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Here, we elaborate a borate glass system with x La 2 O 3 – (79-x) B 2 O 3 – 20.6 Na 2 O – 0.4 CoO; (x = 0, 3, 6 and 9 mol%) glass composition utilizing the melt-quenching method, and studied through density, basic physical parameters, Fourier transforms-infrared (FTIR) and optical absorption spectroscopy. Further addition of La 2 O 3 , up to 9 mol%, affords an enhancement (25 %) in the glass density, besides other structural parameters revealing the role of lanthanum ions on the glass matrix. FTIR findings revealed the essential structural groups of borate glass like trigonal BO 3 units, tetrahedra BO 4 units, and non-bridging oxygen atoms. Here too, a propensity towards the transformation from BO 3 units to BO 4 units was obtained. The optical absorption spectra revealed the existence of Co2+ in octahedral and tetrahedral coordination and the presence of Co3+ in octahedral coordination. The blue color of the present glass was attributed to the absorption band at 571.6–580.9 nm of Co2+ cation within the tetrahedral complexes. Further analysis of the ligand field parameters revealed increased values of the splitting energy parameter of Co2+ in a tetrahedral field with higher La 2 O 3 doping indicating a higher interplay between Co cations and their surrounding ligands. Additionally, the other ligand field parameters described the environments around the cobalt ions such as bonding nature. Finally, the glass refractive index increased with the further addition of lanthanum oxide, enhancing the glass quality for the optical realm. These reported findings show excellent properties of glass host as a promising contender in optical applications. [ABSTRACT FROM AUTHOR]

This study investigates the effect of La³⁺ rare earth ions on the structural, elastic, optical, and radiation shielding features of heavy metal borate glass (B₂O₃-PbO) doped with Cr₂O₃. Density measurements and FT-IR spectra analysis revealed the role of La3+ ions as a network modifier, where successive additions of La 2 O 3 content led to a gradual increase in the density and an increase in the non-bridging oxygen content resulting from the structural transformation between the BO 4 and BO 3 units. The significant improvement in the elastic modulus and microhardness factor moduli was confirmed by calculating the change in ultrasonic velocities through the glassy system. The structural modifications induced by La³⁺ ions narrowed the band gap and increased the Urbach energy, indicating higher disorder within the glass network. The linear refractive indices increased due to increased optical basicity and electronic polarization. Optical absorption results showed that Cr⁶⁺/Cr³⁺ ions occupy octahedral/tetrahedral sites, with the tendency for Cr³⁺ cations to occupy more octahedral sites with increasing La₂O₃ content. The produced samples showed a greenish-yellow color caused by the absorption band centered at ∼415 nm associated with the electronic transition ⁴A₂g(F)→2Eg(G). The ligand field effect highlighted the significance of La³⁺ cations in increasing the crystalline field intensity surrounding Cr³⁺ cations and reducing the nephelauxetic ratio, signifying enhanced covalent character between Cr³⁺ cations and neighboring ions. Moreover, the radiation shielding capabilities of the glassy system were analyzed and compared with standard shielding materials, confirming superior shielding performance in samples with the highest La₂O₃ content. [ABSTRACT FROM AUTHOR]

Previous theoretical studies have revealed that high-spin states possess flatter potential energy surfaces than low-spin states in reactions involving iron(IV)-oxo species of cytochrome P450 enzymes (P450s), nonheme enzymes, or biomimetic complexes. Therefore, actively utilizing high-spin states to enhance challenging chemical transformations, such as C-H bond activation, represents an intriguing research avenue. However, the inherent instability of high-spin states relative to low-spin states in pre-reaction complexes often hinders their accessibility around the transition state, especially in heme systems with strong ligand fields. Counterintuitively, our investigation of the metabolic hydroxylation of paclitaxel by human CYP2C8 using a hybrid quantum mechanics and molecular mechanics (QM/MM) approach showed that the high-spin sextet state exhibits unusually high stability, when the reaction follows a secondary reaction pathway leading to 6β-hydroxypaclitaxel. We thoroughly analyzed the factors contributing to the enhanced stabilization of the high-spin state, and the knowledge obtained could be instrumental in designing competent biomimetic catalysts and biocatalysts for C-H bond activation. [ABSTRACT FROM AUTHOR]

Fluoroboro tellurite glasses containing La2O3 with nominal composition of 43B2O3 + 33TeO2 + (12−x)BaF2 + 12Na2O + xLa2O3x = 0 (La0.0), 0.5 (La0.5), 1 (La1.0), 2 (La2.0), and 3 (La3.0) mol% were fabricated using the melt quenching technique. The effects of La3+ ion content inclusion in the prepared glass matrices, including the structural, physical, and optical properties and γ-ray protection efficacy, were then explored. The amorphous state of the La-glasses was verified by the broad and diffuse dispersion of all XRD patterns at low angles. As La2O3 additives were added from 0 to 3 mol%, the density (ρ) increased from 3.6243 g/cm3 to3.8743 g/cm3 and the molar volume (Vm) decreased from 30.6488 cm3/mol to 29.8364 cm3/mol. Lanthanum ion concentrations (NLa) increased from 0 for La0.0 glasses to 312.1103 × 1020 cm−3 for La3.0 glasses. The polar radius decreased from 0 Å to 3.7813 Å, whereas the ligand field strength between La ions and their surroundings increased from 0 Å−2 to 18.1839 Å−2. Values of optical gap (Eg) varied from 3.07 eV to 2.82 eV. The values of linear refractive index (n0) varied from 2.383 to 2.443, whereas values of nonlinear refractive index (n2) changed from 5.16 × 10−11 esu to 6.40 × 10−11 esu for La0.0 and La3.0 glass specimens. Mass (MAC) and linear (LAC) attenuation coefficients were lowest in La0.0 glasses and highest in La3.0 glasses. The trend of the mean free path (MFP) of La-glasses was inverse to that of the LAC and MAC. The order of the MFP trend, which indicates the influence of La2O3 in the glass matrix, was typically (MFP)La0.0 > (MFP)La0.5 > (MFP)La1.0 > (MFP)La2.0 > (MFP)La3.0. Results show that the recommended glasses appear to be promising materials for various optical devices and radiation protection applications. [ABSTRACT FROM AUTHOR]

Previous theoretical studies have revealed that high-spin states possess flatter potential energy surfaces than low-spin states in reactions involving iron(IV)-oxo species of cytochrome P450 enzymes (P450s), nonheme enzymes, or biomimetic complexes. Therefore, actively utilizing high-spin states to enhance challenging chemical transformations, such as C-H bond activation, represents an intriguing research avenue. However, the inherent instability of high-spin states relative to low-spin states in pre-reaction complexes often hinders their accessibility around the transition state, especially in heme systems with strong ligand fields. Counterintuitively, our investigation of the metabolic hydroxylation of paclitaxel by human CYP2C8 using a hybrid quantum mechanics and molecular mechanics (QM/MM) approach showed that the high-spin sextet state exhibits unusually high stability, when the reaction follows a secondary reaction pathway leading to 6β-hydroxypaclitaxel. We thoroughly analyzed the factors contributing to the enhanced stabilization of the high-spin state, and the knowledge obtained could be instrumental in designing competent biomimetic catalysts and biocatalysts for C-H bond activation. [ABSTRACT FROM AUTHOR]

Three dinuclear Pd(II) complexes (1, 2, and 3) with intense red phosphorescence at room temperature are here synthesized using strong ligand field strength compounds. All three complexes are characterized by nuclear magnetic resonance, high‐resolution mass spectrometry, and elemental analyses. Complexes 2 and 3 are characterized by single‐crystal X‐ray diffraction. The crystalline data of 2 and 3 reveal complex double‐layer structures, with Pd–Pd distances of 2.8690(9) Å and 2.8584(17) Å, respectively. Furthermore, complexes 1, 2, and 3 show phosphorescence at room temperature in their solid states at the wavelengths of 678, 601, and 672 nm, respectively. In addition, they show phosphorescence at 634, 635, and 582 nm, respectively, in the 2 wt.% (PMMA) films, and phosphorescence at 670, 675, and 589 nm, respectively, in the deoxygenated CH2Cl2 solutions. Among three complexes, complex 1 shows red emission at 634 nm with phosphorescent quantum yield Ф = 67% in the 2 wt.% PMMA film. Furthermore, complex 1‐based organic light‐emitting diode is fabricated using a vapor‐phase deposition process, and their maximum external quantum efficiency reaches 20.52%, which is the highest percentage obtained by using the dinuclear Pd(II) complex triplet emitters with the CIE coordinates of (0.62, 0.38). [ABSTRACT FROM AUTHOR]

