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The layered van der Waals material CrCl3 exhibits very strongly bound ligand field excitons that control optoelectronic applications and are connected with magnetic ordering by virtue of their d-orbital origin. Time-resolved photoluminescence of these exciton populations at room temperature shows that their relaxation is dominated by exciton–exciton annihilation and that the spontaneous decay lifetime is very long. These observations allow the rough quantification of the exciton annihilation rate constant and contextualization in light of a recent theory of universal scaling behavior of the annihilation process. [ABSTRACT FROM AUTHOR]

The layered van der Waals material CrCl3 exhibits very strongly bound ligand field excitons that control optoelectronic applications and are connected with magnetic ordering by virtue of their d-orbital origin. Time-resolved photoluminescence of these exciton populations at room temperature shows that their relaxation is dominated by exciton–exciton annihilation and that the spontaneous decay lifetime is very long. These observations allow the rough quantification of the exciton annihilation rate constant and contextualization in light of a recent theory of universal scaling behavior of the annihilation process. [ABSTRACT FROM AUTHOR]

The ground state of 3d1 MnO42− was studied by density functional theory (DFT) and complete active space self-consistent field (CASSCF) methods in terms of a variety of molecular point group structures to ascertain the site and Jahn–Teller (JT) distortion effect. Modeling results from UB3LYP/6-31+G(d) calculations with natural bond orbital analysis show the four Mn–O bonds are coordinate covalent. The one-electron matrix elements from CASSCF(AILFT) (ab initio ligand field theory) with a second order perturbation treatment were used to calculate the parameters of the angular overlap model. These allowed the calculation of JT stabilization energies and first and second order JT coupling constants for MnO42− with C2v and D2d symmetry. Absorption spectra and excited state transition energies were calculated assuming the lattice distorted geometry was C2v with time-dependent DFT (TDDFT) using the unrestricted coulomb-attenuating UCAM-B3LYP density functional and with the spin-adapted spin-flip DFT using the UBH&HLYP density functional, both with the AUG-CC-PVTZ basis set. The mean absolute deviation of the calculations from experimental excited states for the ligand field and ligand-to-metal charge transfer (LMCT) bands was better than 0.1 eV. Several new assignments for LMCT excited states were made on the basis of the TDDFT excitation results. [ABSTRACT FROM AUTHOR]

By employing a recently proposed Hubbard U density-corrected scheme within density functional theory, we provide design principles towards the design of materials exhibiting a spin crossover-assisted gas release. Small molecular fragments are used as case study to identify two main mechanisms behind the change in binding energy upon spin transitions. The feasibility of the proposed mechanism in porous crystals is assessed by correlating the change in binding energy of CO2, CO, N2, and H2, upon spin crossover, with the adiabatic energy difference associated with the spin state change of the square-planar metal in Hofmann-type clathrates (M = Fe, Mn, Ni). A few promising cases are identified for the adsorption of intermediate ligand field strength molecules such as N2 and H2. The latter stands out as the most original result as the strong interaction in low spin, as expected from a Kubas mechanism, results in a large change in binding energy. This work provides a general perspective towards the engineering of open-metal site frameworks exhibiting local environments designed to have a spin crossover upon adsorption of specific gas molecules. [ABSTRACT FROM AUTHOR]

The structures and energetics of the binuclear methylphosphinidene complexes of cyclopentadienylruthenium carbonyls of the type [MePRu2(CO)nCp2] (n = 4, 3, 2, 1) have been investigated for comparison with their previously studied iron analogues. For the tetracarbonyls and tricarbonyls [MePM2(CO)nCp2] (n = 4, 3) substituting ruthenium for iron has relatively little effect on the energetically preferred structures. Thus such structures have two-electron donor bridging MeP groups with no metal-metal bond for the tetracarbonyls and a metal-metal single bond for the tricarbonyls. This leads to favored 18-electron configurations for both ruthenium atoms in all cases. However, the higher ligand field strengths of ruthenium complexes relative to analogous iron complexes have major effects on the energetically preferred structures for the dicarbonyls and monocarbonyls [MePM2(CO)nCp2] (M = Fe, Ru; n = 2, 1). Thus the 11 lowest energy structures for the dicarbonyl [MePFe2(CO)2Cp2] are triplet or quintet spin state structures whereas the 6 lowest energy structures for the ruthenium analogue [MePRu2(CO)2Cp2] are all singlet structures. These low-energy singlet [MePRu2(CO)2Cp2] structures include species in which both ruthenium atoms attain the favored 18-electron configurations in different ways: either by a Ru-Ru single bond and an agostic C-H-Ru interaction from the methyl group, a Ru-Ru single bond and a four-electron donor bridging MeP ligand with P Ru double bonds, or a formal Ru Ru double bond with a two-electron donor bridging MeP ligand. The 8 lowest energy structures for the diiron monocarbonyl [MePFe2(CO)Cp2] are all triplet or quintet spin structures whereas the lowest energy structure for the diruthenium monocarbonyl [MePRu2(CO)Cp2] by more than 20 kcal mol-1 is a singlet structure with a formal Ru Ru double bond and bridging CO and four-electron donor MeP groups. Thermochemical information predicts such monocarbonyl derivatives to be the dominant binuclear decarbonylation products of the tricarbonyls [RPRu2(CO)3Cp2] by thermal or photochemical methods. [ABSTRACT FROM AUTHOR]

