Octahedral Geometry Research Articles

Catalytic Conversion of Levulinic Acid over Sn-BTC and Sn-H3-5-SIP Heterogeneous Acid Catalysts

This work presents the synthesis and characterization of materials that contain Sn metal clusters formed by ligands of trimesic acid (Sn-BTC) or 5-sulfobenzene-1,3-dicarboxylic acid (Sn-H3-5-SIP). These catalysts were used to convert levulinic acid with ethanol to produce ethyl levulinate under mild reaction conditions. The characterization results confirmed that Sn is mainly present in the cassiterite crystalline phase with a tetragonal rutile structure in octahedral and tetrahedral coordination in the materials. The assembly of trimesic acid (a hard base) with metal species (Sn) results in the formation of acid and thermally stable metal–organic frameworks. The use of 5-sulfobenzene-1,3-dicarboxylic acid instead of trimesic acid in the synthesis incorporates sulfonic groups in the material, enhancing the total acidity of the Sn-H3-5-SIP catalyst compared to the Sn-BTC material. The Sn-H3-5-SIP catalyst exhibited the highest catalytic activity when converting levulinic acid with ethanol, resulting in a turnover frequency (TOF) of 0.0495 s−1, which is a 50% increase compared to the TOF of the Sn-BTC catalyst (0.0329 s−1). This result can be attributed to its higher concentration of acid sites (2.23 ± 0.05 mmol H+/gcat) and specific area (139 m2/g). Thus, materials containing tin metal clusters and sulfonic groups are promising materials that could be used as catalysts for synthesizing ethyl levulinate under mild reaction conditions.

Synthesis, characterization, and antioxidant activity of novel diorganotin(IV) complexes derived from Ibuprofen-5-aminosalicylic acid ligand

This study focuses on the preparations of a new ligand prepared by the condensation reaction between two substances ibuprofen and 5-aminosalicylic acid, and complexes of di organotin(IV) salts were prepared using this produced ligand to yield the appropriate complexes. The generated compounds were identified using FTIR and elemental analysis, in addition (tin, proton and carbon) magnetic resonance (119Sn, 1H, and 13C, NMR). Octahedral geometry was suggested for the synthesized complexes based on the observations of the spectra. Two techniques were used to examine the antioxidant activity of the compounds: DPPH and CUPRAC. Because the tin element was present, the resultant complexes exhibited a higher rate of inhibition than the ligand. Di-methyltin-di-IAS also showed a greater effect as antioxidants than the other compounds. KEY WORDS: Diorganotin(IV), Antioxidant activity, Ligand (IAS), DPPH method, CUPRAC method Bull. Chem. Soc. Ethiop. 2025, 39(1), 101-110. DOI: https://dx.doi.org/10.4314/bcse.v39i1.8

Synthesis and structural studies on zinc(II) macrocyclic and hetrocyclic complexes derived from schiff base and mixed ligands of 1,4-dihydroquinoxaline-2,3-dione, orthophenylene diamine and hydroquinone

In this study two new zinc(II) complexes involving oxygen and nitrogen donor sequences derived from 1,4-dihydroquinoxaline-2,3-dione (QXD), o-phenylenediamine (OPD) and hydroquinone (HQ) were synthesized through a template procedure. The structural elucidation of these complexes was carried out using measurement of molar conductance in 1x10-3 M solution of DMSO and various spectral techniques; 1H and 13C NMR, FT-IR, UV-VIS and AAS. The results showed that the zinc(II) ion coordinates with the Schiff base ligands in octahedral geometry, leading to the formation of stable macrocyclic and heterocyclic structures. The cyclic ligand (L) was found to coordinate as NNNN donor, through four imine nitrogen atoms which were formed up on condensation of the –NH2 groups on o-phenylenediamine with C=O group on quinoxaline dione in a 2:2 mole ratio, in the presence of one mole equivalent of ZnCl2 in ethanol medium. It also indicates the formation of a new mixed ligand zinc(II) complex with an OO OO O O coordination around zinc(II). The study contributes to the understanding of the coordination chemistry of zinc(II) with Schiff bases and provides insights into the development of novel zinc-based complex compounds. KEY WORDS: Macrocyclic and mixed ligand, 1,4-Dihydroquinoxaline-2,3-dione, o-Phenylenediamine, Hydroquinone Bull. Chem. Soc. Ethiop. 2025, 39(1), 49-64. DOI: https://dx.doi.org/10.4314/bcse.v39i1.4

