Quasi-reversible Reduction Wave Research Articles

Competition between Cu-Br semi-coordinate bond and C-H∙∙∙Br, C-H∙∙∙S and S∙∙∙S interactions; new two thioalkylazothiophenol (SNS) copper (II) dimers [Cu(L)(µ-Br)

Two new copper dimers [Cu(L)(µ-Br)]2, HL = 2(RS)C6H4N = NC(COCH3)-SC6H5, where R = CH3 (1), C6H5 (2) were synthesized and characterized using a variety of physicochemical methods, including single crystal X-ray diffraction. The molecular structures of the two binuclear copper(II) complexes show that Cu∙∙∙Cu inter-nuclei distances are 3.662 \\AA and 3.392 \\AA in 1 and 2, respectively. Structural analysis of the two dimers supported by QTAIM analysis of electron density indicates the presence of competition between Cu∙∙∙Br semi-coordinate bond and CH∙∙∙Br and CH∙∙∙S hydrogen bonding interactions and S∙∙∙S chalcogen bonding interactions. In complex 1, CH∙∙∙Br and CH∙∙∙S hydrogen bonding interactions exist, in contrast, they are absent in 2. Cu∙∙∙Br semi-coordinate bonds are stronger in 2 as indicated by Cu∙∙∙Br bond distances; Cu∙∙∙Br bond distances are 2.955 and 2.858 Å in 1 and 2.746 Å in 2. There are two weaker S∙∙∙S interactions in 2 and one stronger interaction in 1 as indicated by S∙∙∙S interatomic distances. The two copper dimers and their ligands exhibited good anticancer efficacy against breast (MCF-7), lung (HCT115), and colon human (A549) cancer cell lines. Complex 1 demonstrated strong cancer cell death compared to complex 2. Additionally, the complexes exhibited higher activity than the ligands. Dimer 2 exhibits two quasi-reversible one-electron reduction waves at −0.05 V and −0.37 V. The comproportionating constant for forming the Cu(I/II) mixed-valence complex was 2.57 × 105. The absence of Intervalence transfer (IT) bands in the electronic absorption spectrum for the mixed-valence complex suggested that a single unpaired electron is localized on one copper center.

Rhenium(I) bromo tricarbonyl complexes from anthracenyl derivatized ligands

The ligand 2-(1H-pyrazol-1-yl)pyrazine (pypyr) was prepared by reaction of 2-bromopyrazine with N-lithium pyrazolate with 92.5% yield, while the anthracenyl derivatives 2-(anthracen-9-yl)-5-(1H-pyrazol-1-yl)pyrazine (pypyr-anthra) and 9,10-bis(5-(1H-pyrazol-1-yl)pyrazin-2-yl)anthracene (pypyr-anthra-pypyr) were prepared by reaction of the 9-anthraceneboronic or bis-boronic acid pinacol ester with 2-bromo-5-(1H-pyrazol-1-yl)pyrazine with medium yields (49.6 and 31.5 % respectively). The respective ReI(CO)3Br complexes: [(pypyr)Re(CO)3Br], [(pypyr-anthra)Re(CO)3Br] and [Br(CO)3Re(pypyr-anthra-pypyr)Re(CO)3Br] were prepared in high yields (94, 84 and 78 % respectively) by reaction with bromotricarbonyl(tetrahydrofuran)rhenium(I) dimer. DFT modelling suggests the anthracenyl moiety is not coplanar with the pyrazolyl-pyrazine fragment, defining a dihedral angle of 65° and 67° for [(pypyr-anthra)Re(CO)3Br] and [Br(CO)3Re(pypyr-anthra-pypyr)Re(CO)3Br] respectively. Each one of the three rhenium(I) molecules shows a quasi-reversible reduction wave around − 1.10 V, assigned by comparison with the uncoordinated ligand, the pypyr fragment, while additional reductions waves related to this core or the anthryl arms are present. UV–Vis spectra show absorption bands and/or shoulders around 400–450 nm for the series of compounds in solution. The respective extinction coefficients (∼4 × 103 M−1cm−1), the sensitivity to solvent polarity and DFT modelling suggest they corresponds to MLCT Redπ → π(pyr)* transitions. Despite their high emissivity, the uncoordinated ligands completely lose their emission upon coordinated to ReI(CO)3Br. The rhenium(I) complexes emit around 650 nm upon excitation, although [(pypyr)Re(CO)3Br] is a moderate emissive molecule, while [(pypyr-anthra)Re(CO)3Br] and [Br(CO)3Re(pypyr-anthra-pypyr)Re(CO)3Br] are very weak ones. In contrast these two last molecules showed a remarkably high yield as singlet oxygen sensitizers.