The impacts of the Bi 2 O 3 /BaO ratio on the microstructure, optical, ligand field, and radiation shielding features of BSrFeBaBi glass matrix. The Bi 2 O 3 content of the BSrFeBaBi glasses was increased from 0 to 20 mol%. The density increased from 3.77 g / cm 3 to 5.00 g / cm 3 and the molar volume increased from 24.74 cm 3 / mol to 31.17 cm 3 / mol with increasing Bi 2 O 3 /BaO ratio. The optical analysis confirmed that the transparency of BSrFeBaBi glasses in the visible region is high. Moreover, the presence of Fe cations in the octahedral coordination (FeO 6 units) was confirmed. Furthermore, the fundamental absorption edge of BSrFeBaBi glasses shifts towards lower energies with additional Bi 2 O 3 /BaO concentrations, confirming the reduced behavior of the optical band gap. Also, ligand field splitting values decreased while Racah parameters increased. The obtained results demonstrate a tendency of the bonds between the Fe ions and their surroundings towards higher degree of ionic nature. Furthermore, the Bi 2 O 3 /BaO ratio demonstrated an enhanced radiation shielding behavior. Finally, BSrFeBaBi glasses exhibit favorable attributes for use in the radiation shielding domain due to their efficient radiation shielding features and transparency. [ABSTRACT FROM AUTHOR]

This work presents the impact of the glass matrix Sb 2 O 3 –NiO–Na 2 O–B 2 O 3 on the structure, optical and ligand field parameters of Ni cations inside this glass system. Also, the radiation shielding properties of this glass system were investigated. The Sb 2 O 3 concentrations varied from 0 to 18 mol%, while Na 2 O and NiO were fixed at 19.6 and 0.9 mol%, respectively. The structural analyses confirmed that the glass density changed from 2.13 to 2.76 g/cm3, the molar volumes increased from 31.88 to 39.18 cm3/mol and N 4 ratio (tetrahedrally coordinated boron atoms) decreased from 41.16% to 29.65% with further Sb 2 O 3 /B 2 O 3 contents. The brown color of the glass samples and the absorption band at 419–427 nm also showed that Ni2+ cations in the form of NiO 6 units are present in this glass system. Furthermore, additional Sb 2 O 3 /B 2 O 3 contents moved the fundamental absorption edge toward higher wavelengths, reducing optical band gaps from 3.32 eV to 2.89 eV. Furthermore, the nonlinear refractive index increases with the increased Sb 2 O 3 /B 2 O 3 ratios. Also, Ni ions' ligand field splitting and Racah parameters showed different behaviors. In detail, the ligand field splitting showed decreased behavior from 7434 cm−1 to 7408 cm−1, whereas the Racah parameters showed increased behavior from 907 cm−1 to 942 cm−1. The obtained results support the tendency of the bonds between the Ni ions and their environments toward an ionic nature. Besides, the radiation shielding investigations showed enhanced parameters with further Sb 2 O 3 additives. Further, with increasing Sb 2 O 3 from 0 mol% to 18 mol%, there are increases in the mass attenuation coefficient values. The improved radiation shielding parameters of the studied glass samples propose them for ionizing radiation shielding applications. [ABSTRACT FROM AUTHOR]

The suitability of various nitrogen, sulfur, oxygen, and phosphorus compounds as complexing agents in a silver electrolyte was examined by using potentiometric titration under practical conditions. The setup consisted of three electrodes to measure the pH and the activity of the silver ions simultaneously. Different ratios of silver to complexing agent from 1:10 to 1:1 at a constant ionic strength of 0.2 mol/L were investigated. The type of the complexes and their corresponding critical stability constants were evaluated by fitting the measured data using a self-developed algorithm. The pH and Nernst potential curve were calculated for the assumed complexes based on the law of mass action to find the best approximation. The correct definition of the occurring species is challenging and can lead to significant changes in the calculation of stability constants. For this reason, the measured silver potential curves were primarily used for the rating of the complexing agents. An evaluation of the measurements shows that the donor atom of the complexing agent and its ligand field strongly affected the stability and type of the complexes. Only a few complexing agents were found to be suitable for use in the cyanide-free silver electrolyte. [ABSTRACT FROM AUTHOR]

Octahedral nickel(II) complexes are among the simplest systems that exhibit zero-field splitting by having two unpaired electrons. For the purpose of clarifying the relationship between structure and zero-field splitting in a low-symmetric system, distorted octahedral nickel(II) complexes were prepared with a tetradentate ligand, 2-[bis(2-methoxyethyl)aminomethyl]-4-nitrophenolate(1−) [(onp)−]. The complex [Ni(onp)(dmso)(H2O)][BPh4]·2dmso (1) (dmso = dimethyl sulfoxide) was characterized as a bulk sample by IR, elemental analysis, mass spectrometry, electronic spectra, and magnetic properties. The powder electronic spectral data were analyzed based on the angular overlap model to conclude that the spectra were typical of D4-symmetric octahedral coordination geometry with a weak axial ligand field. Simultaneous analysis of the temperature-dependent susceptibility and field-dependent magnetization data yielded the positive axial zero-field splitting parameter D (H = guβSuHu + D[Sz2 − S(S + 1)/3]), which was consistent with the weak axial ligand field. Single-crystal X-ray analysis revealed the crystal structures of [Ni(onp)(dmso)(H2O)][BPh4]·dmso (2) and [Ni(onp)(dmf)2][BPh4] (3) (dmf = N,N-dimethylformamide). The density functional theory (DFT) computations based on the crystal structures indicated the D4-symmetric octahedral coordination geometries with weak axial ligand fields. This study also showed the importance of considering g-anisotropy in magnetic analysis, even if g-anisotropy is small. [ABSTRACT FROM AUTHOR]

The impact of the As 2 O 3 /B 2 O 3 ratio on the microstructure, linear and nonlinear optical parameters of nickel borate glass was carefully investigated for the As 2 O 3 –NiO–Na 2 O–B 2 O 3 system. The As 2 O 3 content of the present glass were varied from 0 to 16 mol%, while the glass modifiers of Na 2 O and glass intermediate of NiO were fixed at 18 and 1 mol%, respectively. Based on the structural investigations, the density increased from 2.52 g cm − 3 to 2.95 g cm − 3 and the molar volume increased from 27.11 cm 3. mol − 1 to 30.07 cm 3. mol − 1 with increasing As 2 O 3 /B 2 O 3 ratios. Additionally, the presence of Ni2+ ions as NiO 6 units was confirmed by the brown color originating from the absorption band observed at 421–428 nm in the optical absorbance of the studied glass. Furthermore, the Ni3+ ions do not participate in the coloring of the glass. Moreover, the fundamental absorption edges of the glass shift towards lower energy values with increasing As 2 O 3 /B 2 O 3 concentrations, confirming the decreased behavior of the band gaps. Furthermore, the nonlinear refractive index increases with the increased As 2 O 3 /B 2 O 3 concentrations. Additionally, the ligand field parameters of Ni cations, such as the ligand field splitting parameter and Racah parameter, exhibit opposite behaviors upon introducing additional As 2 O 3 /B 2 O 3 ratio. A decrease in values of the ligand field splitting, while the Racah parameter exhibits increased values. The observed outcomes demonstrate a tendency of the bonds connecting the Ni ions and their ligands to possess higher degrees of ionic nature. Besides, the ionizing radiation properties for the prepared glasses were studied using online "Phy-X″ software in the energy range of 0.248–1.33 MeV. The ionizing radiation shielding invistigations showed enhanced parameters with further As 2 O 3 additives. Where, with increasing the amount of As 2 O 3 from 0 mol% to 16 mol%, there are increases in the mass attenuation coefficient values. Additionally, the half value layer values of the studied glass samples are lower than the values of most standard ionizing radiation shielding materials. The effective As 2 O 3 / B 2 O 3 ratio enhanced structure, optical and radiation shielding parameters of the present glass system, making these glasses suitable for ionizing radiation shielding applications. [ABSTRACT FROM AUTHOR]

