Carbonyl Oxygen Atom Research Articles

Synthesis of new Cu(II), Ni(II), and Cd(II)-(N-Glycyl-L-leucine) complexes as peptide metalloantibiotics for targeting pathogenic water with antioxidant effect investigation

Abstract Background In recent efforts to address the critical need for clean and portable water, we have focused on innovative methods to eliminate pathogenic microorganisms. To this aim, the N-Glycyl-L-leucine (Gly-Leu) peptide ligand was complexed with different transition metal ions [Cu(II), Ni(II), and Cd(II)] as new peptide metalloantibiotics. The compounds were characterized and examined using various analytical methods, including elemental analysis (CHN), Fourier transform infrared spectroscopy (FTIR), assessments of magnetic properties, molar conductivity, 1HNMR, thermogravimetric analysis (TGA), and mass spectroscopy. The ligand acted as a di-anionic molecule using the carboxylate and the deprotonated amide nitrogen atom. The coordination sites were completed with carbonyl oxygen atoms and a water molecule. The complexes showed polymeric structures using bridging carboxylate groups. Results The antibacterial properties of the synthesized metal chelate were evaluated using disk diffusion and minimum inhibitory concentration methods on bacterial organisms identified from water samples taken from the Nile River. At a 1 mg/mL dose, the Cu(II)-chelate showed the biggest inhibitory zone of 27 mm against Klebsiella pneumonia, with a MIC value of 62.5 μg/mL, greater than that of the common gentamicin medication. Molecular docking investigations supported these findings, showing that Cu(II)-chelate had the lowest binding energy of − 6.16 kcal/mol, indicating significant, beneficial interactions with the amino acids in the active region of bacterial proteins. Furthermore, the Cu(II) complex and the COVID-19 main protease showed encouraging results in the docking analysis, indicating that the complex may have antiviral properties and be able to inhibit viral propagation successfully. The metal chelates demonstrated noteworthy antioxidant activity, especially against 1,1-diphenyl-2-picrylhydrazyl (DPPH radicals). The IC50 values of the antioxidant assay for Ni(II) and Cu(II) chelates were extremely similar to ascorbic acid, a common antioxidant. Their notable antioxidant capacity was demonstrated by the IC50 values of (14.4, 15.5, and 18 µg/mL) for ascorbic acid, Ni(II), and Cu(II) chelates, respectively. Conclusions Our study successfully demonstrated the potential of a new Gly-Leu peptide ligand complexed with transition metal ions, particularly Cu(II), in eliminating pathogenic microorganisms from water. Cu(II)-chelate exhibited superior antibacterial properties, as confirmed by both experimental and molecular docking results. The chelates also displayed noteworthy antioxidant capacity, comparable to that of ascorbic acid. Additionally, the Cu(II)-chelate demonstrated promising antiviral potential, theoretically interacting effectively with the COVID-19 main protease, which suggests its ability to inhibit viral replication. These results underscore the potential of Cu(II)-chelate as a multi-functional compound with applications in water purification and therapeutic fields.

Remote Spin-Center Shift Enables Activation of Distal Benzylic C─O and C─N Bonds.

A spin-center shift (SCS) is a radical process that commonly involves a 1,2-radical shift along with the elimination of an adjacent leaving group by a two-electron ionic movement. The conventional SCS process is largely limited to 1,2-radical translocation, while a remote SCS event involving 1,n-radical translocation over a greater distance to enable distal bond functionalization remains largely underexplored. Herein, we report the boryl radical-promoted distal deoxygenation and deamination of free benzylic alcohols and simple benzylic amines, respectively, through a remote SCS event. The reaction was initiated by the addition of a 4-dimethylaminopyridine (DMAP)-boryl radical to the carbonyl oxygen atom of a benzoate or benzamide. Then, radical translocation took place across the aromatic ring to promote benzylic C─O or C─N bond cleavage. The resulting radical intermediate subsequently coupled with various alkenes to afford a wide range of alkylated products. The proposed mechanistic pathway was supported by experimental investigations.