Bio functional molecular complexes, ferrocenyl hydrazone based binuclear Cu (II) derivatives: Synthesis, spectral, DNA/BSA binding &in-silico analyses

As a first stage intermediate, designing mononuclear complexes of amine-based phenolic derivatives employing Cu (II) acetate as a central metal ion in a 1:2:1 ratio. In a methanolic solution treated with 1,1′-diacetyl ferrocene dihydrazone and Cu (II) perchlorate hexahydrate to generate a new group of ferrocene based macrocyclic binuclear Cu (II) complexes. To characterize the macrocyclic complexes, physico-chemical studies such as FT-IR, UV–vis, and photoluminescence were used. The binuclear Cu(II) complex [Cu2L1] exhibits two quasi-reversible reduction waves in the potential range The binuclear complex [Cu2L1]hastwowaves of virtually reversible reductionin the potential range of E1pc = −1.01 V and E2pc = −1.37 V in the electrochemical investigation. They show a reduction process that involves two one-electron reductions in steps. The ferrocenyl group of the complexes shows one-electron ferrocene/ferrocenium redox activity, although with differing peak potentials. CT-DNA was used to study DNA binding utilizing spectroscopic techniques such as Circular Dichroism, UV–vis, and Fluorescence. The binding constant (Kb) values for the series of complexes range from 1.3x105 to 5.8 × 105 M−1. The metal complexes all interacted with CT-DNA by an intercalative form of binding, according to fluorescence spectrum analyses. BSA protein binding, on the other hand, indicates a quenching manner of interaction with the binuclear complex system, with binding constants of 1.77 × 106, 1.65 × 106, 2 × 106, 4.8 × 106 and 5.12 × 106 M−1. Molecular docking analysis was used to support and augment the experimental biological studies. Intercalation was seen during the docking of 1BNA with a metal complex due to multiple hydrogen bonding interactions. The ferrocene heterocyclic ring and the naphthyl group of complexes interacted with the BSA protein's ARG and TYR systems.

Improving the Solubility of Hexanuclear Heterometallic Extended Metal Atom Chain Compounds in Nonpolar Solvents by Introducing Alkyl Amine Moieties.

The highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) interaction at the dz2 orbital between two kinds of metal complex is useful for obtaining heterometallic one-dimensional (1D) chains as well as heterometallic metal string compounds (HMSCs). Platinum dinuclear complexes, [Pt2(piam)2(NH2R)4]X2 (piam = pivalamidate, R = CH3, C2H5, C3H7, or C4H9, X = anion), comprising σ* as HOMO were mixed with [Rh2(O2CCH3)4] comprising σ* as LUMO in solvents to afford single crystals of [{Rh2(O2CCH3)4}{Pt2(piam)2(NH2R)4}2]X4 (2–5). Single-crystal X-ray analyses revealed that 2–5 are hexanuclear complexes that are one-dimensionally aligned as Pt–Pt–Rh–Rh–Pt–Pt with metal–metal bonds, where the alkyl moieties at end Pt atoms obstruct further 1D extension. Complexes 2–5 appear as if they are cut off from an infinite chain [{Rh2(O2CCH3)4}{Pt2(piam)2(NH3)4}2]n(PF6)4n·6nH2O (1) aligned as −{Pt–Pt–Rh–Rh–Pt–Pt}n–. The diffuse reflectance spectrum of 1 depicts broad shoulder bands, which are not present in the spectra of 2–5, proving that the infinite chain 1 forms a band structure. Compounds 4 and 5 with propyl or butyl moieties at amine ligands, respectively, are soluble in nonpolar solvents, such as CH2Cl2, without the dissociation of their hexanuclear structures. Taking advantage of their solubility, measurement of cyclic voltammetry in CH2Cl2 become possible, which shows the quasi-reversible oxidation and reduction waves at 4: Eox = 0.86 V and Ered = 0.69 V and 5: Eox = 0.87 V and Ered = 0.53 V.

