Phenolic Oxygen Atoms Research Articles

Synthesis, characterization of Schiff base metal complexes with 1, 3 propanediamine as secondary chelates and their DNA binding, DNA cleavage, cytotoxicity, antioxidant and activities

A series of Cu(II), Co(II), Ni(II), and Zn(II) complexes were synthesised from ternary Schiff base ligand (ts) and 1,3-propanediamine (pda). These complexes were characterised using analytical and spectroscopic techniques. All these metal complexes have an octahedral geometry, which is supported by spectro-analytical experimental data. The fabricated Schiff base coordinates with the metal via imine nitrogen, a phenolic oxygen atom, and carboxylate anion as a monobasic tridentate. Thermal properties were also investigated. Antimicrobial studies were carried out against fungi and pathogenic (bacterial) organisms and a good zone of inhibition was observed irrespective of complexes. Free radical scavenging assays were performed by DPPH and H2O2 methods. The results of these two studies revealed that the Cu(II) and Zn(II) complexes were more active. The binding mode of calf thymus (Ct-DNA) to the metal complexes was analysed by the electronic absorption spectroscopy and viscosity measurement study. The findings revealed that the complex bound with DNA via a groove with electrostatic interactionand the copper complex showed a higher binding constant value. Cytotoxicity of the Schiff base and its complexes were evaluated with the breast cancer (MCF-7) cell line and all complexes exhibited moderate toxicity.

Synthesis, Structural Characterization, Reactivity and Bioactivity Studies of Some Binuclear Salen Type Schiff Base Complexes of Manganese(III)

Four new phenoxy bridged binuclear Salen type Schiff base complexes of manganese(III), [MnLX]2 with tetradentate Schiff base, H2L [H2L = N,N′-O-phenylene bis(salicylaldimine)] containing anionic co-ligands, X (X = benzoate, p-hydroxy benzoate, p-aminobenzoate, 3,5-dinitrobenzoate) have been synthesized from manganese(II) acetate, Schiff base (H2L) and the corresponding co-ligands in methanol medium. Schiff base ligand (H2L) was obtained in situ by condensation of salicylaldehyde and o-phenylenediamine in aqueous methanol. Elemental analyses, FT-IR, molar conductance, UV-visible spectroscopic studies and magnetic moment measurements at room temperature were used to characterize the binuclear Schiff base complexes. The IR spectra of [MnLX]2 (X = benzoate, p-hydroxy benzoate, p-aminobenzoate, 3,5-dinitrobenzoate) complexes showed the characteristic absorptions due to coordinated azomethine nitrogen and phenolic oxygen atoms of the Schiff base. In addition, IR spectra of the compounds also suggest coordination of the co-ligands namely benzoate, p-hydroxy benzoate, p-aminobenzoate, 3,5-dinitrobenzoate in the respective complexes. A consistent presence of a band at ca. 755 cm-1 in all the binuclear complexes arises due to (Mn-O-Mn) moiety originated from interactions of phenoxy oxygen and manganese atoms, resulted in dimeric structure of the compounds. The magnetic moment values ranging from 4.74-4.91 B.M. per manganese centre for the complexes suggest presence of Mn(III) ion in the complexes. The overall coordination geometry around the manganese centres is distorted octahedral. Redox behaviour of the synthesized complexes was ascertained from cyclic voltametric studies. The Schiff base complexes, [Mn(L)X]2 (X = p-aminobenzoate, 3,5-dinitrobenzoate) have demonstrated their catalytic potentials in oxidizing selective organic substrates namely cyclohexene and styrene by hydrogen peroxide as oxidant. The oxidized products were characterized as trans-cyclohexane 1,2-diol and styrene epoxide, respectively. Complex 4 demonstrated a considerable level of effectiveness against a wide variety of pathogenic microorganisms.