Remote Spin‐Center Shift Enables Activation of Distal Benzylic C─O and C─N Bonds

AbstractA spin‐center shift (SCS) is a radical process that commonly involves a 1,2‐radical shift along with the elimination of an adjacent leaving group by a two‐electron ionic movement. The conventional SCS process is largely limited to 1,2‐radical translocation, while a remote SCS event involving 1,n‐radical translocation over a greater distance to enable distal bond functionalization remains largely underexplored. Herein, we report the boryl radical‐promoted distal deoxygenation and deamination of free benzylic alcohols and simple benzylic amines, respectively, through a remote SCS event. The reaction was initiated by the addition of a 4‐dimethylaminopyridine (DMAP)‐boryl radical to the carbonyl oxygen atom of a benzoate or benzamide. Then, radical translocation took place across the aromatic ring to promote benzylic C─O or C─N bond cleavage. The resulting radical intermediate subsequently coupled with various alkenes to afford a wide range of alkylated products. The proposed mechanistic pathway was supported by experimental investigations.

Peptide bonds revisited.

Understanding the structural and chemical properties of peptide bonds within protein secondary structures is vital for elucidating their roles in protein folding, stability and function. This study examines the distinct characteristics of peptide bonds in α-helices and β-strands using a nonredundant data set comprising 1024 high-resolution protein crystal structures from the Protein Data Bank (PDB). The analysis reveals surprising and intriguing insights into bond lengths, angles, dihedral angles, electron-density distributions and hydrogen bonding within α-helices and β-strands. While the respective bond lengths (CN and CO) do not differ much between helices and strands, the bond angles (∠CNCα and ∠OCN) are significantly larger in strands compared with helices. Furthermore, the peptide dihedral angle (ω) in helices clusters around 180° and follows a sharp Gaussian distribution with a standard deviation of 4.1°. In contrast, the distribution of dihedral angles in strands spans a much wider range, with a more flattened Gaussian peak around 180°. This distinct difference in the distribution of dihedral angles reflects the unique structural characteristics of helices and strands, highlighting their respective conformational preferences. Additionally, if the ratio of the electron-density values (2mFo - DFc) at the midpoint of the CO bond and of the CN bond is calculated, a skewed distribution is observed, with the ratio being lower for helices than for strands. Moreover, higher normalized mean atomic displacement parameters (ADPs) for peptide atoms in helices relative to strands suggest increased flexibility or a more dynamic structure within helical regions. Analysis of hydrogen-bond distances between O and N atoms of the main chain reveals larger distances in helices compared with strands, indicative of distinct hydrogen-bonding patterns associated with different secondary structures. All of these observations taken together led us to conclude that peptide bonds in α-helices are different from peptide bonds in β-strands. Overall, α-helical peptide bonds seem to display a more enol-like character. This suggests that peptide oxygen atoms in helices are more likely to be protonated. These findings have several important implications for refining protein structures, particularly in regions susceptible to enol-like transitions or protonation. By recognizing the distinct bond-angle and bond-length variations associated with protonated carbonyl oxygen atoms, current refinement protocols can be adapted to apply more flexible restraints in these regions. This could improve the accuracy of modelling local geometries, where protonation or enol forms lead to subtle structural deviations from the canonical bond parameters typically enforced in refinement strategies.