Proton reduction by phosphinidene-capped triiron clusters

Bis(phosphinidene)-capped triiron carbonyl clusters, including electron rich derivatives formed by substitution with chelating diphosphines, have been prepared and examined as proton reduction catalysts. Treatment of the known cluster [Fe3(CO)9(µ3-PPh)2] (1) with various diphosphines in refluxing THF (for 5, refluxing toluene) afforded the new clusters [Fe3(CO)7(µ3-PPh)2(κ2-dppb)] (2), [Fe3(CO)7(µ3-PPh)2(κ2-dppv)] (3), [Fe3(CO)7(µ3-PPh)2(κ2-dppe)] (4) and [Fe3(CO)7(µ3-PPh)2(µ-κ2-dppf)] (5) in moderate yields, together with small amounts of the corresponding [Fe3(CO)8(µ3-PPh)2(κ1-Ph2PxPPh2)] cluster (x = -C4H6-, -C2H2-, -C2H4-, -C3H6-, -C5H4FeC5H4-). The molecular structures of complexes 3 and 5 have been established by X-ray crystallography. Complexes 1–5 have been examined as proton reduction catalysts in the presence of p-toluenesulfonic acid (p-TsOH) in CH2Cl2. Cluster 1 exhibits two one-electron quasi-reversible reduction waves at –1.39 V (ΔE = 195 mV) and at –1.66 V (ΔE = 168 mV; potentials vs. Fc+/Fc). Upon addition of p-TsOH the unsubstituted cluster 1 shows a first catalytic wave at –1.57 V and two further proton reduction processes at –1.75 and –2.29 V, each with a good current response. The diphosphine-substituted derivatives of 1 are reduced at more negative potentials than the parent cluster 1. Clusters 2–4 each exhibit an oxidation at ca. +0.1 V and a reduction at ca. –1.6 V; for 4 conversion to a redox active successor species is seen upon both oxidation and reduction. Clusters 2–4 show catalytic waves in the presence of p-TsOH, with cluster 4 exhibiting the highest relative catalytic current (icat/i0 ≈ 57) in the presence of acid, albeit at a new third reduction process not observed for 2 and 3. Addition of the dppf ligand to the parent diphosphinidene cluster 1 gave cluster 5 which exhibited a single reduction process at –1.95 V and three oxidation processes, all at positive values as compared to 2–4. Cluster 5 showed only weak catalytic activity for proton reduction with p-TsOH. The bonding in 4 was investigated by DFT calculations, and the nature of the radical anion and dianion is discussed with respect to the electrochemical data.

Diastereoselective Synthesis of Steroid-[60]Fullerene Hybrids and Theoretical Underpinning.

The reaction of C60 with pregnen-20-carboxaldehyde, a biologically active synthetic steroid, by using a 1,3-dipolar cycloaddition reaction (Prato's protocol) results in the formation of pyrrolidine rings bearing a new stereogenic center on the C2 of the five-membered ring. The formation of the fullerene-steroid hybrids proceeds with preference for the Re face of the 1,3-dipole, with formation of a diastereomeric mixture in 73:15 ratio. The investigation of the chiroptical properties of these conjugates allowed determining the absolute configuration of the new fulleropyrrolidines. In addition, a thorough spectroscopical study permitted to determine the structure of the two mono-cycloadducts. The electrochemical properties of the new hybrids were also evaluated by cyclic voltammetry, both systems exhibit three quasi-reversible reduction waves which are cathodically shifted in regard to the parent C60. Theoretical calculations help supporting the experimental data. A conformational study combining semiempirical methods and density functional theory has predicted the most stable diastereomer. On the basis of this agreement, a possible reaction mechanism is presented. Additionally, a molecular docking simulation has been carried out using the HIV-1 protease as receptor, thus paving the way to study the possible application of these stereoisomers in biomedicine.

