Bulletin of the Chemical Society of Ethiopia

Development of cost-effective dispersive liquid-liquid micro-extraction technique for preconcentration of multi-residue herbicides in environmental waters prior to Chromatographic analysis

2024-07-12T06:50:22+00:00

High-density dispersive liquid-liquid microextraction method coupled with high-performance liquid chromatography with a diode array detector (HD-DLLME-HPLC-DAD) was developed for extraction and determination of six commonly used sulfonylurea herbicides in matrices of environmental waters. For simultaneous extraction of the target herbicides, the optimum experimental parameters that 024influence extraction efficiency were investigated. Under optimized conditions, the limit of detection (LOD) and quantification (LOQ) were 0.8-1.5 and 1.9-5.1 ng mL⁻¹, respectively. The precisions in terms of relative standard deviations (% RSDs) of both intra-day and inter-day precisions (n = 6) were found to be 2.92 to 7.08 and 3.01 to 8.13, respectively. Furthermore, applicability of the developed method was investigated by analyzing spiked tap, lake, river and underground water samples and satisfactory recoveries were obtained in the range of 84.3–101.7% with RSDs < 9.8% (n = 6) and the target analytes were not detected in real samples. The proposed method offered several attractive features including fast analysis time, simplicity, sensitivity, and selectivity. Therefore, the trace level enrichment and assessment of sulfonylurea herbicides residues from environmental water matrices using HD-DLLME-HPLC-DAD could be utilized as a reliable alternative in routine laboratory analysis of contaminated environmental waters.

KEY WORDS: Environmental water, High-density dispersive liquid-liquid microextraction, HPLC-DAD, Miniaturization analytical technique, Sulfonylurea herbicides, Trace level enrichment

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1189-1204.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.1

A stable electrochemical sensor for the detection of ascorbic acid based on Fe3O4/ZrO2 nano composite modified carbon paste electrode

2024-07-12T07:01:02+00:00

Magnetite and zirconium oxide (Fe₃O₄/ZrO₂) nano composite, Fe₃O₄ and ZrO₂nanoparticles were synthesized by a chemical co-precipitation method and hydrothermal decomposition of zirconium metal organic framework, respectively. The structural and morphological properties of the as-synthesized materials were characterized by X-ray diffraction and scanning electron microscope. Electrochemical properties of carbon paste electrode (CPE) modified by Fe₃O₄, ZrO₂and Fe₃O₄/ZrO₂nano composites were studied using cyclic voltammetry and electrochemical impedance spectroscopy in the presence of 2 mM K₃Fe(CN)₆/0.1 M KCl aqueous solution. Voltammograms acquired on Fe₃O₄/ZrO₂/CPE showed an enhancement of the oxidation current density compared to the other modified electrodes. By applying the Randles-Sevcik equation, the CPE modified by Fe₃O₄/ZrO₂ nano composite resulted in an electroactive surface area of 0.0978 cm²; about twice to that of the unmodified CPE (0.0458 cm²). The electrochemical sensor was used for the detection of ascorbic acid (AA). Under optimized condition (pH 4) the sensor exhibits sensitivity of 10 µA/µM; LOD of 0.46 µM; LOQ of 1.53 µM and a linear range of 1-6 μM AA. The Fe₃O₄/ZrO₂/CPE has also shown accepted reproducibility (% recoveries 93.54%); RSD of 2.4% and stable response of 96.91% of the initial current after 30 days of storage.

