Coordination Geometry Research Articles

COMBINATION OF ETHNOMATHEMATICS AND THE MOZART EFFECT TO IMPROVE PROBLEM-SOLVING SKILLS AND MATHEMATICAL DISPOSITION

The background of this research is that student learning outcomes in analytical geometry lecture during the transition from pandemic to Covid-19 endemic are still low, which is due to a lack of student interest in learning, and they are still accustomed to online learning, thus having an impact on their low problem-solving skills and mathematical disposition. This research aims to determine to what extent the implementation of ethnomathematics and the Mozart effect can improve students' problem-solving skills and mathematical disposition in analytical geometry lecture during the transition from pandemic to endemic COVID-19, so the research is important to do. The implementation of ethnomathematics and the Mozart effect in mathematics learning is unique because it is a combination of learning approaches that have never been used before in Indonesia and other countries. The research method used was a quasi-experimental non-equivalent control group design because this research was experimental and sample determination was not carried out randomly, but using purposive sampling technique on the second-semester students of the mathematics undergraduate program, Faculty of Mathematics and Natural Sciences, Universitas Padjadjaran. The instruments used in this study were problem-solving skills test, mathematical disposition scale, and students’ attitude questionnaire toward learning with the implementation of ethnomathematics and the Mozart effect. The results showed that: (1) problem-solving skills of students who received learning by implementing ethnomathematics and the Mozart effect are better than students who achieved direct instruction; (2) mathematical disposition of students who received learning by implementing ethnomathematics and the Mozart effect is better than students who achieved direct instruction; and (3) students are interested and motivated to learn mathematics by implementing ethnomathematics and the Mozart effect. This research concludes that the implementation of ethnomathematics and the Mozart effect can improve students' problem-solving skills and mathematical disposition in analytical geometry lecture during the transition period from the pandemic to endemic COVID-19. It can be seen from good average post test scores achieved by students.

Crystal structure of a three-coordinate lithium complex with monodentate phenyloxazoline and hexamethyldisilylamide ligands

The reaction of lithium hexamethyldisilylamide, [Li{N(Si(CH3)3)2}] (LiHMDS), with 4,4-dimethyl-2-phenyl-2-oxazoline (Phox, C11H13NO) in hexane produced colourless crystals of bis(4,4-dimethyl-2-phenyl-2-oxazoline-κN)(hexamethyldisilylamido-κN)lithium, [Li(C6H18NSi2)(C11H13NO)2] or [Li{N(Si(CH3)3)2}(Phox)2] in high yield (89%). Despite the 1:1 proportion of the starting materials in the reaction mixture, the product formed with a 1:2 amide:oxazoline ratio. In the unit cell of the C2/c space group, the neutral molecules lie on twofold rotation axes coinciding with the Li—N(amide) bonds. The lithium(I) centre adopts a trigonal–planar coordination geometry with three nitrogen donor atoms, one from the HMDS anion and two from the oxazolines. All ligands are monodentate. In the phenyloxazoline units, the dihedral angle defined by the five-membered heterocyclic rings is 35.81 (5)°, while the phenyl substituents are approximately face-to-face, separated by 3.908 (5) Å. In the amide, the methyl groups assume a nearly eclipsed arrangement to minimize steric repulsion with the analogous substituents on the oxazoline rings. The non-covalent interactions in the solid-state structure of [Li{N(Si(CH3)3)2}(Phox)2] were assessed by Hirshfeld surface analysis and fingerprint plots. This new compound is attractive for catalysis due to its unique structural features.

Barbituric acid‐derived azo dye metal complexes: Synthesis, characterization, DFT, and antimicrobial analysis

