| 1. |
- Abdel-Magied, Ahmed F., et al.
(författare)
-
Asymmetric hydrogenation of an α-unsaturated carboxylic acid catalyzed by intact chiral transition metal carbonyl clusters-diastereomeric control of enantioselectivity
- 2020
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:14, s. 4244-4256
-
Tidskriftsartikel (refereegranskat)abstract
- Twenty clusters of the general formula [(μ-H)2Ru3(μ3-S)(CO)7(μ-P-P∗)] (P-P∗ = chiral diphosphine of the ferrocene-based Walphos or Josiphos families) have been synthesised and characterised. The clusters have been tested as catalysts for asymmetric hydrogenation of tiglic acid [trans-2-methyl-2-butenoic acid]. The observed enantioselectivities and conversion rates strongly support catalysis by intact Ru3 clusters. A catalytic mechanism involving an active Ru3 catalyst generated by CO loss from [(μ-H)2Ru3(μ3-S)(CO)7(μ-P-P∗)] has been investigated by DFT calculations.
|
|
| 2. |
- Abdelhamid, Hani Nasser, 1986-, et al.
(författare)
-
3D printing of cellulose/leaf-like zeolitic imidazolate frameworks (CelloZIF-L) for adsorption of carbon dioxide (CO2) and heavy metal ions
- 2023
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 52:10, s. 2988-2998
-
Tidskriftsartikel (refereegranskat)abstract
- Metal–organic frameworks (MOFs) have advanced several technologies. However, it is difficult to market MOFs without processing them into a commercialized structure, causing an unnecessary delay in the material's use. Herein, three-dimensional (3D) printing of cellulose/leaf-like zeolitic imidazolate frameworks (ZIF-L), denoted as CelloZIF-L, is reported via direct ink writing (DIW, robocasting). Formulating CelloZIF-L into 3D objects can dramatically affect the material's properties and, consequently, its adsorption efficiency. The 3D printing process of CelloZIF-L is simple and can be applied via direct printing into a solution of calcium chloride. The synthesis procedure enables the formation of CelloZIF-L with a ZIF content of 84%. 3D printing enables the integration of macroscopic assembly with microscopic properties, i.e., the formation of the hierarchical structure of CelloZIF-L with different shapes, such as cubes and filaments, with 84% loading of ZIF-L. The materials adsorb carbon dioxide (CO2) and heavy metals. 3D CelloZIF-L exhibited a CO2 adsorption capacity of 0.64–1.15 mmol g−1 at 1 bar (0 °C). The materials showed Cu2+ adsorption capacities of 389.8 ± 14–554.8 ± 15 mg g−1. They displayed selectivities of 86.8%, 6.7%, 2.4%, 0.93%, 0.61%, and 0.19% toward Fe3+, Al3+, Co2+, Cu2+, Na+, and Ca2+, respectively. The simple 3D printing procedure and the high adsorption efficiencies reveal the promising potential of our materials for industrial applications.
|
|
| 3. |
- Abdelhamid, Hani Nasser, 1986-
(författare)
-
Dye encapsulation and one-pot synthesis of microporous–mesoporous zeolitic imidazolate frameworks for CO2 sorption and adenosine triphosphate biosensing
- 2023
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 52:8, s. 2506-2517
-
Tidskriftsartikel (refereegranskat)abstract
- One-pot co-precipitation of target molecules e.g. organic dyes and the synthesis of a crystal containing microporous–mesoporous regimes of zeolitic imidazolate frameworks-8 (ZIF-8) are reported. The synthesis method can be used for cationic (rhodamine B (RhB), methylene blue (MB)), and anionic (methyl blue (MeB)) dyes. The crystal growth of the ZIF-8 crystals takes place via an intermediate phase of zinc hydroxyl nitrate (Zn5(OH)8(NO3)2) nanosheets that enabled the adsorption of the target molecules i.e., RhB, MB, and MeB into their layers. The dye molecules play a role during crystal formation. The successful encapsulation of the dye molecules was proved via diffuse reflectance spectroscopy (DRS) and electrochemical measurements e.g., cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The materials were investigated for carbon dioxide (CO2) adsorption and adenosine triphosphate (ATP) biosensing. ZIF-8, RhB@ZIF-8, MB@ZIF-8, and MeB@ZIF-8 offered CO2 adsorption capacities of 0.80, 0.84, 0.85, and 0.53 mmol g−1, respectively. The encapsulated cationic molecules improved the adsorption performance compared to anionic molecules inside the crystal. The materials were also tested as a fluorescent probe for ATP biosensing. The simple synthesis procedure offered new materials with tunable surface properties and the potential for multi-functional applications.
|
|
| 4. |
- Abernethy, Robyn J., et al.
(författare)
-
Relative hemilabilities of H2B(az)2 (az = pyrazolyl, dimethylpyrazolyl, methimazolyl) chelates in the complexes [M(η-C3H5)(CO)2{H2B(az)2}] (M = Mo, W)
- 2020
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:3, s. 781-796
-
Tidskriftsartikel (refereegranskat)abstract
- The reactions of [M(η3-C3H5)Br(CO)2(NCMe)2] (M = Mo, W) or [Mo(η3-C3H5)Br(CO)2(PMe2Ph)2] with Na[H2B(mt)2] (mt = methimazolyl) affords the complexes [M(η3-C3H5)(CO)2{κ3-H,S,S′-H2B(mt)2}], the 3-centre, 2-electron B-H-M interaction of which was found to be inert with respect to opening under mild conditions, while more forcing conditions (heating with PMe2Ph) resulted in cleavage of the entire allyl and borate ligands to form [Mo(CO)3(PMe2Ph)3]. In contrast, the reaction of [Mo(η3-C3H5)Br(CO)2(NCMe)2] with Na[H2B(pz)2] affords either [Mo(η3-C3H5)(CO)2{κ3-H,N,N′-H2B(pz)2}] or (more likely) [Mo(η3-C3H5)(CO)2(NCMe){κ2-N,N′-H2B(pz)2}] which in turn reacts with phosphines to provide [[Mo(η3-C3H5)(CO)2(PPhR2){κ2-N,N′-H2B(pz)2}] (R = Me, Ph). The reactions discussed indicate the propensity for 3-centre, 2-electron B-H-Mo interactions increases in the order H2B(pz)2 < H2B(pz∗)2 < H2B(mt)2 (pz∗ = 3,5-dimethypyrazolyl).
|
|
| 5. |
- Adranno, Brando, et al.
(författare)
-
Enhanced stability and complex phase behaviour of organic-inorganic green-emitting ionic manganese halides
- 2023
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 52:19, s. 6515-6526
-
Tidskriftsartikel (refereegranskat)abstract
- Light-emitting materials based on earth-abundant metals, such as manganese hold great promise as emitters for organic lighting devices. In order to apply such emitter materials and, in particular, to overcome the problem of self-quenching due to cross-relaxation, we investigated a series of tetrabromidomanganate ([MnBr4]2−) salts with bulky tetraalkylphosphonium counter cations [Pnnn]+, namely [Pnnnn]2[MnBr4] (n = 4 (1), 6 (2) and 8 (3)), which can be obtained by a straightforward reaction of the respective phosphonium bromide and MnBr2. Variation of the cation size allows control of the properties of the resulting ionic materials. 1 and 3 qualify as ionic liquids (ILs), where 1 features a melting point of 68 °C, and 3 is liquid at room temperature and even at very low temperatures. Furthermore, 1 and 2 show the formation of higher-ordered thermotropic mesophases. For 1 a transition to a thermodynamically metastable smectic liquid crystalline phase can be observed at room temperature upon reheating from the metastable glassy state; 2 appears to form a plastic crystalline phase at ∼63 °C, which persists up to the melting point of 235 °C. The photoemission is greatly affected by phase behaviour and ion dynamics. A photoluminescence quantum yield of 61% could be achieved, by balancing the increase in Mn2+-Mn2+ separation and reducing self-quenching through increasingly large organic cations which leads to adverse increased vibrational quenching. Compared to analogous ammonium compounds, which have been promoted as @#x0308;inorganic hybrid perovskite, the phosphonium salts show superior performance, with respect to photoluminescent quantum yield and thermal and air/humidity stability. As the presented compounds are not sensitive to the atmosphere, in particular moisture, and show strong visible electroluminescence in the green region of light, they are important emitter materials for use in organic light-emitting devices.
|
|
| 6. |
- Bilgic, Mehmet B., et al.