Three dinuclear dysprosium complexes 1–3 with structural formulas [Dy2(bptz)(tta)6]·2CH2Cl2 (1), [Dy2(H2bmtz)(tta)6] (2) and [Dy2(H2bmtz)(hfac)6(H2O)2] (3) (bptz = 3,6-di(2-pyridyl)-1,2,4,5-tetrazine, H2bmtz = 3,6-di(2-pyrimidyl)-1,4-dihydro-1,2,4,5-tetrazine, tta = 2-thenoyltrifluoroacetonate, hfac = hexafluoroacetylacetonate) were synthesized by the use of two tetrazine derivative ligands containing six and eight nitrogen atoms in combination with β-diketonate co-ligands, which are a good research platform to study the synergistic influence of the local coordination environment and magnetic interaction on magnetic relaxation. Complexes 1 and 2 possess the same peripheral co-ligands and nearly the same coordination environment (approaching an ideal triangular dodecahedron), but different multi-nitrogen bridges involving N6 (bptz) and N8 (H2bmtz) tetrazine derivatives. The structural difference leads to distinct magnetic relaxation properties with a hysteresis temperature of 2.5 K and 5.5 K at a rate of 200 Oe s−1 in 1 and 2, respectively, which is most likely due to the different magnetic coupling transmitted by H2bmtz and bptz in the direction close to the vertical magneto axis. Combined with a suitable local coordination environment, the energy barrier of complex 2 bridged by H2bmtz can reach three times that of complex 3. Considering the local ligand field, the important influence of this multi-nitrogen bridge transmitting magnetic coupling on the SMM properties is demonstrated with the aid of ab initio calculations. Also of note is that complexes 2 and 3 are the first reported lanthanide SMMs constructed from dihydro-tetrazine. [ABSTRACT FROM AUTHOR]

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]

Stimuli-responsive luminescent materials can be used to design anti-counterfeit barcodes because even small changes in environmental conditions, such as temperature or the molecules present, can lead to changes in the fluorescence behavior of the materials, enabling dynamic information encoding. Metal–organic frameworks (MOFs) are promising materials for the design of stimuli-responsive barcodes, as their modular structure allows fine tuning of the fluorescence, which in turn can be switched in response to external stimuli. In this work, we present a humidity-responsive fluorescent barcode prototype based on europium- and cobalt-modified MOF-808, which exhibits fluorescence switching in response to changes in relative humidity. The combination of cobalt and europium cations in the same material, along with the coordination ligands on the cobalt cations, are crucial for the functionality of this barcode. By selectively suppressing the fluorescence of europium through the absorption of cobalt complexes in the same energy range, the initial fluorescence intensity of the material can be adjusted. The additional coordination of water molecules to the cobalt centers leads to the formation of cobalt complexes with higher ligand field splitting energy, resulting in a stepwise reactivation of the emission of the europium cations. This can be readily accomplished by exposing the material to different relative humidities. As a result, the barcode provides a higher level of security, as its decoding must be performed under controlled atmospheric conditions, and it is user-friendly since no harmful chemicals are required during the reading process. Additionally, the initial state must be restored before each decoding by heating, as the fluorescence changes dynamically according to the environmental conditions. These characteristics of the material underline the anti-counterfeiting capabilities of the barcode. [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]

Conventionally, octahedral (Oh) coordination symmetry of lanthanide centers is not ideal for constructing high-performance single-molecule magnets (SMMs). However, introducing a strong ligand field in the axial direction to increase crystal field splitting can potentially overcome this limitation. Herein, we successfully obtained two dysprosium(III) single-molecule magnets, [Dy(OCtBu3)X2(py)3] (X = Cl (1), I (2), py = pyridine), in Oh coordination symmetry. The two complexes differ only in the coordinating anions on the equatorial plane, yet their magnetic performances are distinctly different. When chloride is replaced by a weaker donor iodide, the energy barrier is dramatically improved from 29 cm−1 (1) to 860 cm−1 (2), highlighting the importance of weakening the transverse ligand field and maximizing the axial ligand field for high-performance SMMs. [ABSTRACT FROM AUTHOR]

Organometallic dysprosocenium-based molecular magnets are the forefront runners in offering giant magnetic anisotropy and blocking temperatures close to the boiling point of liquid nitrogen. Attaining linearity in the organometallic dysprosocenium complexes is the key to generating giant magnetic anisotropy and blocking barriers. In the present study, we have unravelled the coordination ability of the substituted fullerene (C55X5)− (where X = CCH3, B, and N) generated by fencing around the five-membered ring of fullerene towards stabilizing a new family of exohedral dysprosium organometallic complexes showcasing giant magnetic anisotropy and blockade barriers. Eight exohedral mononuclear dysprosium organometallic complexes, namely [Dy(η5-C55X5)(η4-C4H4)] (1), [Dy(η5-C55X5)(η5-Cp)]+ (2), [Dy(η5-C55X5)(η5-Cp*)]+ (3), [Dy(η5-C55X5)(η6-C6H6)]2+ (4), [Dy(η5-C55X5)(η8-C8H8)] (5), [Dy(η5-C55X5)2]+ (6) (where X = CCH3), [Dy(η5-C55B5)2]+ (7) and [Dy(η5-C55N5)2]+ (8), were studied using scalar relativistic density functional theory (SR-DFT) and the complete active space self-consistent field (CASSCF) methodology to shed light on the structure, stability, bonding and single-ion magnetic properties. SR-DFT calculations predict complexes 1–8 to be highly stable, with a strictly linear geometry around the Dy(III) ion in complexes 6–8. Energy Decomposition Analysis (EDA) predicts the following order for interaction energy (ΔEint value): 5 > 1 > 2 ≈ 3 > 6 > 7 > 8 > 4, with sizable 4f-ligand covalency in all the complexes. CASSCF calculations on complexes 1–8 predict stabilization of mJ ‖±15/2〉 as the ground state for all the complexes except for 5, with the following trend in the Ucal values: 6 (1573 cm−1) ≈ 3 (1569 cm−1) > 1 (1538 cm−1) > 8 (1347 cm−1) > 2 (1305 cm−1) > 7 (1284 cm−1) > 4 (1125 cm−1) > 5 (108 cm−1). Ab initio ligand field theory (AILFT) analysis provides a rationale for Ucal ordering, where π-type 4f-ligand interactions in complexes 1–4 and 6–8 offer giant barrier height while the large (C8H8)2− rings generate δ-type interaction in 5, which diminishes the axiality in the ligand field. Our detailed finding suggests that the exohedral organometallic dysprosocenium complexes are more linear compared to bent [DyCp*2]+ cations and display a giant barrier height exceeding 1500 cm−1 with negligible quantum tunnelling of magnetization (QTM) – a new approach to design highly anisotropic dysprosium organometallic complexes. [ABSTRACT FROM AUTHOR]

