Liviu Mitu

Novel metal-based pharmacologically dynamic agents of transition metal(II) complexes: Designing, synthesis, structural elucidation, DNA binding and photo-induced DNA cleavage activity

Novel Schiff base Cu(II), Ni(II), Co(II) and Zn(II) complexes have been designed and synthesized using the macrocyclic ligand derived from the condensation of diethylphthalate with Schiff base, obtained from benzene-1,2-diamine and 3-benzylidene-pentane-2,4-dione. The ligand and its complexes have been characterized by analytical and spectral techniques. DNA binding properties of these complexes have been investigated by UV-vis, viscosity measurements, cyclic voltammetric and differential pulse voltammogram studies. The intrinsic binding constants for Co(II), Ni(II), Cu(II) and Zn(II) complexes are 1.6x10(6), 1.8x10(6), 2.0x10(6) and 1.5x10(6) M(-1) respectively which are obtained from electronic absorption experiment. Control DNA cleavage experiments using pUC19 supercoiled (SC) DNA and minor groove binder (distamycin) suggest the major groove binding tendency for the synthesized complexes. In the presence of a reducing agent like 3-mercaptopropionic acid (MPA), the synthesized complexes show chemical nuclease activity under dark reaction condition. The complexes also show efficient photo-induced DNA cleavage activity on irradiation with a monochromatic UV light of 360 nm in the presence of inhibitors. Control experiments show inhibition of cleavage in the presence of singlet oxygen quencher like sodium azide and enhancement of cleavage in D(2)O, suggesting the formation of singlet oxygen as a reactive species in a type-II process.

Studies on DNA Cleavage and Antimicrobial Screening of Transition Metal Complexes of 4-Aminoantipyrine Derivatives of N2O2 Type

A new series of transition metal complexes of Cu(II), Ni(II), Zn(II) and VO(IV), were synthesized from the Schiff base (L) derived from 4-aminoantipyrine, 3-hydroxy-4-nitrobenzaldehyde and acetylacetone. The structural features were arrived from their elemental analyses, magnetic susceptibility, molar conductance, Mass, IR, UV-Vis., 1H NMR and ESR spectral studies. The data show that the complexes have composition of [ML]X type. The UV-Vis., magnetic susceptibility and ESR spectral data of the complexes suggest a square-planar geometry around the central metal ion except for VO(IV) complex which has square-pyramidal geometry. The redox behavior of copper and vanadyl complexes were studied by cyclic voltammetry. The antimicrobial screening tests were also recorded and gave good results in the presence of metal ion in the ligand system. The nuclease activity of the above metal complexes shows that the copper and nickel complexes cleave DNA through redox chemistry, whereas other complexes are not effective.

Synthesis, characterization, DNA binding, oxidative damage of DNA strand scission, and antimicrobial activities of β-diketone condensed Schiff-base transition metal complexes

Co(II), Ni(II), Cu(II), Zn(II), and VO(IV) complexes containing a versatile β-diketone Schiff-base ligand (obtained by the condensation of 3-furan-2-ylmethylene-2,4-dione and 2-aminophenol) have been synthesized and characterized. Microanalytical, magnetic, and spectroscopic data reveal that the central metal is coordinated to two oxygens of phenolate and two nitrogens of imine of the ligand. Binding of synthesized complexes with calf thymus DNA has been investigated by spectroscopic and electrochemical methods and viscosity measurements. The complexes are able to form adducts with DNA and to distort the double helix by changing the base stacking. Electrostatic binding of vanadyl complex is observed from the weak hypochromism in electronic absorption spectra and no change in the viscosity with DNA. Oxidative DNA cleavage activities of the complexes are studied with supercoiled pUC19 DNA using gel electrophoresis. The hydroxyl radical (OH•) is likely to be the species responsible for the cleavage of pUC19 DNA by the synthesized complexes. Under our experimental conditions, the vanadyl complex has no significant cleavage of DNA. The compounds have been screened for activity against several bacterial and fungal strains and the results are compared with the activity of standard drugs.

Bio-sensitive activities of coordination compounds containing 1,10-phenanthroline as co-ligand: synthesis, structural elucidation and dna binding properties of metal(II) complexes.