(författare)
-
An unusual zig-zag 2D copper(i) coordination polymer as an outstanding catalyst for azide–alkyne “click” chemistry at room temperature
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:46, s. 17543-17546
-
Tidskriftsartikel (refereegranskat)abstract
- A straightforward method for the synthesis of a two-dimensional (2D) new copper(I) coordination polymer, namely Cu(bzpdc), containing the ligand benzophenone 4,4′-dicarboxylate, and its effective use as catalyst for the azide–alkyne click chemistry at room temperature is reported. Zig-zag formation caused by cuprophilic interactions resulted in an unprecedented crystal structure with a very high copper content (45.5% by weight). The catalyst was stable up until 300 °C and tolerant to various solvents, including water. Cu(bzpdc) showed excellent catalytic activity for click reactions of several organic azides and alkynes having different functional groups at room temperature and is comparable to its homogenous analogues. The recyclability of Cu(bzpdc) was also tested and proven to be effective.
|
|
| 7. |
- Boniolo, Manuel, et al.
(författare)
-
Electronic and geometric structure effects on one-electron oxidation of first-row transition metals in the same ligand framework
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 50:2, s. 660-674
-
Tidskriftsartikel (refereegranskat)abstract
- Developing new transition metal catalysts requires understanding of how both metal and ligand properties determine reactivity. Since metal complexes bearing ligands of the Py5 family (2,6-bis-[(2-pyridyl)methyl] pyridine) have been employed in many fields in the past 20 years, we set out here to understand their redox properties by studying a series of base metal ions (M = Mn, Fe, Co, and Ni) within the Py5OH (pyridine-2,6-diylbis[di-(pyridin-2-yl)methanol]) variant. Both reduced (M-II) and the one-electron oxidized (M-III) species were carefully characterized using a combination of X-ray crystallography, X-ray absorption spectroscopy, cyclic voltammetry, and density-functional theory calculations. The observed metal-ligand interactions and electrochemical properties do not always follow consistent trends along the periodic table. We demonstrate that this observation cannot be explained by only considering orbital and geometric relaxation, and that spin multiplicity changes needed to be included into the DFT calculations to reproduce and understand these trends. In addition, exchange reactions of the sixth ligand coordinated to the metal, were analysed. Finally, by including published data of the extensively characterised Py5OMe (pyridine-2,6-diylbis[di-(pyridin-2-yl)methoxymethane])complexes, the special characteristics of the less common Py5OH ligand were extracted. This comparison highlights the non-innocent effect of the distal OH functionalization on the geometry, and consequently on the electronic structure of the metal complexes. Together, this gives a complete analysis of metal and ligand degrees of freedom for these base metal complexes, while also providing general insights into how to control electrochemical processes of transition metal complexes.
|
|
| 8. |
- Boström, Hanna L. B., et al.
(författare)
-
Spin crossover in the Prussian blue analogue FePt(CN)(6 )induced by pressure or X-ray irradiation
- 2020
-
Ingår i: Dalton Transactions. - : ROYAL SOC CHEMISTRY. - 1477-9226 .- 1477-9234. ; 49:37, s. 12940-12944
-
Tidskriftsartikel (refereegranskat)abstract
- The spin state of the Prussian blue analogue (FePtIV)-Pt-II (CN)(6) is investigated in response to temperature, pressure, and X-ray irradiation. White cooling to 10 K maintains the high-spin state of Fe-II, compression at ambient temperature induces a first-order spin-crossover (SCO) transition with a small hysteresis loop (p up arrow = 0.8 GPa, p down arrow= 0.6 GPa). In addition, the high-spin to low-spin transition can be initiated at lower pressure through increased X-ray irradiation. Our study highlights a cooperative SCO with moderate pressure in a porous Prussian blue analogue.
|
|
| 9. |
- Breijaert, Troy C., et al.
(författare)
-
Tailoring a bio-based adsorbent for sequestration of late transition and rare earth elements
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 51:47, s. 17978-17986
-
Tidskriftsartikel (refereegranskat)abstract
- The demand for new renewable energy sources, improved energy storage and exhaust-free transportation requires the use of large quantities of rare earth (REE) and late transition (LTM, group 8–12) elements. In order to achieve sustainability in their use, an efficient green recycling technology is required. Here, an approach, a synthetic route and an evaluation of the designed bio-based material are reported. Cotton-derived nano cellulose particles were functionalized with a polyamino ligand, tris(2-aminoethyl) amine (TAEA), achieving ligand content of up to ca. 0.8 mmol g−1. The morphology and structure of the produced adsorbent were revealed by PXRD, SEM-EDS, AFM and FTIR techniques. The adsorption capacity and kinetics of REE and LTM were investigated by conductometric photometric titrations, revealing quick uptake, high adsorption capacity and pronounced selectivity for LTM compared to REE. Molecular insights into the mode of action of the adsorbent were obtained via the investigation of the molecular structure of the Ni(II)–TAEA complex by an X-ray single crystal study. The bio-based adsorbent nanomaterial demonstrated in this work opens up a perspective for tailoring specific adsorbents in the sequestration of REE and LTM for their sustainable recycling.
|
|
| 10. |
- Burger, Stefan, et al.
(författare)
-
A new polar perovskite coordination network with azaspiroundecane as A-site cation
- 2020
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:31, s. 10740-10744
-
Tidskriftsartikel (refereegranskat)abstract
- ABX(3) perovskite coordination networks are a rapidly growing subclass of crystalline coordination networks. At present, synthetic efforts in the field are dominated by the use of commercially available building blocks, leaving the potential for tuning properties via targeted compositional changes largely untouched. Here we apply a rational crystal engineering approach, using 6-azaspiro[5.5]undecane ([ASU](+)) as A-site cation for the synthesis of the polar perovskite [ASU][Cd(C2N3)(3)].
|
|
| 11. |
- Chen, Zheng, et al.
(författare)
-
Graphitic nitrogen in carbon catalysts is important for the reduction of nitrite as revealed by naturally abundant N-15 NMR spectroscopy
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; :20
-
Tidskriftsartikel (refereegranskat)abstract
- Metal-free nitrogen-doped carbon is considered as a green functional material, but the structural determination of the atomic positions of nitrogen remains challenging. We recently demonstrated that directly-excited solid state N-15 NMR (ssNMR) spectroscopy is a powerful tool for the determination of such positions in N-doped carbon at natural N-15 isotope abundance. Here we report a green chemistry approach for the synthesis of N-doped carbon using cellulose as a precursor, and a study of the catalytic properties and atomic structures of the related catalyst. N-doped carbon (NH3) was obtained by the oxidation of cellulose with HNO3 followed by ammonolysis at 800 degrees C. It had a N content of 6.5 wt% and a surface area of 557 m(2) g(-1), and N-15 ssNMR spectroscopy provided evidence for graphitic nitrogen besides regular pyrrolic and pyridinic nitrogen. This structural determination allowed probing the role of graphitic nitrogen in electrocatalytic reactions, such as the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and nitrite reduction reaction. The N-doped carbon catalyst (NH3) showed higher electrocatalytic activities in the OER and HER under alkaline conditions and higher activity for nitrite reduction, as compared with a catalyst prepared by the carbonization of HNO3-treated cellulose in N-2. The electrocatalytic selectivity for nitrite reduction of the N-doped carbon catalyst (NH3) was directly related to the graphitic nitrogen functions. Complementary structural analyses by means of C-13 and H-1 ssNMR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and low-temperature N-2 adsorption were performed and provided support to the findings. The results show that directly-excited N-15 ssNMR spectroscopy at natural N-15 abundance is generally capable of providing information on N-doped carbon materials if relaxation properties are favorable. It is expected that this approach can be applied to a wide range of solids with an intermediate concentration of N atoms.
|
|
| 12. |
- Chen, Zheng, et al.
(författare)
-
Increased photocurrent of CuWO4 photoanodes by modification with the oxide carbodiimide Sn2O(NCN)
- 2020
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:11, s. 3450-3456
-
Tidskriftsartikel (refereegranskat)abstract
- Tin(ii) oxide carbodiimide is a novel prospective semiconductor material with a band gap of 2.1 eV and lies chemically between metal oxides and metal carbodiimides. We report on the photochemical properties of this oxide carbodiimide and apply the material to form a heterojunction with CuWO4 thin films for photoelectrochemical (PEC) water oxidation. Mott-Schottky experiments reveal that the title compound is an n-type semiconductor with a flat-band potential of -0.03 V and, as such, the position of the valence band edge would be suitable for photochemical water oxidation. Sn2O(NCN) increases the photocurrent of CuWO4 thin films from 32 mu A cm(-2) to 59 mu A cm(-2) at 1.23 V vs. reversible hydrogen electrode (RHE) in 0.1 M phosphate buffer (pH 7.0) under backlight AM 1.5G illumination. This upsurge in photocurrent originates in a synergistic effect between the oxide and oxide carbodiimide, because the heterojunction photoanode displays a higher current density than the sum of its individual components. Structural analysis by powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) reveals that Sn2O(NCN) forms a core-shell structure Sn2O(NCN)@SnPOx during the PEC water oxidation in phosphate buffer. The electrochemical activation is similar to the behavior of Mn(NCN) but different from Co(NCN).
|
|
| 13. |
- Colbin, Lars Olow Simon, et al.