Two novel metal complexes, C1 and C2, were synthesized through the reaction of an azo dye ligand, obtained by coupling 4‐chloroaniline with 1,3‐dimethyl barbituric acid. The structure of the ligand was confirmed using Fourier‐transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance (NMR). UV–Vis spectroscopy was employed to assess the ligand's sensing ability toward six different metal ions. Comprehensive characterization of the synthesized metal complexes was conducted using elemental analysis, X‐ray photoelectron spectroscopy (XPS), thermogravimetric analysis–difference thermogravimetry (TGA‐DTG), FTIR, UV–Vis spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and single‐crystal X‐ray diffraction (SC‐XRD). X‐ray analysis revealed octahedral coordination geometry with a 2:1 ligand‐to‐metal ratio and dimethylformamide (DMF) coordination with the metal atom in both complexes. Hirshfeld analysis and 2D fingerprint plots were employed to investigate supramolecular and intermolecular interactions within the crystal system. Density functional theory (DFT/B3LYP) calculations were utilized to compute energy gaps and other important theoretical features. Sensing experiments with tetrabutylammonium fluoride (TBAF) were conducted at a concentration of 1 × 10−5 M. Furthermore, the bioactivity of the synthesized metal complexes and ligand L was evaluated through molecular docking studies against Protein Data Bank (PDB IDs) 4XUY (Staphylococcus aureus) and 3BQW (Aspergillus niger). Also, antimicrobial activity was assessed using the agar well diffusion technique, revealing that complexes C1 and C2 exhibited enhanced antimicrobial activities against the tested organisms compared to the parent azo dye ligand. The computational and experimental bioactivity data are in good agreement with each other.

Microbubble-encapsulated Cobalt Nitrato Complexes for Ultrasound-triggerable Nitric Oxide Delivery.

Cobalt complexes exhibit versatile reactivity with nitric oxide (NO), enabling their utilization in applications ranging from homogeneous catalysis to NO-based modulation of biological processes. However, the coordination geometry around the cobalt center is complex, the therapeutic window of NO is narrow, and controlled NO delivery is difficult. To better understand the complexation of cobalt with NO, we prepared four cobalt nitrato complexes and present a structure-property relationship for ultrasound-triggerable NO release. We hypothesized that modulation of the coordination geometry by ligand-modification would improve responsiveness to mechanical stimuli, like ultrasound. To enable eventual therapeutic testing, we here first demonstrate the in vitro tolerability of [Co(ethylenediamine)2(NO)(NO3)](NO3) in A431 epidermoid carcinoma cells and J774A.1 murine macrophages,and we subsequently show successful encapsulation of the complex in poly(butyl cyanoacrylate) microbubbles. These hybrid Co-NO-containing microbubbles may in the future aid in ultrasound imaging-guided treatment of NO-responsive vascular pathologies.

Targeting bacterial nickel transport with aspergillomarasmine A suppresses virulence-associated Ni-dependent enzymes

Microbial Ni2+ homeostasis underpins the virulence of several clinical pathogens. Ni2+ is an essential cofactor in urease and [NiFe]-hydrogenases involved in colonization and persistence. Many microbes produce metallophores to sequester metals necessary for their metabolism and starve competing neighboring organisms. The fungal metallophore aspergillomarasmine A (AMA) shows narrow specificity for Zn2+, Ni2+, and Co2+. Here, we show that this specificity allows AMA to block the uptake of Ni2+ and attenuate bacterial Ni-dependent enzymes, offering a potential strategy for reducing virulence. Bacterial exposure to AMA perturbs H2 metabolism, ureolysis, struvite crystallization, and biofilm formation and shows efficacy in a Galleria mellonella animal infection model. The inhibition of Ni-dependent enzymes was aided by Zn2+, which complexes with AMA and competes with the native nickelophore for the uptake of Ni2+. Biochemical analyses demonstrated high-affinity binding of AMA-metal complexes to NikA, the periplasmic substrate-binding protein of the Ni2+ uptake system. Structural examination of NikA in complex with Ni-AMA revealed that the coordination geometry of Ni-AMA mimics the native ligand, Ni-(l-His)2, providing a structural basis for binding AMA-metal complexes. Structure-activity relationship studies of AMA identified regions of the molecule that improve NikA affinity and offer potential routes for further developing this compound as an anti-virulence agent.

Age-related morphological change in bony segment and cartilage segment of Eustachian tube.

