We present for the first time Gutmann donor and acceptor numbers for a series of 36 different ionic liquids that include 26 distinct anions. The donor numbers were obtained by 23Na NMR spectroscopy ...and show a strong dependence on the anionic component of the ionic liquid. The donor numbers measured vary from −12.3 kcal mol−1 for the ionic liquid containing the weakest coordinative anion emimFAP (1‐ethyl‐3‐methylimidazolium tris(pentafluoroethyl)trifluorophosphate), which is a weaker donor than 1,2‐dichloroethane, to 76.7 kcal mol−1 found for the ionic liquid emimBr, which exhibits a coordinative strength in the range of tertiary amines. The acceptor numbers were measured by using 31P NMR spectroscopy and also vary as a function of the anionic and cationic component of the ionic liquid. The data are presented and correlated with other solvent parameters like the Kamlet–Taft set of parameters, and compared to the donor numbers reported by other groups.
Give and you shall receive: The Gutmann donor and acceptor numbers (DNs and ANs) for a series of 36 different ionic liquids that include 26 distinct anions are presented. The DNs and ANs were obtained by 23Na and 31P NMR spectroscopy, respectively. Both values showed a strong dependence on the anionic and cationic components of the ionic liquid. The data are presented and correlated with other solvent parameters and compared to donor numbers reported by other groups.
Since air pollution is one of the most serious environmental problems, the study of the effects of particulate matter (PM) on physiological processes remains to be an important challenge for ...scientific communities. The presented studies form part of the project ‘Air Pollution versus Autoimmunity: Role of multiphase aqueous Inorganic Chemistry’. In these studies we examined the effect of Standard Reference Material 1648a, supplied by the US National Institute of Standards and Technology (NIST), and its inorganic constituents on the formation of nitrosylcobalamin (CblNO) in the reaction between nitrocobalamin (CblNO2) and ascorbic acid in a weakly acidic medium. We monitored the reaction in the presence of urban NIST PM (SRM 1648a), plasma treated NIST PM (LAP) and a number of metal oxide nanoparticles, including redox active metal oxides. The obtained results clearly demonstrated that the presence of these different nanoparticles affected the rate of formation of CblNO but did not affect the nature of the final product. Special attention was given to systematic studies on the role of inorganic nanoparticles as a part of the selected PM in the reaction between CblNO2 and ascorbic acid.
The graphical presents the effect that redox‐active and non‐redox‐active metal‐oxide nanoparticles can have on the reduction of nitrocobalamin (CblNO2) to nitrosylcobalamin (CblNO−) by ascorbic acid/ascorbate in aqueous solution at pH<5.
Based on computational chemistry calculations (ωB97XD/def2‐tzvp//ωB97XD/def2‐svp/svpfit+ZPE(ωB97XD/def2‐svp/svpfit)), binding energy of tubular3,6,6,6arene to accommodate noble gases and a series of ...29 small gases were calculated. Based on the gained results, Rn (−17.52 kcal/mol) from the series of noble gases is best suited to be accommodated. In the series of noble gases, the binding energy increases linearly with increasing gas radii. From the series of 29 small guests, IF3 and C2I2 (~ −23 kcal/mol) have the best proclivity to be most effectively accommodated in the tubularene, with other 26 exhibiting favorable encapsulation energies on various scales depending on their voluminosity and structure, and only NI3 with the unfavorable complexation energy of 13.87 kcal/mol. Investigated gases, depending on the size, are placed at the different position inside the tube‐like cavity of the tubularene. The structure of the tubularene, independent of the hosted guest species, has remained very rigid, with its atom's rearrangements withing an error margin.
In this paper, we investigated water exchange reactions and substitution of aqua RuII complexes of general formula Ru(terpy)(N^N)(H2O)2+ (where N^N = ethylenediamine (en), 1,2‐(aminomethyl)pyridine ...(ampy) and 2,2′‐bipyridine (bipy)) by ammonia and thioformaldehyde. These reactions were studied in detail by applying conceptual density functional theory. This approach enabled us to gain further insight into the underlying reaction mechanism at the microscopic level (involving only direct participants of the reaction, without the influence of the solvent) and to put the concept of reaction mechanism on a quantitative basis. The course of the chemical reaction along the reaction coordinate ξ, is rationalized in terms of reaction energy, force, dipole moment, and reaction electronic flux (REF). The results yield and characterize the significant influence of an intermolecular hydrogen bond formed between the entering and the spectator ligand to the overall energy barrier of the reactions.
Conceptual DFT calculations can be a powerful tool in providing a better understanding of the reaction mechanism at the microscopic level, without the interference of the solvent molecules. Throughout this paper these kind of calculations were used to investigate water substitution reactions on RuII‐aqua complexes. The results yield and characterize the significant influence of an intermolecular hydrogen bond formed between the entering and the spectator ligand to the overall energy barrier of the reactions.
The nitrogen cycle is one of the most important biogeochemical cycles on Earth. This cycle mainly involves redox conversion of dinitrogen when it is converted into ammonia (nitrogen fixation pathway) ...and the cycle is completed with the conversion of ammonia to dinitrogen (involving nitrification and denitrification pathways). The application of Ru(edta) complexes (edta
4−
= ethylenediaminetetraacetate) in nitrogen cycle-related electrochemical transformation reactions has not been systematically reviewed to date. This review aims to report the research progression on the use of Ru(edta) complexes in catalyzing N-cycle electrochemical transformations. In this review, the role of Ru(edta) complexes in mediating electrochemical reactions pertaining to nitrogen fixation and denitrification in the nitrogen cycle has been discussed, providing in-depth mechanistic knowledge for understanding the varied roles of Ru(edta) complexes pertaining to the many N-cycle-related electrochemical transformations.