The influence of the La 2 O 3 addition on the microstructure, linear and nonlinear optical parameters of nickel borate glass was carefully investigated for the La 2 O 3 –NiO–BaO–B 2 O 3 system. The La 2 O 3 content of the present glass was varied from 0.0 to 10.0 mol%, while the glass modifiers of BaO and glass intermediate of NiO were fixed at 19 and 1.5 mol%, respectively. Based on the structural investigations, the bond density remarkably increased from 7.37 × 10 19 m − 3 to 8.66 × 10 19 m − 3 by a ratio of 18 % with increasing La 2 O 3 /B 2 O 3 ratios. Additionally, the presence of Ni2+ ions as NiO 6 units was confirmed by the brown shade originating from the absorption band observed at 427 nm in the optical absorbance of the studied glass. Furthermore, the Ni3+ ions do not play a role in the coloring of the glass. Moreover, the fundamental absorption edges of the glass shift towards lower energy values with increasing La 2 O 3 concentrations, confirming the decreased behavior of the band gaps. Moreover, the linear and nonlinear refractive indices increase with increasing of La 2 O 3 concentrations. Additionally, the ligand field characteristics of Ni cations, such as the ligand field splitting parameter and Racah parameter, exhibit opposite behaviors upon introducing additional La 2 O 3 content. A decrease in values of the ligand field splitting, while the Racah parameters exhibit increased values. The observed outcomes demonstrate a tendency of the bonds connecting the Ni ions and their ligands to possess higher degrees of ionic nature. Based on the results, the present glass samples can function as solar thermal collectors by collecting sunlight and utilizing it for direct heating and indirect electrical power generation. [ABSTRACT FROM AUTHOR]

The Eu-doped xBaO-(100-x)B 2 O 3 and xBaF 2 -(100-x)B 2 O 3 glasses were prepared by melting method under a reducing atmosphere, exhibiting broadband luminescence peaks of 4f65 d1→4f7 in the excitation range of 300–400 nm. PL, EPR, and XPS were used to analyze the effects of the Ba2+, F−, and Eu ion content on the Eu2+/Eu3+ ratio and Eu2+ emission wavelength and intensity. An excess of Ba2+ ions with a high optical basicity reduced the Eu2+/Eu3+ ratio and enhanced the ligand field strength surrounding the Eu2+ ions, decreasing the Eu2+ luminescence intensity and red-shifting the luminescence peak. The addition of F− had the effect of diminishing the optical basicity, decreasing the OH groups content and eliminating Eu2+ clusters, which not only mitigated the effects of the Ba2+ ions, but also significantly enhanced the luminescence intensity of Eu2+ ions. An increase in the Eu ion concentration led to a red-shift in the Eu2+ fluorescence, which was attributed to the nephelauxetic effect. Therefore, the luminescence color of these glass samples could be manipulated by adjusting the doping concentrations of Ba2+, F−, and Eu2+. [ABSTRACT FROM AUTHOR]

The ligand field theory is an early and yet perennial class of quantum models accounting for the optical and magnetic properties of metal ions as a function of their environment in compounds. In the context of modern quantum chemistry, in order to predict properties from first principles, the ligand field paradigm can serve to illuminate the black box of heavy calculations, extracting heuristic meaning and causal roots. The genuine ligand field models are tacitly affected by an artificial feature, so-called holohedrization. It induces an inversion symmetry, even in cases where the local geometry does not show this element. This aspect received little attention over decades of using the ligand field Hamiltonians. In this work, we systematically investigate, assisted by state-of-the-art ab initio computer experiments, whether holohedrization is a hidden drawback of early models or if it also appears in realistic modeling. We found that the holohedrization trend also appears when using data from modern ab initio calculations. [ABSTRACT FROM AUTHOR]

In order to explain all of the spectral features observed in the U O4,5 x-ray absorption spectrum of uranium dioxide (UO2), it is necessary to include both multielectron effects and multiatomic effects. The 5d (core hole)-5f (electron) angular momentum coupling that gives rise to the giant resonance has been treated within ligand field density functional theory, and the electron scattering that generates the extended x-ray absorption fine structure has been included via the spectral simulation program FEFF: both within a UO8 fluorite cluster picture. An atomic model is insufficient to explain all of the observed spectral features. [ABSTRACT FROM AUTHOR]

Three novel heterometallic Ni/Cd coordination compounds [Ni(en)3][CdCl4]∙3dmso (1), [Ni(en)2(dmf)2][CdBr4] (2), and [Ni(en)3]2[CdI4](I)2 (3) have been synthesized through the self-assembly process in a one-pot reaction of cadmium oxide, nickel salt (or nickel powder), NH4X (X = Cl, Br, I), and ethylenediamine in non-aqueous solvents dmso (for 1) or dmf (for 2 and 3). Formation of the one- (1) or three-dimensional (2 and 3) hydrogen-bonded frameworks has been observed depending on the nature of the [CdX4]2− counter-anion, as well as on the nature of the solvent. The electronic structures of [Ni(en)3]2+ and [Ni(en)2(dmf)2]2+ cations were studied at the DFT and CASSCF levels, including the ab initio ligand field theory (AILFT) calculations. The non-covalent intermolecular contacts between the cationic nickel and anionic cadmium blocks in the solid state were investigated by the QTAIM analysis. The mechanism of ligand substitution at the nickel center in [Ni(en)2(dmf)2]2+ was theoretically investigated at the ωB97X-D4/ma-def2-TZVP//DLPNO-CCSD(T)/ma-def2-TZVPP level. The results demonstrate that thermodynamic factors are structure-determining ones due to low energy barriers of the rotation of dmf ligands in [Ni(en)2(dmf)2]2+ (below 3 kcal mol−1) and the reversible transformation of [Ni(en)2(dmf)2]2+ into [Ni(en)3]2+ (below 20 kcal mol−1). [ABSTRACT FROM AUTHOR]

The nature of the Sm–O bond of samarium-activated alumino-borate-based glasses prepared via the melt-quenching technique was investigated using the Ligand field parameters. Crystal field strength (Dq/B) and Racah parameters B and C were derived from the high-energy region of the absorption spectra. B and C are parameters that describe the influence of the inter-electronic force of repulsion in an atom and hence approximate the strength of the Sm–O bond. The absorption spectra revealed nine bands of transitions from the lower 6H5/2 energy level of Samarium to higher 6P3/2, 4I11/2, 6Hj, and 6Fk levels (j = 15/2, 1/2, k = 11/2, 9/2, 7/2, 5/2, and 3/2). The Sm–O bond in the prepared glass samples is less covalent due to the high values of Dq, B, and C. While the crystal field (Dq) and Racah parameters (B and C) decreased with an increase in Sm3+ contents, the crystal field strength (Dq/B) increased from 7.87 to 7.89. The observed trend affirmed the attenuation of the ionic nature (increase in the covalency) of the Sm–O bond in the glass host. The observed less covalent nature of Sm–O bond was complemented further by the negative values (–0.7444, –0.9018, –0.8821, and –0.8821 for GS0.5, GS1.0, GS1.5, and GS2.0, respectively) of the evaluated bonding parameters of all the glass samples. The prepared glass samples have the required features for laser applications. [ABSTRACT FROM AUTHOR]

The article presents a study identified spin-photon interfaces among more than 1000 charged defects in silicon using high-throughput first-principles computational screening. Topics discussed include most promising spin-photon interface defect candidates, favored interstitial defects, and importance and limits of excitonic defects in silicon.