Eustachian tube dysfunction (ETD) is the predominant cause of otitis media with effusion in children and adults. Balloon dilatation of the Eustachian tube (BDET) provides a new method for restoring the ventilatory function of Eustachian tube (ET). However, the differences in age-related morphological changes in the dimensions and positions of ET in children and adults are unclear. This study aimed to examine age-related morphological changes in bony and cartilage segments of the ET in a three-dimensional space in normal population. A total of 71 randomly selected computed tomography (CT) images of the temporal bones of 46 people were retrospectively studied in four age groups: A (0-3 years old); B (4-8 years old), C (9-18 years old), and D (19-65 years old). Space analytic geometry was assessed to calculate the dimensions and positions of ET. The bony segment of ET lengthened from infancy to adulthood with age in groups A, B and C (r = 0.562**/0.000). The cartilage segment of ET mostly extended with age from infancy to 8 years old in children (r = 0.633**/0.000), but with bending close to the sagittal plane and away from the horizontal plane with age in groups A, B and C (P < .05), and with a constant angle to the coronal plane among the four groups (P > .05). The bony and cartilaginous segments of ET exhibit distinct morphological changes in space with age. The bony segment of ET extends in a constant position from infancy to adulthood. In contrast, the cartilaginous segment of the ET indicates multidimensional positional changes until adulthood, in addition to the elongation from infancy to children. This may provide an accurate morphological basis for comparing the differences in ETD pathogenesis and surgical treatment between children and adults.

Novel schiff base-azide metal complexes: Synthesis, spectral, nonlinear optics, and DFT studies

In order to enhance nonlinear optics (NLO)-based technologies, current research focuses on the design and synthesis of coordination materials. In this context, to investigate spectral and theoretical linear optical (LO)/nonlinear optical (NLO) behaviors, novel metal complexes including azide {[Mn (L1)2(N3)2], (9), [Ni(L1)2(N3)], (10), [Co2(L1)2(N3)2]⋅2H2O, (11); L1: N-(pyridin-2-ylmethylene)methanamine} were synthesized. The vibrational and electronic spectral features of complexes 9–11 were investigated by UV–Vis and FT–IR spectra. Depending on the central metal ion and coordination geometries of complexes, the microscopic static nonlinear behaviors were examined by using the CAM-B3LYP/and ωB97XD/6–311 + G (d,p)//LanL2DZ levels of density functional theory (DFT). Furthermore, the vibrational and electronic properties of complexes 9–11 based on the same levels of time-dependent/density functional theory (TD-DFT/DFT) were surveyed. Additionally, the theoretical χ(1), χ(2), and χ(3) parameters, known as linear optical, second-, and third-order nonlinear optical susceptibility tensors, as well as linear, second-, and third-order polarization parameters (P(1), P(2), and P(3)) for complexes 9–11 were examined. The greatest <β(0; 0,0)> value for complex 10 found to be 262.55 × 10−30 esu using CAM-B3LYP level is 820.5 and 2019.6 times higher than the urea findings (0.32 × 10−30 esu and 0.130 × 10−30 esu). The <γ(0; 0,0,0)> results indicate that complex 9 having the highest value obtained at 2216.40 × 10−36 esu using CAM-B3LYP level is 47.76 and 316.63 times greater than those of pNA (15 × 10−36 esu) and urea (7 × 10−36 esu), respectively. Complexes 10 and 9 demonstrated promising microscopic second-order and third-order NLO features, respectively. Our research is anticipated to provide insight into NLO materials that may have applications in optoelectronics and telecommunication field.

Electronic analysis of n-propyl xanthate complexes with group 12 metals: a theoretical-experimental study.

Xanthates are organic compounds of great interest in coordination chemistry due to their different basic sites, which allow them to form complexes with different coordination modes and geometries. These compounds are relevant in the environment and act as heavy metal collectors in aqueous environments. In this theoretical-experimental work, electronic spectroscopy studies of n-propyl xanthate complexes with group 12 metals were performed. This study verified structural differences in these systems, depending on the environment in which they are inserted. In addition, structural differences were observed when the solid was changed to an n-hexane solution. Thus, it was observed that the complexes assume a mononuclear structure in solution, while they present a polymeric form in the solid phase. The electronic spectra obtained through TD-DFT calculations were compared to those of the previously synthesized complexes. In the final theoretical analysis, the main orbitals involved in these transitions were assigned using population analysis calculations. The synthesis of the complexes was confirmed through infrared (MID and FAR), UV‒Vis, Raman, and NMR-1H spectroscopic analyses. The structures of the mononuclear and polymeric complexes were optimized in vacuum and n-hexane. Under vacuum, DFT levels M06L/6-311 + + G** + LANL2TZ and M06L/def2-TZVP were used for the mononuclear complexes, and M06L/LANL2DZ + LANL2 were used for the polymer complexes. For the calculations of the mononuclear complexes in n-hexane, the same level of theory was used for the solid state. TD-DFT calculations for 300 excited states were performed with the same levels of theory and used the optimized structures of the complexes. Furthermore, population analysis was carried out on all the systems studied. Gaussian 09 software was used for the structure optimization, TD-DFT, and population analysis calculations. GaussSum software was used to evaluate the molecular orbitals and electronic spectra.

