Synthesis and DFT calculations of metal(II) oxime complexes bearing cysteine as coligand and investigation of their biological evolutions in vitro and in silico.

New complexes with the formula of [ML(Cys)(H2O)2] were obtained as a result of the reaction between the oxime ligand [HL: 4-(4-bromophenylaminoisonitrosoacetyl)biphenyl], cysteine (Cys), and the metal(II) salts (Mn, Ni, Co, Zn, Cu). The newly synthesized compounds were characterized using conventional techniques such as molar conductance, magnetic measurements, elemental analysis, infrared spectroscopy, and thermal analysis (TGA/DTA). Based on the conductivity measurements in DMF, it was determined that the complexes were non-electrolytes. The TGA/DTA analysis was performed to examine the thermal stability and degradation behavior of all samples, and results demonstrated that metal oxides or sulfides formed as a result of the decompositions. In conjunction with other data obtained, the elemental analysis confirmed the octahedral coordination of the complexes with deprotonated oxime (O, O-donor) and amino acid (N, S-donor) ligands and two coordinated waters. The compounds' optimized geometries, molecular electrostatic potential diagrams, and frontier molecular orbitals were computed at the DFT/B3LYP level using the 6-311 G(d,p) and LANL2DZ basis sets. The antibacterial and DNA cleavage activities of all synthesized compounds were also screened, and molecular docking simulations were performed. According to the results of molecular docking studies conducted with three different proteins, the best interaction was found to be between HL-1HNJ with a binding energy of -9.5 kcal/mol. The stability of the HL-1HNJ complex was also verified by a molecular dynamics simulation performed for 50 ns.Communicated by Ramaswamy H. Sarma.

Vortex-assisted restricted access-based supramolecular solvent microextraction of trace Pb(II) ions with 4-(benzimidazolisonitrosoacetyl)biphenyl as a complexing agent before microsampling flame AAS analysis.

A new oxime compound, 4-(benzimidazolisonitrosoacetyl)biphenyl (BIBP) was synthesized and used as a complexing agent in this study to preconcentrate trace amounts of Pb(II) ions with vortex-assisted restricted access-based supramolecular solvent microextraction (RA/SUPRAS-LPME) method. The new complexing agent was characterized by a combination of elemental analyses, Proton Nuclear Magnetic Resonance (1H- NMR), Carbon-13 Nuclear Magnetic Resonance (13C NMR) and Fourier Transform Infrared spectroscopy (FT-IR) and techniques. Extraction of the complex which was formed at pH 8.0 was done by using a supramolecular solvent phase of tetrahydrofuran (THF) and 1-decanol. A microsampling flame atomic absorption spectrophotometer was used to measure the lead ion concentrations of the extract. The method optimized and the optimum experimental conditions were found as; pH = 8, amount of the ligand 2,25 mg, supramolecular solvent volume 50 µL, sample volume 20 mL and vortex time 3 min. The limit of detection (LOD), limit of quantification (LOQ) were calculated as 0.69 µg L-1 and 2.29 µg L-1, respectively. Linear range was found between 15.1 µg L-1 and 606 µg L-1. The developed method was applied to Pb(II) determination in real samples after evaluating the accuracy by using the TMDA-53.3 fortified environmental water sample as certified reference material.

Synthesis, structural elucidation, in vitro antibacterial activity, DFT calculations, and molecular docking aspects of mixed-ligand complexes of a novel oxime and phenylalanine.

An oxime ligand (HL) was synthesized by the condensation of 4-biphenylhydroxymoyl chloride with 2-amino-5-bromopyridine. The oxime ligand was reacted with l-phenylalanine and metal(II) acetate salts (Co(II), Ni(II), and Cu(II)) to synthesize mixed-ligand complexes. Structural elucidation of the newly synthesized ligand and complexes was performed by elemental analysis, 13C NMR, 1H NMR, FT-IR, ICP-OES, the measurements of molar conductivity and magnetic susceptibility. The thermal properties of the compounds were characterized by TG/DTA analyses. The antibacterial activities of the compounds were evaluated in vitro by the resazurin-aided broth microdilution method. Optimized molecular geometries of the HL and its metal complexes were calculated using the density functional theory (DFT) of the B3LYP method with 6-311G (d, p) and LANL2DZ basis sets. The NMR chemical shift values, vibrational frequencies, and HOMO-(LUMO or SOMO) energies were also computed using the mentioned level. A molecular docking study was performed to demonstrate the interactions of the synthesized compound with beta-ketoacyl-ACP synthase III (KAS III), an enzyme that has a key role in bacterial survival. Based on the MIC values and binding energy scores, both in vitro and in silico studies showed that the antibacterial activity of the Cu(II) complex was better than the other studied molecules.