Synthesis and Characterization of CuO and NiO Nanoparticles Derived from Schiff Base Complexes

This study reports the synthesizes of such as copper oxide (CuO) and nickel oxide (NiO) nanoparticles (NPs) by thermal decompositions of Schiff base complexes and their physical characterization. A polydentate Schiff base ligand, (E)-2-(((2-chlorobenzyl)imino)methyl)phenol (CIMP), was synthesized by condensing 2-chlorobenzylamine and 2-hydroxybenzaldehyde. The ligand was identified by melting point, FT-IR, UV-Vis, and (1H and 13C NMR) spectroscopy. Cu(II) and Ni(II) complexes were prepared by reacting CIMP with the corresponding molar ratio in a 1:1 (metal: ligand). The complexes (Com1 and Com2) were characterized by melting point, FT-IR, and UV-Vis spectroscopy. The FT-IR spectra of the (Com1 and Com2) showed that the deprotonated CIMP ligand coordinated to the Ni(II) and Cu(II) metal ions through the azomethine nitrogen, aryl chloride, chlorine, and phenolic oxygen atoms. To determine the crystalline structure of the synthesized products, X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) techniques were employed. The formation of copper oxide and nickel oxide as the new products was confirmed by XRD analysis. SEM imaging revealed the uniform and spherical morphology of the nanoparticles, which exhibited a remarkably narrow size distribution with an average diameter of 20 to 22 nm, highlighting their exceptional precision.

Synthesis, characterization, antimicrobial, molecular docking simulation, and antitumor assays of nanometric complexes based on new thiazole Schiff base derivative

For further pharmaceutical applications, a novel Schiff base derivative of aminothiazole and its Co (II), Cu (II), Zn (II), and Th (IV) chelates were designed and prepared. For this purpose, 2‐aminothiazole and 2,4‐dihydroxybenzaldehyde have been coupled before the complexation reaction with the metal salts. Elemental analysis, FT‐IR, 1HNMR, UV–Vis spectra, transmission electron microscopy (TEM), X‐ray powder diffraction (XRD), molar conductance, and magnetic moment measurements were used to determine the structural formula of the ligand and its produced chelates. The acquired data pointed out that the ligand was chelated with metal through the nitrogen of azo group and deprotonated ortho phenolic oxygen atoms. In Cu (II) complex the copper ion chelated with two ligand molecules, whereas in other complexes the metal binds with one molecule only of ligand. It was shown by XRD patterns and high‐resolution TEM images that the complex particles had a uniform distribution across the chelates' surfaces and were nanometric in size. Extremely, antimicrobial and anticancer activity for the prepared ligand and complexes were investigated, which showed high activity, especially after complex formation. Docking studies have been performed to predict the compounds' efficacy as antitumor agents through their interaction with the co‐crystal structure of proteins for breast cancer cells (PDB ID: 3S7S) and protein of liver cancer 2 (PDB ID: 2JW2). The experimental results of the anticancer activity showed promising results, especially for Cu (II) compound which exhibited the greatest antitumor efficacy (IC50 = 12.81 μg/ml) contra HepG‐2 carcinoma and Mcf‐7 cells (IC50 = 18.92 ± 0.91 μg/ml). Antimicrobial activity against the strains Klebsiella pneumoniae (K. pneumoniae), Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), Bacillus subtilis (B. subtilis), C. albicans (C. albicans), and Aspergillus niger (A. niger) also gave very promising results when it is compared with the standard drugs.

Aluminium 8-Hydroxyquinolinate N-Oxide as a Precursor to Heterometallic Aluminium-Lanthanide Complexes.