Magnetic Anisotropy and Relaxation in Four-Coordinate Cobalt(II) Single-Ion Magnets with a [CoIIO4] Core.

A mononuclear four-coordinate Co(II) complex with a [CoIIO4] core, namely, PPN[Li(MeOH)4][Co(L)2] (1) (PPN = bis(phosphoranediyl)iminium; H2L = perfluoropinacol), has been studied by X-ray crystallography, magnetic characterization, and theoretical calculations. This complex presents a severely distorted coordination geometry. The O-Co-O bite angle is 83.42°/83.65°, and the dihedral twist angle between the O-Co-O chelate planes is 55.6°. The structural distortion results in a large easy-axis magnetic anisotropy with D = -104(1) cm-1 and a transverse component with |E| = +4(2) cm-1. Alternating current (ac) susceptibility measurements demonstrate that 1 exhibits slow relaxation of magnetization at zero static field. However, the frequency-dependent out-of-phase (χ"M) susceptibilities of 1 at 0 Oe do not show a characteristic maximum. Upon the application of a dc field or the dilution with a diamagnetic Zn matrix, the quantum tunneling of magnetization (QTM) process can be successfully suppressed. Notably, after dilution with the Zn matrix, the obtained sample exhibits a structure different from that of the pristine complex. In this altered sample, the asymmetric unit does not contain the Li(MeOH)4+ cation, resulting in an O-Co-O bite angle of 86.05° and a dihedral twist angle of 75.84°, thereby leading to an approximate D2d symmetry. Although such differences are not desirable for magnetic studies, this study still gives some insights. Theoretical calculations reveal that the D parameter is governed by the O-Co-O bite angle, in line with our previous report for other tetrahedral Co(II) complex with a [CoIIN4] core. On the other hand, the rhombic component is found to increase as the dihedral angle deviates from 90°. These findings provide valuable guidelines for fine-tuning the magnetic properties of Co(II) complexes.

Development of a numerical model for disassembly phase of hypothetical core disruptive accident and application to a medium-sized mixed oxide fuelled fast reactor

Safety assessment of fast reactors involves analyzing Hypothetical Core Disruptive Accidents (HCDA) that could result in reactor core disassembly. HCDA is generally analyzed in three distinct phases that include pre-disassembly, disassembly and post-disassembly phases. In the present work, a new coupled neutronics-hydrodynamics computer code called FAst Reactor DISassembly (FARDIS-1) is developed in 2-D cylindrical coordinate geometry to model the super-prompt critical power excursion during the disassembly phase of HCDA in a sodium-cooled fast reactor (SFR). The modelling approach followed is essentially similar to the one used in VENUS-II code but with a few improvements. The code is benchmarked against the predictions of VENUS-II for a sample case of HCDA in the FFTF reactor model. This is followed by an analysis of the disassembly phase in a medium-sized (500 MWe) mixed oxide fuelled fast reactor. Two cases are assumed at the beginning of the disassembly phase: a sodium voided core (conservative) and a partially voided core (realistic) and the influence of several core neutronics parameters on the transients is elucidated through parametric studies. The peak power, thermal energy release, peak pressure, maximum temperature and work-potential are estimated and their trends are discussed.

Geogebra As A 21st Century Learning Tool: A Systematic Literature Review

Learning in the 21st century requires the use of media in learning which results in new desires and interests, increases motivation and stimulation in learning, and even has a psychological effect on students. Technology-based learning media can make learning more interesting, because the use of appropriate media can help convey material abstractly, so that students can more easily understand the material. The existence of technology in learning mathematics helps students in understanding mathematical concepts. One form of math learning media is GeoGebra. This study aims to analyze the distribution of education levels, materials, and 21st century skills that are most often used in the application of the GeoGebra application as a 21st Century Mathematics learning media. The research method used was systematic literature review. The research subjects were 33 journal articles obtained from the Scopus, Google Scholars, ScienceDirect, Springer, ResearchGate, OJS (Open Journal System), and Eric databases in the last 7 years. The results showed that the study of 21st century geogebra increased in 2020 and the peak occurred in 2022 with the research method used dominated by quasi-experiments. In addition, the junior high school education level, geometry transformation material and analytic geometry of the field, as well as creative thinking skills become the most dominating and widely conducted research.