(författare)
-
On the compatibility of high mass loading bismuth anodes for full-cell sodium-ion batteries
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 51:44, s. 16852-16860
-
Tidskriftsartikel (refereegranskat)abstract
- Metallic bismuth is here studied as an anode material for sodium-ion batteries. The details of electrochemical redox reactions, rate performance and cycled life were investigated using relatively high mass loading electrodes in two- and three-electrode full-cells. It demonstrated that the rate capability of bismuth anodes with high mass loading are not as good as indicated in previous literatures where low mass loading electrodes were used. It also indicated that the resistances causing a faltering rate performance may be connected to a loss in particle contact during desodiation. Efforts were also made to study the different electrochemical processes that occur during early cycles. Less advantageous characteristics of bismuth electrodes are also discussed. For example, several different electrolyte solutions were tested for compatibility with the bismuth system, where only glyme-based solutions seemed to facilitate robust cycling.
|
|
| 14. |
- Das, Krishna Sundar, et al.
(författare)
-
Utilization of counter anions for charge transportation in the electrical device fabrication of Zn(ii) metal–organic frameworks
- 2020
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 49:46, s. 17005-17016
-
Tidskriftsartikel (refereegranskat)abstract
- The present work reports the fabrication of anion-induced electrical devices with Zn(II) metal–organic frameworks. The essence of our electronic device fabrication is to utilize the anionic species entrapped inside of the three-dimensional network of the MOFs for charge transportation. The idea is to generate MOFs as a host–guest system with encapsulated anions or anion–solvent clusters as guests and a cationic yet insulating three-dimensional framework as the host. Accordingly, we have synthesized two Zn(II) MOFs using a neutral bispyrazole-based ligand, which results in a cationic chassis with substantial void space and porous channels inside the network. For both MOFs, the porous channels are occupied by infinitely hydrogen bonded networks of anions and anion–solvent clusters. This provides an excellent platform for anionic species-induced charge transportation and improved electrical conductivity. Indeed, the impedance spectroscopy data and current density–voltage (J–V) characteristics of the fabricated electrical devices further vindicate our idea. The current–voltage measurements clearly indicate the usefulness of modified host–guest-type MOFs for electronic device fabrication with corroborating conductivity values of 8.71 × 10−5 S m−1 and 5.79 × 10−4 S m−1 for compound 1 and compound 2, respectively.
|
|
| 15. |
- De, Avik, et al.
(författare)
-
Lanthanide clusters of phenanthroline containing a pyridine–pyrazole based ligand : magnetism and cell imaging
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 50:10, s. 3593-3609
-
Tidskriftsartikel (refereegranskat)abstract
- In this contribution, we report the synthesis, characterization and luminescence-magnetic properties of Ln-clusters (Ln = Gd3+, Eu3+and Tb3+) using a new pyridine-pyrazole functionalized ligand fitted with a chromophoric phenanthroline backbone. The unorthodox N-rich ligand forms isostructural trinuclear lanthanide complexes with a topology that closely resembles two interdigitating hairpins. The clusters crystallize in chiral space groups and also exhibit chirality for bulk samples, which were further confirmed using solid state CD spectra. Magnetic studies on the complexes reveal their interesting features while the Gd cluster shows a significant cryogenic magnetic cooling behaviour with a moderately high magnetic entropy change of −23.42 J kg−1K−1at 7 T and 2 K. On the other hand, Eu and Tb complexes exhibit interesting fluorescence properties. The compounds were subsequently used as fluorescent probes for the imaging of human breast adenocarcinoma (MCF7) cells. Live cell confocal microscopy images show that the complexes penetrate beyond the usual cytoplasm region and can be useful in imaging the nucleus region of MCF7 cells.
|
|
| 16. |
- Deka, Rajesh, et al.
(författare)
-
Carbene chemistry of arsenic, antimony, and bismuth : origin, evolution and future prospects
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:22, s. 8540-8556
-
Forskningsöversikt (refereegranskat)abstract
- The discovery of the first isolable N-heterocyclic carbene in 1991 ushered in a new era in coordination chemistry. The remarkable bonding properties of carbenes have led to their rapid proliferation as auxiliary ligands for a wide range of transition metals and main group elements. In the case of group 15, while carbene-stabilized nitrogen and phosphorus compounds are extensively studied, the scope of research has shrunk significantly from arsenic to bismuth. This is essentially attributed to the decrease in stability of the C-E bond upon descending the group. Even so, modulating the carbene backbone or introducing alternative synthetic strategies not only alleviates the stability issues but also offers promising results in terms of the bonding and reactivities of these compounds. The purpose of the present perspective is to provide a comprehensive overview of the origins and development of carbene chemistry of arsenic, antimony, and bismuth, as well as to highlight the future prospects of this field.
|
|
| 17. |
|
|
| 18. |
- El Jamal, Ghada, et al.
(författare)
-
Mixed H2O/H2plasma-induced redox reactions of thin uranium oxide films under UHV conditions
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 50:36, s. 12583-12591
-
Tidskriftsartikel (refereegranskat)abstract
- X-ray photoelectron spectroscopy (XPS) has been used to study the effect of mixed H2O/H2gas plasma on the surfaces of UO2, U2O5and UO3thin films at 400 °C. The experiments were performedin situunder ultra-high vacuum conditions. Deconvolution of the U4f7/2peaks into U(iv), U(v) and U(vi) components revealed the surface composition of the films after 10 min plasma exposure as a function of H2concentration in the feed gas of the plasma. Some selected films (unexposed and exposed) were also analysed using grazing-incidence X-ray diffraction (GIXRD). The XPS results show that U(v) is formed as a major product upon 10 minutes exposure of UO3by a mixed H2O/H2plasma in a fairly wide H2concentration range. When starting with U(v) (U2O5), rather high H2concentrations are needed to reduce U(v) to U(iv) in 10 minutes. In the plasma induced oxidation of UO2, U(v) is never observed as a major product after 10 minutes and it would seem that once U(v) is formed in the oxidation of UO2it is rapidly oxidized further to U(vi). The grazing incidence X-ray diffraction analysis shows that there is a considerable impact of the plasma and heating conditions on the crystal structure of the films in line with the change of the oxidation state. This structural difference is proposed to be the main kinetic barrier for plasma induced transfer between U(iv) and U(v) in both directions.
|
|
| 19. |
- El Jamal, Ghada, et al.
(författare)
-
Time-dependent surface modification of uraniumoxides exposed to water plasma
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 50:14, s. 4796-4804
-
Tidskriftsartikel (refereegranskat)abstract
- Thin UO2 films exposed to water plasma under UHV conditions have been shown to be interestingmodels for radiation induced oxidative dissolution of spent nuclear fuel. This is partly attributed to the factthat several of the reactive oxidizing and reducing species in a water plasma are also identified as productsof radiolysis of water. Exposure of UO2 films to water plasma has previously been shown to lead to oxidationfrom U(IV) to U(V) and (VI). In this work we have studied the dynamics of water plasma inducedredox changes in UO2 films by monitoring UO2 films using X-Ray photoelectron Photoemission (XPS) andUltra-Violet Photoemission (UPS) spectroscopy as a function of exposure time. The surface compositionin terms of oxidation states obtained from U4f7/2 peak deconvolution could be retraced along theexposure time, and compared to the valence band. The spectral analysis showed that U(IV) is initially oxidizedto U(V) which is subsequently oxidized to U(VI). For extended exposure times it was shown that U(VI)is slowly reduced back to U(V). UPS data show that, unlike the U(V) formed on the surface upon oxidationof U(IV), the U(V) formed upon reduction of U(VI) is localized in the bulk of the film. It also displays adifferent reactivity than the initially formed U(V). The experiments can be reproduced using a simplekinetic model describing the redox processes involved.
|
|
| 20. |
- El Jamal, Ghada, et al.