Present work reports the DNA binding and cleavage characteristics of a series of mixed-ligand complexes having the composition [M(L)(phen)2]Cl2 (where M=Cu(II), Ni(II), Co(II) and Zn(II) and phen as co-ligand) in detail. Their structural features and other properties have been deduced from their elemental analyses, magnetic susceptibility and molar conductivity as well as from IR, UV-Vis, (1)H NMR and EPR spectral studies. The UV-Vis, magnetic susceptibility and EPR spectral data of metal complexes suggest an octahedral geometry. The binding properties of these complexes with calf thymus DNA (CT-DNA) have been explored using electronic absorption spectroscopy, viscosity measurement, cyclic voltammetry and differential pulse voltammetry. The DNA-binding constants for Cu(II), Ni(II), Co(II), and Zn(II) complexes are 6.14×10(5)M(-1), 1.8×10(5)M(-1), 6.7×10(4)M(-1) and 2.5×10(4)M(-1) respectively. Detailed analysis reveals that these complexes interact with DNA through intercalation binding. Nuclease activity has also been investigated by gel electrophoresis. Moreover, the synthesized Schiff base and its mixed-ligand complexes have been screened for antibacterial and antifungal activities. The data reveal that the complexes exhibit higher activity than the parent ligand.

Transition Metal Complexes of Isonicotinoyl–hydrazone-4-diphenylaminobenzaldehyde: Synthesis, Characterization and Antimicrobial Studies

A series of complexes of Cu(II), Ni(II), Co(II), Mn(II) and Cd(II) with Isonicotinoylhydrazone-4-diphenylaminobenzaldehyde (INHDAB) has been reported. The complexes have been characterized by analytical data, IR, UV-Vis, NMR spectra, magnetic susceptibility values, thermal analysis and for the Cu(II) complex the ESR spectrum has been registered. The biological activity of these complexes were investigated against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella enteritidis and Shigella flexneri bacteria. The INHDAB ligand is coordinate at the metallic ions by oxygen amide (O=C) and the azomethine nitrogen.

DNA interaction studies of pyrazolone- and diimine-incorporated Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) complexes: synthesis, spectroscopic characterization, and antimicrobial study

Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) mixed-ligand complexes were synthesized using 4-[(furan-2-ylmethylene)amino]-1,2-dihydro-1,5-dimethyl-2-phenyl-3H-pyrazol-3-one as the main ligand and 1,10-phenanthroline/2,2′-bipyridine as co-ligand(s). They were characterized by the usual analytical and spectral techniques. The data obtained reveal that the complexes adopt an octahedral geometry around the central metal ions. These complexes were found to be better antimicrobial agents than the free ligands. The DNA (CT) binding properties of the complexes were explored by UV–Vis, viscosity measurements, cyclic voltammetry, differential pulse voltammetry, and molecular docking studies. Binding constants for the above complexes were found to be on the order of 104, indicating that most of the synthesized complexes are partial intercalators. The DNA-cleavage activities of the complexes were also assessed using supercoiled pUC19 DNA and gel electrophoresis, and the results revealed that the hydroxyl radical is likely to be the reactive species responsible for the cleavage of pUC19 DNA by the synthesized complexes.Graphical abstract.

Synthesis, structural elucidation, biological, antioxidant and nuclease activities of some 5-Fluorouracil-amino acid mixed ligand complexes.

Some biologically active mixed ligand complexes (1-9) have been synthesized from 5-Fluorouracil (5-FU; A) and amino acids (B) such as glycine (gly), L-alanine (ala) and L-valine (val) with Ni(II), Cu(II) and Zn(II) ions. The synthesized mixed ligand complexes (1-9) were characterized by various physico-chemical, spectral, thermal and morphological studies. 5-Fluorouracil and its mixed ligand complexes have been tested for their in vitro biological activities against some pathogenic bacterial and fungal species by the agar well diffusion method. The in vitro antioxidant activities of 5-Fluorouracil and its complexes have also been investigated by using the DPPH assay method. The results demonstrate that Cu(II) mixed ligand complexes (4-6) exhibit potent biological as well as antioxidant activities compared to 5-Fluorouracil and Ni(II) (1-3) and Zn(II) (7-9) mixed ligand complexes. Further, the cleaving activities of CT DNA under aerobic conditions show moderate activity with the synthesized Cu(II) and Ni(II) mixed ligand complexes (1-6) while no activity is seen with Zn(II) complexes (7-9). Binding studies of CT DNA with these complexes show a decrease in intensity of the charge transfer band to the extent of 5-15% along with a minor red shift. The free energy change values (Δ(‡)G) calculated from intrinsic binding constants indicate that the interaction between mixed ligand complex and DNA is spontaneous.