Why are the luminescent properties of the mononuclear and binuclear Eu/Tb-2-hydroxybenzoate complexes with 1,10-phenanthroline so different? An experimental-theoretical study

This study presents a comprehensive investigation into the structural and luminescent properties of lanthanide 2-hydroxybenzoate compounds, focusing on Eu3+ and Tb3+ ions in both single and mixed systems. The X-ray structures of (Hphen)2[Eu2(2-OHBz)8(H2O)2]·2H2O (1a·2H2O) and [Eu(2-OHBz)3(phen)2]·PhMe (2a·PhMe) were determined, where 2-OHBz: 2-hydroxybenzoate and phen: 1,10-phenantroline, revealing triclinic crystal structures with distinct coordination geometries. Compound 1a·2H2O displayed a centrosymmetric dinuclear anion with a coordination number of eight for each Eu3+ center, while compound 2a·PhMe exhibited a neutral mononuclear complex with a decacoordinated Eu3+ center. A comparative analysis of luminescent properties between these compounds unveiled significant differences in the nonradiative decay rates of the 5D0 level of Eu3+ ions, suggesting potential luminescence-quenching channels. The investigation is extended to mixed Eu3+-Tb3+ systems, demonstrating efficient Tb3+ to Eu3+ energy transfer, especially at room temperature. Three models, including two novel ones proposed in this study, were considered to rationalize energy transfer in the mixed systems. Our theoretical-experimental investigation reveals that variations in lifetimes of the emitting level 5D0 of Eu-2-OHBz mononuclear and binuclear complexes, or mixed Eu/Tb-2-OHBz complexes, with 1,10-phenanthrolines, primarily result from multiphonon decay processes; however, low-energy ligand-to-metal charge transfer (LMCT) states play a key role in suppressing luminescence in the binuclear complex compare to the mononuclear ones.

Oxidovanadium(V) complexes with tridentate hydrazone ligands as oxygen atom transfer catalysts

Four isostructural oxovanadium(V) complexes with hydrazone ligands have been synthesised, characterised, and evaluated as epoxidation and sulfoxidation catalysts. The reactions between [VO(acac)2] (acac– = acetylacetonate) and H2Ln (n = 1–4), precursors for monoanionic tridentate hydrazone ligands, afford complexes formulated as [VO(Ln)(bzh)·MeOH] (1–4) when bidentate benzohydroxamic acid (Hbzh) is included as a co-ligand. Single crystal X-ray structure analyses showed that complexes 1–3 have a distorted octahedral coordination geometry with an O5N coordination environment. Cyclic voltammetry showed that all complexes undergo two quasi-irreversible reduction peaks and a single irreversible oxidation peak. The bonding in 1 has been investigated by electronic structure calculations, and these data are discussed with respect to the electrochemical results. Complexes 1–4 were tested as catalysts for the epoxidation of cis-cyclooctene at 50 °C and sulfoxidation of methyl-p-tolylsulfide at room temperature using tert-butyl hydroperoxide (tBuOOH) and aqueous H2O2 as the terminal oxidants.

Analytical Model of Tapered Thread Made by Turning from Different Machinability Workpieces

High-precision tapered threads are widely used in hard-loaded mechanical joints, especially in the aggressive environment of the drilling of oil and gas wells. Therefore, they must be made of workable materials often difficult to machine. This requires the use of high-performance cutting tools, which means the application of non-zero geometric parameters: rake and edge inclination angles. This study is based on analytical geometry methodology and describes the theoretical function of the thread profile as convoluted surfaces dependent on the tool’s geometric angles. The experiments were conducted using a visual algorithm grounded on the obtained function and prove the practical use of the scientific result. They predict the required accuracy of thread made using a lathe tool with a rake angle of up to 12°.