Methylthioninium chloride (MTC) is a standard treatment for methaemoglobinaemia. A preparation of reduced MTC has been reported to increase blood oxygen saturation (SpO2) and lower respiratory rates in patients with severe COVID-19. We have developed a stable form of reduced methylthionine (hydromethylthionine-mesylate, HMTM) having a benign safety profile in two Phase 3 trials in Alzheimer's disease. The aim of this prospective study was to determine the effects of oral HMTM on SpO2 and methaemoglobin (metHb) levels in a cohort of patients with mild hypoxaemia not due to COVID-19. Eighteen participants randomised to a single dose of 4, 75, 100 or 125 mg doses of HMTM had SpO2 levels below 94% at baseline. Patients were routinely monitored by pulse oximetry after 4 h, and after 2 and 6 weeks of twice daily dosing. Significant ~3% increases in SpO2 occurred within 4 h and were sustained over 2 and 6 weeks with no dose differences. There were small dose-dependent increases (0.060–0.162%) in metHb levels over 2 to 6 weeks. Minimum-energy computational chemistry revealed that HMT can bind within 2.10 Å of heme iron by donating a pair of electrons from the central nitrogen of HMT to d orbitals of heme iron, but with lower affinity than oxygen. In conclusion, HMTM can increase SpO2 without reducing metHb by acting as a strong displaceable field ligand for heme iron. We hypothesise that this facilitates a transition from the low oxygen affinity T-state of heme to the higher affinity R-state. HMTM has potential as an adjunctive treatment for hypoxaemia. [ABSTRACT FROM AUTHOR]

Glasses are promising and efficient radiation shielding materials. However, they still suffer from low transparency with different types of additions, which need improvements for better transparency, consistency, and service life. This paper shows the significant improvements in radiation shielding and optical properties of cadmium oxide (CdO) and iron oxide (Fe 2 O 3) sodium borate glass system upon changing CdO/B 2 O 3 ratios. Optical absorbance and transmittance were measured, while the band gap values were obtained from investigating the fundamental absorption edges using Tauc's plot. Our analyses show that all glass samples show good transparency in the visible range; but the transparency slightly decreases with increasing CdO/B 2 O 3 contents. Moreover, with increasing CdO/B 2 O 3 contents, the BO 4 units increase, the density increases, and the BO 3 units decrease. Furthermore, with increasing CdO/B 2 O 3 contents, the fundamental absorption edges shift toward higher wavelengths, and the optical band gaps decrease. Also, with increasing CdO/B 2 O 3 contents, the linear and nonlinear refractive indices increase. These behaviors were justified by electronegativity decreases and electronic polarizability increases. On the other hand, the radiation shielding properties, like the mass attenuation coefficient and half-value layer, show enhanced behaviors with further CdO additions. The combination of enhanced radiation shielding properties and enhanced transparency makes the present glasses good candidates in the radiation shielding field. [ABSTRACT FROM AUTHOR]

A glass system based on the Na 2 O/B 2 O 3 -doped CrO 3 borosilicate has been prepared by the melt quenching technique. The structure, color, optical absorbance and ligand field parameters were investigated for a wide range of Na 2 O additives (20–60 mol%). All X-ray photoelectron spectroscopy (XPS) profiles were used to study the chemical shift states of the glass-constituting elements. Fourier transform infrared (FTIR) analyses explored the internal structure and subnetwork units. Furthermore, from the FTIR results, we concluded the transformation of trigonal borate units (BO 3) to tetrahedral borate units (BO 4) and the possibility of transformation from B 3 -O-Si linkages to B 4 -O-Si linkages. Despite the fixed CrO 3 content, the doped glasses showed a color transition from green to yellow with additional Na 2 O content. The increased intensity of the band at 451–427 nm and the decreased intensity of the band at 619–627 nm are the main reasons for this color transformation. The optical absorption spectra confirmed the existence of Cr3+ and Cr6+ states. A decreasing behavior for the crystal field splitting (10Dq) and an increasing behavior for Racah parameter (B) were obtained with further Na 2 O additives. The decreasing behavior of 10Dq was attributed to reduced oxygen concentrations with more Na 2 O/B 2 O 3 substitutions. The increasing behavior of B reflects the tendency of the bond between the Cr cations and their oxygen ligands towards an ionic nature. Moreover, the Dq/B values indicated that Cr3+ cations are in high-field positions for the glass sample containing 20 mol% Na 2 O, and Cr3+ cations are in intermediate field positions for the glass sample containing 30 mol% Na 2 O. However, for the glass samples doped with 40, 50 and 60 mol% Na 2 O glass samples, Cr3+-cations are in weak field positions. These results of (Dq/B) recommend the glass sample doped with 20 mol% Na 2 O for tunable laser applications. [ABSTRACT FROM AUTHOR]

High sensitivity of the Kβ fluorescence spectrum to electronic state is widely used to investigate spin and oxidation state of first-row transition-metal compounds. However, the complex electronic structure results in overlapping spectral features, and the interpretation may be hampered by ambiguity in resolving the spectrum into components representing different electronic states. Here, we tackle this difficulty with a nonlinear resonant inelastic X-ray scattering (RIXS) scheme, where we leverage sequential two-photon absorption to realize an inverse process of the Kβ emission, and measure the successive Kα emission. The nonlinear RIXS reveals two-dimensional (2D) Kβ-Kα fluorescence spectrum of copper metal, leading to better understanding of the spectral feature. We isolate 3d-related satellite peaks in the 2D spectrum, and find good agreement with our multiplet ligand field calculation. Our work not only advances the fluorescence spectroscopy, but opens the door to extend RIXS into the nonlinear regime. X-ray fluorescence spectroscopy is a powerful tool to investigate atomic properties. Here the authors report a two-dimensional fluorescence spectrum of copper metal using X-ray nonlinear scattering and find two-hole satellite feature resulting from atomic transitions. [ABSTRACT FROM AUTHOR]

A series of new lanthanide(III) coordination polymers with the general formula [Ln(btrm)2(NO3)3]n, where btrm = bis(1,2,4-triazol-1-yl)methane and Ln = Eu3+, Tb3+, Sm3+, Dy3+, Gd3+ were synthesized and characterized by IR-spectroscopy, elemental, thermogravimetric, single-crystal, and powder X-ray diffraction analyses. Europium(III), samarium(III), terbium(III), and gadolinium(III) coordination polymers demonstrate thermal stability up to 250 °C, while dysprosium(III) is stable up to 275 °C. According to single-crystal X-ray diffraction analysis, the ligand exhibits a bidentate-bridging coordination mode, forming a polymeric chain of octagonal metallocycles. The photoluminescence of the free ligand in the polycrystalline state is observed in the ultraviolet range with a quantum yield of 13%. The energy transfer from the ligand to the lanthanide ions was not observed for all obtained coordination polymers. However, there are sharp bands of lanthanide(III) ions in the diffuse reflectance and excitation spectra of the obtained compounds. Therefore, Ln(III) luminescence arises, most probably, from the enhancement of f-f transition intensity under the influence of the ligand field and non-centrosymmetric interactions. [ABSTRACT FROM AUTHOR]

Cadmium-doped borate glass composition was prepared via the melt-quenching technique. The nature of the glass structure was detected by X-ray diffraction (XRD). The physical parameters, such as density (ρ) from Archimedes' principle, molar volume (V m), C d 2 + ions concentration (N C d ), and inter-atomic distance (R i) were evaluated, providing structural information on glass samples. Fourier transform infrared (FT-IR) analysis was used to study the fundamental vibrational modes of structural units, confirming the conversion of B O 3 to B O 4 units, indicating a strongly bonded and high connectivity of the network. Some important optical findings were extracted from the analysis of optical absorption spectra. For example, the mitigation in the optical band gap, the increase in Urbach energy, the deterioration in the metallization criterion, and the enhancement in the electron-phonon interaction were obtained with cadmium oxide addition. The nonlinearity characteristics were enhanced, making these glass samples have viability in the non-linear optics sector. The obtained data from the electron spin resonance (ESR) revealed that the nickel ions exist in a divalent oxidation state with octahedral symmetry. Interestingly, the optical absorption transitions of N i 2 + ions were accurately deconvoluted and assigned to octahedral and tetrahedral positions. The equations of ligand field parameters of octahedral N i 2 + ions were correctly presented. The equation of Racah C parameter was deduced for the first time. Then, the ligand field parameters, such as the ligand field strength (10 Dq), Racah parameters (B and C), and other related parameters, were precisely assessed. The covalent nature between N i 2 + ions and the ligands was detected from the nephelauxetic effect. [ABSTRACT FROM AUTHOR]

