Transition metal complexes of nano bidentate organometallic Schiff base: Preparation,structure characterization,biological activity,DFT and molecular docking studies

An organometallic NO‐bidentate Schiff base, (2‐(1‐((1‐carboxyethyl)imino)ethyl) cyclopenta‐2,4‐dien‐1‐yl)(cyclopenta‐2,4‐dien‐1‐yl) iron (HL) was synthesized by condensation of 2‐acetylferrocene with amino acid alanine. Then its octahedral Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II) and Cd (II) complexes were synthesized. All compounds were characterized on the basis of elemental analysis (C, H, N and M), molar conductivity, FT‐IR, UV–Vis, ¹H‐NMR, SEM, mass analysis and thermal studies. Furthermore, computational studies of HL ligand have been carried out by DFT/B3LYP method. HOMO and LUMO energy values, chemical hardness‐softness, electronegativity, electrophilic index and other parameters were calculated. SEM micrographs of HL ligand and its [Cd (HL)(H₂O)₂Cl₂].2H₂O complex, showed that they were prepared in nano‐structure forms with particle size 54 and 41 nm, respectively. Antifungal and antibacterial activities of HL ligand and its metal complexes have been screened in vitro against different species such as Aspergillus fumigatus, Candida albicans, Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Salmonella typhimurium. The synthesized compounds were evaluated for their anticancer activities against breast cancer cell line (MCF‐7) and normal melanocytes cell line (HFB‐4). It was found that [Co (HL)(H₂O)₂Cl₂].3H₂O complex had the lowest IC₅₀ value (10.9 μg/ml) and hence was the most active one. Finally, the optimized structures of the Schiff base and its Co (II) complex have been used to accomplish molecular docking studies with receptors of 3HB5, 3MIW, 5IBV and 4WM8 to determine the most preferred mode of interaction.     

Physicochemical characterization of nanobidentate ferrocene‐based Schiff base ligand and its coordination complexes: Antimicrobial,anticancer, density functional theory,and molecular operating environment studies

A novel bidentate Schiff base ligand (HL, Nanobidentate Ferrocene based Schiff base ligand L (has one replaceable proton H)) was prepared via the condensation of 2‐amino phenol with 2‐acetyl ferrocene. The ligand was characterized using elemental analysis, mass spectrometry, infrared (IR) spectroscopy, ¹proton nuclear magnetic resonance (H‐NMR) spectroscopy, scanning electron microscopy (SEM), and thermal analysis. The corresponding 1:1 metal complexes with some transition‐metal ions were additionally characterized by their elemental analysis, molar conductance, SEM, and thermogravimetric ana1ysis (TGA). The complexes had the general formula [M(L)(Cl)(H₂O)₃]xCl·nH₂O (M = Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II)), (x = 0 for Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II), x = 1 for Cr(III) and Fe(III)), (n = 1 for Cr(III), n = 3 for Mn(II) and Co(II), n = 4 for Fe(III), Ni(II), Cu(II), Zn(II), and Cd(II)). Density functional theory calculations on the HL ligand were also carried out in order to clarify molecular structures by the B31YP exchange‐correlation function. The results were subjected to molecular orbital diagram, highest occupied mo1ecu1ar orbital–lowest occupied molecular orbital, and molecular electrostatic potential calculations. The parent Schiff base and its eight metal complexes were assayed against four bacterial species (two Gram‐negative and two‐Gram positive) and four different antifungal species. The HL ligand was docked using molecular operating environment 2008 with crystal structures of oxidoreductase (1CX2), protein phosphatase of the fungus Candida albicans (5JPE), Gram(?) bacteria Escherichia coli (3T88), Gram(+) bacteria Staphylococcus aureus (3Q8U), and an androgen‐independent receptor of prostate cancer (1GS4). In order to assess cytotoxic nature of the prepared HL ligand and its complexes, the compounds were screened against the Michigan cancer foundation (MCF)‐7 breast cancer cell line, and the IC₅₀ values of compounds were calculated.     