Quasi-1D Oxides as Electrocatalysts for Water-Splitting: Case Study of Sr9M2Mn5O21 (M = Co, Ni, Cu, Zn).

We have demonstrated that multimetal oxides with a quasi-1D structure can be effective electrocatalysts for water electrolysis. Four materials have been systematically investigated, namely, Sr9Co2Mn5O21, Sr9Ni2Mn5O21, Sr9Cu2Mn5O21, and Sr9Zn2Mn5O21, comprising 1D chains of face-sharing MnO6 octahedra and MO6 trigonal prisms (M = Co, Ni, Cu or Zn), which are held together by strontium ions located between the chains. These materials show a consistent trend in electrocatalytic properties for both half-reactions of water-splitting, i.e., oxygen evolution and hydrogen evolution reactions (OER and HER). In particular, Sr9Ni2Mn5O21 has an outstanding performance for OER, with an overpotential of 0.37 V, which is lower than those of many 3D and 2D oxides, and rivals the activity of noble metal catalysts, such as RuO2. This is important given that the OER is considered the bottleneck of the water-slitting process. Chronopotentiometry studies, combined with X-ray photoelectron spectroscopy (XPS) and X-ray diffraction experiments pre- and post-reaction, indicate that Sr9Ni2Mn5O21 is highly stable and retains its structural integrity upon electrocatalytic reactions. This study highlights the potential of quasi-1D oxides as active electrocatalysts for water-splitting.

Synthesis, characterization, and biological potential of 2-thiophene carbaldehyde o-phenylenediamine Schiff base and its Cr(II), Mn(II), and Fe(II) Complexes

A Schiff base was produced through the chemical reaction of 2-thiophene carbaldehyde with o-phenylenediamine. The corresponding metal (II) chlorides were refluxed with the Schiff base to produce the complexes of Cr (II), Mn (II), and Fe (II). These complexes were then characterized by elemental analysis, FT-IR, atomic absorption spectroscopy, solubility, melting/decomposition temperature, and magnetic susceptibility. The vibrational peak at 1622 cm̄1 in the FT-IR spectral data of the Schiff base was ascribed to the vibration frequencies of azomethine u(C=N). But in the complexes, it was discovered that the azomethine band shifted between 1614 and 1659 cm̄1 , suggesting that they were involved in the complexes’ creation. The complexes’ measured absorption bands in the range of 713–769 cm1 were attributed to the M–N bond, indicating the occurrence of metal–nitrogen bonds. The complexes exhibit non-electrolyte properties attributed to their low molar conductance values ranging from 8.00 to 29 Ohm̄1 cm̄ ²mol̄¹. The determination of the melting point of the Schiff base yielded 120 °C, while the decomposition temperature fell within the range of 149–160 °C for the complexes, indicating their thermal stability. Analysis of magnetic susceptibility indicated an octahedral geometry for all the complexes, with values ranging from 2.24 to 3.12 BM. The elemental should analysis of both the Schiff base and its metal (II) complexes for C, H, and N indicated a close agreement between observed and calculated percentages, suggesting a consistent 1:2 metal-Schiff base ratio across all complexes. The qualitative analysis of the compounds confirmed the presence of chloride, which was quantified and determined to range from 4.62% to 7.90%. The prepared Schiff base and its metal (II) complexes underwent evaluation for their antibacterial efficacy against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa, as well as their antifungal properties against Candida albicans and Aspergillus niger. The results of the experiments indicated that the metal complexes displayed notable antimicrobial effects.