The development of quantum technologies requires a thorough understanding of systems possessing quantum effects that can ultimately be manipulated. In the field of molecular magnetism, one of the main challenges is to measure high-order ligand field parameters, which play an essential role in the relaxation properties of SMMs. The development of highly advanced theoretical calculations has allowed the ab-initio determination of such parameters; however, currently, there is a lack of quantitative assessment of how good the ab-initio parameters are. In our quest for technologies that can allow the extraction of such elusive parameters, we develop an experimental technique that combines the EPR spectroscopy and µSQUID magnetometry. We demonstrate the power of the technique by performing EPR-µSQUID measurement of a magnetically diluted single crystal of Et4N[GdPc2], by sweeping the magnetic field and applying a range of multifrequency microwave pulses. As a result, we were able to directly determine the high-order ligand field parameters of the system, enabling us to test theoretical predictions made by state-of-the-art ab-initio methods. Single molecule magnets (SMMs) are molecules with magnetic states separated by an energy barrier. These two (or more) states can serve as basis for quantum information processing, but this requires a detailed understanding of the ligand field of the molecule that forms the SMM. Here, Taran et al use a combination of two experimental techniques, µSQUID and EPR, to precisely measure the higher-order ligand field parameters. [ABSTRACT FROM AUTHOR]

The choice of gain media significantly affects the efficiency of mid-infrared (MIR) lasers and amplifiers. Transition metal ion-doped glass-ceramics (GCs) are attractive laser gain materials as they have the advantages of both laser crystals and glasses. Transparent GC fibers with efficient MIR emission are currently scarce. The emission properties of Ni2+ ion in GCs are generally studied in an octahedral ligand field, where it emits near-infrared light. The emission properties of tetra-coordinated Ni2+ ions are yet to be explored. Herein, we found a chalcogenide glass host characterized by high crystallinity and prepared transparent Ni2+-doped chalcogenide GC containing ZnS nanocrystals by in-situ crystallization. Moreover, for the first time, we reported the broadband MIR 3–4 μm emission at room temperature from tetra-coordinated Ni2+ in chalcogenide GC fiber embedded with ZnS nanocrystal. The fiber losses were measured to be 18.6 ± 1.1, 9.8 ± 0.6 and 11.4 ± 0.8 dB/m at 2.10, 3.39 and 3.80 μm, respectively. The results indicate that the active chalcogenide GC fiber reported herein can be potentially used to develop MIR-tunable fiber lasers and amplifiers. [ABSTRACT FROM AUTHOR]

Linker functionalization is a common route used to affect the electronic and catalytic properties of metal-organic frameworks. By either pre- or post-synthetically installing linkages with differing linker moieties the band gap, workfunction, and exciton lifetimes have been shown to be affected. One overlooked aspect of linker functionalization, however, has been the impact on the metal d-orbital energies to which they are bound. The ligand field differences should result in substantial changes in d-splitting. In this study we use density functional theory (DFT) to study the energetics of d-orbital energy tuning as a function of linker chemistry. We offer a general descriptor, linker pKa, as a tool to predict resultant band energies in metal-organic frameworks (MOFs). Our calculations reveal that simple functionalizations can affect the band energies, of primarily metal d lineage, by up to 2 eV and illustrate the significance of this band modularity using four archetypal MOFs: UiO-66, MIL-125, ZIF-8, and MOF-5. Together, we show that linker functionalization dramatically affects d-energies in MOF clusters and highlight that linker functionalization is a useful route for fine-tuning band edges centered on the metals, rather than linkers themselves. Linker functionalization is a commonly used strategy to affect the electronic and catalytic properties of metal–organic frameworks, but its impact on the d-orbital energies of the metals to which the linkers are bound has been largely overlooked. Here, DFT calculations are used to study the energetics of d-orbital energy tuning as a function of linker chemistry in UiO-66, MIL-125, ZIF-8 and MOF-5. [ABSTRACT FROM AUTHOR]

Our research group has made incursions into the scarcely known coordination chemistry of rhenium(II). The literature shows that Re(II) mononuclear complexes are attractive in molecular magnetism due to high magnetic anisotropy because of a significant spin-orbit coupling, making them a potential source for new molecule-based magnets. In this work, we present the preparation of four novel Re(II) compounds of general formula NBu4[Re(NO)Br4(L)] [NBu4+ = tetra-n-butylammonium: L = imidazole (1), pyrazole (2), 1,2,4-triazole (3) and 1H-tetrazole (4)]. The four compounds were fully characterized by single-crystal X-ray diffraction, infrared spectroscopy, and cryomagnetic measurements in the temperature range of 1.8–300 K. Their crystal structures consist of mononuclear [Re(NO)Br4(L)]− complex anions and NBu4+ cations. Each Re(II) ion is six-coordinate with a linear nitrosyl group and one monodentate nitrogen-donor (L), which are trans-positioned, plus four bromide groups, building a tetragonally distorted octahedral surrounding. The inter-anionic contacts were thoroughly analyzed using Hirshfeld surface analyses (plots over the dnorm, shape index, and 2D fingerprints). Cryomagnetic measurements show that these complexes behave as quasi-magnetically isolated spin doublets with weak antiferromagnetic interactions at low temperatures. The magnetic behavior of Re(II) was modeled by the influence of the ligand field, tetragonal distortion, spin-orbit coupling, and covalence effects. In addition, the antiferromagnetic exchange coupling was correlated to the nature of the intermolecular interactions. [ABSTRACT FROM AUTHOR]

We model the thermal effects in different 2D spin-crossover (SCO) square lattices within the frame of the Ising-like model using Monte Carlo entropic sampling (MCES) method to enhance the scan of macrostates beyond the most probable thermal ones. In fact, MCES allows access to the metastable states, and it is then well adapted to study thermal hysteresis properties. In this contribution, we distinguish, for the first time, the interaction between molecules located in bulk at the surface and those connecting the bulk and surface regions of an SCO lattice. In addition, an extra ligand field contribution is assigned to surface molecules through an interaction parameter L. In the absence of environmental effects on surface nanoparticles, a single thermal hysteresis loop increasing with the lattice size is simulated with a unique bulk and surface equilibrium temperature T e q = T e q b u l k =   T e q s u r f . When environmental effects are accounted for, a two-step behavior associated with two hysteresis loops of widths ΔTS (for the surface) and ΔTB (for the bulk) with an intermediate plateau 14 K wide is obtained in the thermal dependence of the high-spin (HS) fraction for the 6 × 6 lattice. The surface and bulk equilibrium temperatures are then different, both decreasing towards lower values, and the L parameter controls the three states' behavior as well as the hysteresis loop interval. Size effects show that the equilibrium temperature is governed by the surface atoms for a small lattice size (5 × 5) and by the bulk atoms for a large lattice size (7 × 7). Moreover, a change in the size of the lattice results in a variation of the order–disorder (or Curie) temperature, TO.D., and the surface equilibrium temperature, Teq, while only TO.D. changes in bulk. [ABSTRACT FROM AUTHOR]

Advances in nanomedicine bring the attention of researchers to the molecular targets that can play a major role in the development of novel therapeutic and diagnostic modalities for cancer management. The choice of a proper molecular target can decide the efficacy of the treatment and endorse the personalized medicine approach. Gastrin-releasing peptide receptor (GRPR) is a G-protein-coupled membrane receptor, well known to be overexpressed in numerous malignancies including pancreatic, prostate, breast, lung, colon, cervical, and gastrointestinal cancers. Therefore, many research groups express a deep interest in targeting GRPR with their nanoformulations. A broad spectrum of the GRPR ligands has been described in the literature, which allows tuning of the properties of the final formulation, particularly in the field of the ligand affinity to the receptor and internalization possibilities. Hereby, the recent advances in the field of applications of various nanoplatforms that are able to reach the GRPR-expressing cells are reviewed. [ABSTRACT FROM AUTHOR]

The β− emitter, rhenium-188 (188Re), has long been recognized as an attractive candidate for targeted cancer radionuclide therapy (TRNT). This transition metal shares chemical similarities with its congener element technetium, whose nuclear isomer technetium-99m (99mTc) is the current workhorse of diagnostic nuclear medicine. The differences between these two elements have a significant impact on the radiolabelling methods and should always receive critical attention. This review aims to highlight what needs to be considered to design a successful radiopharmaceutical incorporating 118Re. Some of the most effective strategies for preparing therapeutic radiopharmaceuticals with 188Re are illustrated and rationalized using the concept of the inorganic functional group (core) and a simple ligand field theoretical model combined with a qualitative definition of frontiers orbitals. Of special interest are the Re(V) oxo and Re(V) nitrido functional groups. Suitable ligands for binding to these cores are discussed, successful clinical applications are summarized, and a prediction of viable future applications is presented. Rhenium-188 decays through the emission of a high energy beta particle (2.12 MeV max energy) and a half-life of 16.9 h. An ideal biological target would therefore be a high-capacity target site (transporters, potential gradients, tumour microenvironment) with less emphasis on saturable targets such as overexpressed receptors on smaller metastases. [ABSTRACT FROM AUTHOR]