(författare)
-
X-Ray and ultraviolet photoelectron spectroscopy studies of Uranium(IV),(V) and(VI) exposed to H2O-plasma under UHV conditions
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 50:2, s. 729-738
-
Tidskriftsartikel (refereegranskat)abstract
- Thin films of UO2, U2O5, and UO3 were prepared in situ and exposed to reactive gas plasmas of O-2, H-2 and H2O vapour produced with an ECR plasma source (electron cyclotron resonance) under UHV conditions. The plasma constituents were analysed using a residual gas analyser mass spectrometer. For comparison, the thin films were also exposed to the plasma precursor gases under comparable conditions. Surface analysis was conducted using X-Ray and ultraviolet photoelectron spectroscopy before and after exposure, by measuring the U 4f, O 1s core levels and the valence band region. The evolution of the peaks was monitored as a function of temperature and time of exposure. After interacting with water plasma at 400 degrees C, the surface of UO2 was oxidized to a higher oxidation state compared to when starting with U2O5 while the UO3 film displayed weak surface reduction. When exposed to water plasma at ambient temperature, the outermost surface layer is composed of hexavalent uranium in all three cases.
|
|
| 21. |
- Gahlot, Sweta, et al.
(författare)
-
Room-temperature conversion of Cu2-xSe to CuAgSe nanoparticles to enhance the photocatalytic performance of their composites with TiO2
- 2020
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:11, s. 3580-3591
-
Tidskriftsartikel (refereegranskat)abstract
- Rational design and precise engineering are needed to optimize the structural and chemical parameters of functional materials. In this work, we demonstrate how pre-formed binary metal selenides can be an excellent synthetic choice for the synthesis of ternary coinage metal selenide nanoparticles (NPs) with controlled composition. The mild conditions required to obtain these ternary coinage metal selenide NPs offered an easy synthesis of n% CuAgSe-TiO2 (n = 0.01, 0.1, 0.3 and 1.0 mol%) nanocomposites for photocatalytic applications without compromising the structural and morphological characteristics of TiO2 and without having any organic ligands around the NPs. The use of ternary metal selenide nanocomposites CuAgSe-TiO2 results in a clear improvement in their photocatalytic activity for the photodegradation of formic acid as compared to the well-known benchmark for photocatalysis, TiO2 (P25), and its binary metal selenide nanocomposites Cu2-xSe-TiO2. DFT calculations establish semi-metallic behavior of CuAgSe NPs and show that CuAgSe-TiO2 forms a semimetallic-semiconductor heterojunction allowing a better charge separation to enhance its photocatalytic activity.
|
|
| 22. |
- Garg, Nitish Kumar, et al.
(författare)
-
A mononuclear iron(iii) complex with unusual changes of color and magneto-structural properties with temperature : Synthesis, structure, magnetization, multi-frequency ESR and DFT study
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:6, s. 2338-2345
-
Tidskriftsartikel (refereegranskat)abstract
- From the reaction of 2-hydroxy-6-methylpyridine (L) with iron(ii) tetrafluoroborate, a new mononuclear iron(iii) octahedral complex [FeL6](BF4)3 has been isolated. The color of the complex reversibly changed from red at room temperature to yellow-orange at the liquid nitrogen temperature. Magnetization measurements indicate that iron(iii) in [FeL6](BF4)3 is in a high-spin state S = 5/2, from room temperature to 1.8 K. The high-spin ground state of iron(iii) is also confirmed by DFT calculations. Although the spin-crossover of the complex is not observed, X-band and multifrequency high-field/high-frequency electron spin resonance (ESR) spectroscopy shows rather uncommon iron(iii) spectra at room temperature and an unusual change with cooling. Spectral simulations reveal that the S = 5/2 ground state multiplet of the complex can be characterized by the temperature independent axial zero-field splitting parameter of |D| = +2 GHz (0.067 cm-1) while the value of the rhombic parameter E of the order of some tenths MHz increases on lowering the temperature. Single crystal X-ray diffraction (SCXRD) shows that the iron(iii) coordination geometry does not change with temperature while supramolecular interactions are temperature dependent, influencing the iron(iii) rhombicity. Additionally, the DFT calculations show temperature variation of the HOMO-LUMO gap, in agreement with the changes of color and ESR-spectra of the iron(iii) complex with temperature.
|
|
| 23. |
- Greijer, Björn, et al.
(författare)
-
Factors influencing stoichiometry and stability of polyoxometalate - peptide complexes
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51, s. 9511-9521
-
Tidskriftsartikel (refereegranskat)abstract
- In the pursuit of understanding the factors guiding interactions between polyoxometalates (POMs) and biomolecules, several complexes between Keggin phosphomolybdate and diglycine have been produced at different acidity and salinity conditions, leading to difference in stoichiometry and in crystal structure. Principal factors determining how the POM and dipeptide interact appear to be pH, ionic strength of the medium, and the molar ratio of POM to peptide. An important effect turned out to be even the structure-directing role of the sodium cations coordinating carbonyl functions of the peptide bond. Given the interest in applying POMs in biological systems, these factors are highly relevant to consider. In the view of recent interest in using POMs as nano catalysts in peptide hydrolysis also the potential Keggin POM transformation in phosphate buffered saline medium was investigated leading to insight that nanoparticles of zirconium phosphate (ZrP) can be actual catalysts for breakdown of the peptide bond.
|
|
| 24. |
- Grinderslev, Jakob B., et al.
(författare)
-
Polymorphism and solid solutions of trimethylammonium monocarboranes
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:41, s. 15806-15815
-
Tidskriftsartikel (refereegranskat)abstract
- Metal closo-boranes have recently received significant attention as solid-state electrolytes due to their high thermal and electrochemical stability, and the weak interaction between the cat- and anion, facilitating fast ionic conductivity. Here we report a synthesis method for obtaining a novel mixed closo-carborane compound, [NH(CH3)3][(CB8H9)0.26(CB9H10)0.66(CB11H12)0.08]. The crystal structures are investigated for [NH(CH3)3][CB9H10] and [NH(CH3)3][(CB8H9)0.26(CB9H10)0.66(CB11H12)0.08], revealing that the latter forms a solid solution isostructural to [NH(CH3)3][CB9H10]. The compounds exhibit polymorphism as a function of temperature, and we report the discovery of four polymorphs of [NH(CH3)3][CB9H10] and four isostructural solid solution [NH(CH3)3][(CB8H9)0.26(CB9H10)0.66(CB11H12)0.08], along with a high-temperature decomposition intermediate of the latter. The α-polymorph is an ordered structure, with increasing amounts of disorder for the β- and γ-polymorphs, while the high temperature δ- and ϵ-polymorphs at T > 476 K are fully disordered on both the cation and anion site. These new compounds may be used as precursors for new types of solid-state ionic conductors.
|
|
| 25. |
- Gusev, Alexey, et al.
(författare)
-
Mononuclear copper(i) complexes bearing a 3-phenyl-5-(pyridin-4-yl)-1,2,4-triazole ligand: synthesis, crystal structure, TADF-luminescence, and mechanochromic effects
- 2023
-
Ingår i: Dalton Transactions. - : ROYAL SOC CHEMISTRY. - 1477-9226 .- 1477-9234. ; 52:41, s. 14995-15008
-
Tidskriftsartikel (refereegranskat)abstract
- Three new mononuclear heteroleptic copper(i) halide complexes, [CuL(PPh3)(2)X] (X = Cl, Br, I), based on 3-phenyl-5-(pyridin-4-yl)-1,2,4-triazole (L) and triphenylphosphine (PPh3) ligands, have been prepared by reaction of CuX (X = Cl, Br, I), L and PPh3 in a molar ratio of 1 : 1 : 2 in MeCN solutions. The synthesized complexes exhibit blue light emission in solutions and bright green emission in the crystal state with quantum yields of up to 100%. The luminescence decay analysis and density functional theory calculations revealed that the emission of solid samples at room temperature corresponds to the thermally activated delayed fluorescence, while that at 77 K is assigned to phosphorescence. Utilizing the studied complexes in OLED heterostructures resulted in high-performing green-emitting devices with an external quantum efficiency of up to 13.4%.
|
|
| 26. |
- Hedegård, Erik Donovan, et al.
(författare)
-
New relativistic quantum chemical methods for understanding light-induced therapeutics
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:42, s. 16055-16064
-
Forskningsöversikt (refereegranskat)abstract
- The inorganic platinum complexes currently in clinical use for cancer treatment have severe side effects, and complexes with fewer side effects are required. One option is to use complexes that are inactive until they are light-activated. Theoretical chemistry can contribute to the design of these complexes, but most current theoretical methods lack explicit treatment of relativistic effects (since the target complexes often contain heavy elements). In particular, spin-orbit coupling is required for accurate predictions of the complexes’ photo-physical properties. In this perspective, we summarize relativistic methods developed in recent years that can contribute to our understanding of light-induced reactivity and thereby help predict new, suitable complexes.
|
|
| 27. |
- Jonsson, Helgi Freyr, et al.