In recent years, the electronic structures of organocuprates in general and the complex [Cu(CF3)4]− in particular have attracted significant interest. A possible key indicator in this context is the reactivity of these species. Nonetheless, this aspect has received only limited attention. Here, we systematically study the series of tetra‐alkyl cuprates [MenCu(CF3)4−n]− and their unimolecular reactivity in the gas phase, which includes concerted formal reductive eliminations as well as radical losses. Through computational studies, we characterize the electronic structures of the complexes and show how these are connected to their reactivity. We find that all [MenCu(CF3)4−n]− ions feature inverted ligand fields and that the distinct reactivity patterns of the individual complexes arise from the interplay of different effects. [ABSTRACT FROM AUTHOR]

The controllable formation of a built‐in electric field (IEF) can effectively separate photogenerated electrons and holes and optimize the band structure of a material, thus improving its photocatalytic performance. Here, a novel type of defective metal‐organic framework (MOF), i.e., an MIL‐125(Ti)@Ti‐Ce‐MOF yolk‐shell Z‐scheme heterojunction, is synthesized using a simple ion‐etching‐coupled reconstruction method. By controlling the concentration of ligand defects within the MOF heterojunction, the strength of the IEF within the heterojunction can be effectively regulated. Moreover, the experimental and theoretical results demonstrated that ligand defects within the Z‐scheme heterojunction structure can enhance the efficiency of photogenerated carrier separation and improve the transport capacity by regulating the IEF. The photocatalytic tetracycline (TC) degradation performance of the resultant MIL‐125(Ti)@Ti‐Ce‐MOF yolk‐shell heterojunction is ≈52.5‐ and 5.5‐fold higher than those of Ti‐Ce‐MOF and MIL‐125(Ti), respectively, indicating the efficient spatial charge separation due to the enhanced IEF. This study reveals the precise control of the IEF over the MIL‐125(Ti)@Ti‐Ce‐MOF yolk‐shell Z‐scheme heterojunction, elucidating the relationship between the IEF and ligand defect concentration and promoting the photocatalytic performances of MOF@MOF‐based catalysts via density functional theory and related experiments. [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]

Electron distribution and bonding in extended structures based on square planar gold complexes, traditionally classified as gold (III), have been addressed through solid‐state DFT calculations. The band structure analysis, taken as a diagnostic tool, highlighted that, when the metal is associated with chalcogen atoms, the gold centers are more electron rich than the classic accepted description. This is in agreement with the Inverted Ligand Field (ILF) theory that predicts a metal center d10 configuration with two electrons vacancy on the orbital combinations of the ligands for sulfur, selenium and tellurium cases. A covalent bond is featured in oxygen compounds, a borderline situation between the ILF and the classical Ligand Field description. In conclusion, the gold atom in chalcogenide square planar complexes should be considered electron richer than commonly thought applying the traditional rules for calculating the oxidation state. [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]

The electronic structure and related electronic properties of two novel isostructural octacyanometallates Cd2(H2O)4[MoIV(CN)8]·2H2O and Cd2(H2O)4[WIV(CN)8]·2H2O are described from a combined experimental and computational approach. The impact that the octacoordinated heavy metals W and Mo have on the electronic structure and optical response of isostructural materials whose electronic properties strongly depend on the crystal structure is discussed. It is found that the effect of the polarization power of the metal centers, combined with the ligand field of cyanos, produces considerable changes in the electronic structure and, consequently, in the band gap energy. The ab initio calculations, which were performed with generalized gradient PBE and hybrid HSE06 density functionals, accurately reproduce the electronic structure of [Mo(CN)8]4− and [W(CN)8]4− building units, revealing that the electronic transitions associated with the band gap energy have an origin in the charge transfer phenomena of metal to ligand nature. Moreover, the optical band gap transitions have an allowed indirect behavior in the Γ → M → D direction which is associated with the (x2 − y2) → π* transition. The allowed direct and indirect (experimental and theoretical) band gap energies together with the exciton effective masses are reported. [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]

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]

A well‐judged combination of a high axial ligand field and a bridging radical ligand in a dinuclear lanthanide complex provides a single‐molecule magnet with a higher effective energy barrier for magnetic relaxation and blocking temperature compared to its non‐radical analog due to significant magnetic exchange coupling between radical and Ln(III) ions. In this work, we report two chloranilate (CA) bridged dinuclear dysprosium complexes, [{(bbpen)Dy(μ2‐CA)Dy(bbpen)}] (1Dy) and [{(bbpen)Dy(μ2‐CA⋅)Dy(bbpen)}−{CoCp2}+] (2Dy), where 2Dy is the radical bridged Dy‐complex obtained via the chemical reduction of bridging CA moiety (H2bbpen=N,N′‐bis(2‐hydroxybenzyl)‐N,N′‐bis(2‐methylpyridyl)ethylenediamine). The presence of high electronegative phenoxide moiety enhances the axial anisotropy of pseudo‐square antiprismatic Dy(III) ions. The diffused spin of radical is efficiently coupled with anisotropic Dy(III) centres and decreases the quantum tunnelling of magnetization (QTM) in the magnetic relaxation process. The magnetic relaxation of 1Dy follows Orbach, Raman, and QTM processes whereas for 2Dy it follows Orbach and Raman Processes. Due to less involvement of the QTM relaxation process, 2Dy shows a higher thermal energy barrier (Ueff=700 K) and a high blocking temperature (6.7 K), compared to its non‐radical analog. Remarkably, the radical coupled 2Dy complex shows the highest energy barrier among the radical bridged Dy(III)‐based SMMs to date. [ABSTRACT FROM AUTHOR]

