The redox potentials of bis(tpy)ruthenium(II) (tpy = differently substituted 2,2′:6′,2″-terpyridine) compounds with electron donating substituent groups (pyrrolidinyl, hydroxy, tert-butyl, methoxy, ...phenyl), are lower than complexes with electron withdrawing substituents (Cl or Br). The different redox potentials relate linearly to Hammett parameters and DFT calculated energies.
Display omitted
•Complexes with electron donating substituents is oxidized of at lower potentials.•Electron donating substituents have smaller Hammett substituent parameters.•Complexes with electron donating substituents have higher HOMO and LUMO energies.•Complexes with electron donating groups have lower Mulliken and NBO charges on Ru.•Complexes with electron donating substituent groups have less positive MESP on Ru.
A series of bis(tpy)ruthenium(II) (tpy = differently substituted 2,2′:6′,2″-terpyridine) were prepared. The substituents were chosen to range from electron donating (pyrrolidinyl, hydroxy, tert-butyl, methoxy, phenyl) to electron withdrawing (Cl, Br). Electrochemistry results show that the complex with the most electron donating group in the series, Ru(4′-(N-pyrrolidinyl)-2,2′:6′,2″-terpyridine)22+, oxidizes at 0.363 V vs the redox couple of ferrocene (Fc/Fc+). The oxidation of Ru(4′-chloro-2,2′:6′,2″-terpyridine)22+, containing the electron withdrawing chlorine group, is much higher, 0.992 V vs Fc/Fc+. Theoretical density functional theory calculations confirmed that the oxidation and reduction of bis(tpy)ruthenium(II) are metal and ligand based, respectively. Graphs comparing the experimentally measured redox potentials and theoretically calculated energies, charges, potentials and various global and local reactivity parameters, all show linear relationships associated with the donating/withdrawing nature of the substituents as quantified by Hammett constants. All these relationships may be utilized to quantify the electronic influence of substituent groups on the redox chemistry of bis(tpy)ruthenium(II) complexes. Linear relationships obtained may also be utilized in the design of bis(tpy)ruthenium(II) type of molecules with a required oxidation or reduction potential. DFT calculations also indicate the potential utilization of these complexes as dye sensitizers in dye-sensitized solar cells.
New radio (MeerKAT and Parkes) and X-ray (XMM-Newton, Swift, Chandra, and NuSTAR) observations of PSR J1622-4950 indicate that the magnetar, in a quiescent state since at least early 2015, ...reactivated between 2017 March 19 and April 5. The radio flux density, while variable, is approximately 100× larger than during its dormant state. The X-ray flux one month after reactivation was at least 800× larger than during quiescence, and has been decaying exponentially on a 111 19 day timescale. This high-flux state, together with a radio-derived rotational ephemeris, enabled for the first time the detection of X-ray pulsations for this magnetar. At 5%, the 0.3-6 keV pulsed fraction is comparable to the smallest observed for magnetars. The overall pulsar geometry inferred from polarized radio emission appears to be broadly consistent with that determined 6-8 years earlier. However, rotating vector model fits suggest that we are now seeing radio emission from a different location in the magnetosphere than previously. This indicates a novel way in which radio emission from magnetars can differ from that of ordinary pulsars. The torque on the neutron star is varying rapidly and unsteadily, as is common for magnetars following outburst, having changed by a factor of 7 within six months of reactivation.
Several anthropogenic activities produce radioactive materials into the environment. According to reports, exposure to high concentrations of radioactive elements such as potassium (
40
K), uranium (
...238
U and
235
U), and thorium (
232
Th) poses serious health concerns. The scarcity of reviews addressing the occurrence/sources, distribution, and remedial solutions of radioactive contamination in the ecosystems has fueled data collection for this bibliometric survey. In rivers and potable water, reports show that several parts of Europe and Asia have recorded radionuclide concentrations much higher than the permissible level of 1 Bq/L. According to various investigations, activity concentrations of gamma-emitting radioactive elements discovered in soils are higher than the global average crustal values, especially around mining activities. Adsorption technique is the most prevalent remedial method for decontaminating radiochemically polluted sites. However, there is a need to investigate integrated approaches/combination techniques. Although complete radionuclide decontamination utilizing the various technologies is feasible, future research should focus on cost-effectiveness, waste minimization, sustainability, and rapid radionuclide decontamination. Radioactive materials can be harnessed as fuel for nuclear power generation to meet worldwide energy demand. However, proper infrastructure must be put in place to prevent catastrophic disasters.
Novel fluorine substituted mononuclear Ti(β-diketonato)2Cl2 complexes have been synthesised and shown to be involved in a partial hydrolysis reaction in solution, in which the hydrolyzed dinuclear ...{Ti(β-diketonato)2Cl}2(μ-O) is in equilibrium with the monomer. This is in contrast to the solution behaviour of the non CF3-containing Ti(CH3COCHCOCH3)2Cl2, Ti(PhCOCHCOCH3)2Cl2 and Ti(PhCOCHCOPh)2Cl2 complexes, under the same conditions. Variable temperature ((1)H and (19)F) NMR spectra and X-ray structure analyses reveal that the partially hydrolyzed dinuclear complex exists both in solution and in solid state, bridging through a single μ-oxo bridge and having one labile chloro-ligand per titanium center. Inclusion of electron-withdrawing CF3 groups into the already electron-deficient Ti complexes, led to the formation of {Ti(CF3COCHCOCF3)2Cl}2(μ-O) (dinuclear) and Ti(CF3COCHCOCF3)2(μ-O)4 (tetranuclear) complexes in CDCl3 containing trace amounts of water. DFT calculated free energies of hydrolysis support the existence of Ti(CH3COCHCOCH3)2Cl2 as a monomer and Ti(CF3COCHCOCF3)2Cl2 as a equilibrium mixture of the monomer and partially hydrolyzed dinuclear {Ti(β-diketonato)2Cl}2(μ-O) in CDCl3 solution.