(författare)
-
Studies on gold(I) and gold(III) alcohol functionalised NHC complexes
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 50:15, s. 5128-5138
-
Tidskriftsartikel (refereegranskat)abstract
- Five pairs of novel chiral alcohol functionalised gold(I) and gold(III) NHC complexes derived from chiral amino alcohols, were synthesized and characterised (NMR, IR, HRMS). Single crystal X-ray diffraction data of gold(I) and gold(III) complexes are reported and discussed. The chiral imidazolium preligands were readily synthesized via the oxalamides, subsequent reduction and final orthoformate condensation. An improved method was used for generation of gold(I) NHC complexes (up to 92%) and further oxidation afforded the corresponding gold(III) NHC complexes (up to 99%). All the Au(I) and Au(III) NHC complexes proved far more catalytically active in a 1,6-enyne alkoxycyclization test reaction than our previously tested N,N- and P,N-ligated Au(III) complexes. Comparative gold(I) and gold(III) catalytic studies demonstrated different catalytic ability, depending on the NHC ligand flexibility and bulkiness. Excellent yields (92-99%) of target alkoxycyclization product were obtained with both gold(I) and gold(III) complexes with the bulky N-1-Mes-N-2-ethanol based NHC ligand.
|
|
| 28. |
- Kiraev, Salauat R., et al.
(författare)
-
Improved emission of Yb(iii) ions in triazacyclononane-based macrocyclic ligands compared to cyclen-based ones
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 51:43, s. 16596-16604
-
Tidskriftsartikel (refereegranskat)abstract
- Yb(III) complexes based on ligands with a 1,4,7-triazacyclononane (tacn) macrocyclic core were synthesised. The complexes carry a 4-methoxymethyl-substituted carbostyril chromophore that serves as a light-harvesting antenna. The ligands supply 5 nitrogen and 3 oxygen donors via 1 methylenecarboxamide and 2 picolinate donors, creating +1 charged complexes with an octadentate binding environment. The electronic properties of the picolinates are modulated by varying the substitution at the 4 position with OMe, H, Cl, or CF3. Cyclic voltammetry indicated that the tacn-based Yb(III) complexes were easier to reduce than the analogous cyclen complexes. The first reductive event is likely picolinate-centred, followed by the formation of further reduced species. Antenna excitation yielded Yb(III) luminescence in the near-infrared (NIR) region in all cases. The antenna photophysical properties were consistent with intraligand photoinduced electron transfer from the excited carbostyril to the picolinate groups. The relative quantum yields of Yb(III) luminescence were determined. The lowest value was obtained for the complex with the most efficient antenna-to-picolinate photoinduced electron transfer. Despite intraligand electron transfer quenching of the antenna, the tacn-based Yb complexes were more emissive than their cyclen analogues, highlighting the influence of the ligand structure on the luminescence properties of NIR emissive lanthanide(III) ions.
|
|
| 29. |
- Kloo, Lars
(författare)
-
On the non-existence of a square-planar pentaiodide coordination complex I(i)4−
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:37, s. 14182-14189
-
Tidskriftsartikel (refereegranskat)abstract
- The properties of two conformers of the pentaiodide ion, a V-shaped and regularly observed I5− ion, and a so far undetected square-planar coordination complex of II4− composition, have been investigated by computational methods. The latter compound is indicated by the analogy to the coordination chemistry of gold with halide ligands, as well as isoelectronic main-group compounds. Static and dynamic simulations at density-functional and semi-empirical level including effects of solvent and counter ions indicate that the square-planar II4− indeed represents a well-defined local minimum on the pentaiodide potential energy surface, albeit less stable than the typically observed V-shaped I5−. No simple pathway of transformation between the two forms of the pentaiodide ion can be identified. Molecular dynamics simulations indicate that the presence of cations, unavoidable during the synthesis of polyiodide compounds, may trigger decomposition of the II4− coordination complex into smaller polyiodide building blocks and thus constitute the main reason why this conformer so far has not been identified in solid polyiodide compounds. However, its intrinsic stability indicates that the square-planar form should be possible to isolate in solid compounds given the right conditions of synthesis.
|
|
| 30. |
- Kócsi, Dániel, et al.
(författare)
-
Reduced quenching effect of pyridine ligands in highly luminescent Ln(iii) complexes : the role of tertiary amide linkers
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 50:45, s. 16670-16677
-
Tidskriftsartikel (refereegranskat)abstract
- Luminescent Eu(iii) and Tb(iii) complexes were synthesised from octadentate ligands carrying various carbostyril sensitizing antennae and two bidentate picolinate donors. Antennae were connected to the metal binding site via tertiary amide linkers. Antennae and donors were assembled on a 1,4,7-triazacyclononane (tacn) platform. Solution- and solid-state structures were comparable to those of previously reported complexes with tacn architectures, with nine-coordinate distorted tricapped trigonal prismatic Ln(iii) centres, and distinct from those based on 1,4,7,10-tetraazacyclododecane (cyclen) macrocycles. In contrast, the photophysical properties of these tertiary amide tacn-based complexes were more comparable to those of previously reported systems with cyclen ligands, showing efficient Eu(iii) and Tb(iii) luminescence. This represents an improvement over secondary amide-linked analogues, and is due to a greatly increased sensitization efficiency in the tertiary amide-linked complexes. Tertiary amide-linked Eu(iii) and Tb(iii) emitters were more photostable than their secondary amide-linked analogues due to the suppression of photoinduced electron transfer and back energy transfer.
|
|
| 31. |
- Kovacs, Daniel, et al.
(författare)
-
Electron transfer pathways in photoexcited lanthanide(iii) complexes of picolinate ligands
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 50:12, s. 4244-4254
-
Tidskriftsartikel (refereegranskat)abstract
- A series of luminescent lanthanide(iii) complexes consisting of 1,4,7-triazacyclononane frameworks and three secondary amide-linked carbostyril antennae were synthesised. The metal binding sites were augmented with two pyridylcarboxylate donors yielding octadentate ligands. The antennae carried methyl, methoxymethyl or trifluoromethyl substituents in their 4-positions, allowing for a range of excited state energies and antenna electronic properties. The H-1 NMR spectra of the Eu(iii) complexes were found to be analogous to each other. Similar results were obtained in the solid-state by single-crystal X-ray crystallography, which showed the structures to have nine-coordinate metal ions with heavily distorted tricapped trigonal prismatic geometries. Steady-state and time-resolved luminescence spectroscopy showed that the antennae could sensitize both Tb(iii) and Eu(iii), however, quantum yields were lower than in other octadentate complexes lacking pyridylcarboxylate. Complexes with more electron-poor pyridines were less emissive even when equipped with the same antenna. The oxidation and reduction potentials of the antennae and the pyridinecarboxylates, respectively, were determined by cyclic voltammetry. The obtained values were consistent with electron transfer from the excited antenna to the pyridine providing a previously unexplored quenching pathway that could efficiently compete with energy transfer to the lanthanide. These results show the crucial impact that photophysically innocent ligand binding sites can have on lanthanide luminescence.
|
|
| 32. |
- Kumagai, Yuta, et al.
(författare)
-
gamma-Radiation and H2O2 induced oxidative dissolution of uranium(iv) oxide in aqueous solution containing phthalic acid
- 2020
-
Ingår i: Dalton Transactions. - : ROYAL SOC CHEMISTRY. - 1477-9226 .- 1477-9234. ; 49:6, s. 1907-1914
-
Tidskriftsartikel (refereegranskat)abstract
- This study aims to reveal possible involvements of organic acids in the oxidative dissolution of UO2. Using phthalic acid as a model compound, we have measured adsorption on UO2 and investigated effects on the reaction between H2O2 and UO2 and on oxidative dissolution induced by gamma-irradiation. Significant adsorption of phthalic acid was observed even at neutral pH. However, the reaction between H2O2 and UO2 in phthalic acid solution induced oxidative dissolution of U(vi) similar to in aqueous bicarbonate solution. Moreover, degradation products of phthalic acid were not detected after the reaction of H2O2. These results indicate that even though phthalic acid adsorbs on the UO2 surface, it is not involved in the interfacial reaction of H2O2. In contrast, the dissolution of U by irradiation was inhibited in aqueous phthalic acid solution, whereas H2O2 generated by radiolysis was consumed by UO2. Based on these contrasting results, possible roles of radical species generated by water radiolysis were discussed.
|
|
| 33. |
- Kuzevanova, Iryna, et al.