Cobalt(II) complexes with a novel 2,6-diacetylpyridine-adamantane-1-carbohydrazide ligand

A new Schiff base of 2,6-diacetylpyridine and adamantane-1-carbohydrazide—L, as well as two of its solvatomorphic complexes with Co(II), viz. [Co(L)(H2O)(EtOH)][CoCl4] ∙ EtOH ∙ H2O (1) and [Co(L)(MeCN)2][CoCl4] ∙ MeCN (2), were synthesized. The reaction of CoCl2 ∙ 6H2O with the ligand in a molar ratio 2:1 in ethanol–acetone solvents gives complex 1, while the same reaction in acetonitrile–acetone solvents gives complex 2. Characterization involved elemental analysis, Fourier transform infrared spectroscopy (FTIR), conductometric measurements, thermogravimetric analysis, single-crystal X-ray diffraction (SC-XRD), and antioxidant tests. Structural analysis revealed ligand coordination in its neutral form as N3O2 pentadentate. The cobalt(II) is placed in a pentagonal bipyramidal environment in both complexes, where the donor atoms of the ligand (one pyridine nitrogen, two azomethine nitrogen, and two carbonyl oxygen atoms) form the base of this polyhedron, and solvent donor atoms occupy the axial positions. Detailed comparative analysis of the structural parameters of free ligands and the complexes, as well as their thermal characterization, is given, enabling a better understanding of the measured antioxidant activity. The results suggest the potential these compounds have in further examination of their biological activity, with the complexes being more active than the ligand itself.

Exploration of Novel Nickel(II) and Copper(II)–Levofloxacin Mixed‐Ligand Complexes: Structural Study, DFT Insights, Molecular Docking, and In Vitro Bioactivity Assessment

ABSTRACTIn this study, we combined NiCl2 and CuCl2 with levofloxacin (LEV) in the presence of 2,6‐di(1H‐pyrazol‐1‐yl)pyridine (DPP) to generate two novel NiLEVDPP and CuLEVDPP mixed‐ligand complexes. Evaluating their antibacterial, antifungal, anti‐inflammatory, and antioxidant properties was the goal. Numerous analytical methods, such as elemental analysis, molar conductivity, electronic spectroscopy, infrared spectroscopy, mass spectrometry, magnetic susceptibility measurements, and thermogravimetric analysis, were used to confirm the chelation process and determine the structures of these complexes. The findings demonstrated that the carbonyl and carboxylic oxygen atoms in LEV and the –C=N– nitrogen of DPP's pyridine and pyrazole rings facilitate coordination between LEV and the metal ions. The octahedral geometries of the Ni(II) (NiLEVDPP) and Cu(II) (CuLEVDPP) complexes were proposed and confirmed by density functional theory (DFT) calculations. In addition, metrics including energy gaps, chemical hardness, softness, chemical potential, and electrophilicity index were studied. Frontier molecular orbitals (HOMO and LUMO) and molecular electrostatic potential (MEP) were also investigated. The synthesized compounds showed remarkable efficiency when tested in vitro against a variety of harmful bacteria and fungi for their antibacterial activities. Additionally, the anti‐inflammatory effects were studied, and the antioxidant activity was evaluated using the DPPH test. The results showed that these novel complexes outperformed the free ligands in terms of antibacterial, antioxidant, and anti‐inflammatory effects. Molecular docking experiments further supported the in vitro results by demonstrating the strong binding affinity and activity of the Ni(II) (NiLEVDPP) and Cu(II) (CuLEVDPP) complexes towards the target receptors 1HNJ, 5IJT, and 5IKT.

Recent Advances in the Construction and Application of Anion-Induced Cucurbit[n]uril-Based Supramolecular Assemblies via Outer-Surface Interactions.

Cucurbit[n]urils (abbreviated as Q[n]s or CB[n]s) are synthesized through the condensation of formaldehyde and glycoluril in a hydrochloric acid environment. These molecules exhibit three distinctive properties concerning their charge distribution: a neutral internal cavity, a positively charged outer surface, and a negatively charged portal carbonyl oxygen atoms. These unique characteristics facilitate the formation of supramolecular frameworks with a range of anions and metal polyanions. The primary focus of this review is on the creation of anion-induced Q[n]-based supramolecular self-assemblies and exploring their potential applications in metal ion sequestration and release, gas adsorption, as well as the development of fluorescence probes. Additionally, a concise review of current research on anion-induced Q[n]-based supramolecular compounds is provided, aiming to stimulate future advancements in the field of innovative supramolecular framework materials.