KEY WORDS: Ascorbic acid, Carbon paste electrode, Electrochemical sensor, Nano composite

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1205-1223.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.2

Manganese oxide-coffee husk and khat (Catha edulis) leftover biochar nanocomposites for removal of Cr(VI) from wastewater

2024-07-12T07:07:51+00:00

This study investigates the use of manganese oxide-biochar-nanocomposites synthesized from coffee husk (CH) and khat leftover (KL) for Cr(VI) removal from water. Two pristine biochars of CH and KL were separately synthesized by pyrolyzing their biomasses at 300 ℃ for 1 h. Similarly, biochar-based nanocomposites were synthesized by pretreating 25 g of each biomass with 12.5 mmol of KMnO₄ and pyrolyzing at 300 ℃ for 1 h. The pristine biochars, synthesized by pyrolysis of CH and KL, removed 74.98% and 84.78% of Cr(VI) from aqueous solutions containing 20 mg L^-1, respectively. However, the resulting nanocomposites exhibited a maximum removal efficiency of 99.63% with manganese oxide-coffee husk biochar nanocomposite (MnO_X-CHBNC) and 99.84% with manganese oxide-khat leftover biochar nanocomposite (MnO_X-KLBNC) of the Cr(VI). The adsorption isotherm fitted well with the Langmuir isotherm, indicating favorable monolayer adsorption. The kinetics of adsorption followed the pseudo-first-order model. The MnO_X-CHBNC and MnO_X-KLBNC demonstrated satisfactory removal efficiencies even up to six cycles, indicating their potential effectiveness for large-scale use in removing Cr (VI) from wastewater.

KEY WORDS: Adsorption, Biochar-nanocomposite, Coffee husk, Cr(VI) removal, Khat leftovers

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1225-1240.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.3

Removal of sulfur compounds from Iraqi crude oil using γ-Al2O3 nanoparticles

2024-07-12T07:14:41+00:00

γ-Al₂O₃ nanoparticles have been synthesized using aluminium(III) sulfate as a source of metal. Ceratonia silique leaves extract was used as a reducing agent and sodium hydroxide solution as a precipitating. XRD, BET, FE-SEM, EDX, and DLS Techniques were used to characterize the prepared alumina. The desulfurization process was applied by adsorption of sulfur compounds from Iraqi crude oil using the prepared γ-Al₂O₃ nanoparticles. The efficiency of aluminium oxide nanoparticles as an adsorbent was studied for different factors such as adsorbent quantity, contact time, pH, and temperature. The average size of γ-Al₂O₃ nanoparticles is 12.44 nm, with a size distribution of particles from 90 nm to 900 nm. The mixture was drained at 80 ºC, and then calcined at 600 ºC, BET analysis shows a high surface area (72.03 m² g^-1) and uniform pore sizes of Al₂O₃ NPs. The FE-SEM images showed that the nanoparticles appeared smooth and cylinder-shaped within the average size of 100.53 nm. The obtained results of removal of the sulfur compounds from crude oil using γ-Al₂O₃ nanoparticles showed a high desulfurization and were achieved with adsorbent at specific conditions: 150 min, 0.5 g of adsorbent, temperature at 25 ºC and acidic medium pH = 2.

KEY WORDS: Crude oil, γ-Al₂O₃ nanoparticles, Ceratonia siliqua leaves extract

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1241-1250.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.4

Structure and magnetism of a chiral Perovskite-like dicyanamidometallate framework

2024-07-12T07:19:17+00:00

Perovskite-like compounds have attracted great attention because of their good properties, such as electrical, optical, and magnetic properties, etc. Herein, a new perovskite-like anionic dicyanamidometallate, namely (Bu₃MeP)[Ni(dca)₃] (1) (Bu₃MeP = tributylmethylphosphine cation, dca = dicyanamide), was synthesized and structurally characterized by elemental analysis, IR spectrum, thermogravimetric analysis, and single-crystal X-ray diffraction. The compound crystallizes in the tetragonal crystal system with the chiral space group P4₃2₁2, and exhibits a three-dimensional anionic dicyanamidometallate framework from Ni²⁺ units bridged by dicyanamides, in which tributylmethylphosphine cations are accommodated in the voids. The butyl groups present two conformations in the tributylmethylphosphine cation, resulting in chirality character occurred in compound 1. Variable-temperature magnetic susceptibility analysis indicates that weak ferromagnetic interaction exists between the nickel(II) ions coupling by μ_1,5-bridings.