Polymer complexes. LXX. Synthesis,spectroscopic studies,thermal properties and antimicrobial activity of metal(II) polymer complexes

The monomer 3‐allyl‐5‐(phenylazo)‐2‐thioxothiazolidine‐4‐one (HL) was prepared by the reaction of allyl rhodanine with aniline through diazo‐coupling reaction. Reaction of HL with Ni(II) or Co(II) salts gave polymer complexes ( 1 – 8 ) with general stoichiometries [M(HL)(Cl)₂(OH₂)₂]_n, [M(HL)(O₂SO₂)(OH₂)₂]_n, [M(L)(O₂NO)(H₂O)₂]_n and [M(L)(O₂CCH₃)(H₂O)₂]_n (where M = Ni(II) or Co(II)). The structures of the polymer complexes were identified using elemental analysis, infrared and electronic spectra, molar conductance, magnetic susceptibility, X‐ray diffraction and thermogravimetric analysis. The interaction between the polymer complexes and calf thymus DNA showed a hypochromism effect. HL and its polymer complexes were tested against bacterial and fungal species. Co(II) polymer complex 2 is the most effective against Klebsiella pneumoniae and is more active than penicillin. The results showed that Ni(II) polymer complex 5 is a good antibacterial agent against Staphylococcus aureus and Pseudomonas aeruginosa. Molecular docking was used to predict the binding between the monomer with the receptors of prostate cancer (PDB code: 2Q7L Hormone) and breast cancer (PDB code: 1JNX Gene regulation). Coats–Redfern and Horowitz–Metzger methods were applied for calculating the thermodynamic parameters of HL and its polymer complexes. The thermal activation energy of decomposition for HL is higher than that for the polymer complexes.     

Synthesis,characterization and structural assessment of nitrato,chloro, bromo,perchlorato, thiocyanato and sulphato mono-(benzoin thiosemicarbazonato) copper(II) complexes

Summary Some copper(II) complexes of the type Cu(HL)X·nH₂O (where H₂L = benzoin thiosemicarbazone; X=NO₃; Cl, Br, SCN, ClO₄ or 1/2SO₄; n=O–2) have been prepared and characterized. All complexes have tetragonally distorted octahedral stereochemistry except the sulphatocomplex which is square pyramidal. The i.r. spectra reveal that HL acts as a monobasic tridentate ligand coordinating through the azine group nitrogen atom, thiocarbonyl sulphur atom and hydroxylic oxygen atom while NO₃, Cl, Br and ClO₄ act as terminal monodentate ligands and SCN and SO₄ act as bidentate bridging ligands. The polycrystalline e.s.r. spectra suggest tetragonal symmetry for the copper(II) ion, involving a dx ²–y² ground state.     

Studies ono-hydroxyacetophenone-2-furoylhydrazone complexes of some 3d-bivalent metal ions

Summary Complexes ofo-hydroxyacetophenone-2-furoylhydrazone, H₂L, of the types M(H₂L)C1₂ · nH₂O [Mn = Co^II, n=0; Ni^II, n=2]; Cu(HL)Cl, M(HL)₂ [M = V^IVO, Co^II, Ni^II or Cu^II] and M(L)(H₂O)_n [M = Co^II or Ni^II, n=2; M = Cu^II, n=0] have been prepared and characterized by elemental analyses, molar conductance, magnetic susceptibility, visible, e.s.r. and i.r. spectral studies. The different modes of ligand chelation and the stereochemistry around the metal ions are discussed.     

Mixed‐Ligand Complexes of Zinc(II) with α‐Hydroxycarboxylates and Aromatic N‐N Donor Ligands: Synthesis,Crystal Structures and Effect of Weak Interactions on their Crystal Packing