Crystal structure of [Ni(OH2)6]Cl2·(18-crown-6)2·2H2O

The crystal structure of the title compound, hexaaquanickel(II) dichloride–1,4,7,10,13,16-hexaoxacyclooctadecane–water (1/2/2), [Ni(H2O)6]Cl2·2C12H24O6·2H2O, is reported. The asymmetric unit contains half of the Ni(OH2)6 moiety with a formula of C12H32ClNi0.50O10 at 105 K and triclinic (P 1) symmetry. The [Ni(OH2)6]2+ cation has close to ideal octahedral geometry with O—Ni—O bond angles that are within 3° of idealized values. The supramolecular structure includes hydrogen bonding between the water ligands, 18-crown-6 molecules, Cl− anions, and co-crystallized water solvent. Two crown ether molecules flank the [Ni(OH2)6]2+ molecule at the axial positions in a sandwich-like structure. The relatively symmetric hydrogen-bonding network is enabled by small Cl− counter-ions and likely influences the more idealized octahedral geometry of [Ni(OH2)6]2+.

The crystal structure of R3Fe0.1Ga1.6S7 chalcogenides (R – La, Ce, Pr and Tb)

The paper reports the study of the crystal structure of chalcogenides of the composition R3Fe0.1Ga1.6S7 (R = La, Ce, Pr and Tb) as promising materials predicted to possess interesting nonlinear optical and electrical properties. Samples of stoichiometric composition were synthesized by co-melting the elements in quartz containers evacuated to a residual pressure of 10–2 Pa at the maximum synthesis temperature of 1100 °C. The crystal structure of the chalcogenides La3Fe0.1Ga1.6S7 {a = 10.1884(6) Å, c = 6.0515(4) Å}, Ce3Fe0.1Ga1.6S7 {a = 10.0864(4) Å, c = 6.0440(3) Å}, Pr3Fe0.1Ga1.6S7 {a = 9.9853(3) Å, c = 6.0648(2) Å} and Tb3Fe0.1Ga1.6S7 {a = 9.6692(7) Å, c = 6.0799(5) Å} was studied by X-ray powder method. It was determined that the structure of the synthesized phases belongs to the hexagonal symmetry (La3CuSiS7 structure type; space group P63). The structure of the complex chalcogenides (A), (B), (C) and (D) is based on the R3Ga1.67S7 sulfides (R = La, Ce, Pr, and Tb) by substituting gallium atoms in the 2a sites with atoms of statistical mixture M1{0.57(2) Ga + 0.10(2) Fe}, M2{0.56(1) Ga + 0.10(2) Fe}, M3 {0.61(8) Ga + 0.09(1) Fe} and M4 {0.57(2) Ga + 0.10(2) Fe}, respectively. Rare earth atoms are localized in the 6c sites and center sulfur atoms to form trigonal prisms with an additional atom [R 3S13S21S3]. Atoms of statistical mixtures M1, M2, M3, M4 are localized in the 2a sites forming [M 6S2] octahedra. Ga atoms in the 2b sites are surrounded by four sulfur atoms [Ga 3S11S3].

Synthesis, Structural Characterization, Optical Properties, and Biological Potency of Co(II), Cu(II), and Cd(II) Complexes With Heterocyclic Thiosemicarbazide Ligand: Insights From Molecular Docking Studies