KEY WORDS: Perovskite-like, Dicyanamidometallate, Crystal structure, Magnetic properties

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1251-1260.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.5

Platinum(II) and palladium(II) thiolate complexes; synthesis, characterization, crystal structure, DFT, Hirshfeld surface analysis and anticancer studies

2024-07-12T07:25:14+00:00

The synthesis and characterization of platinum(II) and palladium(II) mixed ligand complexes, [M(mtzS)₂(dppm)] (M = Pt or Pd), have been described. These complexes were synthesized through a one-pot reaction involving K₂MCl₄, KmtzS (prepared from HmtzS and KOH), and dppm. The prepared complexes 1 and 2 have been characterized by using various analytical techniques including conductivity measurements, IR spectroscopy, UV-Vis spectroscopy, ³¹P and ¹H NMR spectroscopy and 1 by X-ray crystallographic studies. The in vitro anti-cancer activity of complexes 1 and 2 against breast cancer cells (MCF7 cell line), was evaluated using the MTT assay showed a moderate activity with an IC₅₀value of 27.59 µg/ml for 1 and 28.82 µg/ml for 2. Additionally, the ligands and complexes underwent full geometry optimization using density functional theory (DFT). The calculated geometric and spectral data were found to be in good agreement with the experimental results. Theoretical calculations of molecular orbitals (HOMO-LUMO) and their energies suggested the occurrence of charge transfer within the complexes.

KEY WORDS: Platinum(II), Palladium(II), Thiolate, Diphosphine, X-ray crystallography

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1261-1273.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.6

Vanillin and 4-nitroanilline derived Schiff-base and its nickel(II) complex: spectral analysis and antibacterial investigation

2024-07-12T07:28:57+00:00

Ni(II) metal complex of Schiff base (SB) ligand 2-methoxy-4-[(4-nitrophenyl) iminomethyl]phenol (MNIMP); derived from vanillin and 4-nitroanilline was synthesized in 1:2 M:L by refluxing solution containing metal salt (NiCl₂.6H₂O, 97.0%) and SB in ethanol and characterized based on powder (XRD), NMR, FT-IR, UV-Vis spectrophotometer, and physicochemical measurements. The FT-IR spectra revealed that the complex is coordinated through azomethine nitrogen and phenolic oxygen of the bi-dentate ligands. The chemical shift δ = 9.8 ppm in ¹H-NMR of SB; corresponds to the azomethine proton of the ligand suggesting the presence of -C=N- linkage and ¹³C-NMR confirms the presence of 14C in the ligand and the complex. The shift to a lower wavelength of UV-Vis spectra of the complex compared to the ligand signifying complex formation. The powder (XRD) pattern put forward the crystalline phase of the complex through nickel(II) occupying the center of octahedron geometry. The higher molar conductance value of the complex confirms its electrolytic nature. In-vitro antibacterial activities for synthesized compounds have been evaluated towards human pathogenic microbes Staphylococcus aureus and Escherichia coli and compared with standard, gentamicin. The result demonstrated that Ni(II) complex; [Ni (MNIMP)₂(H₂O)₂]Cl₂has greater zone of inhibition against the tested organism than free MNIMP ligand as antibacterial agent.

KEY WORDS: Derivatization, Schiff base ligand, Vanillin, Nickel (II) complex, Bi-dentate, Antibacterial activity

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1275-1289.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.7

Synthesis, evaluation, and structural characterization of antioxidant diorganotin(IV) Complexes derived from ampicillin: a comprehensive study

2024-07-12T07:34:45+00:00

This study offerings the preparation, structural analysis, and estimation of novel diorganotin(IV) complexes derived from an ampicillin as a ligand in terms of their antioxidant activity. The diorganotin complexes were yielded by a direct reaction between ampicillin and a different number of diorganotin(IV) chloride precursors. Various spectroscopic techniques, including CHNS, FTIR and nuclear magnetic resonance (¹H, ¹³C, ¹¹⁹Sn NMR), were used to explain the molecular structures of the produced complexes. Through in vitro experiments such as the CUPRAC and DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging technique, the novel diorganotin complexes' antioxidant activity were assessed. The results were compared to that of ligand antioxidants to evaluate the effectiveness of the complexes that were produced. The structural properties of the complexes were linked to their antioxidant capacity to identify the connection between molecular structure and biological function.