Several new two‐ligand complexes of zinc(II) with the aromatic N, N‐donor ligands 2, 2′‐bipyridine or 1, 10‐phenanthroline and one of three different α‐hydroxycarboxylates (HL′) derived of the α‐hydroxycarboxylic acids (H₂L′) (2‐methyllactic, H₂mL; mandelic, H₂M or benzilic, H₂B) were prepared. The compounds of formula [Zn(HL′)₂(NN)]·nH₂O (HL′ = HM, HB) were isolated as white powders and characterized by elemental analysis, IR spectroscopy and thermogravimetric analysis. The complexes of general formula [Zn(HL′)(NN)₂](HL′)·nH₂O (HL′ = HmL, HM) and [Zn(HB)₂(NN)₂], were obtained as single crystals and were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis and X‐ray diffractometry. In all cases, the zinc atom is in a distorted octahedral environment. In [Zn(HL′)(NN)₂](HL′)·nH₂O the α‐hydroxycarboxylato ligands behave as bidentate chelating monoanion and an α‐hydroxycarboxylate as counterion is also present. In [Zn(HB)₂(NN)₂], the monoanionic benzilato ligand behaves as monodentate through one oxygen atom of the carboxylate function. The effect of the classical and no‐classical hydrogen bonding and of the π‐π and C‐H…π interactions in the 3D supramolecular arrangement of these molecular complexes is analyzed.     

Synthesis,characterization, biological activity,and corrosion inhibition in acid medium of unsymmetrical tetradentate N2O2 Schiff base complexes

Four divalent metal(II) complexes, namely [Co(II)L(H₂O)Cl]·2H₂O, [Ni(II)L(H₂O)Cl]·4H₂O, [Cu(II)L(H₂O)Cl]·3H₂O, and [Zn(II)L(H₂O)Cl]·5H₂O, {L = 2‐furan‐2‐ylmethyleneamino‐phenyl‐iminomethylphenol}, were synthesized and characterized by several techniques. The molar conductance measurement of all analyzed complexes in DMSO showed their non‐electrolytic nature. The new Schiff base ligand (HL) acts as tetradentate ligand, coordinated through deprotonated phenolic oxygen, furan ring oxygen, and two azomethine nitrogen atoms. The ligand field parameters were measured for the metal complexes, which were found to be in the range notified for an octahedral structure. The molecular structural parameters of the synthesized HL ligand and its related metal(II) complexes were calculated and correlated with the experimental parameters such as infrared (IR) data. The investigated ligand and metal complexes were screened for their in vitro antimicrobial activities against different types of fungal and bacterial strains. The resulting data confirmed the examined compounds as a highly promising bactericides and fungicides. The antitumor activities of all inspected compounds were evaluated against colon carcinoma (HCT‐116) and mouse myelogenous leukemia carcinoma (M‐NFS‐60) cell lines. The inhibition effect of HL ligand and its isolated complexes on the corrosion carbon in the form of a rod of area 0.35 cm² in HCl was investigated by measuring the weight loss at 25 °C.     

Synthesis and Characterization of Transition Metal Complexes of Potassium 3‐(Pyridine‐4‐Carbonylmethyl)‐Dithiocarbazate

The preparation and characterization of some dipositive metalion complexes de rived from potassium 3‐(pyridine‐4‐carbonylmethyl)‐dithiocarbazate (PCDHK) are reported. The solid complexes of the composition ML·nH₂O (M=Cu(II), Co(II), Mn(II), Zn(II), Cd(II), Ni(II), Pb(II), L = PCD^?2, n = 0, 1, PCD^?2=PCDHK‐K⁺‐H⁺) and ML₂·2H₂O (M=UO₂(IV), L=PCDH^?1, PCDH^?1=PCDHK‐K⁺) have been characterized by elemental analyses, IR, UV, and ¹HNMR spectra. The IR spectral data indicate that PCDHK be haves as either a mononegative or binegative ligand and coordinates in a tridentate or bridging tetradentate manner.     