Oxime-functionalized cryogel disks for catalase immobilization.

Catalase is a protective enzyme against oxidative stress and converts hydrogen peroxide into water and molecular oxygen. In the current study, catalase immobilization was applied onto the oxime-functionalized cryogel disks. Cryogel disks were produced by free radical polymerization. After cutting as circular disks, oxime ligand (4-biphenylchloroglyoxime, BPCGO) was attached and oxime-functionalized cryogel disks were obtained. After optimization of several immobilization parameters such as pH, initial catalase concentration, temperature and ionic strength, maximum catalase load was detected as 261.7 ± 11.2mg/g for cryogel disk at pH5.0. Activity studies indicated that immobilization enhanced the enzyme activity in basic pH region, the temperature range of 15-35°C and at ionic strengths between 0.2 and 1.0M NaCl. Km was detected as 9.9 and 11.0mM and Vmax was 357.1 and 769.2µmol min-1 for free and immobilized catalase, respectively. kcat and Km/kcat values showed that immobilization enhanced the catalytic efficiency. Storage stability experiments demonstrated that immobilization increased the usability period. Furthermore, catalase desorption was achieved by 1.0M NaSCN at pH8.0 successfully and catalase adsorption capacity of oxime-functionalized cryogel disk was decreased by 9.9% at the end of 5 adsorption-desorption cycle.

Synthesis and characterization of novel organocobaloximes as potential catecholase and antimicrobial activity agents.

An asymmetric, potentially bidentate dioxime ligand (H2L) was formed by condensation of 4-biphenylchloroglyoxime and napthyl-1-amine. Two equivalents of H2L were reacted with CoCl2 · 6H2O under appropriate conditions with deprotonation of the dioxime ligand. A series of new organocobaloxime derivatives of the type [CoR(HL)2Py], [CoRL2PyB2F4], and [CoRL2Py(Cu(phen))2] (H2L = 4-(napthyl-1-amino)biphenylglyoxime; phen = 1,10-phenathroline; R = izopropyl and benzyl; Py = pyridine) were synthesized. The products were characterized by elemental analysis, molar conductance, FT-IR, ¹H NMR, and magnetic susceptibility measurements. Catecholase-like activity properties of all complexes were also studied. All complexes are catalysts for the oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butyl-1,2-benzoquinone in methanol. Antimicrobial activity studies of H2L and the six complexes were carried out on standard strains (human pathogenic) of bacteria (Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Bacillus cereus, Enterococcus faecalis, Streptococcus pneumoniae, Listeria monocytogenes, Bacillus subtilis, Escherichia coli, Pseudominas aeruginosa, Salmonella typhi) and the yeast Candida albicans. The compounds showed a significant inhibition of the growth of the Gram-positive bacteria tested. Among the tested microorganisms, S. aureus was the most sensitive strain, especially to H2L and its complexes.

Synthesis, characterization and DNA cleaving studies of new organocobaloxime derivatives.

Dioxime ligand (H2L) was synthesized by condensation reaction between 4-biphenylchloroglyoxime and 4-chloroaniline. The metal complexes of the types, [Co(HL)2(i-Pr)Py], [CoL2(i-Pr)PyB2F4] and [CoL2(i-Pr)Py(Cu(phen))2](ClO4)2 [H2L = 4-(4-chlorophenylamino)biphenylglyoxime; phen = 1,10-phenanthroline; i-Pr = isopropyl; Py = pyridine] were synthesized and characterized by elemental analysis, FT-IR, 1H NMR and magnetic susceptibility, conductivity measurements. The results of elemental analyses, IR and NMR confirmed the stoichiometry of the complexes and the formation of ligand frameworks around the metal ions. The magnetic moment measurements of the complexes indicated that the complexes are diamagnetic (low-spin d6 octahedral) except trinuclear complex. Furthermore the interaction between the dioxime ligand and its complexes with DNA has also been investigated by agarose gel electrophoresis. The trinuclear Cu2Co complex with H2O2 as a cooxidant exhibited the strongest DNA cleaving activity.

Structural, antimicrobial and computational characterization of 1-benzoyl-3-(5-chloro-2-hydroxyphenyl)thiourea.