The slow bidirectional conversion and fast shuttling of lithium polysulfides (LiPSs) remain the main obstacles that inhibit the practical application of lithium sulfur batteries (LSBs). Here, by engineering the in‐spin state of spinel oxides, V doping‐induced hexagonal nanosheets (V‐Co3O4 NS) with intermediate spin state (IS, t2g5 eg1) can form stable bond order toward LiS* based on the ligand field theory and molecular orbital theory, thus effectively accelerating the sulfur conversion kinetics. Owing to these merits, the V‐Co3O4 NS modified separator base battery achieves a high areal capacity of 15.37 mAh cm−2 with sulfur loading of 15.4 mg cm−2, and it displays a low‐capacity attenuation of 0.015% each cycle at 3.0 C for 1900 cycles. [ABSTRACT FROM AUTHOR]

Numerous zinc complexes based on N‐ and O‐donor Schiff‐base ligands have shown great promise in the ring‐opening polymerization (ROP) of lactides, which are cyclic dimers of lactic acid, to produce poly(lactic acid) (PLA). This is primarily because zinc is a borderline metal, making it non‐cytotoxic, inexpensive, abundant, biocompatible, and environmentally safe. Additionally, Schiff‐based ligands offer stability, stereoselectivity, desirable electronic and steric environments, and resistance to impurities. As a result, zinc complexes are easy to synthesize, colourless, have high reactivity and solubility in organic solvents, and are manageable under typical circumstances. Furthermore, these complexes are free to adopt a variety of coordination numbers since zinc does not have ligand field stabilization energy (LFSC). Zinc complexes possess high catalytic activity due to their distinctive properties, including high Lewis acidity, high electron transfer ability, stability concerning the reactive intermediate, and the ability to monitor polymerization by nuclear magnetic resonance (NMR) spectroscopy. Moreover, these complexes also have reasonable control over stereochemistry, number‐average molecular weight (Mn), and dispersity index (Ð). These advantages make it possible to produce colourless PLA with a high yield, high molecular weight, and narrow dispersity index in bulk and solvent‐based conditions. [ABSTRACT FROM AUTHOR]

A new Co(II) complex, [Co(NCS)2(L)2] (1) has been synthesized based on levamisole (L) as a new ligand. Single‐crystal X‐ray diffraction analyses confirm that the Co(II) ion is having a distorted tetrahedral coordination geometry in the complex. Notably strong intramolecular S⋅⋅⋅S and S⋅⋅⋅N interactions has been confirmed by employing Quantum Theory of Atoms in Molecules (QTAIM). These intramolecular interactions occur among the sulfur and nitrogen atoms of the levamisole ligands and also the nitrogen atoms of the thiocyanate. Direct current (dc) magnetic analyses reveal presence of zero field splitting (ZFS) and large magnetic anisotropy on Co(II). Detailed ab initio ligand field theory calculations quantitatively predicted the magnitude of ZFS. Prominent field‐induced single‐ion magnet (SIM) behavior was observed for 1 from dynamic magnetization measurements. Slow magnetic relaxation follows an Orbach mechanism with the effective energy barrier Ueff=29.6 (7) K and relaxation time τo=1.4 (4)×10−9 s. [ABSTRACT FROM AUTHOR]

The isoelectronic molecules UN and UO+ are known to have Ω = 3.5 and Ω = 4.5 ground states, respectively (where Ω is the unsigned projection of the electronic angular momentum along the internuclear axis). A ligand field theory model has been proposed to account for the difference [Matthew and Morse, J. Chem. Phys. 138, 184303 (2013)]. The ground state of UO+ arises from the U3+(5f3(4I4.5))O2− configuration. Owing to the higher nominal charge of the N3− ligand, the U3+ ion in UN is stabilized by promoting one of the 5f electrons to the more polarizable 7s orbital, reducing the repulsive interaction with the ligand and rendering U3+(5f27s(4H3.5))N3− the lowest energy configuration. In the present work, we have advanced the characterization of the UN ground state through studies of two electronic transitions, [18.35]4.5-X(1)3.5 and [18.63]4.5-X(1)3.5, using sub-Doppler laser excitation techniques with fluorescence detection. Spectra were recorded under field-free conditions and in the presence of static electric or magnetic fields. The ground state electric dipole moment [μ = 4.30(2) D] and magnetic ge-factor [2.160(9)] were determined from these data. These values were both consistent with the 5f27s configurational assignment. Dispersed fluorescence measurements were used to determine vibrational constants for the ground and first electronically excited states. Electric dipole moments and magnetic ge-factors are also reported for the higher-energy electronically excited states. [ABSTRACT FROM AUTHOR]

Molecular magnets have received significant attention because of their potential applications in quantum information and quantum computing. A delicate balance of electron correlation, spin–orbit coupling (SOC), ligand field splitting, and other effects produces a persistent magnetic moment within each molecular magnet unit. The discovery and design of molecular magnets with improved functionalities would be greatly aided by accurate computations. However, the competition among the different effects poses a challenge for theoretical treatments. Electron correlation plays a central role since d- or f-element ions, which provide the magnetic states in molecular magnets, often require explicit many-body treatments. SOC, which expands the dimensionality of the Hilbert space, can also lead to non-perturbative effects in the presence of strong interaction. Furthermore, molecular magnets are large, with tens of atoms in even the smallest systems. We show how an ab initio treatment of molecular magnets can be achieved with auxiliary-field quantum Monte Carlo, in which electron correlation, SOC, and material specificity are included accurately and on an equal footing. The approach is demonstrated by an application to compute the zero-field splitting of a locally linear Co2+ complex. [ABSTRACT FROM AUTHOR]

Herein, we report the syntheses, crystal structures, and magnetic properties of the title compounds [Fe(III)L2]Cl·CH3OH, 1 and [Fe(III)L2]NH(C2H5)3, 2 formulated from pyrazolone-based thiosemicarbazone ligand (L) at room temperature. Structurally, the Fe(III) spin centre was chelated under N2O2S2 coordination environment and then completed by charge-neutralizing counter ions for charge balance, i.e., the anion chloride (Cl−) for 1 and the cation triethylammonium (NH(C2H5)3+) for 2. Interestingly, the counter ions guided extended arrangement facilitated by halogen bonding of the Cl− and hydrogen bonding of the NH(C2H5)3+ were mainly responsible for obtaining the diamond- and hexagonal-shaped spin centre arrangements for 1 and 2, respectively. Magnetic examination revealed that both compounds are high-spin (HS) at all the measurement temperature ranges, and the experimental bond distances (at 300 K) were also in good agreement for the HS state. Strong ligand field chemical modification on the ligand that stabilizes the low spin (LS) state is suggested to realize the spin crossover (SCO) phenomenon. Moreover, further biological and catalytic investigation of the reported new compounds is suggested, as thiosemicarbazone-containing HS metal complexes are good candidates for these applications. [ABSTRACT FROM AUTHOR]