2,2'-[(4-But-oxy-phen-yl)methyl-ene]bis-(3-hy-droxy-5,5-di-methyl-cyclo-hex-2-en-1-one).

In the title compound, C27H36O5, the dihedral angles between the planes of the benzene ring and the cyclo-hexenone rings are 60.87 (10) and 65.04 (10)°, while the dihedral angle between the mean planes of the two cyclo-hexenone rings is 39.33 (10)°. Each cyclo-hexenone ring has a carbon atom bonded to two methyl groups, which acts as the flap atom, resulting in an envelope conformation. The opposite orientation of the hy-droxy and carbonyl oxygen atoms allows for the formation of two intra-molecular O-H⋯O hydrogen bonds and C-H⋯π (ring) inter-actions also help to establish the molecular conformation.

Regio- and Redox Divergent Hydrated Ring Expansion of Butafulvenes.

By providing highly functionalized building blocks in an efficient approach, catalytic hydration of alkenes plays a significant role in fundamental chemical transformations and pharmaceutical synthesis. However, hydration reactions have predominantly involved addition reactions of water and alkenes double bond. Herein, we developed a regio- and redox divergent hydrated ring expansion protocol of butafulvenes. With the aid of PdII or acid catalysis, various highly functionalized and unsaturated cyclopentanone derivatives could be obtained in high regioselectivities under oxidative or redox neutral conditions. Isotope labeling experiments suggest that the carbonylic oxygen atom of target product is derived from water. In addition, the unsaturated cyclopentanone intermediate could undergo divergent transformations and serve as a key molecule to create skeletal editing compounds of butafulvenes via one-pot protocol, which highlights the potential applications of this strategy.

QUANTUM-CHEMICAL CALCULATIONS OF CURCUMIN AND SOME METAL COMPLEXES BASED ON IT

Using the semi-empirical PM7 method in combination with the SPARKLE model, the structure of isomeric forms and the energetics of conformational and tautomeric transformations of the curcumin molecule were calculated, the geometry of the ligandand transition metal complexes (Zn(II), Dy(III), Ag(I)) based on it were optimized: ZnCur2∙2H2O, ZnCur2∙Phen, DyСur3∙3H2O, AgZnСur3∙H2O∙AcOH. The energetic characteristics of the compounds were calculated, described and analyzed, such as the total energy of the molecules, the enthalpy of formation, the dipole moment, the energies of the highest occupied molecular orbital (ЕHOMO) and the lowest unoccupied molecular orbital (ЕLUMO), the ionization potential, the electron affinity, the rigidity, the softness and the main bondlengths and the charges on the atoms. Based on the calculated values of the heat of formation, the energy gap ∆E and the overall rigidity, it is assumed that the enol form of the curcumin molecule is more energetically favorable and more chemically reactive compared to the ketoform. In addition, the stability of Curenol is additionally due to the presence of intramolecular hydrogen bonding. Curcuminate metal complexes, regardless of the metal, arecharacterized by a non-planar structure in which the curcumin ligands are coordinated bidentately-chelately through the β-diketone fragment with the formation of 6-membered metalcycles [OМOCCC]. Analysis of the values ​​of the enthalpy of formation of the complexes showed that the process of molecule formation is exothermicand ΔH increases in the series AgZnСur3∙H2O∙AcOH > DyCur3∙3H2O > ZnCur2∙2H2O > ZnCur2∙Phen. The least stable is the ZnCur2∙Phen complex, which is also confirmed by the smallest energy gap value (ΔE = -6.66 eV). It is shown that in the heterometallic complex AgZnСur3∙H2O∙AcOH there is a tendency to form a more compact structure, which may be due to the formation of weak hydrogen bonds between the carbonyl oxygen atoms of curcumin molecules coordinated to the Zn and Ag atoms.

Stereochemical Editing at sp3-Hybridized Carbon Centers by Reversible, Photochemically Triggered Hydrogen Atom Transfer.