Antimicrobial and anticancer activities of Schiff base ligand and its transition metal mixed ligand complexes with heterocyclic base

A new Schiff base ligand (HL) was prepared via a condensation reaction of quinoline‐2‐carboxaldhyde with 2‐aminophenol in a molar ratio of 1:1. Its transition metal mixed ligand complexes with 1,10‐phenanthroline (1,10‐phen) as co‐ligand were also synthesized in a 1:1:1 ratio. HL and its mixed ligand complexes were characterized using elemental analysis, infrared, ¹H NMR, mass and UV–visible spectroscopies, molar conductance, magnetic measurements, solid reflectance, thermal analysis, electron spin resonance and X‐ray diffraction. Molar conductance measurements showed that all complexes have an electrolytic nature, except Cd(II) complex. From elemental and spectral data, the formulae [M(L)(1,10‐phen)(H₂O)]Cl_x?nH₂O (where M = Cr(III) (x = n = 2), Mn(II) and Ni(II) (x = 1, n = 2), Fe(III) (x = n = 2), Co(II), Cu(II) and Zn(II) (x = 1, n = 2)) and [Cd(L)(1,10‐phen)Cl]?3H₂O for the metal complexes have been proposed. The geometric structures of complexes were found to be octahedral. Powder X‐ray diffraction reflected the crystalline nature of the complexes; however, the Schiff base is amorphous. HL and its mixed ligand complexes were screened against Gram‐positive bacteria (Streptococcus pneumoniae and Bacillus subtilis) and Gram‐negative bacteria (Pseudomonas aeruginosa and Escherichia coli). Antifungal activity was determined against Aspergillus fumigatus and Candida albicans, the data showing that most complexes had activity less than that of the Schiff base while Mn(II), Fe(III) and Ni(II) complexes showed no significant antifungal activity. The anticancer activity of HL and its metal complexes was also studied against breast and colon cell lines. The metal complexes showed IC₅₀ higher than that of HL, especially the Cu(II) complex which showed the highest IC₅₀ against breast cell line.     

Cobalt(II) Complexes of 4,6-Dimethylpyrimidine-2(1H)-one

Some cobalt(II) complexes of 4,6-dimethylpyrimidine-2(1H)-one (HL) have been prepared and studied by infrared and electronic spectra and by magneto-chemical and conductometric measurements. The ligand is coordinated through the unprotonated ring-nitrogen atom and in one case also through the carbonylic oxygen atom. The “blue” complexes [CoX₂ · 2HL] (X₂ = Cl₂, ClBr, Br₂, (NCS)₂) and [CoX₂ · 2HL] · 2HL (X = Cl, Br) have a distorted C_2v [CoX₂N₂] coordination; the thiocyanate ion is N-bonded to the metal. The “green” complexes CoX₂ · 2HL (X = Cl(4H₂O), Br) have a square-pyramidal [CoX₂N₂O] coordination. The “pink” CoX₂ · 4HL · nH₂O (X = ClO₄, n = 2; X = BF₄, n = 8; X = F₃Ac, n = 4) and “cream” CoX₂ · 4HL · 6 H₂O (X = I, ClO₄) complexes have an octahedral coordination; only the F₃Ac^? ion is coordinated. The “cyclamen” CoAcL · 2HL · 2 H₂O and Co₃Ac₄L₂ · 2HL · 2H₂O complexes have a polynuclear constitution; the Ac^? ion behaves as bidentate ligand.     

Synthesis,spectral and thermal characterization of 6-hydroxymethyl pyridine-2-carboxylic acid methyl ester and its complexes

New pincer ligand, 6-hydroxymethylpyridine-2-carboxylic acid methyl ester, HL, and its bipositive, tripositive and uranyl metal complexes have been synthesized and characterized by elemental and thermal analyses, IR, diffuse reflectance and ¹H NMR spectra, molar conductance and magnetic moment measurements. The downfield shift of the aliphatic OH signal (from 3.87 vs. 2.96 ppm in the ligand) upon complexation indicates the coordination by protonated aliphatic OH group. Zn(II) and UO2(II) complexes are found to be diamagnetic as expected. The low molar conductance values indicate that Ni(II) and Zn(II) complexes are non electrolytes; Fe(II), Co(II), Cu(II) and UO₂(II) complexes are 1:2  electrolytes while Fe(III) complex is a 1:3 electrolyte. The general compositions of the complexes are found to be [M(HL)X₂]·nH₂O where M=Ni(II) (X=Cl, n=1) and Zn(II) (X=Br, n=0); and [M(HL)₂]X_m·nH₂O where M=Fe(II) (X=Cl, m=2, n=0), Fe(III) (X=Cl, m=3, n=4), Co(II) (X=Cl, m=2, n=0), Cu(II) (X=Cl, m=2, n=0) and UO₂(II) (X=NO₃, m=2, n=0). The thermal behaviour of the complexes has been studied and different thermodynamic parameters are calculated using Coats-Redfern method.     