Understanding the electronic structure of active sites is crucial in efficient catalyst design. The spin state, spin configurations of d-electrons, has been frequently discussed recently. However, its systematic depiction in electrocatalysis is lacking. In this tutorial review, a comprehensive interpretation of the spin state of metal centers in electrocatalysts and its role in electrocatalysis is provided. This review starts with the basics of spin states, including molecular field theory, crystal field theory, and ligand field theory. It further introduces the differences in low spin, intermediate spin, and high spin, and intrinsic factors affecting the spin state. Popular characterization techniques and modeling approaches that can reveal the spin state, such as X-ray absorption microscopy, electron spin resonance spectroscopy, Mössbauer spectroscopy, and density functional theory (DFT) calculations, are introduced as well with examples from the literature. The examples include the most recent progress in tuning the spin state of metal centers for various reactions, e.g., the oxygen evolution reaction, oxygen reduction reaction, hydrogen evolution reaction, carbon dioxide reduction reaction, nitrogen reduction reaction, nitrate reduction reaction, and urea oxidation reaction. Challenges and potential implications for future research related to the spin state are discussed at the end. [ABSTRACT FROM AUTHOR]

The trans influence of anionic ligands on the nature of the cobalt–carbon bond in trans-[Co(TIM)RX]+-type complexes (R is a C-bound ligand and TIM is 2,3,9,10-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene) was probed through the incorporation of cyanide as the second monoanionic axial ligand (X). Salt metathesis reactions between KCN and the corresponding halide precursors readily generate trans-[Co(TIM)(C(CH2)Ph)(CN)]+ (1), trans-[Co(TIM′′)(C(CH3)C6H4-4-tBu)(CN)]+ (2, TIM′′ is the reduced TIM derivative following the formation of an aza-cobalt-cyclopropane moiety), and trans-[Co(TIM)(CH3)(CN)]+ (3). The molecular structures of 1 and 2 were established via single-crystal X-ray diffraction studies. FT-IR spectroscopy revealed a red-shift in the ν(C≡N) stretching frequency from 1 to 3 to 2. The absorption spectra of 1–3 exhibit d–d bands which are substantially blue-shifted from their halide precursors as a result of the enhanced ligand field imbued by the cyanide. Cyclic voltammograms of 1 and 3 consist of an irreversible Co4+/3+ oxidation and an irreversible Co3+/2+ reduction. In 2, a reversible Co-centered reduction is observed at −1.75 V vs. Fc1+/0. Also reported are the crystal structures of trans-[Co(TIM)(CN)2]PF6 (4), trans-[Co(TIM)(CH3)I]PF6 (5) and trans-[Co(TIM)(CH3)2]PF6 (6). The π-accepting capabilities of the cyanide reduce the dπ(Co)-π*(imine) backdonation in 4, while the solely strong σ-donating nature of the –CH3 ligands in 6 exerts a large trans influence and significantly increases the Co-TIM interactions. [ABSTRACT FROM AUTHOR]

In the present work, we have explored a series of unsaturated hexa-18-crown-6 (U18C6) ligands towards designing highly anisotropic Dy(III) based single-ion magnets (SIMs) with the general formula [Dy(U18C6)X2]+ (where U18C6 = [C12H12O6] (1), [C12H12S6] (2), [C12H12Se6] (3), [C12H12O4S2] (4), [C12H12O4Se2] (5) and X = F, Cl, Br, I, OtBu and OSiPh3). By analysing the electronic structure, bonding and magnetic properties, we find that the U18C6 ligands prefer stabilising the highly symmetric eight-coordinated hexagonal bipyramidal geometry (HBPY-8), which is the source of the near-Ising type anisotropy in all the [Dy(U18C6)X2]+ complexes. Moreover, the ability of sulfur/selenium substituted U18C6 ligands to stabilize the highly anisotropic HBPY-8 geometry makes them more promising towards engineering the equatorial ligand field compared to substituted saturated 18C6 ligands where the exodentate arrangement of the S lone pairs results in low symmetry. Magnetic relaxation analysis predicts a record barrier height over 2700 K for [Dy(C12H12O6)F2]+ and [Dy(C12H12S6)X2]+ (where X = F, OtBu and OSiPh3) complexes, nearly 23% higher than those of the top performing Dy(III) based SIMs in the literature. [ABSTRACT FROM AUTHOR]

The combination of planar‐directing, strong‐field [N4] ligands with a weak axial field component is known to stabilize five‐coordinate iron(III) complexes in otherwise uncommon spin states. In this work, a series of axially perturbed iron(III) complexes of an [N4] macrocyclic ligand of the Jäger type, [Fe(L)X] (with X: Cl, Br, I, NCS) gave intermediate‐spin ground states with axially steered admixture of the high‐spin state, S=3/2; 5/2. The nature of the electronic ground‐state as deduced from SQUID magnetometry, 57Fe Mössbauer spectroscopy in the solid, and 1H NMR and EPR spectroscopies in (frozen) solutions was discussed in the light of the solid‐state structures, which were obtained from single‐crystal X‐ray diffraction. A DFT‐based protocol was established to quantify the axial field effects and, by including relevant [N4] systems, predict the differential equatorial ligand field components. [ABSTRACT FROM AUTHOR]