(författare)
-
Spin crossover in iron(ii) Hofmann clathrates analogues with 1,2,3-triazole
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 50, s. 9250-9258
-
Tidskriftsartikel (refereegranskat)abstract
- Hofmann-like cyanometallic complexes represent one of the biggest and well-known classes of FeII spin-crossover compounds. In this paper, we report on the first FeII Hofmann clathrate analogues with unsubstituted 1,2,3-triazole, which exhibit temperature induced spin transition. Two new coordination polymers with the general formula [FeII(1,2,3-triazole)2MII(CN)4] (M = Pt, Pd) undergo abrupt hysteretic spin crossover in the range of 190–225 K as revealed by magnetic susceptibility measurements. Two compounds are isostructural and are built of infinite cyanometallic layers which are supported by 1,2,3-triazole ligands. The thermal hysteresis loop is very stable at different scan rates from 0.5 to 10 K min−1. The compounds display strong thermochromic effect, changing their colour from pink in the low-spin state to white in the high-spin state. Our findings show that 1,2,3-triazole is suitable for elaboration of spin-crossover Hofmann clathrate analogues, and its use instead of more classical azines can advantageously expand this family of complexes.
|
|
| 34. |
- Lalaoui, Noemie, et al.
(författare)
-
Gold nanoparticle-based supramolecular approach for dye-sensitized H-2-evolving photocathodes
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 51:41, s. 15716-15724
-
Tidskriftsartikel (refereegranskat)abstract
- Solar conversion of water into the storable energy carrier H-2 can be achieved through photoelectrochemical water splitting using light adsorbing anodes and cathodes bearing O-2 and H-2 evolving catalysts, respectively. Herein a novel photocathode nanohybrid system is reported. This photocathode consists of a dye-sensitized p-type nickel oxide (NiO) with a perylene-based chromophore (PCA) and a tetra-adamantane modified cobaloxime reduction catalyst (Co) that photo-reduces aqueous protons to H-2. An original supramolecular approach was employed, using beta-cyclodextrin functionalized gold nanoparticles (beta-CD-AuNPs) to link the alkane chain of the PCA dye to the adamantane moieties of the cobaloxime catalyst (Co). This new architecture was investigated by photoelectrochemical measurements and via femtosecond-transient absorption spectroscopy. The results show that irradiation of the complete NiO|PCA|beta-CD-AuNPs|Co electrode leads to ultrafast hole injection into NiO (pi = 3 ps) from the excited dye, followed by rapid reduction of the catalyst, and finally H-2 evolution.
|
|
| 35. |
- Larsson, Ernst D., et al.
(författare)
-
Is density functional theory accurate for lytic polysaccharide monooxygenase enzymes
- 2020
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:5, s. 1501-1512
-
Tidskriftsartikel (refereegranskat)abstract
- The lytic polysaccharide monooxygenase (LPMO) enzymes boost polysaccharide depolymerization through oxidative chemistry, which has fueled the hope for more energy-efficient production of biofuel. We have recently proposed a mechanism for the oxidation of the polysaccharide substrate (E. D. Hedegård and U. Ryde, Chem. Sci., 2018, 9, 3866-3880). In this mechanism, intermediates with superoxide, oxyl, as well as hydroxyl (i.e. [CuO2]+, [CuO]+ and [CuOH]2+) cores were involved. These complexes can have both singlet and triplet spin states, and both spin-states may be important for how LPMOs function during catalytic turnover. Previous calculations on LPMOs have exclusively been based on density functional theory (DFT). However, different DFT functionals are known to display large differences for spin-state splittings in transition-metal complexes, and this has also been an issue for LPMOs. In this paper, we study the accuracy of DFT for spin-state splittings in superoxide, oxyl, and hydroxyl intermediates involved in LPMO turnover. As reference we employ multiconfigurational perturbation theory (CASPT2).
|
|
| 36. |
- Laun, Konstantin, et al.
(författare)
-
Site-selective protonation of the one-electron reduced cofactor in [FeFe]-hydrogenase
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 50:10, s. 3641-3650
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrogenases are bidirectional redox enzymes that catalyze hydrogen turnover in archaea, bacteria, and algae. While all types of hydrogenase show H-2 oxidation activity, [FeFe]-hydrogenases are excellent H-2 evolution catalysts as well. Their active site cofactor comprises a [4Fe-4S] cluster covalently linked to a diiron site equipped with carbon monoxide and cyanide ligands. The active site niche is connected with the solvent by two distinct proton transfer pathways. To analyze the catalytic mechanism of [FeFe]-hydrogenase, we employ operando infrared spectroscopy and infrared spectro-electrochemistry. Titrating the pH under H-2 oxidation or H-2 evolution conditions reveals the influence of site-selective protonation on the equilibrium of reduced cofactor states. Governed by pK(a) differences across the active site niche and proton transfer pathways, we find that individual electrons are stabilized either at the [4Fe-4S] cluster (alkaline pH values) or at the diiron site (acidic pH values). This observation is discussed in the context of the complex interdependence of hydrogen turnover and bulk pH.
|
|
| 37. |
- Laurans, Maxime, et al.
(författare)
-
Immobilising molecular Ru complexes on a protective ultrathin oxide layer of p-Si electrodes towards photoelectrochemical CO2 reduction
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 50:30, s. 10482-10492
-
Tidskriftsartikel (refereegranskat)abstract
- Photoelectrochemical CO2 reduction is a promising approach for renewable fuel generation and to reduce greenhouse gas emissions. Owing to their synthetic tunability, molecular catalysts for the CO2 reduction reaction can give rise to high product selectivity. In this context, a Ru-II complex [Ru(HO-tpy)(6-mbpy)(NCCH3)](2+) (HO-tpy = 4 '-hydroxy-2,2 ':6 ',2 ''-terpyridine; 6-mbpy = 6-methyl-2,2 '-bipyridine) was immobilised on a thin SiOx layer of a p-Si electrode that was decorated with a bromide-terminated molecular layer. Following the characterisation of the assembled photocathodes by X-ray photoelectron spectroscopy and ellipsometry, PEC experiments demonstrate electron transfer from the p-Si to the Ru complex through the native oxide layer under illumination and a cathodic bias. A state-of-the-art photovoltage of 570 mV was determined by comparison with an analogous n-type Si assembly. While the photovoltage of the modified photocathode is promising for future photoelectrochemical CO2 reduction and the p-Si/SiOx junction seems to be unchanged during the PEC experiments, a fast desorption of the molecular Ru complex was observed. An in-depth investigation of the cathode degradation by comparison with reference materials highlights the role of the hydroxyl functionality of the Ru complex to ensure its grafting on the substrate. In contrast, no essential role for the bromide function on the Si substrate designed to engage with the hydroxyl group of the Ru complex in an S(N)2-type reaction could be established.
|
|
| 38. |
- Leubner, S., et al.
(författare)
-
Hexahydroxytriphenylene for the synthesis of group 13 MOFs - a new inorganic building unit in a beta-cristobalite type structure
- 2020
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:10, s. 3088-3092
-
Tidskriftsartikel (refereegranskat)abstract
- Two new, microporous MOFs of framework composition ((CH3)(2)NH2)(2)[M3O(HHTP)(HHTP center dot)], M = Al3+, Ga3+, H6HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene, are described. Electron diffraction combined with molecular simulations show that these compounds crystallize in the beta-cristobalite structure, containing a new type of trinuclear inorganic building unit for MOFs and radical anions.
|
|
| 39. |
|
|
| 40. |
- Li, Ge, et al.
(författare)
-
Computational comparison of Ru(bda)(py)2 and Fe(bda)(py)2 as water oxidation catalysts
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:22, s. 8618-8624
-
Tidskriftsartikel (refereegranskat)abstract
- Ru(bda)(py)2 (bda = 2,2′-bipyridine-6,6′-dicarboxylate, py = pyridine) has been a significant milestone in the development of water oxidation catalysts. Inspired by Ru(bda)(py)2 and aiming to reduce the use of noble metals, iron (Fe) was introduced to replace the Ru catalytic center in Ru(bda)(py)2. In this study, density functional theory (DFT) calculations were performed on Fe- and Ru(bda)(py)2 catalysts, and a more stable 6-coordinate Fe(bda)(py)2 with one carboxylate group of bda disconnecting with Fe was found. For the first time, theoretical comparisons have been conducted on these three catalysts to compare their catalytic performances, such as reduction potentials and energy profiles of the radical coupling process. Explanations for the high potential of [FeIII(bda)(py)2-H2O]+ and reactivity of [FeV(bda)(py)2-O]+ have been provided. This study can provide insights on Fe(bda)(py)2 from a computational perspective if it is utilized as a water oxidation catalyst.
|
|
| 41. |
- Li, Junyi, et al.