Synthesis and antibacterial activity of cephalexin metal complexes

The interactions of cephalexin (Hcepha) with transition and d¹⁰ metal ions have been investigated. The complexes [M(cepha)Cl]nH₂O [M?=?Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II)] were characterized by physicochemical and spectroscopic methods. The IR and ¹H NMR spectra of the complexes suggest that cephalexin behaves as a monoanionic tridentate ligand. In vitro antibacterial activities of Hcepha and the complexes were tested.     

Synthesis and characterization of cobalt(II), nickel(II) and copper(II) perchlorate complexes with bis [(diphenylphosphinyl)methyl] phenylphosphine oxide,bis [(disphenylphosphinyl)methyl]ethyl phosphinate,and bis [(diphenylphosphinyl)methyl] phosphinic acid

The synthesis and characterization of cobalt(II), nickel(II) and copper(II) perchlorate complexes containing bis [(diphenylphosphinyl)methyl] [phenylphosphine oxide (RPPH), bis [(diphenylphosphinyl)methyl] ethyl phosphinate (RPOEt), and bis [(diphenylphosphinyl)methyl] phosphinic acid (RPOH) have been studied. The substituent at the central phosphorus atom of the ligand is responsible for the types of complexes formed. The new complexes [M(RPPh)₂(ClO₄)₂.nH₂O, [M(RPPh)₃](ClO₄)₂.4H₂O, [M(RPOEt)₂](ClO₄)₂.2H₂O, and [M(RPOH)₃] (ClO₄)₂.nH₂O are characterized as high spin and most of them have an octahedral or distorted octahedral geometry [M = Co(II), Ni(II), or Cu(II); n = 2?5]. The coordination of two P = O groups from one ligand to the metal has been proposed for most of the complexes formed. The coordination of all three P = O groups has been assumed for complexes [M(RPPh)₂](ClO₄)₂.nH₂O and [M(RPOEt)₂](ClO₄)₂.2H₂O.     

Mono- and Bi-Nuclear Metal Complexes of Schiff-Base Hydrazone (ONN) Derived from o-Hydroxyacetophenone and 2-Amino-4-Hydrazino-6-Methyl Pyrimidine

A tridentate ONN donor Schiff-base hydrazone ligand, H₂L, was synthesized by the condensation of 2-amino-4-hydrazino-6-methyl pyrimidine with o-hydroxyacetophenone. The structure of the ligand was elucidated by IR and ¹H NMR spectra which indicated the presence of three different coordinating groups, the oxygen atom of the phenolic OH group, the nitrogen atom of the azomethine, C=N, group and one of the nitrogen atoms of the heterocyclic ring. The ligand behaves either as a tridentate (N₂O sites) neutral, mono- or di-basic ligand or as a bidentate (NO sites) monobasic ligand depending on the pH of the reaction medium and the metal ion. The mass spectrum of the ligand showed the presence of the molecular ion peak. Different types of metal complexes, mononuclear such as [(HL)M(OAc)]·xH₂O (M = Cu or Zn), [(HL)M(OAc)H₂O]·xH₂O (M = Ni or UO₂), [(HL)Co(OH₂)Cl]·2H₂O, [(H₂L)FeCl₃]·3½H₂O, [(L)FeCl(H₂O)₂]· 2¼H₂O, [(HL)L'FeCl(H₂O)]·H₂O (L' = 8-hydroxyquinoline, 8-HQ), [(HL)L'FeCl]Cl·xH₂O (L' = 1,10-phenanthroline, phen, or 2,2'-bipyridyl, bpy) and [(HL)L'Cu]·ClO₄ (L' = phen). Also, binuclear complexes with oxalic acid of the type [(HL)ClFe(ox)FeCl(HL)], [(HL)Cu(ox)Cu(HL)] were obtained. The IR spectra of the binuclear complexes indicated that the oxalate anion acts as a bridging tetradentate ligand. Elemental analyses, IR, electronic and ESR spectra as well as conductivity and magnetic susceptibility measurements were used to elucidate the structures of the newly prepared metal complexes. Square-planar geometry is suggested for the Cu(II) complex, octahedral geometry for the Fe(III), Ni(II) complexes, tetrahedral geometry for the Co(II) and Zn(II) complexes and pentagonal-bipyramidal geometry for the UO₂(VI) complex.     