A reaction in anhydrous toluene between the formally unsaturated fragment [Ln(hfac)3] (Ln3+ = Eu3+, Gd3+ and Er3+; Hhfac = hexafluoroacetylacetone) and [Al(qNO)3] (HqNO = 8-hydroxyquinoline N-oxide), here prepared for the first time from [Al(OtBu)3] and HqNO, affords the dinuclear heterometallic compounds [Ln(hfac)3Al(qNO)3] (Ln3+ = Eu3+, Gd3+ and Er3+) in high yields. The molecular structures of these new compounds revealed a dinuclear species with three phenolic oxygen atoms bridging the two metal atoms. While the europium and gadolinium complexes show the coordination number (CN) 9 for the lanthanide centre, in the complex featuring the smaller erbium ion, only two oxygens bridge the two metal atoms for a resulting CN of 8. The reaction of [Eu(hfac)3] with [Alq3] (Hq = 8-hydroxyquinoline) in the same conditions yields a heterometallic product of composition [Eu(hfac)3Alq3]. A recrystallization attempt from hot heptane in air produced single crystals of two different morphologies and compositions: [Eu2(hfac)6Al2q4(OH)2] and [Eu2(hfac)6(µ-Hq)2]. The latter compound can be directly prepared from [Eu(hfac)3] and Hq at room temperature. Quantum mechanical calculations confirm (i) the higher stability of [Eu(hfac)3Al(qNO)3] vs. the corresponding [Eu(hfac)3Alq3] and (ii) the preference of the Er complexes for the CN 8, justifying the different behaviour in terms of the Lewis acidity of the metal centre.

Halide mediated modulation of magnetic interaction and anisotropy in dimeric Co(II) complexes.

The burgeoning interest in the field of molecular magnetism is to perceive the high magnetic anisotropy in different geometries of metal complexes and hence to draw a magneto-structural correlation. Despite a handful of examples to exemplify the magnetic anisotropy in various coordination geometries of mononuclear complexes, the magnetic anisotropies for two different coordination geometries are underexplored. Employing an appropriate synthetic strategy utilizing the ligand LH2 [2,2'-{(1E,1'E)-pyridine2,6-diyl-bis(methaneylylidine)}-bis(azaneylylidine)diphenol] and cobalt halide salts in a 1 : 2 stoichiometric ratio in the presence of triethylamine allowed us to report a new family of dinuclear cobalt complexes [CoII2X2(L)(P)(Q)]·S with varying terminal halides [X = Cl, P = CH3CN, Q = H2O, S = H2O (1), X = Br, P = CH3CN, Q = H2O, S = H2O (2), X = I, P = CH3CN, and Q = CH3CN (3)]. All these complexes are characterized through single crystal X-ray crystallography, which reveals their crystallization in the monoclinic system P21/n space group with nearly identical structural features. These complexes share vital components, including Co(II) centers, a fully deprotonated ligand [L]2-, halide ions, and solvent molecules. The [L]2- ligand contains two Co(II) centers, where phenolate oxygen atoms bridge the Co(II) centers, forming a Co2O2 four-membered ring. Co1 demonstrates a distorted pentagonal-bipyramidal geometry with axial positions for solvent molecules, while Co2 displays a distorted tetrahedral geometry involving phenolate oxygen atoms and halide ions. Temperature-dependent dc magnetic susceptibility measurements were conducted on 1-3 within a range of 2 to 300 K at 1 kOe. The χmT vs. T plots exhibit similar trends, with χmT values at 300 K higher than the spin-only value, signifying a significant orbital contribution. As the temperature decreases, χmT decreases smoothly in all the complexes; however, no clear saturation at low temperatures is observed. Field-dependent magnetization measurements indicate a rapid increase below 20 kOe, with no hysteresis and a low magnetic blocking temperature. DFT and CASSCF/NEVPT2 theoretical calculations were performed to perceive the magnetic interaction and single-ion anisotropies of Co(II) ions in various ligand-field environments.

Exploring Bismuth (III) Sulpha Drugs Schiff Base Coordination Complexes: Design, Synthesis, Structural, Spectroscopic Characterization, and Biological Evaluations

The present study aimed to prepare and then evaluate the tetra and coordinated Bismuth (III) complexes [BiCl2 (L)] (LH = N, O donor Schiff base employed by the condensation of 1-acetyl-2-naphthol and 2-acetyl-1-naphthol using sulpha drugs as ligand) were derived by the reaction of bismuth (III) trichloride and sodium salt of an N, O donor Schiff base ligand and characterized. The authenticity of all the synthesized ligands and their Bi (III) complexes had been identified by microanalysis, various spectroscopic techniques like FT-IR, 1H NMR, and elemental analysis. The spectral evidence of the complexes has revealed the bidentate complexing nature of the Schiff base through phenolic oxygen and azomethine nitrogen atoms. The Schiff base ligand and Bismuth (III) complexes were assessed for antimicrobial activity. Assessment of antimicrobial activity against Gram-negative & Gram-positive bacteria and fungi has demonstrated that the complex (III) was more active than the Schiff base.