KEY WORDS: Ampicillin, DPPH method, Diorganotin(IV) complexes, Antioxidants

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1291-1300.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.8

Synthesis and characterization of potential antioxidant agent of novel pyridylazo ligand and its palladium complex

2024-07-12T07:44:01+00:00

A new azo dye ligand namely ((E)-1-(4-hydroxy-3-(pyridin-3-yldiazenyl)phenyl)ethan-1-one) (HPPE) was synthesized by the coupling reaction of diazoinium salt of 3-aminopyridine and 4-hydroxyacetophenone. The palladium complex was prepared by reacting palladium chloride with the HPPE ligand. These compounds were characterized by different techniques such as mass, ¹H-NMR, infrared, UV-Vis spectroscopies. The infrared data reveal that azo ligand reacting as bidentate via oxygen and nitrogen atom of azo group and it reveals the important functions as carbonyl group, methyl group, and azo group in the ligand and the complex such. The palladium complex is square planer. The ligand showed a visible colorimetric pH sensitive chemosensor, fast response time and is fully reversible and exhibited a large wavelength shift more than170 nm accompanied by excellent sensitivity of pH in the range of 3-9. The HPPE ligand and palladium complex showed potential antioxidant activity especially the ligand showed activity so close to the ascorbic acid.

KEY WORDS: Antioxidant, Palladium complex, Pyridyl, Azo dye, Acidity

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1301-1310.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.9

Spectrophotometric, quantum chemical and molecular docking investigations of 4H-1-benzopyran-derived Pd(II) complexes

2024-07-12T07:47:39+00:00

Transition metal complexes are an appealing target in the development of functional materials used frequently in industrial and therapeutic world. The quantum chemical investigations help to obtain a thorough comprehension of the interplay between complexes and biological materials. It necessitates sufficient modeling of chemical phenomena in the system, occasionally involving assistance of classical or semi-empirical computational techniques. Identification of the factors influencing complexes and their optimization is essential for electronic structure calculations and the relevant biochemical potential. The present study aims at correlating analytical studies with the theoretical behavior involving identification of structural features and bonding interactions of the three 4H-1-benzopyrans and their spectrophotometrically analyzed palladium complexes using DFT calculations to get acquainted with pharmacological profile of the complexes. FMO studies indicated a higher Egap for ligand in all the cases than their respective Pd(II) complexes. Furthermore, according to the other chemical descriptors, interaction between the ligands and respective complexes, cause chromogenic ligand’s chemical hardness to decrease indicating that the formed complexes have lower kinetic stability and more chemical reactivity. Efficiency of the studied ligands further was analyzed by molecular docking against the target proteins, of which 2O0U, a transferase exhibited mutual interactions with all the examined ligands.

KEY WORDS: Palladium(II), 4H-1-benzopyran complexes, DFT, MEP, Molecular docking

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1311-1327.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.10

Antioxidant properties of triphenyltin(IV) complexes derived from a novel ibuprofen-5-aminosalicylic acid ligand: synthesis and characterization

2024-07-12T07:53:53+00:00

In this study, new ligand was prepared by condensation reaction between Ibuprofen and 5-amino salicylic acid (IAS), this prepared ligand was used to prepare three complexes of triorgnotin(IV) salts to obtain the corresponding complexes. The ligand (IAS) and complexes were characterized by several techniques such as infrared spectroscopy, (tin, proton and carbon) magnetic resonance (¹H, ¹³C, ¹¹⁹Sn NMR), elemental analyses. The antioxidant activity of the complexes was also studied. It was produced by two methods: DPPH and CUPRAC. The resulting complexes gave a higher rate of inhibition than the ligand due to the presence of the tin element in the complexes. Complex 1 (tri phenyltin-IAS) also shown greater antioxidant activity than the other compounds.