Metal complexes of novel Schiff base derived from iron sandwiched organometallic and 4‐nitro‐1,2‐phenylenediamine: Synthesis,characterization, DFT studies,antimicrobial activities and molecular docking

The condensation of 2‐acetylferrocene with 4‐nitro‐1,2‐phenylenediamine in a 1:1 molar ratio, resulting in formation of a novel bi‐dentate organometallic Schiff base ligand (L), (2‐(1‐((2‐amino‐5‐nitrophenyl)imino)ethyl)cyclopenta‐2,4‐dien‐1‐yl)(cyclopenta‐2,4‐dien‐1‐yl)iron. Also, its Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes have been synthesized. The stoichiometric ratios of the prepared compounds were estimated using elemental analysis (C, H, N, M), molar conductivity, FT‐IR, UV‐Vis, ¹H‐NMR, SEM and mass spectral analysis. Furthermore, their TG and DTG properties were studied. The geometrical structure of the complexes was found to be octahedral. From spectral analysis, the Schiff base coordinated to metal ions through the azomethine and amine groups. DFT‐based molecular orbital energy calculations of the synthesized ligand have been studied, in which the ligand was theoretically optimized. The Schiff base and its metal complexes have been screened for their antimicrobial activities against different bacterial and fungal species by using disc diffusion method. The anticancer activities of the ligand and its metal complexes have also been studied towards breast cancer (MCF‐7) and human normal melanocytes (HFB‐4) cell lines. Molecular docking was also used to identify the interaction between the Schiff base ligand and its Cd(II) complex with the active site of the receptors of breast cancer mutant oxidoreductase (PDB ID: 3HB5), crystal structure of Staphylococcus aureus (PDB ID: 3Q8U) and yeast‐specific serine/threonine protein phosphatase (PPZ1) of Candida albicans (PDB ID:5JPE).     

Stabilization of Human Telomeric G‐Quadruplex and Inhibition of Telomerase Activity by Propeller‐Shaped Trinuclear PtII Complexes

Two novel propeller‐shaped, trigeminal‐ligand‐containing, flexible trinuclear Pt^II complexes, {[Pt(dien)]₃(ptp)}(NO₃)₆ ( 1 ) and {[Pt(dpa)]₃(ptp)}(NO₃)₆ ( 2 ) (dien: diethylenetriamine; dpa: bis‐(2‐pyridylmethyl)amine; ptp: 6′‐(pyridin‐3‐yl)‐3,2′:4′,3′′‐terpyridine), have been designed and synthesized, and their interactions with G‐quadruplex (G4) sequences are characterized. A combination of biophysical and biochemical assays reveals that both Pt^II complexes exhibit higher affinity for human telomeric (hTel) and c‐myc promoter G4 sequences than duplex DNA. Complex 1 binds and stabilizes hTel G4 sequence more effectively than complex 2 . Both complexes are found to induce and stabilize either antiparallel or parallel conformation of G4 structures. Molecular docking studies indicate that complex 1 binds into the large groove of the antiparallel hTel G4 structure (PDB ID: 143D) and complex 2 stacks onto the exposed G‐quartet of the parallel hTel G4 structure (PDB ID: 1KF1). Telomeric repeat amplification protocol assays demonstrate that both complexes are good telomerase inhibitors, with IC₅₀ values of (16.0±0.4) μM and (4.20±0.25) μM for 1 and 2 , respectively. Collectively, the results suggest that these propeller‐shaped flexible trinuclear Pt^II complexes are effective and selective G4 binders and good telomerase inhibitors. This work provides valuable information for the interaction between multinuclear metal complexes with G4 DNA.     