ABSTRACTA novel heterocyclic thiosemicarbazide ligand, [(Z)‐N‐(2‐oxoindolin‐3‐ylidene)nicotinohydrazide] (H2L), and its Co(II), Cu(II), and Cd(II) metal chelates were synthesized and characterized using a variety of analytical methods, including elemental analysis, FT‐IR, UV–Visible spectroscopy, EI‐mass, fluorescence spectroscopy, X‐ray powder diffraction, and TGA. The structures and geometries of the complexes were determined using these methods as [Co2(H2L)2Cl2(H2O)4]·2H2O, [Cu(H2L)2Cl2(H2O)2]·2H2O, and [Cd(H2L)2Cl2(H2O)2], all having octahedral geometry. The particulate diameters for [Co2(H2L)2Cl2(H2O)4]·2H2O, [Cu(H2L)2Cl2(H2O)2]·2H2O, and [Cd(H2L)2Cl2(H2O)2] were 192.68, 68.48, and 192.74 nm, respectively using Debye–Scherrer equation and FWHM approach. The corresponding FWHM values were 0.0078, 0.0217, and 0.0075, whereas the crystal strain was calculated as (ε) = 0.0018, 0.0056, and 0.0054, and the dislocation density (δ) as 2.69 × 10−5, 2.13 × 10−4, 2.69 × 10−5 Å−2. Quantum chemical calculations for the ligand and its solid metal complexes were carried out utilizing DFT with the DMOL3 module. Furthermore, the optical sensing response of the free ligand H2L to Co(II), Cu(II), and Cd(II) ions was investigated, revealing that the presence of these metal ions enhanced the fluorescence spectra of the ligand. Additionally, the antibacterial effects of these compounds, as well as their cytotoxicity in human cancer cells, were investigated. Compared to its metal complexes, the ligand, H2L exhibits increased antibacterial activity against various bacteria. Tests on HepG‐2 and MCF‐7 cells were conducted to evaluate the compounds' anticancer efficacy against the standard, Doxorubicin. The ligand, H2L, demonstrated greater cytotoxicity against the HepG‐2 cell line than its metal complexes. Docking experiments were conducted to assess the interaction of the ligand and its complexes with HepG‐2 (PDB ID: 2OH4) and MCF‐7 (PDB ID: 3W2S) cells, using the XP glide technique and Schrödinger suite software.

Synthesis and Spectral Studies of New Azomethine Metal Complexes With Biological Activity and Docking Studies Utilizing 3‐Methylpyridin‐2‐Amine as a Complexing Agent

ABSTRACTThe novel Schiff base, (Z)‐2‐(1‐((3‐methylpyridin‐2‐yl)imino)ethyl)phenol (HL), was synthesized by reacting 1‐(2‐hydroxyphenyl)ethanone with 3‐methylpyridin‐2‐amine. Metal complexes [M (L)n (H2O)2] (M = Co and Cu, n = 2) were synthesized and characterized utilizing various analytical techniques including UV–visible spectroscopy, FTIR, elemental analysis, molar conductance, 1H NMR, thermal analysis, and magnetic moment measurement. The findings indicated that the Co+2 and Cu+2 complexes exhibited octahedral geometries. In vitro biological activity testing was conducted to evaluate the antimicrobial potential of the complexes against Bacillus subtilis (B. subtilis) and Escherichia coli (E. coli) bacteria strains. Similarly, molecular docking was conducted to elucidate the interactions between the active sites of protein–metal complexes and dihydrofolate reductase as well as ferrochelatase.

Strategically Modified Ligand Incorporating Mixed Phosphonate and Carboxylate Groups to Enhance Performance in All‐Iron Redox Flow Batteries

AbstractIron redox flow batteries (Fe‐RFBs) hold significant promise for achieving cost‐effectiveness and utilizing abundant materials for stationary energy storage applications. Here, a design of a novel Fe complex utilizing a nitrogenous phosphonate/carboxylate mixed ligand, N,N‐Bis(phosphonomethyl)glycine (BMPG), is presented to achieve high performance Fe anolyte. Compared to its all‐phosphonate form, nitrilotri(methylphosphonic acid) (NTMPA), the new complex Fe(BPMG)2 demonstrates a negatively shifted redox potential, resulting in ≈0.07 V (≈10%) increase in battery output voltage. Full battery testing paired with ferrocyanide catholyte demonstrates stable cycling (capacity degradation <0.0001%/cycle) over 730 consecutive charge/discharge cycles with Coulombic Efficiency of 100% at a current density of 20 mA cm−2 under near neutral pH (≈8). Of particular interest, density functional theory (DFT) studies and operando Raman measurements provide strong evidence supporting a molecular structure in BPMG, which reveals the mixed phosphonate/carboxylate groups in BPMG maintain the octahedral coordination of the Fe ion center with phosphonates exclusively, while leaving the carboxylate unbound for both Fe(II) and Fe(III) complexes. This structural similarity between BPMG‐based Fe(II) and Fe(III) complexes effectively mitigates the slow redox reaction kinetics observed in Fe(NTMPA)2 anolyte, where significant ligand reorientation occurs between Fe(II) and Fe(III) complexes.