Water-soluble chiral coordination polymers of Li+, Na+, K+, and Ba2+ with an anionic iron(III) complex of a L-threonine derivative and a significant red shift of visible spectra with Al3+ salt.

Four salts of an anionic iron(III) bis-complex, [Fe(LL-thr)2]1-, were synthesized from water or methanol. H2LL-thr is a tridentate ligand derived from the L-threonine amino acid, and the cations used are Li+ (1), Na+ (2), K+ (3), and Ba2+ (4). Single-crystal X-ray diffraction showed that all the complexes are coordination polymers of different dimensionalities. The iron(III) complex binds to cations through its coordinated phenolate and non-coordinated carboxylate oxygen atoms. While Li+ forms a linear chain, all others have a pair of bridged cations intervening the iron(III) complexes. The 3D network of Ba2+ salt has a sizeable solvent-accessible space occupied by aquated chloride ions. The differences in circular dichroism (CD) spectra and significantly lower conductance values in water and methanol support partial retention of the polymeric nature in methanol. The visible spectra of 4 in methanol or water showed an ∼10 nm shift of the charge transfer bands from 3. However, the addition of Al3+ salt to 2 showed a significant colour shift. Further investigation confirmed that the colour shift is due to partial protonation of the complex with protons generated from salt hydrolysis. Most reports on visual aluminium detection consider aluminium's binding as the shift's source. The present results show that protonation due to hydrolysis of aluminium salt can skew the observation.

Synthesis and characterization of Co (II), Ni (II) and Cu (II) complexes with unsymmetrical tetradentate Schiff base ligand

A novel series of cobalt (II), nickel (II) and copper (II) complexes of unsymmetrical Schiff base ligand 1-(2-hydroxynaphthalideneimino)-2-(5 methoxysalicylidene imino)-4 chlorobenzene-1,2-diamine was synthesised by condensation reaction of 1:1:1 molar ratio of 2-hydroxynaphthalene-1-carbaldehyde, 4-chlorobenzene -1,2-diamine and 5-methoxysalicyidehyde in alcoholic medium. The synthesised ligand and its metal complexes were characterised by elemental analysis, molar conductance measurements, magnetic susceptibility measurements, UV-Vis and infrared spectral data. The molar conductance of synthesised metal complexes in DMSO solution indicates their non-electrolytic nature. The analytical data show the general formula for the complexes to be [M(L)2] where L = Schiff base ligand and M = Co (II), Ni (II) and Cu (II). The spectral data and magnetic moment suggested that Schiff base behaves as a tetradentate ligand, coordinating through azomethine nitrogen and phenolic oxygen atoms to the metal ion. Magnetic susceptibility measurements, UV-Vis and infrared spectral data geometry of metal complexes were proposed to be square planar.

Facile synthesis of ZnO nanoparticles by thermal decomposition of Schiff base complexes for the effective removal of organic pollutants in an aqueous medium