Synthesis,characterization, spectroscopic and theoretical studies of transition metal complexes of new nano Schiff base derived from l‐histidine and 2‐acetylferrocene and evaluation of biological and anticancer activities

A new Schiff base derived from the condensation of 2‐acetylferrocene with l ‐histidine was prepared and characterized using elemental analyses and spectroscopic methods. Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes of the Schiff base were prepared and characterized using various physicochemical methods such as elemental analysis, Fourier transform infrared and UV–visible spectroscopies, molar conductance, thermal analysis and scanning electron microscopy (SEM). Both ligand and complexes were investigated for their biological and anticancer activities. The elemental analyses showed that complexes were formed in a metal‐to‐ligand ratio of 1:1 stoichiometry. The spectral analyses proved that the ligand was tridentate and all complexes had an octahedral geometry, except the Zn(II) complex that was tetrahedral. SEM showed that the ligand and its Cd(II) complex were of nanometric structure. The molecular and electronic structure of the free ligand was optimized theoretically and the quantum chemical parameters were calculated. The molecular structure can be used to investigate the coordination sites and the total charge density around each atom. According to anticancer studies, Cd(II) complex was recommended to be used as anti‐breast cancer drug as it had very low IC₅₀ (3.5 μg ml^?1). Molecular docking was used to predict the binding between the free ligand and its Cd(II) complex and crystal structure of Staphylococcus aureus (PDB ID: 3Q8u), receptors of breast cancer mutant oxidoreductase (PDB ID: 3Hb5) and crystal structure of Escherichia coli (PDB ID: 3 T88) and to identify the binding mode and the crucial functional groups interacting with the three proteins.     

Structural, spectroscopic and thermal characterization of 2-tert-butylaminomethylpyridine-6-carboxylic acid methylester and its Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and UO(2)(II) complexes

Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and UO(2)(II) complexes with the ligand 2-tert-butylaminomethylpyridine-6-carboxylic acid methylester (HL(2)) have been prepared and characterized by elemental analyses, molar conductance, magnetic moment, thermal analysis and spectral data. 1:1 M:HL(2) complexes, with the general formula [M(HL(2))X(2)].nH(2)O (where M = Co(II) (X = Cl, n = 0), Ni(II) (X = Cl, n = 3), Cu(II) (grey colour, X = AcO, n = 1), Cu(II) (yellow colour, X = Cl, n = 0) and Zn(II) (X = Br, n = 0). In addition, the Fe(III) and UO(2)(II) complexes of the type 1:2 M:HL(2) and with the formulae [Fe(L(2))(2)]Cl and [UO(2)(HL(2))(2)](NO(3))(2) are prepared. From the IR data, it is seen that HL(2) ligand behaves as a terdentate ligand coordinated to the metal ions via the pyridyl N, carboxylate O and protonated NH group; except the Fe(III) complex, it coordinates via the deprotonated NH group. This is supported by the molar conductance data, which show that all the complexes are non-electrolytes, while the Fe(III) and UO(2)(II) complexes are 1:1 electrolytes. IR and H1-NMR spectral studies suggest a similar behaviour of the Zn(II) complex in solid and solution states. From the solid reflectance spectral data and magnetic moment measurements, the complexes have a trigonal bipyramidal (Co(II), Ni(II), Cu(II) and Zn(II) complexes) and octahedral (Fe(III), UO(2)(II) complexes) geometrical structures. The thermal behaviour of the complexes is studied and the different dynamic parameters are calculated applying Coats-Redfern equation.     