The data presented in this paper are related to the research article entitled “Synthesis, characterisation and electrochemistry of eight Fe coordination compounds containing substituted ...2-(1-(4-R-phenyl-1H-1,2,3-triazol-4-yl)pyridine ligands, R=CH3, OCH3, COOH, F, Cl, CN, H and CF3.” (Conradie et al., 2019) 1. This paper presents electrochemical and density functional theory data of 4-phenyl-substituted dichloro(bis{2-1-(4-R-phenyl)-1H-1,2,3-triazol-4-yl-κN3pyridine-κN})iron(II) compounds, containing differently substituted 2-(1-(4-R-phenyl)-1H-1,2,3-triazol-1-yl)pyridine ligands (L2 – L9) (Tawfiq et al., 2014) 2. Density functional theory calculated data of five different structural isomers for each compound, consistently show that the title compounds are octahedral and that the isomer with the chloride atoms, the pyridine nitrogens and the triazol nitrogens trans to each other, has the lowest energy. Natural bonding orbital (NBO) data and quantum theory of atoms in molecules (QTAIM) data of dichloro(bis{2-1-(phenyl)-1H-1,2,3-triazol-4-yl-κN3pyridine-κN})iron(II) show origin for the preference of the trans isomer.
Traditional spiral inflectors of the Belmont-Pabot type are commonly used for axial injection of external ion beams into cyclotrons. These inflectors are designed to control the trajectory of the ...central path, and do not actively focus the beam in the vertical and longitudinal directions. This can introduce effects such as a large vertical divergence and a debunching longitudinal spread, making it difficult to match the injection line emittance to the cyclotron acceptance. In an attempt to overcome this, some recent inflectors have started incorporating electrodes specially shaped to produce field gradients along the central path, thereby influencing the inflector optics. This method has shown some success, and at iThemba LABS an inflector was built exhibiting good vertical focusing. However, it performed poorly longitudinally, worse than traditional spiral inflectors. In this article a generalized field gradient spiral inflector design is presented, based on a mathematical description of all possible first-order field gradients along the central path. Such a design is numerically optimized to simultaneously focus longitudinally and vertically. Experimental studies of this design show a 60% improvement in overall current extracted from the cyclotron.
Synopsis and pictogram for Table of contents The Cr 2p3/2 peaks obtained from X-ray photoelectron spectra (XPS) of a series of chromium(III) β-diketonato complexes were fitted with calculated ...multiplet peaks. The ratio of the fac and mer isomers obtained from XPS compared very well with the Boltzmann calculated ratio. The electronegativity of the R-groups on the β-diketonato ligand influences the XPS peak positions.
•β-diketonato complexes Cr(RCOCHCOR’)3•Cr 2p3/2 XPS peaks fitted with calculated multiplet peaks.•Different calculated multiplet peaks fit the Cr 2p3/2 peak for fac and mer isomers.•XPS peak positions influenced by the electronegativity of the R- and R'-group.
X-ray photoelectron spectra (XPS) measurements of a series of chromium(III) β-diketonato complexes of the Cr 2p spectra was fitted with calculated multiplet peaks. The XPS of these Cr(III) complexes did not exhibit fine structure, however, well-defined line shapes could be fitted to the Cr 2p3/2 envelope. The splitting patterns obtained for the Cr(III) β-diketonato complexes compared well with the multiplet splitting predicted by Gupta and Sen for the free Cr(III) ion. The Cr(III) β-diketonato complexes containing unsymmetrically substituted β-diketonato ligands, which display both the fac and mer isomers, could be fitted with two sets of multiplets and were useful in determining the ratio between the fac and mer isomers, which was compared with the Boltzman calculated ratio obtained from density functional theory energies. The obtained binding energy of the first multiplet splitting peak of the Cr 2p3/2 envelope was found to be dependent on the combined Gordy group electronegativity of the R-groups substituted on the β-diketonato ligand (RCOCHCOR′)−.
A series of copper(II) β-diketonato complexes Cu(R1CHCOCHR2)2, with R1 = R2 = C6H5 (1); R1 = C6H5 and R2 = CH3 (2); R1 = R2 = CH3 (3); R1 = C6H5 and R2 = CF3 (4); R1 = CH3 and R2 = CF3 (5) and R1 ...= R2 = CF3 (6), was subjected to a systematic XPS study of the Cu 2p core-level photoelectron lines, their satellite structures and the LMM Auger lines. The binding energies of the main Cu 2p core-level photoelectron lines are sensitive towards chemical environment (initial state effects) and are described by linear correlations with the combined Gordy scale group electronegativity of the R-groups on the β-diketonato ligands, ΣχR, and the first electrochemical reduction potential, Epc, of the Cu compounds. The modified Auger parameters were determined from the constructed Wagner plot of the copper(II) β-diketonato complexes, which also showed that the initial state effects are dominant during the photoemission process.
Display omitted
•A series of copper(II) β-diketonato complexes is studied in detail by means of X-ray Photoelectron Spectroscopy.•The main Cu 2p3/2 photoelectron lines, core-hole lifetime and charge transfer are dependent on the electronic environment.•The initial state effects dominate during the photoemission process of the Cu compounds.•It was found that there is a stabilization response upon creation of a core-hole and Auger de-excitation process.
PDF