Recently we have proposed a simple method for obtaining the parameters of a ligand field multiplet model for L-edge spectra calculations from density functional theory. Here we generalize the method to systems where the metal site has arbitrary point symmetry. The ligand field-induced splitting of the metal d-level becomes a hermitian matrix with cross-terms between the different d-orbitals. The anisotropy of the covalency is fully taken into account and it rescales the electron–electron interaction and the oscillator strength in an orbital-dependent way. We apply the method to polarization-dependent V L-edge spectra of vanadium pentoxide and obtain very good agreement with the experiment. [ABSTRACT FROM AUTHOR]

Metal complexes with pyridine ligands (py) have not been crystallographically characterized in large numbers, while a large number of 2,2′-bipyridine (bpy) complexes have been structurally characterized. Against this background of scarcity of py complexes, the aim of this study was to characterize the structures and magnetic properties of complexes with pyridine ligands. In this study, new py complexes, trans-[Ni(H2O)2(py)4][BPh4]2·4py (1) and trans-[Co(H2O)2(py)4][BPh4]2·4py (2), were prepared and characterized by the single-crystal X-ray diffraction method and magnetic measurements. In the crystal structure analysis, both complexes were found to have octahedral trans-N2O4 coordination geometry, and the coordination of the trans-aqua ligands was found to be enhanced by the hydrogen-bonded pyridine molecules as a base. In the simultaneous analysis of magnetic susceptibility and magnetization, both complexes were found to show strong magnetism in one direction (χz > χx, χy; Mz > Mx, My), and this was explained by the enhancement of the axial aqua ligands. In the nickel(II) complex, the strong axial ligand field was found to cause negative zero-field splitting (D < 0) to show the magnetic behavior, while in the cobalt(II) complex, the strong axial π-orbital effect was found to cause negative ligand field splitting (Δ) in the 4T1 ground state to show the magnetic behavior. [ABSTRACT FROM AUTHOR]

For applications such as near-infrared (NIR) spectroscopy requiring energy-efficient and compact broadband NIR light sources, a variety of Ni2+-doped phosphors emitting in the 1100–2000 nm range has been developed. However, the commercialization of Ni2+-doped NIR phosphors has not yet been achieved, and material exploration is ongoing. To gain insight into the luminescence properties of Ni2+, including emission wavelength and efficiency influenced by compositional and structural variations, Ni2+-doped double-perovskite AE LaMgTaO 6 :Ni2+ (AE = Ba, Sr, or Ca) ceramic samples were synthesized, and their optical properties were examined. Because the energy of the Ni2+ 3d-3d transition is sensitive to structural variations in the local environment around the Ni2+ ions, we investigated the variation in optical properties by indirect ligand field engineering of NiO 6 octahedra following the substitution of alkaline earth ions AE 2+. The prepared AE LaMgTaO 6 :Ni2+ samples were Ba-Sr or Ba-Ca complete solid solution systems with cubic-to-monoclinic phase transitions. The broad NIR luminescence band at ∼1350–1700 nm was blue-shifted by ∼100 nm, accompanied by Sr2+ or Ca2+ substitution. The local symmetry of the NiO 6 octahedra was reduced from O h to C i owing to the phase transition, resulting in an enhancement of the NIR luminescence intensity and an increase in the quenching temperature. This study demonstrated that Ni2+ phosphors with the desired optical properties for NIR spectroscopy applications can be designed by controlling the composition ratio of the host compounds and the resultant variation in the local environment of the solid solution compounds. [Display omitted] • Ni2+-doped NIR phosphors with complete solid-solution composition were synthesized. • By changing composition, the broadband NIR luminescence blue-shifted up to ∼100 nm. • The cubic-to-monoclinic phase transition enhanced the Ni2+ luminescence intensity. • The quenching temperature of NIR luminescence was improved in the monoclinic lattice. [ABSTRACT FROM AUTHOR]

The coordination environment between the metal center and ligands in single atom catalysts (SACs) is a curial factor influencing their catalytic activity. Herein, two types of Fe-centered SACs were synthesized for peroxymonosulfate (PMS) activation. The result showed that SACs enriched with pyrrolic ligands (Fe-N 4 C 12) exhibited significantly higher PMS activation performance compared to those with pyridinic ligands (Fe-N 4 C 10). Density functional theory (DFT) calculations revealed that electron delocalization in pyrrolic ligands is more effective, rendering a stronger reactivity of Fe in Fe-N 4 C 12. The adsorption of PMS onto Fe-N 4 sites regulated the ligand field surrounding Fe from a square planar to a pseudo-octahedral field, thereby significantly activating the delocalization orbital. Pyrrolic ligands further maintained a lower d‐band center of Fe in the Fe-N 4 C 12 configuration than Fe-N 4 C 10 by pyridinic ligand. This led to a higher electron occupancy in antibonding band of Fe-N 4 C 12 when PMS was adsorbed, and consequently, for better oxidation performance. [Display omitted] • SACs enriched with pyrrolic and pyridinic ligands were synthesized separately. • PMS adsorption on Fe-N 4 sites altered the electric field from square planar to octahedral for better reactivity. • A ligand-Fe-PMS electron flux caused by electron delocalization was created for PMS activation. • Pyrrolic ligands were adept at maintaining a low d‐band center for higher electron occupancy. [ABSTRACT FROM AUTHOR]

The conditions for achieving the maximal unquenched orbital angular momentum L = 3 and the highest magnetic anisotropy in mononuclear 3d complexes with axial coordination symmetry are examined in terms of the ligand field theory. It is shown that, apart from the known linear two-coordinate 3d7 complex CoII(C(SiMe2ONaph)3)2 characterized by record magnetic anisotropy and single-molecule magnet (SMM) performance (with the largest known spin-reversal barrier Ueff = 450 cm−1), the maximal orbital angular momentum L = 3 can also be obtained in linear two-coordinate 3d2 complexes (V3+, Cr4+) and in trigonal-prismatic 3d3 (Cr3+, Mn4+) and 3d8 (Co+, Ni2+) complexes. A comparative assessment of the SMM performance of the 3d2, 3d3 and 3d8 complexes indicates that they are unlikely to compete with the record linear complex CoII(C(SiMe2ONaph)3)2, whose magnetic anisotropy is close to the physical limit for a 3d metal. [ABSTRACT FROM AUTHOR]

A novel multi-channel barcode module was developed by using chiral co-crystals which contain field-induced SMM behavior and different emission bands. The chiral co-crystals [Zn(H2L)Dy(DBM)2]4(ClO4)4⋅9CH3OH⋅H2O (1a) and [Zn(H2L)Dy(DBM)2]4(ClO4)4⋅8CH3OH⋅0.5H2O (1b) (H4L = 2,2′-[1,2-ethanediylbis[(hydroxyethylimino)methylene]]bis[6-methoxy-4-methyl-phenol], HDBM = dibenzoylmethane) were obtained through one-pot reaction of ZnII and DyIII with the achiral ligands H4L and HDBM. X-ray single crystal diffraction and CD spectroscopy confirmed that they are enantiomers crystallized in P43 (1a) and P41 (1b), both consisting of two ∆-[Zn(H2L)Dy(DBM)2]+ cations, two Λ-[Zn(H2L)Dy(DBM)2]+ cations and four (ClO4)− anions. The presence of DyIII ions endow them with the property of field-induced slow magnetic relaxation. The relatively low energy barrier of 35.0(9) K for complex 1 may be due to the poor axiality of the ligand field caused by the long Dy-Ophenoxy bond lengths and the small Ophenoxy-Dy-Ophenoxy bond angles. Moreover, when the organic ligands H4L (λex = 350 nm) and DyIII (λex = 420 nm) are excited, different emission spectra are observed. [ABSTRACT FROM AUTHOR]