White-green photoluminescence of manganese(II) complexes with pyrazolo[1,5-a][1,10]phenanthroline-3-carbonitrile

Five manganese(II) complexes with a bidentate pyrazolo[1,5-a][1,10]phenanthroline-3-carbonitrile ligand (L) have been prepared and their structures have been determined. The anion effect on the structural diversity of the complexes has been studied using manganese(II) salts with different anions such as Cl¯, ClO4¯, and Ts¯. A reaction between manganese(II) chloride and L in organic solvents leads to complexes [MnL2Cl2]·xCH2Cl2 (1) and [Mn2L2(H2O)Cl4]·L (2), the use of manganese(II) tosylate in the rection yields in [MnL(H2O)3Ts]Ts·L·H2O (3) and [MnL(H2O)3Ts]Ts (4), and finally, in the case of manganese(II) perchlorate [MnL2(H2O)2](ClO4)2·L (5) is formed. According to the single-crystal X-ray analysis the coordination environment of the Mn(II) ions in the complexes is a distorted octahedron with MnN4Cl2 (1), MnN2O4 (3) and MnN4O2 (5) chromophores; the complex 2 is binuclear, in which two manganese atoms have different coordination geometries – distorted octahedron (MnN2Cl3O) and square pyramid (MnN2Cl3). Chloride ions are coordinated anions; perchlorate ions are in the outer coordination sphere. Tosylate ions can play both coordinating and non-coordinating roles in complexes. X-ray analysis shows that in 2 and 5 one molecule of L has no bonds with manganese atoms, and reveals only intermolecular interactions through π-π stacking. This leads to the formation of cocrystals [Mn2L2(H2O)Cl4]·L or [MnL2(H2O)2](ClO4)2·L, that affects the photophysical properties of these compounds. In order to compare the effect of L coordination on the photoluminescence properties of manganese(II) complexes, the complexes [Mn(phen)3](ClO4)2·xSolv with unsubstituted 1,10-phenanthroline have been synthesized. In contrast to [MnL2(H2O)2](ClO4)2·L, the 1,10-phenanthroline-based compound [Mn(phen)3](ClO4)2·H2O has no emission. Complexes 1, 3, 4 and 5 exhibit a white-green emission in the microsecond range with maxima at 530–565 nm in the solid state, and the photoluminescence properties of 5 are studied in solution.

Tuning the bandgap of Cu(II) phosphinate coordination polymers by ligand selection and coordination geometry

Five coordination polymers, denoted as ICR-15, ICR-16, ICR-17, ICR-18, and ICR-19, were prepared using three previously reported phosphinic acids, namely H2PBP(Me), H2PBP(Ph), H2BBP(Me), and one new ligand H3TPBTP(Me), in conjunction with Cu2+ cations. These coordination polymers were characterized with single crystal X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, thermal analysis, and UV-vis spectroscopy. The crystal structures of the coordination polymers were analysed, revealing a variety of coordination environments and distinct structural motifs. Optical band gaps determined from the UV-vis spectra of the coordination polymers range from 2.8 eV to 3.5 eV, corresponding to wide bandgap semiconductors. Interestingly, the coordination geometry of Cu2+ was found to have a negligible influence on the size of the direct or indirect band gap.

Coordination number impact on magnetic properties of Schiff base Co(II) complexes

Two mononuclear Co(II) complexes with a tetrahedral and octahedral coordination geometry with a Schiff base ligand L− (anion of 4-[(2-fluoroanilino)-phenyl-methylene]-5-methyl-2-phenyl-pyrazol-3-one) having the formulas [CoL2]·2MeCN (1) and [CoL2(H2O)2]·2MeCN (2) have been synthesized and structurally characterized. Notably, their coordination geometry and magnetic relaxation behaviors can be tuned by variation of reaction conditions. Static magnetic studies reveal that complex 1 exhibits considerable easy-axis magnetic anisotropy. Frequency-dependent susceptibility measurements revealed slow magnetic relaxation behavior with spin-reversal barriers of 79.2 K at an applied external field of 500 Oe. Clear magnetic hysteresis loops were observed for 1 at 2 K. Complex 2 show field-induced slow magnetic relaxation with Raman and direct relaxation processes. The observed magnetic behavior of 1 and 2 is confirmed by high-level ab initio calculations and simulation of χMT(T) curves.