KEY WORDS: Ligand, Antioxidant activity, Triorganotin(IV), DPPH method, CUPRAC method

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1329-1336.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.11

Synthesis and characterization of some transition metal complexes with Schiff base derived from 2,6-diaminopyridine

2024-07-12T07:57:39+00:00

Schiff base labeled as H₂L₁ was synthesized, which was derived from pyridine-2,6-diamine and 2-hydroxynaphthaldehyde. Types of complexes [ML]Cl₂ and [ML(py)₂]Cl₂, were formed with Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺. Additionally, adduct complexes [ML(py)₂] were prepared in a ratio of 2:1. Diverse analytical techniques, elemental analyses, (FT-IR, UV-Vis, ¹H NMR), conductance measurements, and magnetic susceptibility, were employed to characterize these complexes and adducts. The data acquired validated that the ligands donor atoms act as (ONNO) tetra-dentate bibasic chelating ligands with metal ions. Depending on spectral and magnetic measurements, the suggested shapes of these complexes were reported to be either tetrahedral/octahedral in geometry. Density functional theory (DFT) was used to get some theoretical data about the generated complexes. The data obtained includes the energy of the highest and lowest occupied molecular orbitals (HOMO and LUMO), electron density, ionization potential (IP), electron affinity (EA), electronegativity (En), electrophilicity (ὠ), chemical hardness (η), and dipole moment (μ). Different characteristics of the complexes have been investigated and explained based on these studied parameters. The molecular docking of target microorganisms of these complexes will be studied. The interaction of DNA gyrase 4ckk with the compounds visualized by LigPlot software.

KEY WORDS: 2,6-Diaminopyridine, 2-Hydroxynaphthaldehyde, Metal complexes, Spectral studies

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1337-1350.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.12

Synthesis, molecular modelling and choline esterase enzyme inhibitory activity of novel enaminone derivatives of sulfonamides

2024-07-12T08:01:33+00:00

The enaminone derivatives of sulfonamides (1–11) were obtained in good yield and high purity. Choline esterase (ChE) inhibitory activities of the novel compounds against AChE and BChE were determined by Ellman’s method. Ki values of compounds for AChE and BChE enzymes were obtained in the ranges of 14.28˗160.17 µM, and 8.30˗324.27 µM, respectively. Compound, 9 presented good activity towards AChE and BChE with Ki values of 14.28 µM and 8.30 µM, respectively. Compounds 2 and 10 were found to be the most potent compounds showing cytotoxic effect (IC₅₀ = 71.54 µg/mL and IC₅₀ = 83.59 µg/mL), respectively, on lung cancer cell line (A549) and normal cells (Beas-2B) (IC₅₀ = 164.62 µg/mL and IC₅₀ = 155.64 µg/mL), respectively. The compounds have interacted with various proteins like AChE enzyme protein (PDB ID: 4M0E) and BChE enzyme protein (PDB ID: 5NN0). Finally, ADME/T analysis was performed to predict the movements of molecules in human metabolism.

KEY WORDS: Sulfonamides, Enaminone, Enzyme inhibition, Molecular docking

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1351-1368.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.13

Target-based anticancer glycyrrhetinic derivatives: Design, synthesis, biological assessment and molecular docking studies

2024-07-12T08:08:43+00:00

18-Glycyrrhetinic acid (GA) is regarded as the principal active component isolated from the Chinese medicinal plant of licorice root, and it has considerable anticancer actions. This work was built on the discovery and design of brand-new 18-glycyrrhetinic acid (GA) amino acid peptides and peptide ester analogs. The cytotoxic evaluation exhibited that despite the promising cytotoxic activity of the tested peptides 2, 3, 4, 6, and 7 in MCF-7 and HCT-116 cancer cells, with IC₅₀ values ranging from 5.1-7.4 and 6.6-72.7 µg/mL, respectively. Furthermore, all freshly produced GA-peptides with moderate to high activity on tumor cell lines produced a favorable safety profile versus typical human dermal fibroblasts (BJ-1) cellular lineage. Interestingly, 2, 4 and 6 demonstrated excellent multitargeting inhibitory profiles against CDK-2, VEGFR-2, and PDGFR-α kinases. Moreover, since peptide 6 was the most active cytotoxic agent, it was chosen as an illustrative candidate to examine its influence on many apoptotic markers in invitro studies, including Bax, caspase-3 and 7, DNA fragmentation, BCl-2, p53, and tubulin polymerization inhibition. All novel analogs were tested for their antimicrobial efficacy versus a panel of microbial strains. The peptide 6 was also subjected to molecular docking simulations in the active sites of the prior kinases.