T Ni(II) complexes of Schiff's base macrocyclic ligands i.e. 2,3,9,10-tetraphenyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene (BDP), 2,4,10,12-tetramethyl-1,5,9,13 tetraazacyclohexadeca-1,4,9,12-tetraene (ADP) and 2,3,9,10-tetramethyl-1,4,8,11 tetraazatetradeca-1,3,8,10-tetraene (DDP) have been synthesized. All these synthesized complexes have been characterized by elemental analysis, molar conductance, magnetic susceptibility measurement, IR and UV-Visible spectral studies. On the basis of elemental analysis, the complexes have been found to have the general composition Ni(Lig)X2 where Lig = BDP, ADP, DDP and X = Cl-, SO42- and NCS-. Molar conductance of complexes has been measured in DMSO solvent and the obtained values indicate non-electrolytic nature of all complexes i.e. counter ions are present inside the coordination sphere. Magnetic moments and electronic spectral data suggested six coordinated octahedral geometry for the Ni(II) complexes. The ligand field parameters have been calculated for metal complexes by using various energy level diagrams. In vitro synthesized complexes have been examined against the growth of the some plant pathogenic fungi in order to assess their microbial properties. [ABSTRACT FROM AUTHOR]

Iron(II)-Schiff base complexes are a well-studied class of spin-crossover (SCO) active species due to their ability to interconvert between a paramagnetic high spin-state (HS, S = 2, 5T2) and a diamagnetic low spin-state (LS, S = 0, 1A1) by external stimuli under an appropriate ligand field. We have synthesized two mononuclear FeII complexes, viz., [Fe(L1)2](ClO4)2.CH3OH (1) and [Fe(L2)2](ClO4)2.2CH3CN (2), from two N6–coordinating tridentate Schiff bases derived from 2,6-bis[(benzylimino)methyl]pyridine. The complexes have been characterized by elemental analysis, electrospray ionization–mass spectrometry (ESI-MS), Fourier-transform infrared spectroscopy (FTIR), solution state nuclear magnetic resonance spectroscopy, 1H and 13C NMR (both theoretically and experimentally), single-crystal diffraction and magnetic susceptibility studies. The structural, spectroscopic and magnetic investigations revealed that 1 and 2 are with Fe–N6 distorted octahedral coordination geometry and remain locked in LS state throughout the measured temperature range from 5–350 K. [ABSTRACT FROM AUTHOR]

When employing molecular dynamics (MD) simulations for computer-aided drug design, the quality of the used force fields is highly important. Here we present reparametrisations of the force fields for the core molecules from 9 different β -lactam classes, for which we utilized the force field Toolkit and Gaussian calculations. We focus on the parametrisation of the dihedral angles, with the goal of reproducing the optimised quantum geometry in MD simulations. Parameters taken from CGenFF turn out to be a good initial guess for the multiplicity of each dihedral angle, but the key to a successful parametrisation is found to lie in the phase shifts. Based on the optimised quantum geometry, we come up with a strategy for predicting the phase shifts prior to the dihedral potential fitting. This allows us to successfully parameterise 8 out of the 11 molecules studied here, while the remaining 3 molecules can also be parameterised with small adjustments. Our work highlights the importance of predicting the dihedral phase shifts in the ligand parametrisation protocol, and provides a simple yet valuable strategy for improving the process of parameterising force fields of drug-like molecules. [ABSTRACT FROM AUTHOR]

The elimination of propane is particularly important in volatile organic compounds (VOCs) emissions control. We designed a special Cu-type α-MnO 2 with tunnel-restrained Cu2+ chain for propane total oxidation. It can effectively elevate the reaction rate and reduce the apparent activation energy. Cu2+ mainly stabilizes as tunnel [CuO 4 ] configurations, changing the charge distribution and ligand field inside the tunnel, compared to the original ionic [KO 8 ] and [KO 12 ] in α-MnO 2. The covalency between Cu−O as well as exacerbated Jahn-Teller distortion of [MnO 6 ] occur. The resulting charge transfer of Cu−O−Mn units via bridging O atoms further affects the outside-tunnel properties, specifically, facilitating oxygen vacancy formation and lattice oxygen activation. Moreover, abundant oxygen vacancies can promote the dehydrogenation of propane to generate alcohols at low temperatures. The above intermediates undergo successively oxidation with activated lattice oxygen to produce C 3 ∼C 1 carboxylates as temperature elevates. [Display omitted] • Tunnel-restrained Cu2+ chain could improve the propane oxidation activity of α-MnO 2. • Cu2+ facilitates oxygen vacancy formation and boosts lattice oxygen activity. • [CuO 4 ] configurations change the charge distribution and ligand fields inside the tunnel. • The covalency of Cu−O−Mn affects the outside-tunnel properties via bridging O charge transfer. • Abundant oxygen species promote the successive dehydrogenation and oxygenation of propane. [ABSTRACT FROM AUTHOR]

In this work, the heavy metal borate glass system (B 2 O 3 -PbO) was doped with a hybrid of transition metal and rare earth ions via a fixed ratio of MnO 2 and a variable La 2 O 3 ratio. X-ray diffraction spectra confirmed the amorphous nature of the manufactured glassy system. The effect of La 2 O 3 ions in causing modifications to the internal structure was examined through density measurements and Fourier-transform infrared spectroscopy. According to structural studies, the density increases gradually with increasing La 2 O 3 /B 2 O 3 concentrations, in addition to an increase in the ratio of non-bridging oxygen resulting from structural transformations between the BO 4 and BO 3 units. The optical absorption bands were deconvoluted and studied, where the samples acquired a light brown color resulting from the absorption band at ∼466 nm and the electronic transition 6A 1 g (S) → 4A 1 g (G). The detected absorption bands verified the existence of Mn2+/Mn3+ in octahedral/tetrahedral sites. However, photoluminescence spectra indicated the tendency of Mn2+ ions to occupy more octahedral coordination. The shift of the fundamental absorption edges to lower energy with La 2 O 3 addition confirmed the successive narrowing of the optical band gap. In addition, the entry of La3+ ions improved the optical basicity and electronic polarization, raising linear/nonlinear refractive indices. The ligand field effect showed the role of La3+ ions in reducing the crystal field intensity around Mn2+ ions and increasing the nephelauxetic ratio, indicating a gradual increase in the ionic bonding nature between the Mn2+ cations and the adjacent ions. • The optical spectra of Mn2+/Mn3+ ions can be tuned in the visible region by La3+ additions. • The linear/nonlinear refractive indices increased by La 2 O 3 addition. • Ligand field parameters showed an increase in the ionic nature of Mn2+ ions • The Mn2+ ions occupied tetrahedral and octahedral sites. [ABSTRACT FROM AUTHOR]

Here, a sol‐gel method is used to prepare a Prussian blue analogue (NiFe‐PBA) precursor with a 2D network, which is further annealed to an Fe3O4/NiCx composite (NiFe‐PBA‐gel‐cal), inheriting the ultrahigh specific surface area of the parent structure. When the composite is used as both anode and cathode catalyst for overall water splitting, it requires low voltages of 1.57 and 1.66 V to provide a current density of 100 mA cm−2 in alkaline freshwater and simulated seawater, respectively, exhibiting no obvious attenuation over a 50 h test. Operando Raman spectroscopy and X‐ray photoelectron spectroscopy indicate that NiOOH2–x active species containing high‐valence Ni3+/Ni4+ are in situ generated from NiCx during the water oxidation. Density functional theory calculations combined with ligand field theory reveal that the role of high valence states of Ni is to trigger the production of localized O 2p electron holes, acting as electrophilic centers for the activation of redox reactions for oxygen evolution reaction. After hydrogen evolution reaction, a series of ex situ and in situ investigations indicate the reduction from Fe3+ to Fe2+ and the evolution of Ni(OH)2 are the origin of the high activity. [ABSTRACT FROM AUTHOR]

Only one (trans(O5)-Na[Rh(ED3AP)]∙3H2O) of possible two isomers was synthesized and characterized by single crystal X-ray analysis, IR and UV-Vis spectroscopy. Computational analysis of both isomers was performed with three levels of theory (B3LYP/TZV, BP86/TZV, OPBE/TZV), which gave consistent results. The more stable isomer by total energy and ligand field stabilization energy (LFSE) was trans(O5) which appeared in synthesis. The calculation of excited state energies complied with UV-Vis spectra, especially with OPBE functional. The results of excited state energy pointed out the differences among isomers in means of a splitting pattern of 1T2g excited state term. Both isomers have a strongly delocalized structure, according to the natural bonding orbital (NBO) analysis. NBO analysis shows that the trans(O5) isomer is more stable than trans(O5O6) for approx. 87 kJ/mol. Therefore, only the trans(O5) isomer is present in the reaction mixture. [ABSTRACT FROM AUTHOR]

The β− emitter, rhenium-188 (188Re), has long been recognized as an attractive candidate for targeted cancer radionuclide therapy (TRNT). This transition metal shares chemical similarities with its congener element technetium, whose nuclear isomer technetium-99m (99mTc) is the current workhorse of diagnostic nuclear medicine. The differences between these two elements have a significant impact on the radiolabelling methods and should always receive critical attention. This review aims to highlight what needs to be considered to design a successful radiopharmaceutical incorporating 118Re. Some of the most effective strategies for preparing therapeutic radiopharmaceuticals with 188Re are illustrated and rationalized using the concept of the inorganic functional group (core) and a simple ligand field theoretical model combined with a qualitative definition of frontiers orbitals. Of special interest are the Re(V) oxo and Re(V) nitrido functional groups. Suitable ligands for binding to these cores are discussed, successful clinical applications are summarized, and a prediction of viable future applications is presented. Rhenium-188 decays through the emission of a high energy beta particle (2.12 MeV max energy) and a half-life of 16.9 h. An ideal biological target would therefore be a high-capacity target site (transporters, potential gradients, tumour microenvironment) with less emphasis on saturable targets such as overexpressed receptors on smaller metastases.

