dien)]2+ cations transmitted by intermolecular pathways. The cyclic voltammetry showed the one-electron process associated with the Cu3+/Cu2+ oxidation followed by the multi-electron catalytic wave due to water oxidation with a faradaic yield of 86%. The title compound was thus employed in homogeneous water oxidation catalysis using tris(bipyridine)ruthenium photosensitizer. At pH 8.0, efficiency of the catalytic system attained 0.19 turnovers per second supported by the relatively mild water oxidation overpotential of 0.54 V.
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| 4. |
- Eremets, Mikhail I., et al.
(författare)
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High-Temperature Superconductivity in Hydrides : Experimental Evidence and Details
- 2022
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Ingår i: Journal of Superconductivity and Novel Magnetism. - Berlin : Springer Nature. - 1557-1939 .- 1557-1947. ; 35:4, s. 965-977
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Tidskriftsartikel (refereegranskat)abstract
- Since the discovery of superconductivity at ~ 200 K in H3S, similar or higher transition temperatures, Tcs, have been reported for various hydrogen-rich compounds under ultra-high pressures. Superconductivity was experimentally proved by different methods, including electrical resistance, magnetic susceptibility, optical infrared, and nuclear resonant scattering measurements. The crystal structures of superconducting phases were determined by X-ray diffraction. Numerous electrical transport measurements demonstrate the typical behavior of a conventional phonon-mediated superconductor: zero resistance below Tc, shift of Tc to lower temperatures under external magnetic fields, and pronounced isotope effect. Remarkably, the results are in good agreement with the theoretical predictions, which describe superconductivity in hydrides within the framework of the conventional BCS theory. However, despite this acknowledgement, experimental evidences for the superconducting state in these compounds have recently been treated with criticism, which apparently stems from misunderstanding and misinterpretation of complicated experiments performed under very high pressures. Here, we describe in greater detail the experiments revealing high-temperature superconductivity in hydrides under high pressures. We show that the arguments against superconductivity can be either refuted or explained. The experiments on the high-temperature superconductivity in hydrides clearly contradict the theory of hole superconductivity and eliminate it.
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| 5. |
- Kucheriv, Olesia I., et al.
(författare)
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Four‐Step Spin Crossover in a New Cyano‐Bridged Iron‐Silver Coordination Polymer
- 2022
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Ingår i: Chemistry - A European Journal. - : John Wiley & Sons. - 0947-6539 .- 1521-3765. ; 28:44
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Tidskriftsartikel (refereegranskat)abstract
- A new guest-free Hofmann clathrate analogue Fe(2-ethoxypyrazine)2{Ag(CN)2}2 which undergoes a four-step spin crossover during the transition from the low-spin to the high-spin state is reported. At the first step 1/3 of centers become high spin, at the second step another 1/3 of centres become high spin, at the third step spin mixed crystallographic centres are observed, and after the fourth step all centers are high spin.
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| 6. |
- Sirenko, Valerii Y., et al.
(författare)
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Nature of cyanoargentate bridges defining spin crossover in new 2D Hofmann clathrate analogues
- 2024
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 53:9, s. 4251-4259
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Tidskriftsartikel (refereegranskat)abstract
- Chemical composition is leading among the numerous factors that determine the spin transition properties of coordination compounds. Classic dicyanometallic bridges {M(CN)2}− are commonly used to build Hofmann-like spin-crossover frameworks, but some extended bridges are also synthetically available. In this paper, we describe a successful synthesis of two very similar spin-crossover frameworks that differ in the cyanometallic bridges involved, namely [Fe(etpz)2{Ag(CN)2}2] (1) and {Fe(etpz)2[Ag2(CN)3][Ag(CN)2]} (2) (where etpz = 2-ethylpyrazine). Magnetic and Mössbauer studies demonstrated the occurrence of abrupt one-step high-spin (HS) ↔ low-spin (LS) transitions for both complexes. The spin transition temperatures are T1/2 ↓ = 233 K and T1/2 ↑ = 243 K for 1 and T1/2 ↓ = 188 K and T1/2 ↑ = 191 K for 2 with thermal hysteresis loops of 10 K for 1 and 3 K for 2. The bridging mononuclear [Ag(CN)2]− units and FeII cations assemble to form infinite 2D layers in the structure of 1. Interestingly, compound 2 forms 2D layers of FeII cations bridged by both binuclear [Ag2(CN)3]− and mononuclear [Ag(CN)2]− units. The structures of 1 and 2 comprise different types of intermolecular interactions including Ag⋯Ag and Ag⋯Netpz, which induce the creation of supramolecular 3D frameworks. The synergy between metallophilic interactions and the spin transition is also confirmed by the variation of Ag⋯Ag distances during spin crossover. The characterization of such analogues allowed us to analyze in detail the effect of the cyanometallic bridge on the structure of new frameworks and on the bistability in Hofmann-like complexes.
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| 7. |
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| 8. |
- Abi Ghaida, Fatima, et al.
(författare)
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Enzymatic N2 activation : general discussion
- 2023
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Ingår i: Faraday discussions. - : Royal Society of Chemistry. - 1359-6640 .- 1364-5498. ; 243, s. 287-295
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 9. |
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| 10. |
- Bibik, Yurii S., et al.
(författare)
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Cooperative Spin Crossover above Room Temperature in the Iron(II) Cyanoborohydride–Pyrazine Complex
- 2022
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 61:37, s. 14761-14769
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Tidskriftsartikel (refereegranskat)abstract
- Hysteretic spin crossover in coordination complexes of 3d-metal ions represents one of the most spectacular phenomena of molecular bistability. In this paper we describe a self-assembly of pyrazine (pz) and Fe(BH3CN)2 that afforded the new 2D coordination polymer [Fe(pz)2(BH3CN)2]∞. It undergoes an abrupt, hysteretic spin crossover (SCO) with a T1/2 of 338 K (heating) and 326 K (cooling) according to magnetic susceptibility measurements. Mössbauer spectroscopy revealed a complete transition between the low-spin (LS) and the high-spin (HS) states of the iron centers. This LS-to-HS transition induced an increase of the unit cell volume by 10.6%. Meanwhile, a modulation of multiple [C–Hδ+···Hδ−–B] dihydrogen bonds stimulates a contraction in direction c (2.2%). The simplicity of the synthesis, mild temperatures of transition, a pronounced thermochromism, stability upon thermal cycling, a striking volume expansion upon SCO, and an easy processability to composite films make this new complex an attractive material for switchable components of diverse applications.
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