Removal of Chromium(III) Using Synthetic Polymers, Copolymers and their Sulfonated Derivatives as Adsorbents

This study is concerned with the development of some synthetic polymers, copolymers and their sulfonated derivatives as adsorbents. The effectiveness of these adsorbents in removing Cr(III) from aqueous solution was evaluated by batch technique. The influence of different experimental parameters on removal process such as solution pH, contact time, adsorbent dose, Cr(III) concentration and temperature were evaluated. Adsorption equilibrium was achieved in 20 to 30 min. at pH > 5. The Langmuir, Freundlich and Temkin adsorption isotherms were used to elucidate the observed sorption phenomena. The maximum Cr(III)37.8 mg/gram of PS(polystyrene) and 37.2 mg/g of SAN (styrene/acrylonitrile copolymer) was removed as evaluated from Langmuir isotherm while the heat of sorption was in the range 0.21–7.65 kJ/mol as evaluated from Temkin isotherm. It can be concluded that PS developed in this study exhibited considerable adsorption potential for application in removal of Cr(III) from aqueous media as compared to its copolymers and other derivatives used in this study.

NOVEL, BIOLOGICALLY IMPERATIVE, HIGHLY VERSATILE AND PLANAR SYSTEMS: SYNTHESIS, CHARACTERIZATION, ELECTROCHEMICAL BEHAVIOR, DNA BINDING AND CLEAVAGE PROPERTIES OF SUBSTITUTED β-DIKETIMINE COPPER(II) AND ZINC(II) COMPLEXES WITH DIPYRIDO (3,2-A:2 ', 3'C) PHENAZINE LIGAND

Novel copper(II) and zinc(II) complexes of the type [ML(dppz)]Cl2, [L = Schiff base derived from the condensation of 3-(3- phenyl-allylidene)-pentane-2,4-dione and para-substituted aniline; X = -NO2 (L1), -H (L2), -OH (L3) and -OCH3 (L4); dppz = dipyrido (3,2-a:2′, 3′ -c)phenazine] were synthesized and characterized by various analytical and spectral techniques. The physicochemical studies and spectral data indicated that all the complexes were monomeric and cationic with square-planar geometry. Spectroscopic data and viscosity measurements showed that the complexes intercalated to DNA with large binding constants. The substituted groups such as -NO2, -H, -OH and -OCH3 in aniline moiety influenced the observed trend in the redox potentials of the complexes. The peak potential separation and formal potential of complexes were independent of sweep rate or scan rate (ν) indicating a quasireversible one-electron redox process. In all the cases, ip was linear function of ν1/2, as expected for diffusion controlled process, and ipa/ipc ≈ 1 at all sweep rates. It was found that the decrease in ipc was due to the higher binding of copper complexes and slowly diffusing DNA. In the presence of a reducing agent like 3-mercaptopropionic acid (MPA), the chemical nuclease activity order of the copper complexes under dark reaction condition was -NO2 > -H > -OH > -OCH3. The hydrolytic cleavage of DNA by the zinc complexes was supported by the evidence from free radical quenching and T4 ligase ligation.

Electrochemical deposition of a Zn-HNT/p(EDOT-co-EDOP) nanocomposite on LN SS for anti-bacterial and anti-corrosive applications

A copolymer composite of Zn-HNT/p(EDOT-co-EDOP) was deposited on low nickel stainless steel (LN SS) using an electrochemical polymerization method. The structure of the copolymer and the composite was confirmed by various analytical studies. In this work, the anticorrosion ability of the coatings was assessed in acidic solutions using an electrochemical method and their antibacterial activity was examined against marine bacteria.