ConspectusMillions of chiral compounds contain a stereogenic sp3-hybridized carbon center with a hydrogen atom as one of the four different substituents. The stereogenic center can be edited in an increasing number of cases by selective hydrogen atom transfer (HAT) to and from a photocatalyst. This Account describes the development of photochemical deracemization reactions using chiral oxazole-annulated benzophenones with a bonding motif that allows them to recognize chiral lactam substrates by two-point hydrogen bonding. The backbone of the catalysts consists of a chiral azabicyclo[3.3.1]nonan-2-one with a U-shaped geometry, which enables substrate recognition to occur parallel to the benzoxazole part of the aromatic ketones. The photocatalysts facilitate a catalytic photochemical deracemization of several compound classes including hydantoins, N-carboxyanhydrides, oxindoles, 2,5-diketopiperazines, and 4,7-diaza-1-isoindolinones. In addition, if more than one stereogenic center is present, the editing delivers a distinct diastereoisomer upon the appropriate selection of the respective photocatalyst enantiomer. The chiral photocatalysts operate via the benzophenone triplet that selectively abstracts a properly positioned hydrogen atom in exclusively one of the two substrate enantiomers. The photochemical step creates a planar carbon-centered radical and erases the absolute configuration at this position. While returning HAT to the same position would likely recreate the stereogenic center with the same absolute configuration, spectroscopic and quantum chemical studies suggest that the hydrogen atom is delivered from the photocatalyst to a heteroatom that is in conjugation to the radical center. Two scenarios can be distinguished for the hydrogen atom shuttling process. For hydantoins, N-carboxyanhydrides, and 4,7-diaza-1-isoindolinones, the back HAT occurs to a carbonyl oxygen atom or an imine-type nitrogen atom which is not involved in binding to the catalyst. For oxindoles and 2,5-diketopiperazines, a single lactam carbonyl group in the substrate is available to accept the hydrogen atom. It is currently assumed that back HAT occurs to this group, although the carbonyl oxygen atom is involved in hydrogen bonding to the catalyst. In comparison to the former reaction pathway, the latter process appears to be less efficient and more prone to side reactions. For both cases, an achiral enol or enamine is formed, which delivers upon dissociation from the catalyst statistically either one of the two stereoisomers of the substrate. Since only one substrate enantiomer (or diastereoisomer) is processed, a high enantioselectivity (or diastereoselectivity) results. Even though the editing is a contra-thermodynamic process, the described decoupling of a photochemical and a thermal step allows the usage of a single catalyst in loadings that vary between 2.5 and 10 mol % depending on the specific mode of action.

Preparation, characterization, antimicrobial evaluation, and molecular docking study of paracetamol and niacin mixed-drugs of Mn(II), Fe(II), and Co(II) complexes

The mixed drugs of paracetamol (PCM) and niacin (NCT) complexes of the form [Co(PCM)(NCT)H2OCl], [Fe(PCM)(NCT)SO4], and [Mn(PCM)(NCT)SO4] were synthesized by direct combination through refluxing and characterized using melting point/decomposition determination, solubility, conductivity, magnetic moment measurement, percentage metal analysis, and electronic and infrared spectroscopies. The lone drugs and complexes were also tested in-vitro against clinical bacteria. The strains- Staphylococcus aureus, Bacillus cereus (Gram-positive); Pseudomonas aeruginosa, Escherichia coli (Gram-negative) and Aspergillus niger, Fusarium species (fungi) were employed. Quickprep tool entrenched in molecular operating environments (MOE) software was used for the optimization of the compounds and the descriptors obtained were reported.The complexes’ infrared spectra revealed their bidentate nature, indicating paracetamol binding sites with metal ions as oxygen of carbonyl (C=O) and hydroxyl (O–H) groups; and to the niacin as the nitrogen (N) of pyridine ring and carbonyl oxygen (C=O) atoms. All the complexes assumed an octahedral geometry as supported and suggested by electronic spectra, magnetic moments, and percentage metal analysis. Conductivity measurements also established the covalent nature of the complexes, with the values range 13.78–18.35 Ω−1cm2mol−1. The antimicrobial screening revealed that the Mn(II) complex has the greatest antibacterial potency and fungicidal strength with inhibitory values (30.00–36.67 mm) and (36.67–38.33 mm) respectively, compared to others. The calculated descriptors also revealed that the studied compounds possess antimicrobial activities and this was further supported by molecular docking studies with the calculated binding affinity for the Co(II) complex, Fe(II) complex, and, Mn(II) complex against all the studied targets were − 4.89 kcal/mol, − 5.52 kcal/mol and − 5.83 kcal/mol (PDB ID: 2C1G); − 5.18 kcal/mol, − 5.42 kcal/mol and − 5.97 kcal/mol (PDB ID: 6TY6) and − 5.57 kcal/mol, − 6.17 kcal/mol and − 7.55 kcal/mol (PDB ID: 4WMZ) respectively.The complexes were good potential antibacterial and antifungal candidates with broad-spectrum as corroborated by molecular docking studies.Graphical abstract