Model Complexes for Ureases: A Dinickel(II) Complex with a Novel Asymmetric Ligand and Comparative Kinetic Studies on Catalytically Active Zinc,Cobalt, and Nickel Complexes

The dinuclear nickel(II) complex of the asymmetric ligand 1‐[N,N‐bis(2‐pyridylmethyl)amino]‐3‐[2‐(3,5dimethyl‐1H‐pyrazol‐1‐yl)ethoxy]‐2‐hydroxypropane (HL1) was prepared as a model for the active site of urease. The novel complex [Ni₂(L1)(MeCOO)(ClO₄)(EtOH)₂](ClO₄) · 0.5 Et₂O ( 1 ) crystallizes in the triclinic space group P 1 with a = 11.639(2) Å, b = 12.571(3) Å, c = 16.341(3) Å, α = 92.29°, β = 106.54°, and γ = 113.73°. The nickel ions (c.n. 6) are bridged by the alkoxy donor substituent of the ligand and an acetate anion. The dinuclear nickel(II), cobalt(II), and zinc(II) complexes of the ligands 1‐[N,N‐bis(2‐benzimidazolylmethyl)amino]‐3‐[2‐(3,5‐dimethyl‐1 H‐pyrazol‐1‐yl)ethoxy]‐2‐hydroxypropane (HL2), N‐methyl‐N,N',N'‐tris(2‐benzimidazolylmethyl)‐2‐hydroxy‐1,3‐diaminopropane (HL3), and N,N,N',N'‐tetrakis(2‐benzimidazolylmethyl)‐2‐hydroxy‐1,3‐diaminopropane (HL4) were investigated for their activity towards the hydrolysis of the test substrate p‐nitrophenyl acetate (npa) in ethanol‐water (1 : 1). The second‐order rate constants for the cleavage of npa were determined for all complexes. The profile of the pH dependence indicates that a hydroxide initially binds to the metal ion. The bound nucleophile subsequently attacks the test substrate. The results are discussed in terms of a refined model for the structure activity relationships of the dinuclear active site of urease.     

Synthesis,spectroscopic, thermal analyses,biological activity and molecular docking studies on mixed ligand complexes derived from Schiff base ligands and 2,6‐pyridine dicarboxylic acid

Two novel Schiff base ligands (L^a and L^b) were prepared from the condensation of quinoline 2‐aldehyde with 2‐aminopyridine (ligand L^a) and from the condensation of oxamide with furfural (ligand L^b). Mixed ligand complexes of the type M⁺²L^a/b L^c were prepared, where (L^a and L^b) the primary ligands and L^c was 2,6‐pyridinedicarboxylic acid as secondary ligand. Metal ions used were Fe(II), Co(II), Ni(II) and Zn(II) for mixed ligands L^a L^c and Fe(II), Co(II), Ni(II), Cu(II), Hg(II) and Zn(II) for L^bL^c mixed ligands. L^a and L^b Schiff base ligands were both characterized using elemental analyses, molar conductance, IR, ¹H and ¹³C NMR. Mass spectra for L^b, [Zn(L^a)L^cCl]Cl and [Cu(L^b)L^cCl]Cl were also studied. ESR spectrum of the [Cu(L^b) L^cCl]Cl complex was also recorded The metal complexes were synthesized and characterized using elemental analyses, spectroscopic (IR, ¹H NMR, UV‐visible, diffused reflectance), molar conductance, magnetic moment and thermal studies. The IR and ¹H NMR spectral data revealed that 2,6‐pyridinedicarboxalic acid ligand coordinated to the metal ions via pyridyl N and carboxylate O without proton displacement. In addition, the IR data showed that L^a and L^b ligands behaved as neutral bidentate ligands with N₂ donation sites (quinoline N and azomethine N for L^a and two azomethine N for L^b). Based on spectroscopic studies, an octahedral geometry was proposed for the complexes. The thermal stability and degradation of the metal complexes were investigated by thermogravimetric analysis. The binding modes and affinities of L^a, L^b and Zn(II) complexes towards receptors of crystal structure of E. coli (PDB ID: 3 t88) and mutant oxidoreductase of breast cancer (PDB ID: 3 hb5) receptors were also studied. The antimicrobial activity against two species of Gram positive, Gram negative bacteria and fungi were tested for the Schiff base ligands, 2,6‐pyridinedicarboxylic acid and the mixed ligand complexes and revealed that the synthesized mixed ligand complexes exhibited higher antimicrobial activity than their free Schiff base ligands.