DNA binding and cleavage studies of copper(II) complex containing N2O2 Schiff base ligand

A new series of copper (II) complexes [Cu(L1-5)](ClO4)] [1–5] were synthesized by condensation of salicylaldehyde with various diamines (1,2-diamino ethane, 1,3-diamino propane, 1,2-diamino benzene, 2-aminobenzyl amine and 1,8-diamino naphthalene) and characterized by several analytical techniques. The precursor ligand structure was confirmed by single crystal X-ray diffraction (XRD) techniques. The viscosity measurement and molecular docking studies were also carried out for newly synthesized Cu(II) complexes. Cyclic voltametry (CV) study showed a quasi-reversible reduction wave in cathodic region confirm the presence of Cu2+. From the electronic spectral and DNA binding studies (Kb values are within the range from 0.47 × 104 M−1 to 1.18 × 105 M−1) it evidences that Cu(II) complexes were intercalated with DNA, this observation was further confirmed by fluorescence measurement studies (Kapp∼0.22 × 105 M 1–0.26 × 106 M−1). Comparatively the maximum DNA cleavage was observed in the complex (5) and the possible mechanism of DNA cleavage activity has also been discussed. In addition, the interaction of complexes (1–5) with bovine serum albumin (BSA) was also examined. These encouraging results may pave the way towards the development of novel therapeutic agents in cancer biology.

High Second-Order NLO Response Exhibited by the First Example of Polymeric Film Incorporating a Diimine–Dithiolate Square-Planar Complex: The [Ni(o-phen)(bdt)

A novel square-planar diimine–dithiolate nonlinear optical (NLO) chromophore, the complex [Ni(o-phen)(bdt)] (1), is reported in this paper (o-phen = dianion of 1,2-phenylendiamina; bdt =1,2-benzenedithiolate). This compound has been fully characterized by single-crystal X-ray diffraction, UV–vis–NIR spectroscopy, cyclic voltammetry, DFT, and TD-DFT calculations. 1 crystallizes in the P21 space group and shows an almost planar molecule. The cyclic voltammetry measurements present an irreversible anodic peak at 0.87 V and reversible and quasi-reversible reduction waves at −0.35 and −1.13 V, respectively. A medium-intense (e = 1.91 × 104 mol–1 dm3 cm–1) absorption with a maximum at 728 nm appears in the UV–vis–NIR spectrum. The molecular second-order NLO properties of 1 have been measured by the electric field induced second-harmonic generation technique in DMF solution, giving values of −1000 × 10–48 esu for μβ1.907 and −356 × 10–48 esu for μβ0. Furthermore, remarkable solid-state responses have been measur...

Copper(II) complex of a Schiff base of dehydroacetic acid: Characterization and aerobic oxidation of benzyl alcohol

The copper complex of a tetradentate ligand based on dehydroacetic acid 1 has been prepared and its crystal structure redetermined, showing a copper pair. EPR spectroscopy shows that the dimeric structure is preserved in CH2Cl2 and CH3CN (triplet signal with D=480±50MHz, E=50±25MHz), but complex 1 is converted into a monomer in coordinating solvents (MeOH, DMF and DMSO). By DFT calculations it is seen that the copper ion geometry in the monomer is essentially square planar in MeOH and DMF, but evolves towards square pyramidal in DMSO due to solvent ligation in axial position. The hydroxyl of the methanol molecules are involved in hydrogen bonds with the carbonyl oxygen of the ligand. Complex 1 displays a quasi-reversible reduction wave at E1/2=−0.86V vs. Fc+/Fc, which is assigned to the CuII/CuI redox couple. It catalyzes the aerobic oxidation of benzylalcohol, with a conversion that reaches 70% after 2h, by using a loading of 1mol%.