Experimental and DFT Studies of Intermolecular Interaction-Assisted Oxindole Cyclization Reaction of Di-t-butyl 2-Aminophenyl-2-methyl Malonate

Density functional theory calculations on the cyclization of di-t-butyl 2-(2-aminophenyl)-2-methyl malonate (1) to t-butyl 3-methyloxindole-3-carboxylate (2) reveal that acetic acid-assisted protonation of the carbonyl oxygen atom reduces the activation Gibbs free energy significantly lower than methanol-assisted pathways. Experimental data confirm that reaction concentration plays a pivotal role in oxindole formation. Experimental results also indicate distinct reaction mechanisms at low and high concentrations. Achieving high enantioselectivity for chiral compound 2 in high-concentration reactions requires discovering a novel chiral acid.

Primary radical ions in irradiated carbonates.

This study focuses on primary radical ionic species created in liquid carbonates upon high-energy radiation. We studied the radiation-induced fluorescence intensity decays observed from solutions of luminophores in dimethyl, diethyl, ethylene, and propylene carbonates. Based on the effects of external magnetic and electric fields on the fluorescence decays on a timescale of 1-60 ns and quantum chemical calculations, we found that in all studied carbonates, solvent ionization was rapidly followed by the formation of comparatively long-lived positive charge and unpaired electron spin carriers. These carriers are complexes in which two carbonate molecules are oriented to each other by carbonyl groups, with the charge and spin density primarily distributed over these two CO groups. In the case of diethyl carbonate, the formation of such a complex occurs with a probability that depends on the conformation of ionized molecules and on the rate of parallel reaction of intramolecular proton transfer from the methyl or methylene groups to the carbonyl oxygen atom. In low-polarity carbonates, evidence for the existence of solvent radical anions with molecular mobility was found.

New Mononuclear Metal Complexes Based on 3‐Acetyl‐4‐Hydroxy Coumarin as Potential Antitumor Agents: Full Structural Elucidation, Theoretical Calculations, and Biological Activity Studies

ABSTRACTNew transition metal complexes (M‐AHyC) have been prepared: M = Ni2+, Co2+, and Zn2+ metal ions; AHyC = 3‐acetyl‐4‐hydroxy coumarin. The synthesized complexes (M‐AHyC) were also subjected to elemental and TGA analysis, magnetic moment, and molar conductivity measurements with comprehensive spectral characterization (Fourier transform‐IR, UV‐visible, NMR, and XR diffraction). Ni2+, Co2+, and Zn2+ metal ions react with AHyC to form complexes with a stoichiometric ratio 1:2 (M:L). The results of spectral data revealed that the AHyC coordinated the central metal ions in a monoanionic bidentate manner via the carbonyl oxygen and phenolic oxygen atoms forming octahedral geometry. Against HepG‐2 cell lines, the cytotoxic properties of fabricated M‐AHyC compounds were assessed. The cytotoxic study revealed that the Zn‐AHyC complex showed significant activity to inhibit the growth of the HepG‐2 cell line. Additionally, the binding properties of M‐AHyC complexes with herring sperm DNA (HS‐DNA) have been identified using UV‐visible spectroscopy. The interaction between M‐AHyC complexes and DNA revealed a moderately strong interaction depending on the intercalative binding mode. The interaction of M‐AHyC complexes with DNA was further investigated with molecular docking simulation, which supports previously spectroscopic findings. A study on DNA cleavage using agarose gel electrophoresis has also been performed. The DFT calculations were utilized to compute chemical quantum parameters, validate the proposed structures, and provide evidence for the biological findings.