A series of mononuclear Schiff base transition metal complexes of the type [M(LS)(temed)] (where, M = Co(II), Ni(II), Cu(II), and Zn(II); LS = Schiff base ligand derived from L-leucine and Salicylaldehyde and co-ligand temed = N,N,N’N’- tetramethylethylenediamine) have been synthesized and characterized by spectroscopic studies such as Mass, NMR, UV–Visible, FT-IR, and TGA analysis. Spectral results reveal that the metal ions are coordinated to imine nitrogen, phenolic oxygen, and oxygen atom present in the carboxylate group of the Schiff base ligand and two nitrogen atoms from ligand (L2) temed. The scavenging activity of the complexes was carried out by the DPPH method with different concentrations, and all the complexes possesses good antioxidant activity in the range 58.93 to 78.79 %. Among them Zn(II) complex showed higher scavenging activity 78.79 % using 10 mg concentration. Furthermore, an investigation was conducted to assess the antibacterial properties of the complexes. It was observed that all of the metal complexes exhibited significant antimicrobial activity. Notably, the copper complex demonstrated enhanced activity, particularly against S. aureus and Mucor species, with zone of inhibition measurements of 19 mm and 20 mm, respectively. The Zn(II) complex has been used as a precursor to produce zinc oxide nanoparticles by the thermal decomposition method. ZnO nanoparticles have been characterized by powder X-ray diffraction (PXRD), UV–Vis spectroscopy techniques, scanning electron microscopy (SEM), FT-IR spectroscopy. The photocatalytic activity of zinc oxide nanoparticles was investigated in the presence of ultraviolet light. ZnO nanoparticles can efficiently catalyze the degradation of methyl orange, methylene blue, and rhodamine B in the aqueous suspension, and the highest percentage of degradation was observed against methylene blue (99 %). Furthermore, the impact of altering dye concentration, pH, catalyst quantity and kinetics on the photodegradation of model pollutant methylene blue was investigated.

Exploring the antimalarial, antioxidant and antimicrobial properties of newly synthesized diorganotin(IV) complexes with ONO-donor hydrazone ligands

Inspired by the role of organotin(IV) compounds as potential pharmaceutical agents, we have synthesized a series of new diorganotin(IV) complexes (5–20) of hydrazone ligands (1–4) derived from 2-chlorophenoxyacetic hydrazide and salicylaldehyde derivatives. Numerous techniques such as FT-IR, UV–Vis, (1H, 13C, 119Sn) NMR, mass spectrometry, powder XRD, SEM, EDAX, TGA and molar conductance were used to elucidate the structure of the synthesized compounds. These techniques ascertain that the hydrazone ligands coupled with diorganotin(IV) in a tridentate manner via imine nitrogen, phenolic oxygen atom and deprotonated hydroxyl group generating pentacoordinated geometry of the complexes. The low molar conductance values of synthesized compounds indicated their non-electrolytic nature. SnO2 was the final product formed as a result of the thermal breakdown of complexes which suggested the thermal stability of the complexes up to about 176°C. In vitro antimalarial (P.falciparum) activity was performed using microassay protocol which advocated for the higher potency of complexes 16,20 (IC50 = 0.62–0.67 µM). The antioxidant activity also supported the results of antimalarial data suggesting 16,20 complexes as active compounds. In vitro, the antimicrobial potential of the compounds has been tested against six pathogens including four bacterial and two fungal strains by serial dilution assay taking ciprofloxacin and fluconazole as reference drugs. Among the synthesized compounds, complexes 8 and 12 (MIC value = 0.0048, 0.0045 µmol/mL) exhibited superior activity. Additionally, the compounds were subjected to in silico ADME analysis suggesting that the compounds can be employed as orally active drugs.

Preparation and physico-chemical properties of lanthanide(III) complexes with 2-((E)- (tert- butylimino)methyl)-6-methoxyphenol

ABSTRACT. The reactions of lanthanide nitrates with 2-((E)-(tert-butylimino)methyl)-6-methoxyphenol (HL1) have yielded five complexes that are described by the formulae [Ce(HL1)2(NO3)3]∙MeOH and [Ln(HL1)2(NO3)3] (Ln = Nd(III), Gd(III), Ho(III) and Er(III)) and were characterized using physico-chemical techniques including single-crystal X-ray diffraction spectroscopy. The cerium complex crystallized in a triclinic P-1 space group, while the rest of the complexes crystallized in the monoclinic P21/c space group. All the complexes are ten-coordinate, adopting a tetradecahedron geometry with two HL1 molecules coordinated through the phenolic and methoxy oxygen atoms. The coordination sphere is completed by six oxygen atoms from three bidentately coordinated nitrate ligands. Electronic data reveals that only the neodymium, holmium and erbium complexes exhibit weak f-f transitions in the visible region.
 KEY WORDS: Preparation, Physico-chemical properties, Lanthanide, Schiff base complexes, Crystal structure, Geometry
 Bull. Chem. Soc. Ethiop. 2023, 37(6), 1397-1410. DOI: https://dx.doi.org/10.4314/bcse.v37i6.8