Effect of alkyl chain length of tri-n-alkyl phosphate extractants on the electrochemical behaviour of U(VI) in ionic liquid medium

Higher homologs of trialkyl phosphates have been proposed for the separation of U(VI) from fast reactor dissolver solution by liquid – liquid extraction. The electrochemical behaviour of U(VI) in tri-n-octyl phosphate (TOP) in the ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C4mimNTf2) was studied by cyclic voltammetry. The results were compared with those obtained with reference extractant, tri-n-butyl phosphate in C4mimNTf2. The cyclic voltammogram of U(VI) in C4mimNTf2 exhibited a prominent quasi-reversible reduction wave at −0.24V(Vs. Fc/Fc+) was due to the reduction of U(VI) to U(V) and a couple of oxidation waves at +0.5V(Vs. Fc/Fc+). The cathodic peak current was lowered and peak potential shifted cathodically in the presence of TBP and TOP due to the formation of co-ordinate complex of these ligands of with U(VI). The diffusion coefficient (D, cm2/s) of U(VI) and the heterogeneous charge transfer rate constant (ks, cm/s) were determined for various systems and they increased with increase of temperature and decreased in the presence of ligands. Both these quantities decreased in the order U(VI) in C4mimNTf2>U(VI) – TBP in C4mimNTf2>U(VI) – TOP in C4mimNTf2. The stability constant and the stoichiometry of U(VI)-TBP and U(VI)-TOP in ionic liquid medium was determined by cyclic voltammetry.

Synthesis, Structure and Electrochemistry of Tetranuclear Oxygen-Centered Copper(II) Clusters with Acetylacetone and Benz-pyrazole Hydrolyzed Derivatives as Ligand

Two copper(II) clusters Cu(4)OCl(6)(pyrazole)4, 1, and Cu(4)OBr(6)(Br-pyrazole)4, 2, have been synthesized by reacting acetylacetone and benzohydrazide (1:1 ratio) with CuX(2) (X = Cl for 1 and X= Br for 2) in methanol solutions. The structures of both clusters have been established by X-ray crystallography. The clusters contain four Cu, one O, six μ(2)-X atoms, and four pyrazole ligands. The pyrazoles was prepared in situ by the reaction of acetylacetone with benzohydrazide in methanol under reflux. In 2, the methine hydrogens of the pyrazole ligands have been replaced by bromine atoms. The four copper atoms encapsulate the central O atom in a tetrahedral arrangement. All copper atoms are five-coordinate and have similar coordination environments with slightly distorted trigonal bipyramidal geometry. The cyclic voltammogram of the clusters 1 and 2 show a one-electron quasi-reversible reduction wave in the region 0.485 to 0.731 V, and a one-electron quasi-reversible oxidation wave in the region 0.767 to 0.898 V. In 1, one irreversible oxidative response is observed on the positive of side of the voltammogram at 1.512 V and this can be assigned to Cu(II) to Cu(III) oxidation.

Voltammetric Studies on the Complexing Behavior of Eu(III) with Acidic Extractants in 1-Butyl-1-methylpyrrolidinium Bis(trifluoromethanesulfonyl)imide

Di(2-ethylhexyl)phosphoric acid (D2EHPA) and diglycolamic acids (HDGA) has been proposed for the mutual separation of lanthanides and actinides at the back end of nuclear fuel cycle. The electrochemical behavior of Eu(III) in the room temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([C4mpy][NTf2]) was studied in the presence and absence of D2EHPA and HDGA by various transient electrochemical techniques. The cyclic voltammogram of Eu(III) in [C4mpy][NTf2] recorded at glassy carbon electrode exhibited a prominent quasi-reversible reduction wave at −0.40 V (vs. Fc/Fc+) was due to the reduction of Eu(III) to Eu(II). The cathodic peak current was lowered and the cathodic peak potential shifted cathodically in the presence of ligands, due to the co-ordination of Eu (III) with ligands in ionic liquid phase. The stability constant and stoichiometry of Eu(III)-ligand complex was determined from the cyclic voltammograms recorded at various ligand concentrations. The Eu (III) diffusion coefficient was determined to be in the range of ∼10−11 m2/s by various electrochemical methods and the charge transfer rate constant (ks, m/s) for the electron transfer reaction across the electrode – electrolyte inter phase was determined to be in the range of ∼10−7 m/s by cyclic voltammetry.