Bottom-up construction of chiral metal-peptide assemblies from metal cluster motifs.

The exploration of artificial metal-peptide assemblies (MPAs) is one of the most exciting fields because of their great potential for simulating the dynamics and functionality of natural proteins. However, unfavorable enthalpy changes make forming discrete complexes with large and adaptable cavities from flexible peptide ligands challenging. Here, we present a strategy integrating metal-cluster building blocks and peptides to create chiral metal-peptide assemblies and get a family of enantiopure [R-/S-Ni3L2]n (n = 2, 3, 6) MPAs, including the R-/S-Ni6L4 capsule, the S-Ni9L6 trigonal prism, and the R-/S-Ni18L12 octahedron cage. X-ray crystallography shows MPA formation reactions are highly solvent-condition-dependent, resulting in significant changes in ligand conformation and discrete cavity sizes. Moreover, we demonstrate that a structure transformation from Ni18L12 to Ni9L6 in the presence of benzopyrone molecules depends on the peptide conformational selection in crystallization. This work reveals that a metal-cluster building block approach enables facile bottom-up construction of artificial metal-peptide assemblies.

Copper-Based Electrochemical Sensor Derived from Thiosemicarbazide for Selective Detection of Neurotransmitter Dopamine.

This paper presents the synthesis of the ligand 1-picolinoyl-4-cyclohexyl-3-thiosemicarbazide (H2pctc) and new metal complexes [Ni(Hpctc)2] (1), [Cu(Hpctc)Cl] (2), and [Cd(Hpctc)2] (3). The synthesized metal complexes were precisely characterized using single crystal X-ray diffraction (SC-XRD). In addition, complexes 1-3 were also characterized by UV-vis, fluorescence, and infrared spectroscopy. SC-XRD data confirmed the distorted octahedral geometry around the Ni(II) and Cd(II) centers and the distorted square planar geometry around the Cu(II) center. Data derived from the emission spectra depict that higher fluorescence intensity was exhibited by complexes 1, 2, and 3 in comparison to that of the free ligand H2pctc, and complex 3 showed the maximum intensity. Further, these metal complex-modified GCEs (glassy carbon electrodes) were utilized for electrochemical sensing of dopamine (DPM). The electrochemical studies of these complexes were performed using modified glassy carbon electrodes supported by electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. In contrast to complexes 1 and 3, complex 2 is a superior electrode material with a high effective surface area for the electrochemical oxidation of DPM, according to the electrochemical response results. The derived sensor had a wide linear detection range of 1 to 1400 μM, an acceptable sensitivity of 0.01531 μA cm-2 μM-1, and a low LOD of 0.38 μM. The proposed approach was free of the interfering effects of ascorbic acid, uric acid, aminophenol, and other substances. During the successive scans, no fouling of the electrode surface was observed. The proposed electrochemical sensor had excellent stability, sensitivity, and a low detection limit making it suitable for the analysis of a variety of real samples. Additionally, it was proven to be useful for analyzing biological fluids.