KEY WORDS: Peptides, Glycyrrhetinic acid, Anticancer, Cytotoxicity, Molecular docking, Antimicrobial activity

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1369-1392.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.14

Design, synthesis and molecular docking study of novel bis-oxazolone derivatives as potent antioxidant and antibacterial agents

2024-07-12T08:14:52+00:00

In response to the challenge of antibiotic-resistant microorganisms, oxazolone analogs are frequently used for bacterial, antiviral, and anti-inflammatory treatments. However, few studies have shown bis-oxazolone analogs possess antibacterial activities. In this study, we modified bis-oxazolone molecules with various aromatic amines to create new bis-benzamide and bis-imidazolone derivatives. These derivatives were analyzed using FT-IR, ¹H-NMR, and ¹³C-NMR spectroscopy. Molecular docking revealed favorable interactions with DNA gyrase, with compounds 3, 4a, and 5e showing higher binding affinities than penicillin G and ampicillin. These findings suggest their potential as future antimicrobial agents. The tested compounds demonstrated efficacy against bacterial strains, particularly E. coli and S. aureus, with significant activity observed in compounds 4a, 4e, 5d, and 5e. Antioxidant activity, assessed using the DPPH method, showed bis-compounds with excellent results comparable to ascorbic acid. This encourages further studies to explore their potential. Overall, the synthesized bis-oxazolone derivatives demonstrated increased medicinal activity and high potential as future antimicrobial and antioxidant agents.

KEY WORDS: Bis-oxazolone, Bis-benzamide, Bis-imidazolone, Docking study, Antibacterial, Antioxidant

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1393-1404.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.15

A synthesis of 1,3-dienes using a Ni(II) mediated Suzuki-Miyaura reaction

2024-07-12T08:18:29+00:00

Synthesis of the 1,3-dienes from arylboronic acids with propargyl alcohols using a Ni(II) precatalysts is presented. Through detailed reaction screening NiCl₂(PCy₃)₂ has been identified as the optimal catalyst for this transformation. The reaction is thought to proceed through a Ni(II) allenyl complex, which undergoes a base free Suzuki-Miyaura cross-coupling through arylboronic acids, with the resultant aryl allene rearranging to its 1,3-diene. Application of these optimized reaction conditions then provides several dienes in reasonable to good, isolated yields.

KEY WORDS: Suzuki-Miyaura, NiCl₂(PCy₃)₂, 1,3-Dienes, Allenyl, Base free

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1405-1412.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.16

Dual fluorescence emission of p-N,N-(dialkylamino) benzyl-idenemalononitrile and related systems: Evidence for direct excitation of ground state twisted intramolecular charge transfer (TICT) conformer

2024-07-12T08:22:25+00:00

The mechanism of dual fluorescence emission of a fluorophore is controversial ever since its first observation in p-N,N-dimethylaminobenzonitrile (DMABN). Excited state twisted intramolecular charge transfer (TICT) and planarized intramolecular charge transfer (PICT) models have been the two prominent theories used to explain the dual fluorescence mechanism in several systems. These mechanisms are based on excited state adiabatic structural changes of the fluorophore. Nevertheless, pieces of evidences based on excitation spectral measurements at different emission windows suggest the possibility of additional and/or alternative mechanisms based on ground state structural changes of the fluorophore. In this paper, we have presented a systematic steady-state absorption and fluorescence spectroscopy of a donor-πacceptor system, p-N,N-(dialkylamino)benzylidenemalononitrile, and related compounds in solvents of different polarities. The excitation spectrum of p-N,N-(dialkylamino) benzylidenemalononitrile is found to be dependent on the emission window. Furthermore, the emission spectra of the molecule are dependent on the excitation wavelength which suggest that the molecule consists of two stable ground state conformational isomers. The spectroscopic pieces of evidence together with results from DFT calculations are in favor of the solvent-induced ground state structural change of the fluorophore. Hence, two ground state conformers of p-N,N-(dialkylamino)benzylidenemalononitrile are attributed to the dual emission of the molecule.