Synthesis, Crystal Structure, and Properties of Copper(II) Complexes with 1,4,7-Tris(2-Aminoethyl)-1,4,7-Triazacyclononane

Three kinds of copper(II) complexes with 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane (taetacn), [Cu(taetacn)](ClO4)2 (1), [Cu(Htaetacn)](ClO4)3 (2), and [Cu(Htaetacn)](BF4)3 (3) were synthesized and characterized by elemental analyses, IR and UV-Vis spectroscopies. The spectral features are in harmony with an octahedral geometry for 1 and a square-pyramidal coordination for 2 and 3. The crystal structure of 2 was determined by the single-crystal X-ray diffraction method at 293 K. It crystallizes in the orthorhombic space group Pnma with a = 20.605(3) A, b = 12.7944(18) A, c = 9.8972(14) A, V = 2609.2(6) A3, Dx = 1.582 g/cm 3, and Z = 4. The R1 [I > 2σ(I)] and wR2 (all data) values are 0.0723 and 0.2389, respectively, for all 3253 independent refl ections. The compound consists of squarepyramidal copper(II) cation with protonated Htaetacn and tetrahedral ClO4 – anions. The temperature dependence of magnetic susceptibilities obeyed the Curie-Weiss law with Ɵ = –2.4, –5.2 and –7.2 K for 1, 2, and 3, respectively. Cyclic voltammetry of 2 in DMF showed two quasi-reversible reduction waves (Epc = –0.98, Epc = –0.92; Epc = –1.30, Epc = –1.22 V versus Fc/Fc +).

Electrochemical behavior of Eu(III) in imidazolium ionic liquid containing tri- n- butyl phosphate and N,N -dihexyloctanamide ligands

Abstract The electrochemical behavior of Eu(III) in room temperature ionic liquid, 1-hexyl-3-methylimidazolium bis(trifluoromethylsulphonyl)imide (C6mimNTf2), was studied in the presence and absence of ligands such as tri-n-butyl phosphate (TBP) and N,N-dihexyloctanamide (DHOA) by cyclic voltammetry. The cyclic voltammogram of Eu(III) in C6mimNTf2, recorded at glassy carbon electrode, exhibited a prominent quasi-reversible reduction wave occurring at the onset of − 0.25 V (Vs Fc/Fc+), culminating in a peak at − 0.84 V (Vs Fc/Fc+) was due to the reduction of Eu(III) to Eu(II). The cathodic peak current was lowered and the peak potential shifted cathodically in the presence of ligands, due to the co-ordination of Eu(III) with ligands in ionic liquid phase. The diffusion coefficient (D, cm2/s) of Eu(III) and the rate constant (ks, cm/s) for the electron transfer reaction across the electrode–electrolyte inter-phase in various systems were determined and they increased with increase of temperature. The stability constant and stoichiometry of Eu(III)–ligand complex were determined from the voltammograms recorded at various ligand concentrations. The emission spectra of Eu(III) in ionic liquid phase suggested that the coordination environment of Eu(III) in TBP was different from that in DHOA.