Electrocatalytic facets of a newly designed cobalt(III) complex towards sustainable hydrogen evolution

A hybrid cobalt complex (C7H10ON)[Co(L)2].CH3OH (Co-complex) bearing an organic cation and anionic cobalt complex has been designed, synthesized, and structurally characterized. The tridentate chelator, 2-((2-hydroxybenzylidene)amino)-4-methylphenol (H2L), was prepared by the condensation reaction between salicylaldehyde and 4-methyl-2-amino phenol. Crystal structure analysis reveals a slight distortion in the octahedral coordination geometry of the cobalt(III) centre. This complex was evaluated in the hydrogen evolution reaction using a glassy carbon working electrode within acetonitrile (ACN), using tBu4NClO4 as the supporting electrolyte. The catalyst exhibited heightened catalytic activity when acetic acid was introduced, leading to a significant elevation in the catalytic wave at −1.6 V versus Ag wire. The most pronounced activity was observed by adding 15 mM acetic acid, with a turnover number (TON) of 10.1. The catalyst’s durability was confirmed through controlled potential electrolysis (CPE) at −1.6 V for 2 h, displaying a steady current for the initial 20 min, followed by a gradual increase over the subsequent 2 h. A negligible amount of metallic cobalt through a ligand dissociation on the surface of the glassy carbon electrode was also evident during the electrocatalytic studies, as ensured by X-ray Photoelectron Spectroscopy (XPS) analysis. Further, the presence of ligand-centric reduction wave in the complex signifies the synergistic effect of the M−L cooperation and offers a plausible ECEC mechanistic route for the release of molecular hydrogen.

Synthesis, Spectroscopy and Biological Activity Study of Some New Complexes with Schiff Base Derived From Malonic Acid Dihydrazide with 2-pyridine Crboxaldehyde

تم تحضير ثلاث معقدات جديدة Ni (II)و Cu (II) و Zn (II) باستخدام الليكند المحضر الجديد من تفاعل حامض مالونيك ثنائي هيدرازايد مع 2-بيريدين كربوكسالديهايد. حيث شخصت المعقدات لمحضرة وكذلك الليكند باستخدام تقنيات مختلفة مثل FT-IR و UV-Vis و Mass و 1H-NMR و 13C-NMR وتحليل العناصر CHN و تقدير محتوى الكلور والموصلية المولارية والحساسية المغناطيسية والامتصاص الذري لتشخيص هذه المركبات. لكل معقد محضر جديد من النيكل والنحاس والزنك ، كشفت نتائج التشخيص عن معقدات ذات شكل هندسي ثماني السطوح سداسي التناسق. تمت دراسة تأثير المواد المحضرة على الفعالية البيولوجية لاثنين من البكتريا موجبة الغرام Staphylococcus aureus و Bacillus subtitles واثنين من البكتيريا سالبة الجرام Escherichia coli و Pseudomonas aeruginosa ، بالإضافة إلى candida fungusاثبتت جميع المركبات المحضرة قابلية تثبيطيه جيدة باستثناء معقد النيكل، الذي فشل في إحداث أي تأثيرات مثبطة فعالة ضد pseudomonas.

Synthesis, Characterization and Antimicrobial Activity of V(IV) Complexes Containing 2,6-Pyridinedicarboxylate (DPA) Ligand

A novel molecular coordination compound, [V4IVO4(DPA)4(OH2)4]∙2H2O, 1, and known [VIVO(DPA)(OH2)2].2H2O compound, 2, were obtained from V2O5 and 2,6-pyridine dicarboxylic acid (H2DPA) reactions with water or ethyl alcohol by using hydro/solvothermal synthetic methods. 1 was fully characterized by IR spectroscopy, manganometric titration, magnetic susceptibility, thermogravimetric and single crystal XRD analyses. The single-crystal XRD analysis revealed that it was a molecular consist of four-nuclear coordination compound. DPA ligand in 1 acted chelating and bridging modes through carboxylate groups. Four V(IV) ions exhibit a distorted octahedral coordination geometry {VNO5}. 1 and 2 were investigated for antimicrobial activity. The results of antimicrobial activity show that they have an antimicrobial effect against the microorganisms P. aeruginosa, E. coli, S. aureus, E. faecalis, L. monocytogenes, B.subtilis, C. albicans.