KEY WORDS: Dual fluorescence, Charge transfer, TICT, PICT, Excitation, Benzylidenemalononitriles

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1413-1427.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.17

Liquid-combustion synthesis of spinel LiMn2O4 cathode material for enhanced electrochemical performance lithium-ion batteries

2024-07-12T08:28:12+00:00

A cubic spinel LiMn₂O₄ cathode material with nanoscale was synthesized via a facile liquid-combustion method at 600, 750 and 850 ℃. The crystal structure and surface morphology of LiMn₂O₄ electrodes have been characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) technique. The samples have an average diameter of 200 nm with an octahedral structure with high crystallinity. Benefiting from the excellent structure, the sample prepared at 750 ℃ delivers the highest first discharge capacity of 115.3 mAh·g⁻¹ with remaining 101.5 mAh·g⁻¹ after 400 cycles at 1 C. Moreover, it exhibits a good cycling performance at 55 ℃, still had the capacity of 105.4 mAh·g⁻¹ with a capacity retention of 71.2% following 282 cycles. The facilely synthesized octahedral LiMn₂O₄ provides a practical application strategy for lithium-ion batteries.

KEY WORDS: Spinel LiMn₂O₄, Liquid-combustion method, Lithium-ion batteries

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1429-1437.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.18

Mechanical and heat transfer behaviour of electro-deposited nickel-zirconia coating

2024-07-12T08:34:50+00:00

Thermal barrier coatings (TBCs) are often applied to base metals exposed to excessive temperatures to protect them from the harsh operating thermal cycle load conditions and to enhance their functionality. For this research, nickel and zirconia was coated over a mild steel substrate by electro-deposition or co-deposition method. While selecting appropriate electro-deposition parameters, this study analyses the convection and conduction heat transfer characteristics and mechanical behaviours of a nickel-zirconia co-deposit over a mild steel substrate. The better-quality deposition is formed with thicknesses of 10 μm and 50 μm. The microstructure and morphological analyses were conducted using scanning electron microscope (SEM). The phase analysis was conducted using X-ray diffraction analysis (XRD). The porosity, hardness and wear behaviours were measured as per the American Society for Testing and Materials (ASTM). The results showed that nickel-zirconia coating has better performance. The coating's convection and conduction heat transfer potential are investigated using a specially designed and constructed experimentation apparatus. Compared to an uncoated panel, heat transfer studies on nickel-zirconia coatings demonstrate that nano-coatings with a particle size of about 92 nm show a significant temperature drop with varied coating thicknesses and heat inputs for different heat inputs.

KEY WORDS: Thermal barrier coatings, Electro deposition, Conduction heat transfer, Convection heat transfer, Nickel-Zirconia

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1439-1452.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.19

A novel composite la-conversion coatings for enhanced anti-corrosion performance under a harsh aqueous environment