Explorations on the synthesis, structure, DFT, DNA binding properties and molecular docking of tridentate Schiff base Copper (II) complexes

Copper(II) Schiff base complexes of (2-Hydroxy-benzaldehyde)-amino acid have been synthesized and characterized. The complexes' single-crystal X-ray structures were studied, and it was discovered that the 4,4-bipyridine functions as a bidentate bridging ligand connecting two Cu(II) ions. In order to assemble the complicated components into a three-dimensional chain structure and arrange the 4,4-bipyridine molecules into parallel sheets, intermolecular hydrogen bonds are essential. A robust intermolecular hydrogen bond network including water oxygen atoms strengthens the connection between water molecules and phenolate oxygen atoms from the ligand, which is produced from salicylaldehyde. The complexes' interaction with DNA was investigated by UV–Visible, fluorescence and CD spectrophotometric methods, which indicate that the complexes favourably bind to the groove in the DNA. The DNA binding affinity was confirmed by molecular docking. Additionally, DFT calculations were used to determine the stable geometry for these complexes. A thorough understanding of the interactions of these synthesized complexes was achieved through an intensive molecular docking research. These findings show that the complexes have a high affinity for DNA binding and considerable groove binding. Notably, Complex 1 showed a greater affinity for DNA than Complex 2.

Efficient detection of metronidazole by a glassy carbon electrode modified with a composite of a cyclotriveratrylene-based metal–organic framework and multi-walled carbon nanotubes

Constructing a sensitive and efficient sensor for determination of metronidazole (MNZ) is crucial in food field. Herein, a new cyclotriveratrylene-based metal–organic framework (MOF), namely, [Cd6L2(cyclen)2(H2O)2] (1), was constructed by self-assembly of functionalized 5,6,12,13,19,20-hexacarboxy-propoxy-cyclotriveratrylene (H6L), 1,4,7,10-tetraazacyclododecane (cyclen) and Cd(II) cation under solvothermal condition. In 1, adjacent Cd(II) cations are linked by L6− to produce a 2D polymeric structure with carboxylate and phenolic oxygen atoms. To enhance conductivity of 1, it was combined with conducting carbon materials, including mesoporous carbon (MC), reduced graphene oxide (RGO) and multi-walled carbon nanotubes (MWCNT), respectively, producing a series of composite materials. Remarkably, electrochemical tests showed that 1@MWCNT(1:1) featured a much better electrochemical detection performance for metronidazole (MNZ) than 1@MC and 1@RGO. The linear range for the detection of MNZ is up to 0.4–500 μM and the limit of detection (LOD) for MNZ reached 0.25 μM. Importantly, the fabricated sensor 1@MWCNT(1:1) was employed for the detection of MNZ in honey and egg with satisfactory result. High-performance liquid chromatography (HPLC) validated the high accuracy of the electrochemical method for the determination of honey and egg.