(författare)
-
Meta-studtite stability in aqueous solutions. Impact of HCO3-, H2O2and ionizing radiation on dissolution and speciation
- 2021
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 50:19, s. 6568-6577
-
Tidskriftsartikel (refereegranskat)abstract
- Two uranyl peroxides meta-studtite and studtite exist in nature and can form as alteration phases on the surface of spent nuclear fuel upon water intrusion in a geological repository. Meta-studtite and studtite have very low solubility and could therefore reduce the reactivity of spent nuclear fuel toward radiolytic oxidants. This would inhibit the dissolution of the fuel matrix and thereby also the spreading of radionuclides. It is therefore important to investigate the stability of meta-studtite and studtite under conditions that may influence their stability. In the present work, we have studied the dissolution kinetics of meta-studtite in aqueous solution containing 10 mM HCO3-. In addition, the influence of the added H2O2 and the impact of γ-irradiation on the dissolution kinetics of meta-studtite were studied. The results are compared to previously published data for studtite studied under the same conditions. 13C NMR experiments were performed to identify the species present in aqueous solution (i.e., carbonate containing complexes). The speciation studies are compared to calculations based on published equilibrium constants. In addition to the dissolution experiments, experiments focussing on the stability of H2O2 in aqueous solutions containing UO22+ and HCO3- were conducted. The rationale for this is that H2O2 was consumed relatively fast in some of the dissolution experiments.
|
|
| 42. |
- Li, L., et al.
(författare)
-
Ruthenium containing molecular electrocatalyst on glassy carbon for electrochemical water splitting
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:20, s. 7957-7965
-
Tidskriftsartikel (refereegranskat)abstract
- Electrochemical water splitting constitutes one of the most promising strategies for converting water into hydrogen-based fuels, and this technology is predicted to play a key role in the transition towards a carbon-neutral energy economy. To enable the design of cost-effective electrolysis cells based on this technology, new and more efficient anodes with augmented water splitting activity and stability will be required. Herein, we report an active molecular Ru-based catalyst for electrochemically-driven water oxidation (overpotential of ∼395 mV at pH 7 phosphate buffer) and two simple methods for preparing anodes by attaching this catalyst onto glassy carbon through multi-walled carbon nanotubes to improve stability as well as reactivity. The anodes modified with the molecular catalyst were characterized by a broad toolbox of microscopy and spectroscopy techniques, and interestingly no RuO2 formation was detected during electrocatalysis over 4 h. These results demonstrate that the herein presented strategy can be used to prepare anodes that rival the performance of state-of-the-art metal oxide anodes.
|
|
| 43. |
- Liseev, Timofey, et al.
(författare)
-
Synthetic strategies to incorporate Ru-terpyridyl water oxidation catalysts into MOFs : direct synthesis vs. post-synthetic approach
- 2020
-
Ingår i: Dalton Transactions. - : ROYAL SOC CHEMISTRY. - 1477-9226 .- 1477-9234. ; 49:39, s. 13753-13759
-
Tidskriftsartikel (refereegranskat)abstract
- Incorporating molecular catalysts into metal-organic frameworks (MOFs) is a promising strategy for improving their catalytic longevity and recyclability. In this article, we investigate and compare synthetic routes for the incorporation of the potent water oxidation catalyst Ru(tda)(pyCO(2)H)(2) (tda = 2,2':6',2 ''-terpyridine-6,6 ''-dicarboxylic acid, pyCO(2)H = iso-nicotinic acid) as a structural linker into a Zr-based UiO-type MOF. The task is challenging with this particular metallo-linker because of the equatorial dangling carboxylates that can potentially compete for Zr-coordination, as well as free rotation of the pyCO(2)H groups around the HO(2)Cpy center dot center dot center dot Ru center dot center dot center dot pyCO(2)H axis. As a consequence, all attempts to synthesize a MOF with the metallo-linker directly under solvothermal conditions led to amorphous materials with the Ru(tda) (pyCO(2)H)(2) linker coordinating to the Zr nodes in ill-defined ways, resulting in multiple waves in the cyclic voltammograms of the solvothermally obtained materials. On the other hand, an indirect post-synthetic approach in which the Ru(tda)(pyCO(2)H)(2) linker is introduced into a preformed edba-MOF (edba = ethyne dibenzoic acid) of UiO topology results in the formation of the desired material. Interestingly, two distinctly different morphologies of the parent edba-MOF have been discovered, and the impact that the morphological difference has on linker incorporation is investigated.
|
|
| 44. |
- Lundberg, Daniel, et al.
(författare)
-
Coordination chemistry effects of the space-demanding solvent molecule N,N′-dimethylpropyleneurea
- 2024
-
Ingår i: Dalton Transactions. - 1477-9226 .- 1477-9234. ; 53:4, s. 1817-1832
-
Tidskriftsartikel (refereegranskat)abstract
- Crystallographic investigations of eight homoleptic N,N '-dimethylpropyleneurea (dmpu) coordinated metal ions in the solid state, [Mg(dmpu)(5)]I-2 (1), [Ca(dmpu)(6)]I-2 (2), [Ca(dmpu)(6)](ClO4)(2) (3), [Ca(dmpu)(6)](CF3SO3)(2) (4), [Sr(dmpu)(6)](CF3SO3)(2) (5), [Ba(dmpu)(6)](CF3SO3)(2) (6), [Sc(dmpu)(6)]I-3 (7), and [Pr(dmpu)(6)]I(I-3)(2) (8), and the complex [CoBr2(dmpu)(2)] (9) as well as the structures of the dmpu coordinated calcium, strontium, barium, scandium(III) and cobalt(II) ions and the cobalt(II) bromide complex in dmpu solution as determined by EXAFS are reported. The methyl groups in the dmpu molecule are close to the oxygen donor atom, causing steric restrictions, and making dmpu space-demanding at coordination to metal ions. The large volume required by the dmpu ligand at coordination contributes to crowdedness around the metal ion with often lower coordination numbers than for oxygen donor ligands without such steric restrictions. The crowdedness is seen in M & ctdot;H distances equal to or close to the sum of the van der Waals radii. To counteract the space-demand at coordination, the dmpu molecule has an unusual ability to increase the M-O-C bond angle to facilitate as large coordination numbers as possible. M-O-C bond angles in the range of 125-170 degrees are reported depending on the crowdedness caused by the coordination figure and the M-O bond distance. All reported structures of dmpu coordinated metal ions in both the solid state and dmpu solution are summarized to study the relationship between the M-O-C bond angle and the crowdedness around the metal ion. However, highly symmetric complexes seem to be favoured in the solid state due to favourable lattice energies. As a result, the dmpu coordinated lanthanoid(III) ions are octahedral in the solid state, while they, except lutetium, are seven-coordinate in the dmpu solution.
|
|
| 45. |
- Lundberg, Daniel, et al.
(författare)
-
Coordination chemistry effects of the space-demanding solvent molecule N,N′-dimethylpropyleneurea
- 2023
-
Ingår i: Dalton Transactions. - 1477-9226 .- 1477-9234. ; 53, s. 1817-1832
-
Tidskriftsartikel (refereegranskat)abstract
- Crystallographic investigations of eight homoleptic N,N '-dimethylpropyleneurea (dmpu) coordinated metal ions in the solid state, [Mg(dmpu)(5)]I-2 (1), [Ca(dmpu)(6)]I-2 (2), [Ca(dmpu)(6)](ClO4)(2) (3), [Ca(dmpu)(6)](CF3SO3)(2) (4), [Sr(dmpu)(6)](CF3SO3)(2) (5), [Ba(dmpu)(6)](CF3SO3)(2) (6), [Sc(dmpu)(6)]I-3 (7), and [Pr(dmpu)(6)]I(I-3)(2) (8), and the complex [CoBr2(dmpu)(2)] (9) as well as the structures of the dmpu coordinated calcium, strontium, barium, scandium(III) and cobalt(II) ions and the cobalt(II) bromide complex in dmpu solution as determined by EXAFS are reported. The methyl groups in the dmpu molecule are close to the oxygen donor atom, causing steric restrictions, and making dmpu space-demanding at coordination to metal ions. The large volume required by the dmpu ligand at coordination contributes to crowdedness around the metal ion with often lower coordination numbers than for oxygen donor ligands without such steric restrictions. The crowdedness is seen in M & ctdot;H distances equal to or close to the sum of the van der Waals radii. To counteract the space-demand at coordination, the dmpu molecule has an unusual ability to increase the M-O-C bond angle to facilitate as large coordination numbers as possible. M-O-C bond angles in the range of 125-170 degrees are reported depending on the crowdedness caused by the coordination figure and the M-O bond distance. All reported structures of dmpu coordinated metal ions in both the solid state and dmpu solution are summarized to study the relationship between the M-O-C bond angle and the crowdedness around the metal ion. However, highly symmetric complexes seem to be favoured in the solid state due to favourable lattice energies. As a result, the dmpu coordinated lanthanoid(III) ions are octahedral in the solid state, while they, except lutetium, are seven-coordinate in the dmpu solution.
|
|
| 46. |
- Mahoro, Gilbert Umuhire, et al.