This mini review chronicles the role of Ru(edta) (edta
4−
= ethylenediaminetetraacetate) towards catalysing the electrochemical transformation of nitrogen cycle reactions, elucidating the complex mechanistic schemes.
In earlier work performed in our laboratories, the reaction of FeII(edta)(H2O)2– with ·NO(g) was studied as a trap for ·NO(g) and found to be very efficient with a formation constant of ca. 106 M–1 ...at 25 °C. The formed nitrosyl complex was shown to have substantial FeIII‐NO–, i.e. nitroxyl, character in line with detailed computational studies performed before. In recent years, we developed an interest in the chemistry of HNO/NO– (nitroxyl) and decided to use FeIII(edta)(H2O)– as starting material to see whether the reaction of this complex would lead directly to the formation of the nitroxyl complex by using a source for HNO. In the present study, Piloty's acid (benzenesulfonylhydroxamic acid) was used as source for HNO, since it cleanly hydrolysis in basic aqueous solution to release HNO. The results of our studies clearly indicate that the same reaction product as found for the reaction of FeII(edta)(H2O)2– with ·NO(g), was formed in the reaction of FeIII(edta)(H2O)– with Piloty's acid. A detailed spectroscopic and mechanistic study of the latter reaction is reported.
In earlier work, the reaction of FeII(edta)(H2O)2– with ·NO(g) was studied as a trap for ·NO(g) and found to be very efficient. The formed nitrosyl complex was shown to have substantial FeIII‐NO–, i.e. nitroxyl, character. We have now used FeIII(edta)(H2O)– as starting material and studied the reaction with Piloty's acid as source for HNO/NO– (nitroxyl) to produce the same reaction product.
With the application of DFT calculations (ωB97XD/def2-SVP/SVPfit), the ability and mechanism of noble gas encapsulation by cryptophane was investigated. Based on the applied model reaction, by ...monitoring geometric changes and investigating the non-covalent interactions between the studied hosts and the noble gases, the size of the host did not necessarily play a decisive role in the selective encapsulation of the guests. Rather the adjustment of the host's interior and functionalization of its "gates" can be significant in tuning the affinity of cryptophanes.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The extensive speciation of copper(II) chloride in organic solvents varies with concentration, temperature, pressure and oxygen content, providing the ability to switch between different chlorophyll ...transmetalation pathways. We found that one of them is exceptionally suitable for the formation and stabilisation of the chlorophyll π‐cation radical. This is due to unique redox cycling, which is coupled to the generation and transformation of various reactive oxygen species. In the presence of a proton donor, our system shows behavior which resembles that of superoxide dismutase (SOD). Regardless of light, chlorophyll acts as an electron transfer mediator.
Generation of the π‐cation radical of chlorophyll a is observed in organic media in the presence of O2 and particular Cu(II) salts. The stability of this radical, as observed spectroscopically, is assigned to a redox cycling controlled by the copper speciation in the presence of O2 and proton donors. Under such conditions, regardless of light, chlorophyll a can act as the electron‐transfer mediator, which mimics, in a way, the superoxide dismutase catalytic activity.
A Personal Account on Inorganic Reaction Mechanisms Polaczek, Justyna; Kieca, Konrad; Oszajca, Maria ...
Chemical record,
December 2023, 2023-Dec, 2023-12-00, 20231201, Letnik:
23, Številka:
12
Journal Article
Recenzirano
Odprti dostop
The presented Review is focused on the latest research in the field of inorganic chemistry performed by the van Eldik group and his collaborators. The first part of the manuscript concentrates on the ...interaction of nitric oxide and its derivatives with biologically important compounds. We summarized mechanistic information on the interaction between model porphyrin systems (microperoxidase) and NO as well as the recent studies on the formation of nitrosylcobalamin (CblNO). The following sections cover the characterization of the Ru(II)/Ru(III) mixed‐valence ion‐pair complexes, including Ru(II)/Ru(III)(edta) complexes. The last part concerns the latest mechanistic information on the DFT techniques applications. Each section presents the most important results with the mechanistic interpretations.
The manuscript presents the research in the field of coordination chemistry involving the interaction of small molecules with microperoxidase and cobalamin. Characterization of mixed‐valence Ru(II)/Ru(III) ion‐pair complexes; electrochemistry, redox‐reactions and catalytic significance of RuIII/II(edta) complexes, as well as mechanistic information from DFT studies.
Cytochrome P450 enzymes are highly versatile biological catalysts in our body that react with a broad range of substrates. Key functions in the liver include the metabolism of drugs and xenobiotics. ...One particular metabolic pathway that is poorly understood relates to the P450 activation of aliphatic groups leading to either hydroxylation or desaturation pathways. A DFT and QM/MM study has been carried out on the factors that determine the regioselectivity of aliphatic hydroxylation over desaturation of compounds by P450 isozymes. The calculations establish multistate reactivity patterns, whereby the product distributions differ on each of the spin‐state surfaces; hence spin‐selective product formation was found. The electronic and thermochemical factors that determine the bifurcation pathways were analysed and a model that predicts the regioselectivity of aliphatic hydroxylation over desaturation pathways was established from valence bond and molecular orbital theories. Thus, the difference in energy of the OH versus the OC bond formed and the π‐conjugation energy determines the degree of desaturation products. In addition, environmental effects of the substrate binding pocket that affect the regioselectivities were identified. These studies imply that bioengineering P450 isozymes for desaturation reactions will have to include modifications in the substrate binding pocket to restrict the hydroxylation rebound reaction.
Tipping the balance: A comprehensive density functional theory and quantum mechanics/molecular mechanics study proposes a model for the regioselectivity of substrate hydroxylation over desaturation by cytochrome P450 Compound I.
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