Novel Co2+ and Cd2+ Complexes Derived From a New N‐Donor Pyridyl‐Functionalized Thiophosphoric Triamide Ligand: Structural Investigation, DNA/COVID‐19/Monkeypox Molecular Docking, and Biological Assays

ABSTRACTA thiophosphoric triamide (SPT) ligand P(S)[NH‐2Py]3 was synthesized and utilized as a ligand to make novel binuclear and mononuclear Co2+ and Cd2+ complexes. The compounds are the first examples of discrete chelate SPT complexes with a [N]3P(S)‐based backbone in which the SPT acts as a flexible tridentate N,N,N‐donor or N,N,O‐donor ligand. The metal cation features a hexacoordinate environment M(N)3(Cl)3/M(N)4(O)2 adopting a distorted octahedral geometry. Hirshfeld surface analysis affirms that the pyridinyl nitrogen is a more dominant H‐bond acceptor than the thiophosphoryl sulfur atom. The inhibitory activity against the MDA‐MB‐231 cancer cell line in vitro indicated a good inhibitory effect for all compounds. The mononuclear Co2+ complex showed a stronger inhibitory activity against cancer cells than other studied compounds with an IC50 of 62 ± 1.4 nM. Antioxidant and antihemolytic activity of the compounds showed appreciable performance with the highest activities for the Cd2+ complex. A computational DNA binding study by molecular docking indicated a good affinity of the compounds with the DNA receptor by a mixed mode of interactions. Docking was also performed on SARS‐CoV‐2 and monkeypox (Mpox), resulting in binding energies (−5.5 to −8.9 kcal/mol) that are competitive with current effective drugs.

Structural Aspects, Binding Interactions, Biological Activity of Co(II)‐ and Ni(II)‐N′‐(2‐fluorobenzoyl)benzo[d]thiazole‐2‐carbohydrazide Chelatess

ABSTRACTN′‐(2‐Fluorobenzoyl)benzo[d]thiazole‐2‐carbohydrazide (OFBBTCH, HL) and its chelates with Co(II) and Ni(II) have been synthesized and characterized by elemental analysis, liquid chromatography‐mass spectrometry (LC–MS), Fourier transform infrared spectroscopy (FT‐IR), ultra‐violet visible (UV–vis), nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA), and powder X‐ray diffraction. The conductance measurements reveal that the chelates are non‐electrolytic, and the spectral analysis indicates octahedral geometry of the chelates. The kinetic and thermodynamic parameters were obtained by Coats–Redfern relations, which shows positive Gibbs's free energy and negative entropy for both chelates. The equilibrium studies carried out by pH‐metry revealed the dissociation constant (pKa) of OFBBTCH as 8.13 and the formation of 1:1 and 1:2 Co(II)‐L and Ni(II)‐L complexes in solution. The CT‐DNA binding studies carried out by electron absorption, fluorescence quenching, steady state emissions and viscosity studies revealed hyperchromism and groove binding for HL and chelates. The Kb values calculated from electron absorption studies are 2.4 × 106, 4 × 106, and 9 × 106 M−1, from the fluorescence quenching studies Ksv values are 0.1722, 0.278, and 0.748 M−1, and Kapp values are 5.9 × 104, 1.3 × 105, and 2.9 × 105 M−1 for HL, Co(II)‐OFBBTCH and Ni(II)‐OFBBTCH, respectively. Bovine serum albumin (BSA) and human serum albumin (HSA) binding interactions were carried out by electron absorption and fluorescence quenching studies. The light switching properties of the chelates, the hydrolytic and oxidative cleavage of CT‐DNA, and the antioxidant properties were evaluated. Anti‐microbial studies carried out by pour plate method showed high activity for Ni(II)‐OFBBTCH chelate. Cytotoxicity of the compounds was performed for HeLa and MCF cell lines by MTT assay. Molecular docking studies revealed the docking of HL and Co(II)‐HL at the minor groove, and Ni(II)‐HL was docked at the major groove with hydrogen bonding.