Synthesis, Characterization and Catalytic/Antimicrobial Activities of Some Transition Metal Complexes Derived from 2-Floro-N-((2-Hydroxyphenyl)Methylene)Benzohydrazide.

In the last few decades, the field of coordination chemistry has grown very fast, especially in the fields of pharmaceutical, biological and catalytic studies. In ancient times, metals were thought to be beneficial to health issues but nowadays the link between organic-metal substances and different industrial and medicinal properties is well established. A Schiff base ligand (2-fluoro-N'-[(E)-2-hydroxyphenyl) methylene] benzohydrazide) was reacted with a series of transition metals to produce complexes with a general formula [ML2(NO3)]NO3.nH2O, where [M = Zn, Cu, Co, Ni, Mn], and [n = 0, 1], corresponding to complexes 1-5. The nature of the bond was determined in the solid state and solution using spectral studies (1H-NMR, 13C-NMR, UV-Vis and FT-IR), TGA, EPR, elemental analysis and molar conductivity measurement. All M(II) complexes are 1:1 electrolytes, as illustrated by their molar conductivities. The results demonstrate that all synthesized complexes present a coordination number of six by the bonding of the bidentate ligand via its azomethine nitrogen atoms and carbonyl oxygen atoms, as well as with one nitrate group as a bidentate ligand via two oxygen atoms. The DPPH radical scavenging technique was used to investigate the antioxidant activities of the ligand [L] and the metal complexes. It is clear that the activity increased in M (II) complexes compared to the Schiff base ligand. Complex 5 showed the highest activity, with an excellent activity of 90.4%, while complex 4 showed the lowest. The antibacterial activities of the Schiff base and its complexes have been examined against various pathogenic bacteria to measure their inhibition potential. Complex 2 showed remarkable activity against Gram (+) bacteria and fungi with an MIC value of 8 μg/mL, which is greater than that of the positive controls, oxytetracycline and fluconazole. The catalytic activities of all complexes were examined in the oxidation of aniline, and the results illustrated that all complexes had a 100% selectivity in producing only azobenzene, and complex 4 had the highest activity (91%). The obtained results from this study show that the antioxidant and antibacterial properties of both the Schiff base ligand and its derived complexes are promising, with some demonstrating remarkable activities. Moreover, the catalytic activities and selectivities of the prepared complexes in aniline oxidation are interesting.

Synthesis, Characterization, Biological, and Antioxidant Activity of New Metal Ion Complexes with Schiff Base Derived from 2-Hydroxybenzohydrazide

The study involved the synthesis of new complexes with tetradentate ligand (LH). The general formula of complexes was [M(LH)(H2O)2] with M of Ni2+, Co2+, Cu2+, and Zn+. The ligand was synthesized by treating the 2-hydroxybenzohydrazide with salicylaldehyde. The structural characteristics of ligands and complexes were analyzed using various techniques, including elemental analyses, magnetic susceptibility, molar conductivity, infrared, ultraviolet absorption, mass, and NMR spectroscopy studies. The physical measurements indicated that the prepared complexes are non-electrolyte and showed that the ligand is tetradentate when coordinated with metal ions through the nitrogen of azomethine (–C=N–), two oxygen atoms of O–H phenolic, and an oxygen atom of carbonyl (C=O) for benzohydrazide. It was found that Co2+, Cu2+, and Zn2+ complexes are octahedral, while Ni2+ complexes are square planar. The biological screening of the complexes demonstrates that the Schiff base metal complexes exhibit remarkable efficacy in combating microorganisms by utilizing Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) and Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli) bacteria, as well as Candida albicans fungi. Hence, their results were good in inhibition. Then, the potential of these prepared compounds as antioxidants was determined by inhibiting free radicals.