Two lanthanide complexes with formulae [DyIII(LN5)(pentafluoro-PhO)3] (1) and [DyIII(LN5)(2,6-difluoro-PhO)2](BPh4) (2) (LN5 = 2,14-dimethyl-3,6,10,13,19-pentaazabicyclo[13.3.1]nonadecal (19),2,13,15,17-pentaene) were structurally and magnetically characterized. DyIII ions lie in the cavity of a five coordinate nitrogen macrocycle, and in combination with the introduction of multi-fluorinated monodentate phenoxyl coligands a high axiality coordination symmetry is built. Using the pentafluorophenol co-ligand, complex 1 with a D2d coordination environment, is obtained and displays moderate single-molecule magnets (SMMs) behavior. When difluorophenol co-ligands were used, a higher local axisymmetric pentagonal bipyramidal coordination geometry was observed in complex 2, which displays apparent slow magnetic relaxation behavior with a hysteresis temperature of up to 5 K. Further magnetic studies of diluted samples combined with ab initio calculations indicate that the high axiality plays a crucial role in suppressing quantum tunneling of magnetization (QTM) and consequently results in good slow magnetic relaxation behavior. Different fluoro-substituted phenoxyl co-ligands have phenoloxy oxygen atoms with different electrostatic potentials as well as a different number of phenoloxy coligands along the magnetic axis, resulting in different ligand field strengths and coordination symmetries. [ABSTRACT FROM AUTHOR]

Four new tetradentate Schiff-base ligands were prepared in situ from the 1 : 2 condensation of 1,3-diaminopropane and either 2-thiazolecarboxaldehyde (L2thiazole), 4-thiazolecarboxaldehyde (L4thiazole), 4-oxazolecarboxaldehyde (L4oxazole), or 5-bromopyridine-2-aldehyde (L5Br-pyridine), and complexed with [Fe(NCS)2(pyridine)4] to give four monometallic FeII complexes, [Fe(Lheterocycle)(NCS)2]. Structural characterisation shows the expected octahedral FeII centres in all cases, with Lheterocycle occupying the equatorial plane and the two thiocyanate ligands trans to each other, resulting in an N6 coordination sphere. Solid state magnetic measurements showed that the two complexes with the thiazole-based ligands exhibit the beginning of a spin transition above 300 K, with T1/2 = 350 K for [Fe(L4thiazole)(NCS)2] and 400 K for [Fe(L2thiazole)(NCS)2], whereas the 4-oxazole-based ligand gives [Fe(L4oxazole)(NCS)2] which remains high spin at all measured temperatures (50–400 K). Interestingly, [Fe(L5Br-pyridine)(NCS)2] crystallised as two solvent-free polymorphs: magnetic measurements on samples with both polymorphs present showed a two step SCO with an abrupt transition at T1/2 = 245 K assigned to the transition in polymorph A (as this was also seen in a sample of pure polymorph A), and a gradual transition at T1/2 = 304 K assigned to polymorph B. These findings show that the order of increasing ligand field strength for these heterocycles is 4-oxazole ≪ 5Br-pyridine < 4-thiazole < 2-thiazole. [ABSTRACT FROM AUTHOR]

The electronic structure of [OsF6]2− and PtF6 complexes was studied by means of CASSCF/NEVPT2 multiconfigurational calculations, including spin–orbital coupling, which is very relevant in the case of these metals. From these calculations, it is possible to establish that in the octahedral symmetry (Oh), the ground state is non-magnetic (Jeff = 0) because of the strong ligand field, and the interaction with paramagnetic excited states is almost negligible, resulting in a non-magnetic behavior, which is in agreement with the experimental evidence. [ABSTRACT FROM AUTHOR]

Three new hetero-metallic CuII-LnIII complexes [(CuL)Gd(NO3)3(CH3OH)]n (1), [(CuL)Tb(NO3)3(H2O)]· [CuL] (2) and [(CuL)Dy(NO3)3(H2O)]·[CuL] (3) have been synthesized using a mono-nuclear Cu(II) complex, [CuL], of an unsymmetrically di-condensed N2O3 donor Schiff base ligand, N-(3-methoxysalicylidene)-N-(salicylidene)-1,2-ethylenediamine (H2L). Single crystal X-ray crystallography revealed that complex 1 is a nitrate bridged 1D chain of dinuclear Cu(II)-Gd(III) units whereas in 2 and 3, the dinuclear Cu(II)-Ln(III) units are co-crystallized with a [CuL] unit. The Ln(III) centers are nine coordinated with the geometry of a spherical capped square antiprism for Gd and spherical tricapped trigonal prism for Tb and Dy. The geometry of the Cu(II) center is distorted octahedral for complex 1 and distorted square planar for complexes 2 and 3. Temperature-dependent molar magnetic susceptibility measurements in 1-3 revealed the presence of overall ferromagnetic coupling between the Cu(II) and Ln(III) centers. Notably, field induced single-molecule magnet behavior was witnessed in the Tb(III) derivative (2). The ab initio calculations indicated that upon application of an external magnetic field, the tunneling in the ground state of complex 2 gets reduced and thereby field-induced SMM behaviour is observed. Besides, in the case of complex 1, BS-DFT calculations were carried out to gain further insights into the magnetic exchange coupling interactions between the Cu(II) and Gd(III) centers. [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 article provides an overview of the progress and challenges in the field of nickel-catalyzed C–H activation. It emphasizes the importance of this process in converting readily available chemicals into valuable small molecules. The authors compare nickel and palladium catalysts, discussing their reactivity and mechanistic features. The article also highlights the need for further research to understand the mechanisms involved and to develop more efficient transformations. It explores the use of different bases and directing groups, as well as the thermochemical properties and selectivity of the reactions. The text includes examples of primary C-H activation reactions and discusses recent developments in this area. It also addresses the limitations and future directions for research, such as the preference for methyl groups and the exploration of more remote C-H groups. [Extracted from the article]

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]