Herein, we present the systematic, comparative computational study of the d − d transitions in a series of first row transition metal hexaaqua complexes, [M(H2O)6]n+ (M2+/3+ = V 2+/3+, Cr2+/3+, Mn2+/3+, Fe2+/3+, Co2+/3+, Ni2+) by the means of Time-dependent Density Functional Theory (TD-DFT) and Ligand Field Density Functional Theory (LF-DFT). Influence of various exchange-correlation (XC) approximations have been studied, and results have been compared to the experimental transition energies, as well as, to the previous high-level ab initio calculations. TD-DFT gives satisfactory results in the cases of d2, d4, and low-spin d6 complexes, but fails in the cases when transitions depend only on the ligand field splitting, and for states with strong character of double excitation. LF-DFT, as a non-empirical approach to the ligand field theory, takes into account in a balanced way both dynamic and non-dynamic correlation effects and hence accurately describes the multiplets of transition metal complexes, even in difficult cases such as sextet-quartet splitting in d5 complexes. Use of the XC functionals designed for the accurate description of the spin-state splitting, e.g., OPBE, OPBE0, or SSB-D, is found to be crucial for proper prediction of the spin-forbidden excitations by LF-DFT. It is shown that LF-DFT is a valuable alternative to both TD-DFT and ab initio methods. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Co 4 N 8 -gra exhibits outstanding NH 3 selectivity and excellent thermal stability. • Magnetic transitions pathways exhibit the dependence of solvent conditions. • High catalytic performance is attributed to the combined effect of external potential and magnetic-state transitions on the adsorption of reaction species. Exploration of magnetic phase transitions during electrochemical processes is of great importance for rational design of supported magnetic-metal electrocatalysts. Herein, we systematically investigated the magnetic transition between ferromagnetism (FM) and anti-ferromagnetism (AFM) in one-dimensional ferromagnetic Co chain supported on graphene (Co 4 N 8 -gra) during NO electroreduction (NORR) process, focusing on the impact of potential and acidity on the catalytic property and magnetic transition. A combination of catalytic kinetics calculations and microkinetic simulations reveals that the Co 4 N 8 -gra exhibits excellent NH 3 selectivity and thermal stability. In the implicit solvent model, the general reaction follows optimal pathway: * + NO(g) → *NO → *HNO → *H 2 NO → *H 2 NOH → *NH 2 → *NH 3 → * + NH 3 , with the potential-determining step (PDS) identified as *NO → *HNO. In acidic solvent, the magnetic transitions follow the pathway (FM → AFM2 → AFM2 → AFM2 → AFM1 → AFM1 → AFM1 → FM) under an applied potential of −0.20 V/RHE. In neutral solvent, the magnetic transitions occur according to this pathway (FM → AFM2 → AFM2 → FM → AFM1 → AFM1 → AFM1 → FM) under an applied potential of −0.14 V/RHE. In an alkaline solvent, the magnetic transitions proceed along this sequence (FM → AFM1 → AFM2 → FM → AFM1 → AFM1 → AFM1 → FM) under an ultralow potential of −0.08 V/RHE. Essentially, the improvement of catalytic property is attributed to the synergistic influence of external potential and magnetic-state transition on the adsorption of reaction species (e.g., NO and NH 3). Magnetic transitions are closely associated with ligand field effect of metal site with variable valence electron induced by applied potential. In general, this study provides valuable insights for the controllable design of magnetic metal catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pd catalysts are used for nonalternating copolymerization of ethylene with CO. • Alkyl substituents on phosphorus moiety exhibits 29.2 mol% extra C2 incorporation. • T m value of nonalternating polyketone was reduced to 162 °C. • Such Pd catalyst exhibits high thermally robust nature in this copolymerization. Production of polyketone realizes the direct conversion of cost effective and abundant olefin and carbon monoxide (CO) monomers. However, copolymerization of ethylene with CO shows a high tendency for the formation of strictly alternating structures, and they feature a high melting temperature (T m) of 260 °C that impedes the processing by using the conventional injection molding and extrusion. Nonalternating preference in such copolymerization is a very promising method to circumvent the processability issues. In this study, we present a series of phosphine-sulfonate Pd catalysts for nonalternating copolymerization of ethylene and CO, since rare study has investigated the electronic and steric nature systematically in such ligand platform in this field. The usage of dicyclohexyl substituents on phosphorus moiety exhibits unexpected nonalternating preference with up to 29.2 mol% extra ethylene incorporation, thus lowing the T m values to 162 °C. Notably, such alkyl substituted phosphine sulfonate Pd catalyst exhibits high thermally robust nature in this nonalternating copolymerization. [ABSTRACT FROM AUTHOR]

• [(TpPh,Me) 2 Ni] crystallizes as a mixture of monoclinic and triclinic polymorphs. • The polymorphs exhibit different melting points and complex conformations. • The conformations are distinguished by non-covalent interactions between opposing co-ligands. • The conformations can be recognized broadly in structures of related complexes. The homoleptic scorpionate sandwich complex [(TpPh,Me) 2 Ni] (1), where TpPh,Me = hydrotris(3-phenyl-5-methylpyrazol-1-yl)borate, crystallizes as a mixture of two polymorphs. A major monoclinic fraction crystallizes as well-formed parallelepipeds and a minor triclinic fraction forms irregularly shaped, anhedral crystals. These exhibit distinct melting points (288 and 294 °C, respectively) as observed by differential scanning calorimetry. We obtained X-ray crystal structures of both polymorphs at 100 K. The complex adopts different conformations between the two lattices. These are supported by distinctive ensembles of intramolecular non-covalent interactions, specifically π-stacking and perpendicular C–H···π contacts between opposing 3-phenylpyrazolyl arms on the co-ligands. The conformation found in the major monoclinic polymorph consists of a counter-rotation of the ligands that reduces the ideal complex symmetry from D 3d to D 3 and results in three-fold pair-wise association of 3-phenylpyrazolyl arms. In contrast, an alternate conformation of 1 in the minor triclinic polymorph consists of two triads, with an ideal complex symmetry of C 2h. Also affected are the tetragonality of the ligand fields and interligand N–Ni–N′ bond angles. A review of sandwich complex structures [(TpR) 2 M], where R is an aromatic substituent, shows these conformations are adopted broadly. Hence, substituent effects in second-generation scorpionate ligands are not merely steric in origin. The homoleptic scorpionate sandwich complex [(TpPh,Me) 2 Ni], where TpPh,Me = hydrotris(3-phenyl-5-methylpyrazol-1-yl)borate, crystallizes as two polymorphs, with differing motifs of intramolecular π-stacking and C–H···π interactions between opposing 3-phenylpyrazolyl arms. The major monoclinic polymorph hosts pairwise associations, while the minor triclinic polymorph adopts a distinctive conformation of triads. [Display omitted] [ABSTRACT FROM AUTHOR]

The importance of watching and understanding color of chemical compounds and linking it to diverse physical and chemical properties is illustrated here using transition metal oxides at the highest achievable oxidation state of a metal. Analyses are based on qualitative thinking supported by Molecular Orbital theory in its simplest implementation. [ABSTRACT FROM AUTHOR]