Synthesis, characterization, crystal structures and biological activity of molybdenum complexes derived from bis(acetylacetonato)dioxomolybdenum(VI) and Schiff bases

Reaction of bis(acetylacetonato)dioxomolybdenum(VI) with 4-fluoro-2-((pyridin-2-ylmethylene)amino)phenol and 3-methyl-2-((pyridin-2-ylmethylene)amino)phenol, respectively in methanol afforded two new molybdenum complexes [MoO2L1] and [MoO2L2], where L1 and L2 are the dianionic form of 3-(((5-fluoro-2-hydroxyphenyl)amino)(pyridin-2-yl)methyl)pentane-2,4-dione (H2L1) and 3-(((2-hydroxy-6-methylphenyl)amino)(pyridin-2-yl)methyl)pentane-2,4-dione (H2L2). Both complexes have been characterized by elemental analysis, IR, UV–Vis, 1H and 13C NMR spectra. Molecular structures of the complexes have been determined by X-ray crystallography. In the complexes, the ligands coordinated to the Mo atoms via pyridine nitrogen, amino nitrogen, phenolate oxygen, and enolate oxygen atoms. The octahedral coordination of the Mo atoms is furnished by two oxido oxygen atoms. The complexes were evaluated for their antibacterial activities on Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas fluorescens, and antifungal activities on Candida albicans and Aspergillus niger, and gave interesting results.

A tetrahedron from homooxacalix[3]arene, the fifth Platonic polyhedron from calixarenes and uranyl.

A self-assembled tetrahedral cage results from two C 3-symmetry building blocks, namely, homooxacalix[3]arene tricarboxylate and uranyl cation, as demonstrated by X-ray crystallography. In the cage, four metals coordinate at the lower rim with the phenolic and ether oxygen atoms to shape the macrocycle with appropriate dihedral angles for tetrahedron formation, whereas four additional uranyl cations further coordinate at the upper-rim carboxylates to finalize the assembly. Counterions dictate the filling and porosity of the aggregates, whereas potassium induces highly porous structures, and tetrabutylammonium yields compact, densely packed frameworks. The tetrahedron metallo-cage complements our previous report (Pasquale et al., Nat. Commun., 2012, 3, 785) on uranyl-organic frameworks (UOFs) from calix[4]arene and calix[5]arene carboxylates (octahedral/cubic and icosahedral/dodecahedral giant cages, respectively) and completes the assembly of all five Platonic solids from just two chemical components.

New bis[MoO2] and [MoO(O2)] compounds: An artificial enzyme with peroxidase activity against o-phenylenediamine and dopamine

In this study, two binuclear dioxido- and oxidoperoxido molybdenum (VI) complexes, [{MoVIO2}2(L)(H2O)2] 1 and [{MoVIO(O2)}2(L)(H2O)2] 2, were synthesized. Complex 1 was obtained through a 1:2 reaction of ligand I with MoO2(acac)2, while complex 2 was synthesized in situ by reacting MoO3 with H2O2 in a 1:2 ratio. The structures and characteristics of the complexes were examined employing several techniques such as elemental (CHN) analysis, spectroscopy (FT-IR, UV–Vis, 1H, and 13CNMR), and thermal study (TGA). SC-XRD analysis of complex 1a revealed that the molybdenum central atom adopts an octahedral geometry and is bonded to phenolic oxygen, enolate oxygen, and azomethine nitrogen atoms. Powder X-ray diffraction was used to determine the purity of the bulk material, and the results were compared to single crystal data. Computational calculations were performed using density functional theory (DFT) at the B3LYP/6-31G(d, p) level of theory for the ligand and the LANL2DZ level of theory for the complexes, yielding geometry optimized structures that were then employed in frequency and NMR-calculations. These theoretical findings were compared to the experimental results and showed a good correlation. Furthermore, the complexes exhibited peroxidase-like activity in the presence of hydrogen peroxide as evidenced by the oxidation of o-phenylenediamine and dopamine.