Here, we combined magnetometry, multi‐frequency electronic paramagnetic resonance, and wave function based ab initio calculations to investigate magnetic properties of two high spin Co(II) complexes Co(BDPRP) (BDPRP=2,6‐bis((2‐(S)‐di(4‐R)phenylhydroxylmethyl‐1‐pyrrolidi‐nyl)methyl)pyridine, R=H for 8; R=tBu for 9). Complexes 8 and 9 featuring effective D3h symmetry were found to possess D=24.0 and 32.0 cm−1, respectively, in their S=3/2 ground states of 1e''dxz/yz41e'dxy/x2-y221a1'dz21 ${{\left(1{{\rm e}}^{{\rm { {^\prime}}}{\rm { {^\prime}}}}\right({d}_{xz/yz}\left)\right)}^{4}{\left(1{{\rm e}}^{{\rm { {^\prime}}}}\right({d}_{{xy/{x}^{2}-y}^{2}}\left)\right)}^{2}{\left(1{{\rm a}}_{1}^{{\rm { {^\prime}}}}\right({d}_{{z}^{2}}\left)\right)}^{1}}$. Ligand field analyses revealed that the low‐lying d‐d excited states make either positive or vanishing contributions to D. Hence, total positive D values were measured for 8 and 9, as well as related D3h high spin Co(II) complexes. In contrast, negative D values are usually observed for C3v congeners. In‐depth analyses suggested that lowering symmetry from D3h to C3v induces orbital mixing between 1edxz/yz ${1{\rm e}\left({d}_{xz/yz}\right)}$ and 2edxy/x2-y2 ${2{\rm e}\left({d}_{{xy/{x}^{2}-y}^{2}}\right)}$ and admixes excited state 4A21e→2e ${{}^{4}{{\rm A}}_{2}\left(1e\to 2e\right)}$ into the ground state. Both factors turn the total D value progressively negative with the increasing distance (δ) of the Co(II) center out of the equatorial plane. Therefore, δ determines the sign and magnitude of final D values of five‐coordinate trigonal bipyramidal S=3/2 Co(II) complexes as measured for a series of such species with varying δ. [ABSTRACT FROM AUTHOR]

We employed density functional theory to investigate Co-N4/Gra single-atom catalysts, focusing on the modification of axial ligand (X=-F, -CN and -C3H4N2) and examined the influence of ligand field and electric potential on eNORR. Our results demonstrate that Co-N4[X]/Gra exhibit favorable thermodynamic adsorption (Δ G *NO < 0) and remarkable activation activity toward NO molecules. Co-N4/Gra demonstrates a limiting potential of −0.13 V with the potential-determining step (PDS) of *NH3 → * + NH3(g). Notably, under the introduction of ligands, Co-N4[F]/Gra achieves the most favorable overpotential of −0.07 V, superior to most of NORR electrocatalysts, and meanwhile shows an exceptional selectivity of 99.99% for eNORR compared to competitive hydrogen evolution reaction. Under the solvent environment, Co-N4/Gra features the triggering potentials of −0.33 V for a pH of 1, −0.71 V for a pH of 7, and −1.10 V vs RHE for a pH of 13, respectively. Additionally, the potential reduces the desorption energy and adsorption energy of NH3, facilitating the accessibility of the NH3 desorption step (PDS) and promoting NO reduction. Thus, under realistic conditions, the Co ion's active site displays variable valence electrons and forms a dynamic interplay with the ligand field effect, rendering a crucial effect on the adsorption of reaction species during the eNORR. [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 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]

Metal complexes are pivotal in diverse fields due to their wide array of functionalities, including magnetism, conductivity, and photoresponsiveness. These functionalities are intricately linked to the phenomenon of ligand field splitting, yet controlling the magnitude of this splitting within metal complexes presents a significant challenge. This study aims to address this challenge by developing a novel 2D spectrochemical series, integrating two critical parameters: metal ions and ligands. Employing the DV-Xα molecular orbital method, we directly calculated ligand field splitting width, enabling a detailed assessment of energy splitting trends. Our results reveal that the magnitude of ligand field splitting, encompassing 17 metal types and 29 ligand types, can be precisely controlled. This represents a significant advancement over traditional spectrochemical series, such as those proposed by R. Tsuchida, which predominantly focus on either ligands or metals in isolation. Additionally, our study extends to the calculation of spin states in these metal complexes, contributing valuable insights for the development of magnetic materials. We demonstrate that the relative ligand field splitting and spin polarization can be used to predict spin states, offering a new perspective in material design and functionality. These findings not only enhance our understanding of ligand field splitting in metal complexes but also provide a comprehensive framework for predicting their electronic and magnetic properties, paving the way for innovative applications in material science and coordination chemistry. [ABSTRACT FROM AUTHOR]

A simple glass system [Li2O–B2O3–NiO] was prepared via the melt-quenching method. This article attempts to outline the structural-optical relationships of Ni ions-bearing lithium borate glass. XRD confirmed the glassy nature of the samples. The increase in density confirmed the formation of a rigid network constructed by BO 4 units. Infrared spectra analysis confirmed a strong structure conversion from BO 3 to BO 4 units, with observed mitigation in non-bridging oxygen bonds. Optical absorbance spectra were analyzed to extract optical features. Nickel ions were exploited to disclose the surrounding environment in glass. A set of optical transitions of nickel ions in octahedral forms were assigned at 1287, 815, 487 and 425 nm, which are exploited to probe ligand field effects. A decrease in splitting energy values and increased interelectronic repulsion values were obtained. This is owing to the weak intensity of the interaction of Ni ions with surrounding ligands and the localization of d-electrons, respectively. These variations led to a strong enhancement in the ionicity of bonding nature. Furthermore, the brown color of the samples confirmed the occupancy of Ni 2 + in octahedral sites. Moreover, the indirect optical band gap increased due to the harsh reduction in NBO. These findings pave the way toward developing optical materials with the desired optical features. [ABSTRACT FROM AUTHOR]