(författare)
-
Towards rainbow photo/electro-luminescence in copper(i) complexes with the versatile bridged bis-pyridyl ancillary ligand
- 2021
-
Ingår i: Dalton Transactions. - : ROYAL SOC CHEMISTRY. - 1477-9226 .- 1477-9234. ; 50:32, s. 11049-11060
-
Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of a family of copper(i) complexes bearing a bridged bis-pyridyl ancillary ligand is reported, highlighting how the bridge nature impacts the photo- and electro-luminescent behaviours within the family. In particular, the phosphonium bridge led to copper(i) complexes featuring good electrochemical stability and high ionic conductivity, as well as a stark blue-to-orange luminescence shift compared to the others. This resulted in high performance light-emitting electrochemical cells reaching stabilities of 10 mJ at ca. 40 cd m(-2) that are one order of magnitude higher than those of the other complexes. Overall, this work sheds light onto the crucial role of the bridge nature of the bis-pyridyl ancillary ligand on the photophysical features, film forming and, in turn, on the final device performances.
|
|
| 47. |
- Maier, Annika Carolin, et al.
(författare)
-
On the change in UO2 redox reactivity as a function of H2O2 exposure
- 2020
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:4, s. 1241-1248
-
Tidskriftsartikel (refereegranskat)abstract
- To assess the long-term leaching behaviour of UO2, the main constituent of spent nuclear fuel, the oxidative dissolution of UO2 pellets was studied at high H2O2 exposures ranging from 0.33 mol m(-2) to 1.36 mol m(-2). The experiments were performed in aqueous media containing 10 mM HCO3- where the pellets were exposed to H2O2 three consecutive times. The results indicate that the dissolution yield (amount of dissolved uranium per consumed H2O2) at high H2O2 exposures is significantly lower compared to previous studies of both pellets and powders and decreases for each H2O2 addition for a given pellet. This implies a change in redox reactivity, which is attributed to irreversible alteration of the pellet surface. Surface characterization after the exposure to H2O2, by SEM, XRD and Raman spectroscopy shows, that the surface of all pellets is significantly oxidized.
|
|
| 48. |
- Melis, Diana R., et al.
(författare)
-
Quinoline-triazole half-sandwich iridium(iii) complexes : Synthesis, antiplasmodial activity and preliminary transfer hydrogenation studies
- 2020
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 49:33, s. 11543-11555
-
Tidskriftsartikel (refereegranskat)abstract
- Iridium(iii) half-sandwich complexes containing 7-chloroquinoline-1,2,3-triazole hybrid ligands were synthesised and their inhibitory activities evaluated against the Plasmodium falciparum malaria parasite. Supporting computational analysis revealed that metal coordination to the quinoline nitrogen occurs first, forming a kinetic product that, upon heating over time, forms a more stable cyclometallated thermodynamic product. Single crystal X-ray diffraction confirmed the proposed molecular structures of both isolated kinetic and thermodynamic products. Complexation with iridium significantly enhances the in vitro activity of selected ligands against the chloroquine-sensitive (NF54) Plasmodium falciparum strain, with selected complexes being over one hundred times more active than their respective ligands. No cross-resistance was observed in the chloroquine-resistant (K1) strain. No cytotoxicity was observed for selected complexes tested against the mammalian Chinese Hamster Ovarian (CHO) cell line. In addition, speed-of-action assays and β-haematin inhibition studies were performed. Through preliminary qualitative and quantitative cell-free experiments, it was found that the two most active neutral, cyclometallated complexes can act as transfer hydrogenation catalysts, by reducing β-nicotinamide adenine dinucleotide (NAD+) to NADH in the presence of a hydrogen source, sodium formate.
|
|
| 49. |
- Menon, Ashok S., et al.
(författare)
-
Synthesis-structure relationships in Li- and Mn-rich layered oxides : phase evolution, superstructure ordering and stacking faults
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 51:11, s. 4435-4446
-
Tidskriftsartikel (refereegranskat)abstract
- Li- and Mn-rich layered oxides are promising positive electrode materials for future Li-ion batteries. The presence of crystallographic features such as cation-mixing and stacking faults in these compounds make them highly susceptible to synthesis-induced structural changes. Consequently, significant variations exist in the reported structure of these compounds that complicate the understanding of how the crystallographic structure influences its properties. This work investigates the synthesis-structure relations for three widely investigated Li- and Mn-rich layered oxides: Li2MnO3, Li1.2Mn0.6Ni0.2O2 and Li1.2Mn0.54Ni0.13Co0.13O2. For each compound, the average structure is compared between two synthetic routes of differing degrees of precursor mixing and four annealing protocols. Furthermore, thermodynamic and synthesis-specific kinetic factors governing the equilibrium crystallography of each composition are considered. It was found that the structures of these compounds are thermodynamically metastable under the synthesis conditions employed. In addition to a driving force to reduce stacking faults in the structure, these compositions also exhibited a tendency to undergo structural transformations to more stable phases under more intense annealing conditions. Increasing the compositional complexity introduced a kinetic barrier to structural ordering, making Li1.2Mn0.6Ni0.2O2 and Li1.2Mn0.54Ni0.13Co0.13O2 generally more faulted relative to Li2MnO3. Additionally, domains with different degrees of faulting were found to co-exist in the compounds. This study offers insight into the highly synthesis-dependent subtle structural complexities present in these compounds and complements the substantial efforts that have been undertaken to understand and optimise its electrochemical properties.
|
|
| 50. |
- Mishra, Manish Kumar, et al.
(författare)
-
CO2 capture from ambient air via crystallization with tetraalkylammonium hydroxides
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:46, s. 17724-17732
-
Tidskriftsartikel (refereegranskat)abstract
- Aqueous solutions of a series of short carbon chain tetra(n-alkyl)ammonium hydroxides, [Nnnnn][OH] with n = 2: n-ethyl, 3: n-propyl, 4: n-butyl, have been serendipitously found to be potential candidates for direct air carbon capture (DAC) when being used as reagents in more complicated reactions. Aqueous solutions of [N3333][OH], [N2222][OH], or [N3333][OH] with UO2SO4·3H2O and 1,4-diamidoximylbenzene, and [N4444][OH] with cytosine (HCyt) directly absorb CO2 from the atmosphere upon mild heating in the open atmosphere crystallizing in complexes reaching up to 2 : 1 CO2/[Nnnnn]OH ratio. [N2222][HCO3]·3H2O (1), [N2222]2[H(HCO3)3]·5H2O (2), [N3333][HCO3]·0.5H2O (3), [N3333][H(HCO3)2] (4), [N3333]2[(tpa)(H2CO3)2] (5; tpa = terephthalate), [N4444][H(Cyt)(HCO3)]·H2O (6) and [N4444][H2(Cyt)2(HCO3)]·H2O (7) have been isolated in crystalline form and structurally characterized by single crystal X-ray diffraction. The compounds are characterized by complex polyanionic formations from bicarbonate dimers ([(HCO3)2·(H2O)]24−) or chains ([H(HCO3)2]nn− or [H2(tpa)(HCO3)2]n2n−) to water-bicarbonate associates ([(HCO3)2·6H2O]2− and [(H2CO3·(HCO3)2)2·6H2O·2H2O]2−) and three-component anionic layers ([H(Cyt)(HCO3)·H2O]nn− and [H2(Cyt)2(HCO3)·H2O]nn−) frequently showing proton sharing. While some hydroxides themselves can maintain a high CO2/[Nnnnn][OH] ratio, particularly 2 and 4, the presence of secondary hydrogen bond donors/acceptors may increase the sorption efficiency through decreased solubility and enhanced crystallization.
|
|