Sulfonamide derived Schiff base Mn (II), Co (II), and Ni (II) complexes: Crystal structures, density functional theory and Hirshfeld surface analysis

The three transition metal complexes of the ligand named as 2,4‐dibromo‐6‐{[2‐(1,1‐dioxo‐1H‐benzoisothiazole‐3‐yl‐amino)‐ethylimino]‐methyl}‐phenol 3 were synthesized with divalent manganese, cobalt and nickel metal ions and characterized by employing different analytical methods including UV–visible, FT‐IR and elemental analyses. The crystal structures of Mn (II) complex 4, Co (II) complex 5, and Ni (II) complex 6 are determined by single beam X‐rays crystallography, which confirm the distorted octahedral coordination of the complexes 4–6. The non‐covalent interactions of the complexes 4–6 are investigated by the Hirshfeld surface analysis. The tendency of the pair of chemical species to form crystal packing interactions are computed, which provide the favorable contacts in the crystal packing for the complexes 4–6. For the sake of computing strength of the crystal packing, void analysis is performed for the complexes 4–6. The non‐electrolytic nature of synthesized metal complexes was confirmed by molar conductance. The spectral analyses suggested that sulfonamide functionalized Schiff base behaves as bidentate ligand and coordinates with the metal center through phenolic oxygen and iminic nitrogen atoms. The density functional theory (DFT) studies were performed for the Mn (II), Co (II), and Ni (II) metal complexes at the B3LYP/LANL2DZ level of theory. The structural characteristics, vibrational analysis (IR), NMR analysis, UV–Vis, natural bonding orbital (NBO), frontier molecular orbital (FMO), charges (Mulliken and NPA), global reactivity descriptors, molecular electrostatic potential (MEP), and dipole moments were investigated using this method. The large values of stabilization energy, that is, 12.02, 15.25, and 23.81 kcal/mol were found for the complexes Mn (II) 4, Co (II) 5, and Ni (II) 6, respectively by NBO analysis. The global reactivity findings suggested the positive values of electron affinity for all complexes, which indicate the involvement of charge transfer reaction. Among these complexes, complex 6 is the most stable and complex 4 is the least. Further, FMO analysis indicated large HOMO‐LUMO gap (3.85–3.97 eV) with higher LUMO values for all metal complexes.

Preparation, Characterization, Antioxidant and Antibacterial Studies of New Metal (II) Complexes with Schiff Base for 3-amino-1-phenyl-2- pyrazoline-5-one

A new ligand complexes have been synthesis from reaction of metal ions of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), Pd(II) and Pt(II) with schiff base LH. 5-[(2-Hydroxy-naphthalen-1-ylmethylene)-amino]-2-phenyl-2,4-dihydro-pyrazol-3-one, this ligand was characterized by Fourier transform infrared (FTIR), UV-vis, 1H, 13CNMR, and mass spectra. All complexes were characterized by techniques micro analysis C.H.N, UV-vis and FTIR spectral studies, atomic absorption, chloride content, molar conductivity measurements and magnetic susceptibility. The ligand acts as bidentate, coordination through nitrogen atom from azomethin group and deprotonated phenolic oxygen atom. The spectroscopic and analytical measurements showed that the geometric shape of the prepared complexes is octahedral, while the square planar of the palladium and platinum complexes. The ligand and its complexes were having been screened for their antimicrobial activities and antioxidant

Biological Studies and Spectroscopic investigation of 4-Methyl Benzylimine Schiff Base Metal Complexes

Primary benzyl amines are highly important building blocks in the pharmaceutical and polymer industry. A new Schiff base ligand named (4-Methyl benzyl 2-Hydroxy 5-NitroAceto) imine was prepared through condensation reaction of 4-Methyl Benzyl amine and 2-hydroxy 5-Nitro Acetophenone in 1:2 molar ratios. The new ligand was characterized by spectral techniques. The coordination behaviour of a series of transition metal ions named Mn(II), Co(II), Zn(II) and Cd(II) with the newly prepared Schiff base ligand is reported. From IR spectra, it was observed that the ligand is a neutral bidentate ligand which coordinates to the metal ions through protonated phenolic oxygen, azomethine nitrogen and nitrogen atom of NH2 group. The molecular structures of the Schiff base ligand and its metal complexes were optimized theoretically. The synthesized ligand and its complexes were screened for antimicrobial activities against bacterial species. It was found that the compounds have shown activity against the organisms like Candida albicans, Bacillus subtilis and Salmonella typhi.