Magnetic lanthanide (Ln) metal complexes exhibiting magnetic bistability can behave as molecular nanomagnets, also known as single-molecule magnets (SMMs), suitable for storing magnetic information at the molecular level, thus attracting extensive interest in the quest for high-density information storage and quantum information technologies. Upon encapsulating Ln ion(s) into fullerene cages, endohedral metallofullerenes (EMFs) have been proven as a promising and versatile platform to realize chemically robust SMMs, in which the magnetic properties are able to be readily tailored by altering the configurations of the encapsulated species and the host cages. In this review, we present critical discussions on the molecular structures and magnetic characterizations of EMF-SMMs, with the focus on their peculiar molecular and electronic structures and on the intriguing molecular magnetism arising from such structural uniqueness. In this context, different families of magnetic EMFs are summarized, including mononuclear EMF-SMMs wherein single-ion anisotropy is decisive, dinuclear clusterfullerenes whose magnetism is governed by intramolecular magnetic interaction, and radical-bridged dimetallic EMFs with high-spin ground states that arise from the strong ferromagnetic coupling. We then discuss how molecular assemblies of SMMs can be constructed, in a way that the original SMM behavior is either retained or altered in a controlled manner, thanks to the chemical robustness of EMFs. Finally, on the basis of understanding the structure–magnetic property correlation, we propose design strategies for high-performance EMF-SMMs by engineering ligand fields, electronic structures, magnetic interactions, and molecular vibrations that can couple to the spin states. [ABSTRACT FROM AUTHOR]

Cobalt(III) corroles are the most commonly studied types of metallocorroles, yet the details of their electronic structure, ground spin states and place of redox events are not always straightforward. Corroles are redox active, potentially non‐innocent ligands, and it has been found through various experimental and computational techniques, that the innocent or non‐innocent behavior is modulated by the apical ligands bound to the cobalt center. In this work, we aim to analyze the effect of corrole substituents and number and type of apical ligands on the electronic structure of cobalt corroles through density functional and wavefunction theories, and to determine the relative energies between closed‐ and open‐shell states. We further perform preliminary analyses on the place of electron abstraction upon oxidation and on the effect of the corrole and apical ligands on the cobalt ligand field splittings. We find that both ligand field and electron‐donating or withdrawing effects determine the relative energies of open‐shell and closed shell singlet states. [ABSTRACT FROM AUTHOR]

Herein, we report for the first time the use of the nitrogen‐based bidentate molecule [2.2]pyridinophane (N2) as a ligand for metal complexes. Additionally, its improved synthesis allows for electronic modification of the pyridine rings to access the new para‐dimethylamino‐[2.2]pyridinophane ligand (p‐NMe2N2). These ligands bind nickel in an analogous fashion to other pyridinophane ligands, completing the series of tetra‐, tri‐, and bidentate pyridinophane‐nickel complexes. The new compounds exhibit geometrically enforced C−H anagostic interactions between the ethylene bridge protons and the nickel center that are not present in other pyridinophane systems. These ethylene bridge groups also act as an unusual form of steric encumbrance, enforcing square planar geometries in ligand fields that would otherwise adopt tetrahedral structures. In addition, these anagostic interactions inhibit the catalytic performance in Csp3–Csp3 Kumada cross coupling reactions relative to other common bidentate N‐ligand platforms, possibly by preventing the formation of the 5‐coordinate oxidative addition intermediates. [ABSTRACT FROM AUTHOR]

The copper(II)-ammonia coordination ion represents a quintessential model for understanding the coordination equilibrium and distribution characteristics of coordination compounds in the teaching of analytical chemistry. Current textbooks, however, often limit their scope to providing stability constants for select copperammonia coordination ions, without delving into the correlation between their coordination numbers and stability. This study leverages density functional theory to firstly establish a connection between the stability of copper-ammonia coordination ions and their coordination numbers, achieved through structural optimization. Subsequently, it offers a qualitative interpretation by examining the molecule spatial configuration, shedding light on the fundamental nature of these structures. This research not only enhances the effectiveness of pedagogical approaches, but also cultivates students' interest in the application of the theoretical calculations within the realm of analytical chemistry. [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]

We have synthesized the first silver(III) carbene complexes, (CF3)3Ag(NHC), by direct reaction of the silver(III) fluoride precursor complex [PPh4][(CF3)3AgF] with different imidazolium salts. This novel methodology circumvents the use of free NHC molecules. The silver(III) carbene complexes thus prepared are unprecedented and show remarkable thermal stabilities. They display square‐planar or square‐pyramidal geometry. Following our calculations, the electronic structure of a model representative complex exhibits Inverse Ligand Field (ILF). The compounds reported herein are synthetic analogues of the elusive difluorocarbene and carbonyl species proposed as intermediates in the acidic decomposition of [Ag(CF3)4]−. The synthetic procedure reported is envisaged to enable access to carbene complexes of other late transition‐metals in high oxidation states. [ABSTRACT FROM AUTHOR]

Monomeric [Co(SDZ)2phen] (1) and [Co(SDZ)(bq)Cl] (2) complexes (SDZ = sulfadiazine, phen = 1,10-phenanthroline, and bq = 2,2′-biquinoline) have been synthesized and characterized. X-ray diffraction studies indicate that SDZ acts as a bidentate ligand coordinating through the sulfonamide and the pyrimidine N atoms in both compounds. In complex 1, the coordination sphere consists of two SDZ ligands and a bis-chelating phen ligand, giving rise to a CoN6 coordination sphere. On the other hand, 2 has a CoN4Cl core, with two N-atoms from SDZ and two from the bq ligand. Both compounds have been studied by dc and ac magnetometry and shown to display slow magnetic relaxation under an optimum external dc field (1 kOe) at low temperatures. Moreover, compound 2 displays long range magnetic ordering provided by spin-canted antiferromagnetism, which has been characterized by further field-dependent magnetic susceptibility measurements, FC/ZFC curves, hysteresis loops and frequency-independent ac curves. The signs of the calculated D parameters, positive in 1 and negative in 2, have been rationalized according to the two lowest-lying transitions in the orbital energy diagrams derived from ab initio ligand field theory (AILFT). In a subsequent attempt to reveal the possible hidden zero-field SMM behaviour, Ni(II)-based 3 and Co(II)-doped Ni(II)-based (with a Ni : Co ratio of 0.9 : 0.1) heterometallic compound 2Ni were synthesized. [ABSTRACT FROM AUTHOR]