Synthesis and cationic polymerization of oxyranyl-functionalized indandiones

Monomers and polymers containing arylmethylene-1,3-indandione and arylmethylene-1,3-bisdicyanovinylindane moieties were synthesized. The number average molecular weights of the polymers were found to be of 6030 and 7230 and polydispersity indices of 3.76 and 3.07, respectively. Thermal, optical, photophysical, photoelectrical and electrochemical properties of the synthesized compounds were studied. Their 5 % weight loss temperatures ranged from 261 to 300 °C. Both the monomers and the polymers were found capable to form glasses with glass transition temperatures of 43–104 °C. Cyclic voltammograms of the synthesized compounds showed one quasi-reversible oxidation couple and quasi-reversible reduction waves. The ionization potentials of the solid samples of the synthesized materials established by photoelectron spectrometry were found to be in the range of 5.25–5.41 eV.

Nuclease activity and interaction studies of unsymmetrical binuclear Ni(II) complexes with CT-DNA and BSA.

New unsymmetrical binuclear nickel(II) complexes [Ni2L(1-5)] (ClO4)2 (1-5) were synthesized by using [NiL] [(3-((9E)-(2-((E)-(3-formyl-2-olato-5-methylbenzylideneamino)methyl) phenylimino)methyl)-3-formyl-5-methyl-2-olato)nickel(II)] with various diamines like 1,2-diaminoethane (L(1)), 1,3-diaminopropane (L(2)), 1,4-diaminobutane (L(3)), 1,2-diaminobenzene (L(4)) and 1,8-diaminonaphthalene (L(5)) and characterized by elemental analysis and spectroscopic methods. The molecular structure of binuclear nickel(II) complex 1 is determined by a single crystal X-ray diffraction method. Cyclic voltammograms of binuclear Ni(II) complexes exhibit two quasi-reversible reduction waves in the cathodic region and two oxidation waves in the anodic region. DNA binding, protein binding and DNA cleavage studies were investigated. The interactions of complexes (1-5) with calf thymus DNA were studied by spectroscopic techniques, including absorption and fluorescence methods. The binding affinities of complexes (1-5) with CT-DNA and nuclease activities are in the following order: 5> 4>3 >2>1 . Binuclear Ni(II) complex 1 cleaved the plasmid DNA by a hydrolytic pathway. The hydrolytic cleavage of DNA by the complexes is supported by evidence from free radical quenching and T4 ligase ligation. Binuclear Ni(II) complexes (1-5) displayed significant protein (bovine serum albumin) interactions. The experimental results showed that the interaction between binuclear Ni(II) complexes and BSA was mainly a static quenching process.

Hetero-metallic trigonal cage-shaped dimeric Ni 3 K core complex of L-proline ligand: Synthesis, structural, electrochemical and DNA binding and cleavage activities

Hetero-metallic trigonal cage-shaped dimeric Ni3K core complex of L-proline ligand has been synthesized and characterized. Single crystal X-ray diffraction analysis showed that the hetero-metallic Ni(II)–K(I) complex has a dimeric structure with nine coordinated potassium atoms and six coordinated nickel atoms. The cyclic voltammograms of the complex exhibited two successive quasireversible reduction waves at (\(E_{\text {pc}}^{1} = -\)1.02 V and \(E_{\text {pc}}^{2} = -\)1.33 V) and two successive irreversible oxidation waves (\(E_{\text {pa}}^{1} =\) 0.95 V and \(E_{\text {pa}}^{2} =\) 1.45 V) versus Ag/AgCl in DMF solution. Interaction of the complex with calf-thymus DNA (CT DNA) has been studied using spectroscopic techniques. The complex is an avid DNA binder with a binding constant of 3.6 × 108 M−1. The complex showed efficient oxidative cleavage of supercoiled pBR322 DNA in the presence of the reducing agent hydrogen peroxide involving hydroxyl radical (∘OH) species. As evidenced from the control experiment, DNA cleavage in the presence of∘OH radical was inhibited by quenchers, viz. DMSO and KI. The complex showed in vitro antimicrobial activity against four bacteria and two fungi and the activity is greater than that of the free ligand. Hetero-metallic trigonal cage-shaped dimeric Ni3K core complex of ligand L-proline was synthesized. The complex is an avid DNA binder. The complex showed efficient oxidative cleavage of supercoiled pBR322 DNA in the presence of H2O2 involving hydroxyl radical species.