Fluorine‐Lodged High‐Valent High‐Entropy Layered Double Hydroxide for Efficient, Long‐Lasting Zinc‐Air Batteries

AbstractEfficient and stable bifunctional oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts are urgently needed to unlock the full potential of zinc‐air batteries (ZABs). High‐valence oxides (HVOs) and high entropy oxides (HEOs) are suitable candidates for their optimal electronic structures and stability but suffer from demanding synthesis. Here, a low‐cost fluorine‐lodged high‐valent high‐entropy layered double hydroxide (HV‐HE‐LDH) (FeCoNi2F4(OH)4) is conveniently prepared through multi‐ions co‐precipitation, where F− are firmly embedded into the individual hydroxide layers. Spectroscopic detections and theoretical simulations reveal high valent metal cations are obtained in FeCoNi2F4(OH)4, which enlarge the energy band overlap between metal 3d and O 2p, enhancing the electronic conductivity and charge transfer, thus affording high intrinsic OER catalytic activity. More importantly, the strengthened metal‐oxygen (M−O) bonds and stable octahedral geometry (M−O(F)6) in FeCoNi2F4(OH)4 prevent structural reorganization, rendering long‐term catalytic stability. Furthermore, an efficient three‐phase reaction interface with fast oxygen transportation was constructed, significantly improving the ORR activity. ZABs assembled with FeCoNi2F4(OH)4@HCC (hydrophobic carbon cloth) cathodes deliver a top performance with high round‐trip energy efficiency (61.3 % at 10 mA cm−2) and long‐term stability (efficiency remains at 58.8 % after 1050 charge–discharge cycles).

Fluorine-Lodged High-Valent High-Entropy Layered Double Hydroxide for Efficient, Long-Lasting Zinc-Air Batteries.

Efficient and stable bifunctional oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalysts are urgently needed to unlock the full potential of zinc-air batteries (ZABs). High-valence oxides (HVOs) and high entropy oxides (HEOs) are suitable candidates for their optimal electronic structures and stability but suffer from demanding synthesis. Here, a low-cost fluorine-lodged high-valent high-entropy layered double hydroxide (HV-HE-LDH) (FeCoNi2F4(OH)4) is conveniently prepared through multi-ions co-precipitation, where F- are firmly embedded into the individual hydroxide layers. Spectroscopic detections and theoretical simulations reveal high valent metal cations are obtained in FeCoNi2F4(OH)4, which enlarge the energy band overlap between metal 3d and O 2p, enhancing the electronic conductivity and charge transfer, thus affording high intrinsic OER catalytic activity. More importantly, the strengthened metal-oxygen (M-O) bonds and stable octahedral geometry (M-O(F)6) in FeCoNi2F4(OH)4 prevent structural reorganization, rendering long-term catalytic stability. Furthermore, an efficient three-phase reaction interface with fast oxygen transportation was constructed, significantly improving the ORR activity. ZABs assembled with FeCoNi2F4(OH)4@HCC (hydrophobic carbon cloth) cathodes deliver a top performance with high round-trip energy efficiency (61.3 % at 10 mA cm-2) and long-term stability (efficiency remains at 58.8 % after 1050 charge-discharge cycles).

Structural Rigidification Strategy Based on Self-Assembly Enabled Reversible Excited-State Conversion of Iridium(III) Complexes for Multiple-Stimulus-Responsive Data Encryption.

Stimulus-responsive chromic materials exhibit color-switching properties under specific external stimuli and have been widely used in various fields. Transition-metal complexes show great potential applications as promising candidates for stimulus-responsive chromic materials, as their excited states not only depend on the chemical composition but are also affected by the intermolecular stacking modes. Owing to the intrinsic difficulty in the ordered stacking of the octahedral configuration, changing the stacking modes of iridium(III) complexes for multiple-stimulus responsiveness remains a significant challenge. In this work, we propose a structural rigidification strategy based on self-assembly to reversibly regulate the excited states of iridium(III) complexes, therefore achieving color switch under different stimulus conditions. We prepare cationic iridium(III) complexes by using tetrakis(perfluorophenyl)-borate ([B(PhF5)4]-) as the counterion, whose matching tetrahedral configuration and electron-deficient aromaticity enables polar-π interaction with the octahedral iridium(III) cations, inducing self-assembly to form structural rigidification. The structural rigidity restricts the large conformational changes of the metal-to-ligand charge transfer (3MLCT) excited state, and facilitates the conversion from the 3MLCT to the ligand-center (3LC) excited state in aggregated states. The excited-state conversion results in a 54 nm blue shift (from yellow to sky blue) in the photoluminescence spectra. As a result, we report a series of cationic iridium(III) complexes with different responses to low temperature, vapor fuming, and mechanical force, therefore achieving multiple-stimulus-responsive data encryption. Our work provides a novel strategy to achieve ordered stacking of octahedral complexes, shows a deeper understanding of the photophysical processes of transition-metal complexes, and offers a new perspective to develop multiple-stimulus-responsive chromic materials.