A new thiourea derivative, 1-benzoyl-3-(5-chloro-2-hydroxyphenyl)thiourea (bcht) has been synthesized from the reaction of 2-amino-4-chlorophenol with benzoyl isothiocyanate. The title compound has been characterized by elemental analyses, FT-IR, (13)C, (1)H NMR spectroscopy and the single crystal X-ray diffraction analysis. The structure of bcht derived from X-ray diffraction of a single crystal has been presented. The structural and spectroscopic data of the molecule in the ground state were calculated by using density functional method using 6-311++G(d,p) basis set. The complete assignments of all vibrational modes were performed on the basis of the total energy distributions (TED). Isotropic chemical shifts ((13)C NMR and (1)H NMR) were calculated using the gauge-invariant atomic orbital (GIAO) method. Theoretical calculations of bond parameters, harmonic vibration frequencies and nuclear magnetic resonance are in good agreement with experimental results. The UV absorption spectra of the compound that dissolved in ACN and MeOH were recorded. Bcht was also screened for antimicrobial activity against pathogenic bacteria and fungi.

Synthesis, characterization, thermal behavior, and DNA-cleaving studies of cyano-bridged nickel(II)-copper(II) complexes of 4-(pyridin-2-ylazenyl)resorcinol.

We present here the syntheses of a mononuclear Cu(II) complex and two polynuclear Cu(II)-Ni(II) complexes of the azenyl ligand, 4-(pyridin-2-ylazenyl)resorcinol (HL; 1). The reaction of HL (1) and copper(II) perchlorate with KCN gave a mononuclear complex [CuL(CN)] (4). Using 4, one pentanuclear complex, [{CuL(NC)}(4) Ni](ClO(4))(2) (5) and one trinuclear complex, [{CuL(CN)}(2) NiL]ClO(4) (6), were prepared and characterized by elemental analyses, magnetic susceptibility, molar conductance, IR, and thermal analysis. Stoichiometric and spectral results of the mononuclear Cu(II) complex indicated that the metal/ligand/CN ratio was 1 : 1 : 1, and the ligand behaved as a tridentate ligand forming neutral metal chelates through the pyridinyl and azenyl N-, and resorcinol O-atom. The interaction between the compounds (the ligand 1, its Ni(II) and Cu(II) complexes without CN, i.e., 2 and 3, and its complexes with CN, 4-6) and DNA has also been investigated by agarose gel electrophoresis. The pentanuclear Cu(4) Ni complex (5) with H(2) O(2) as a co-oxidant exhibited the strongest DNA-cleaving activity.

Synthesized some 4-(2-thiazolylazo)resorcinol complexes: characterization, thermal and optical properties.

Some transition metal complexes of the type [ML2].nH2O (n=0 or 2) of the title ligand, 4-(2-thiazolylazo)resorcinol, HL (TAR) have been synthesized and characterized by various analytical and physicochemical (elemental, thermal analyses, AAS, electrolytic conductance and magnetic susceptibility measurements) and spectral (UV-vis and IR) techniques for structure determination and optical properties. The complexes have the formulae [ML2] for M=Fe(II), Cu(II) and Zn(II); [CdL2].2H2O. An octahedral structure is proposed for all complexes. IR spectra show that the ligand is coordinated to the metal ions in a tridentate manner with ONN donor sites of the resorcinol OH, azo N and thiazole N. The effect of varying pH and solvent on the absorption behavior of the ligand and complexes has been investigated. The optical constants such as, refractive index, extinction coefficient, dielectric constant were determined for the ligand and its complexes. These parameters changed with different metal complexes. The optical absorption data revealed that the band gap of the films was direct transitions. The optical band gap and Urbach energy of the films were determined using the known theory. The optical dispersion parameters were determined according to Wemple and DiDomenico method.

Novel homo- and hetero-nuclear copper(II) complexes of tetradentate Schiff bases: synthesis, characterization, solvent-extraction and catalase-like activity studies.

Twelve homo- and hetero-nuclear copper(II) complexes of tetradentate Schiff base ligands containing N(4) donor sets have been prepared by employing several steps. The characterization and nature of bonding of the complexes have been deduced from elemental analysis, FT-IR, molar conductivity, magnetic moment measurements and thermal analysis. The three Schiff base ligands were further identified using (1)H and (13)C NMR spectra. All copper(II) complexes are 1:2 electrolytes as shown by their molar conductivities (Lambda(M)) in DMF and paramagnetic. The subnormal magnetic moment values of the di- and tri-nuclear complexes explained by a very strong anti-ferromagnetic interaction. The extraction ability of the ligands has been examined by the liquid-liquid extraction of selected transition metal (Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Pb(2+), Cd(2+), Hg(2+)) cations. The ligands show strong binding ability toward copper(II) ion. Furthermore the homo- and hetero-nuclear copper(II) complexes were each tested for their ability to catalyse the disproportionation of hydrogen peroxide in the presence of the added base imidazole.