2024-07-12T08:39:01+00:00

The ceramic lanthanum nanoparticles with uniformly dispersed spherical nanostructures were successfully synthesized using sonication-assisted synthesis. The morphologies and phase compositions were assessed and investigated. The electrochemical impedance analysis potentio-dynamic polarisation measurements were used to calculate the corrosion protection properties of prepared ceramic lanthanum nanoparticles. The La₂O₃ nanoparticles were added as a surface coating layer to enhance the corrosion resistance of low-carbon steel. The particles' impact on coating development, morphology, and corrosion inhibition efficacy were studied. After particle integration, results show a dramatic reduction in porosity and thickness, affecting corrosion resistance. Incorporating ceramic lanthanum nanoparticles into a coating reduces porosity and increases hardness, improving corrosion resistance; the result implies the suggested technique is viable for creating functionalized coatings on low-carbon-based materials. The results also demonstrated that these methods may increase the development and protectiveness of the coating. There was a crucial nano particulate La₂O₃ level at which the conversion coatings exhibited the best protective qualities. As it increased the corrosion potential and lowered the anodic current, the composite La-conversion coatings may offer substantial corrosion protection for prolonged immersion in a 3.5% NaCl solution.

KEY WORDS: Ceramic nanoparticles, Low carbon steel, Corrosion prevention, Polarization

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1453-1468.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.20

Theoretical study on the molecular and crystal structures of myricetin

2024-07-12T09:02:07+00:00

The molecular and crystal structures of myricetin have been studied using density functional theory. The geometry parameters are calculated based on the optimized molecular structure, and the thermodynamic properties “heat capacity, enthalpy and entropy” are performed using our self-programmed programme, the calculated results are consistent with literature reports. Crystal structures were predicted using the Dreiding force field and refined by DFT-GGA-RPBE method. The crystal form tends to crystalline in P-1 space group. The large calculated band gap (E_g) of the crystal proves it is stable, which is consistent with the conclusion from gas phase. The conduction band (LUCO) is mainly contributed from the p state of C atom and valence band (HOCO) from the p state of O atom.

KEY WORDS: Molecular structure, Crystal structure, Myricetin, Theoretical study

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1469-1478.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.21

Investigation of the electrical potential of whey using a river sediment microbial fuel cell

2024-07-13T06:54:03+00:00

This study aimed to use whey and river sediment microbial fuel cells (SMFCs) to produce electrical potential, which has been investigated rarely in previous studies. In this study, the majority of the microorganisms in the river SMFC mixed culture were Bacteroides and Clostridium. After the voltage and internal resistance were measured, the current and power density were calculated. The power density (279*10-3 mW/cm2 ) and maximum current density (1100*10-6 mA/cm2 ) were determined through computations. Bacteria present in river SMFCs showed the potential to generate electricity without any external mediators. By utilizing organic materials, bioelectricity can be produced affordably and sustainably.

KEY WORDS: Electrical potential, SMFC, Treatment, Whey, River sediment

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1479-1491.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.22

Investigation on sulfur substituted cadmium ions with superhydrophobic nature and long-term anticorrosion performance

2024-07-12T08:55:43+00:00

Cadmium sulfide nanoparticles (CdS) were effectively prepared using ultrasonication-assisted synthesis. The high hydrophobicity and excellent dispersibility of the synthesised CdS nanoparticles in ethanol could increase their anti-penetrant effect against corrosive media. We evaluated and examined the corrosion prevention properties of CdS nanoparticle coatings on MS steel using Tafel polarisation and electrochemical impedance spectroscopy in HCl, NaCl, and KOH. The experimental results demonstrated that CdS nanoparticle coatings had higher corrosion performance than uncoated MS plates. Besides, CdS nanoparticles may be adsorbed on steel to produce a hydrophobic anti-corrosion layer, enhancing corrosion resistance. The impedance of CdS coatings increased continuously during electrolyte immersion. The results show that CdS acted as a suitable inhibitor and this inhibition efficiency and the polarization curves indicated that CdS nanoparticles performed as mixed inhibitors. The inhibition effect on the surface of the MS plate using CdS nanoparticle coating was investigated with inhibitors confirmed by nanoindentation techniques. The revolutionary approach for creating hydrophobic CdS nanoparticles suggested in this exertion may stimulate the development of high-performance anticorrosion materials and their corrosive protection applications.

KEY WORDS: CdS nanoparticles, Mild steel plate coating, Anticorrosion applications

Bull. Chem. Soc. Ethiop. 2024, 38(5), 1493-1507.

DOI: https://dx.doi.org/10.4314/bcse.v38i5.23