Quaternary Mixed Oxides of Non-Noble Metals with Enhanced Stability during the Oxygen Evolution Reaction.

Robust electrocatalysts required to drive the oxygen evolution reaction (OER) during water electrolysis are still a missing component toward the path for sustainable hydrogen production. Here a new family of OER active quaternary mixed-oxides based on X-Sn-Mo-Sb (X = Mn, Fe, Co, or Ni) is reported. These nonstoichiometric mixed oxides form a rutile-type crystal structure with a random atomic motif and diverse oxidation states, leading to the formation of cation vacancies and local disorder. The successful incorporation of all cations into a rutile structure was achieved using oxidizing agents that facilitates the formation of Sb5+ required to form the characteristic octahedral coordination in rutile. The mixed oxides exhibit enhanced stability in both acidic and alkaline environments under anodic potentials with no changes in their crystal structure after extensive electrochemical stress. The improved stability of these mixed oxides highlights their potential application as scaffolds to host and stabilize OER active metals.

Application of the flexible and polarisable hydration ion model to study Th(IV) aqueous solutions

Th(IV) hydration in aqueous solution is studied by means of molecular dynamics simulations based on a polarisable Th(IV)- H 2 O interaction potential developed in the framework of the hydrated ion concept. Molecular Dynamics (MD) simulations provide as the only in-solution representative motif the ennea-aqua ion, [ Th ( H 2 O ) 9 ] 4 + , with first shell water molecules at an average distance of 2.47 Å from the ion, in accordance with most of the experimental estimates. A well-defined second hydration shell is also identified, hosting ca. 19 solvent molecules at 4.65 Å. Non-structural aspects of the Th(IV) hydration phenomenon, such hydration enthalpy and ion diffusion are well reproduced by the simulation results. The analysis of the O-Th-O angle distribution suggests that the capped square antiprism arrangement prevails over the trigonal tricapped prism. The well-balanced definition of the ion–water and water–water interactions in such a demanding ion neighbourhood is confirmed by the EXAFS and XANES spectroscopies. The theoretical spectra, computed from the MD trajectory, are in fine agreement with some of the experimentally recorded. The sensitivity of the XAS spectroscopy to structural changes confirms how the presented potential manages in a proper way the response of the water molecules to the highly polarising electric field generated by the tetravalent ion.

A 2-D coordination polymer based on 3-(2-pyridyl)-5-(4-chlorophenyl)-1,2,4-triazine ligands and lead(II) bromide: synthesis, structure, luminescent properties, and application in organic light-emitting diodes

The combination of PbBr2 with 3-(2-pyridyl)-5-(4-chlorophenyl)-1,2,4-triazine (PCPT) results in a 2-D Pb(II) coordination polymer, denoted as [Pb9(PCPT)4Br18] n . This compound has been identified and studied through CHN analysis, FT-IR, and 1H NMR spectroscopy, in addition to detailed analysis using single-crystal X-ray diffraction techniques. Considering the primary and secondary Pb–N and Pb–Br bonds, Pb1 and Pb2 exhibit hemidirected pentagonal bipyramidal geometries, whereas Pb3, Pb4, and Pb5 demonstrate holodirected octahedral geometries. The 2-D structure transitions into a 3-D arrangement due to the presence of non-covalent C–H…Br and π…π stacking interactions. The interactions highlighted above enhance the structural stability and support the transfer of charge and energy between metal centers, positioning the polymer as a potential candidate for luminescence applications. Analysis of the electro-optical characteristics of this compound indicates its suitability as a luminescent material for incorporating into organic light-emitting diodes.