Synthesis and Properties of 1,3-Indandione-Disubstituted Derivatives of Carbazole, Phenothiazine, and Phenoxazine

Donor-acceptor type 1,3-indandione derivatives were synthesized and their thermal, optical, photophysical, electrochemical, and photoelectrical properties were studied. They form glasses with the glass transition temperatures ranging from 164 to 249°C. 3,6-di(1,3-indandionyl)-10-methyl-phenothiazine showed the lowest energy emission bands in all the investigated solvents, as well as the largest Stokes shifts. Cyclic voltammograms of the synthesized compounds showed one reversible oxidation couple and quasi-reversible reduction waves. The ionization potentials of the solid samples of the synthesized materials were found to be in the range of 5.52–6.01 eV.

Structural, Electrochemical, DNA Binding and Cleavage Properties of Nickel(II) Complex [Ni(H2biim)2(H2O)2]2+of 2,2'-Biimidazole

A nickel(II) complex <TEX>$[Ni(H_2biim)_2(H_2O)_2</TEX><TEX>]</TEX><TEX>(ClO_4)_2{\cdot}H_2O$</TEX> (1) of biimidazole ligand has been synthesized and characterized (Where <TEX>$H_2biim$</TEX> = 2,2'-biimidazole). The single crystal X-ray diffraction of the complex shows a dimeric structure with six coordinated psudo-octahedral geometry. The cyclic voltammograms of complex exhibited one quasireversible reduction wave (<TEX>$E_{pc}=-0.61V$</TEX>) and an irreversible oxidation wave (<TEX>$E_{pa}=1.28V$</TEX>) in DMF solution. The interaction of the complex with Calf-Thymus DNA (CT-DNA) has been investigated by absorption and fluorescence spectroscopy. The complex is an avid DNA binder with a binding constant value of <TEX>$1.03{\times}10^5M^{-1}$</TEX>. The results suggest that the nickel(II) complex bind to CT-DNA via intercalative mode and can quench the fluorescence intensity of EB bind to CT-DNA with <TEX>$K_{app}$</TEX> value of <TEX>$3.2{\times}10^5M^{-1}$</TEX>. The complex also shown efficient oxidative cleavage of supercoiled pBR322 DNA in the presence of hydrogen peroxide as oxidizing agent. The DNA cleavage by complex in presence of quenchers; viz. DMSO, KI, <TEX>$NaN_3$</TEX> and EDTA reveals that hydroxyl radical or singlet oxygen mechanism is involved. The complex showed invitro antimicrobial activity against four bacteria and two fungi. The antimicrobial activity was nearer to that of standard drugs and greater than that of the free ligand.

Mononuclear copper(II) complexes of bis-triazole-based macrocyclic Schiff base hydrazones: direct synthesis, EPR studies, magnetic and thermal properties

Mononuclear copper(II) complexes of 1,2,4-triazole-based Schiff base macrocyclic hydrazones, III and IV, have been reported. The prepared amorphous complexes have been characterized by spectroscopic methods, electron spray ionization mass spectrometry, and elemental analysis data. Electrochemical studies of the complexes in DMSO show only one quasi-reversible reduction wave at +0.43 V (ΔE = 70 mV) and +0.42 V (ΔE = 310 mV) for III and IV, respectively, which is assigned to the Cu(II) → Cu(I) reduction process. Temperature dependence of magnetic susceptibilities of III and IV has been measured within an interval of 2–290 K. The values of χM at 290 K are 1.72 × 10−3 cm3 mol−1 and 1.71 × 10−3 for III and IV, respectively, which increases continuously upon cooling to 2 K. EPR spectra of III and IV in frozen DMSO and DMF were also reported. The trend g|| > g⊥ > ge suggests the presence of an unpaired electron in the dx2−y2 orbital of the Cu(II) in both complexes. Furthermore, spectral and antimicrobial properties of the prepared complexes were also investigated.