Symmetry Breaking of Electronic Structure upon the π→π* Excitation in Anthranilic Acid Homodimer.

The main purpose of this study is to characterize the nature of the low-energy singlet excited states of the anthranilic acid homodimer (AA2) and their changes (symmetry breaking) caused by deformation of the centrosymmetric, ground state structure of AA2 towards the geometry of the S1 state. We employ both the correlated ab initio methods (approximate Coupled Clusters Singles and Doubles-CC2 and CASSCF/NEVPT2) as well as the DFT/TDDFT calculations with two exchange-correlation functionals, i.e., B3LYP and CAM-B3LYP. The composition of the wavefunctions is investigated using the one-electron transition density matrix and difference density maps. We demonstrate that in the case of AA2, small asymmetric distortions of geometry bring about unproportionally large changes in the excited state wavefunctions. We further provide comprehensive characterization of the AA2 electronic structure, showing that the excitation is nearly completely localized on one of the monomers, which stands in agreement with the experimental evidence. The excitation increases the π-electronic coupling of the substituents and the aromatic ring, but only in the excited monomer, while the changes in the electronic structure of the unexcited monomer are negligible (after geometry relaxation). The increased electronic density strengthens both intra- and intermolecular hydrogen bonds formed by the carbonyl oxygen atom of the excited monomer, making them significantly stronger than in the ground state. Although the overall pattern of changes remains qualitatively consistent across all methods employed, CC2 predicts more pronounced excitation-induced modifications of the electronic structure compared to the more routinely used TDDFT approach. The most important deficiency of the B3LYP functional in the present context is locating two charge-transfer states at erroneously low energies, in close proximity of the S1 and S2 states. The range-corrected CAM-B3LYP exchange-correlation functional gives a considerably improved description of the CT states at the price of overshot excitation energies.

Crystal structure, DFT and Hirshfeld surface analysis of acylpyrazolone based square pyramidal Cu(II) complex: In-vitro anticancer activity

Crystal structure, DFT and Hirshfeld surface analysis of acylpyrazolone based square pyramidal Cu(II) complex: In-vitro anticancer activity

Internal Electron-Donation Allocation Design for Intrinsic Solubilization of Lithium Nitrate in Ester Electrolyte for Stable Lithium Metal Batteries.

Lithium metal batteries (LMBs) have become a hot topic in the research of next-generation advanced battery technology due to their high specific energy. However, the high reaction activity between lithium metal and electrolyte is considered one of the key bottlenecks limiting large-scale applications of LMBs. As a classic electrolyte additive, lithium nitrate (LiNO3) significantly improves the stability of lithium metal in ether-based electrolytes. However, its solubility in carbonate-based electrolytes widely used in lithium-ion batteries is extremely low, causing limited protective capability on lithium metal, which has become a key obstacle to the commercial application of lithium metal batteries. Here, we enhanced the local negative charge density of carbonyl oxygen atoms in carbonate molecules by introducing electron donors, making it easier for them to coordinate with Li+, thereby weakening the interaction between Li+ and NO3 -, and significantly increasing the solubility of LiNO3 in ester electrolytes. The modified ester solvent promotes the derivatization and decomposition of salt anions, leading to the formation of a dense SEI layer rich in LiF and LiNxOy. This significantly improves the stability of lithium metal in ester-based electrolytes. The assembled Li||Li symmetric battery shows excellent cycling performance of over 4000 hours.