Synthesis, spectroscopic characterization and DNA nuclease activity of Cu(II) complexes derived from pyrazolone based NSO-donor Schiff base ligands

Two neutral mononuclear Cu(II) complexes have been prepared in EtOH using Schiff bases derived from 4-toluoyl pyrazolone and thiosemicarbazide. Both the ligands have been characterized on the basis of elemental analysis, IR, (1)H NMR, (13)C NMR and mass spectral data. The molecular geometry of one of these ligands has been determined by single crystal X-ray study. It reveals that these ligands exist in amine-one tautomeric form in the solid state. Microanalytical data, Cu-estimation, molar conductivity, magnetic measurements, IR, UV-Visible, FAB-Mass, TG-DTA data and ESR spectral studies were used to confirm the structures of the complexes. Electronic absorption and IR spectra of the complexes suggest a square-planar geometry around the central metal ion. The interaction of complexes with pET30a plasmid DNA was investigated by spectroscopic measurements. Results suggest that the copper complexes bind to DNA via an intercalative mode and can quench the fluorescence intensity of EB bound to DNA. The interaction between the complexes and DNA has also been investigated by agarose gel electrophoresis, interestingly, we found that the copper(II) complexes can cleave circular plasmid DNA to nicked and linear forms.     

Spectral characterization of iron(III) complexes of 2-benzoylpyridine N(4)-substituted thiosemicarbazones

Three iron(III) complexes (1-3) of 2-benzoylpyridine N(4)-phenyl thiosemicarbazone (HL1) and one iron(III) complex (4) of 2-benzoylpyridine N(4)-cyclohexyl thiosemicarbazone (HL2) were synthesized and characterized by means of different physicochemical techniques viz., molar conductivity measurements, magnetic susceptibility studies and electronic, infrared and EPR spectral studies. The analytical data and the molar conductance measurements of the complexes reveal that two molecules of the ligand and the anion are coordinated to the metal atom in all the four complexes. The magnetic moments of the complexes suggest that they are of low spin. From the infrared spectra of the ligands and the complexes it is confirmed that the ligands coordinate to iron(III) as an anion coordinating via the azomethine nitrogen, pyridyl nitrogen, and the thiolate sulphur. The EPR spectra of the complexes in the polycrystalline state at 298 and 110 K and in DMF solution at 110 K were recorded and all the spectra show three g values indicating that these complexes have rhombic distortion. All the iron(III) complexes in DMF solution at 110 K have similar anisotropic spectra with almost the same gav values, indicating that the bonding in all the complexes is similar and is unaffected by the coordination of the anion.     

Heteroleptic platinum(II) complexes of 8-quinolinolates bearing electron withdrawing groups in 5-position

A series of novel luminescent platinum(II) complexes bearing orthometalated 2-phenylpyridine ligands (C N), namely 2-phenylpyridine (4) and 3-hexyloxy-2-phenylpyridine (5), and several 5-substituted quinolinolate ligands (5-X-Q), where X = NO2 (a), X = CHO (b), X = Cl (bearing another Cl in 7-position of the Q-ligand) (c) and X = H (d) have been synthesized, characterized and their photophysical properties were studied. All complexes were obtained as a single isomer with N atoms of the C N and Q ligands trans-coordinated to the platinum center as evidenced using single-crystal X-ray crystallography and NMR spectroscopy. Absorbance, luminescence as well as lifetime measurements in solution and in the solid state have been performed to establish a qualitative relationship between structure and luminescence properties. The compounds under investigation absorb intensively via an intraligand charge transfer (ILCT) in the visible range (460-480 nm) and emit from fluid solution and in the solid state at room temperature at 600-630 nm. The complexes show quantum yields up to 25% and lifetimes in the range of 20-30 micros in deoxygenated organic solvents at room temperature. The emitting state can be best described as a triplet intraligand charge-transfer state localized mainly on the quinolinolate ligand. In these complexes the phenylpyridine ligand can be essentially regarded as an ancillary ligand. Density functional theory (DFT) calculations were carried out on both the ground (singlet) and excited (triplet) states of these complexes and revealed the influence of the substitution of the quinolinolate ligand on the HOMO/LUMO energies and the oscillator strengths. Substitution on 3-position of the phenylpyridine ligand does not impact on the transition energies, and is thus suited to introduce other functional moieties, such as a solubilizing hexyloxy group.     

Structural and thermal decomposition characteristics of mixed-ligand complexes of Cu(II), Ni(II), Co(II) and Zn(II)

Mixed-ligand complexes of Cu(II), Ni(II), Co(II) and Zn(II) with 8-hydroxyquinoline and thiophene-2-carboxylic acid as two different ligands, have been isolated in pure state. The formation of these complexes has been inferred potentiometrically. The isolated complexes have been characterized by their elemental analyses, IR and electronic spectra, conductivity and magnetic measurements. Solid state dehydration of the hydrated complexes and subsequent decomposition of the anhydrous complexes have been studied by simultaneous DTA and TG techniques. The thermal stability order of the hydrated compounds is Cu>Co>Ni>Zn, but in the decomposition process the trend observed is Co>Zn>Ni>Cu. Some parameters like activation energy and order of reaction for each process have been computed.     

Synthesis, properties and thermal studies of oxorhenium(V) complexes with 3-hydrazino-5,6-diphenyl-1,2,4-triazine, benzimidazolethione and 2-hydrazinobenzimidazole. Mixed ligand complexes, pyrolytical products and biological activity

A series of biologically active complexes of oxorhenium(V), were prepared by using the organic ligands 3-hydrazino-5,6-diphenyl-1,2,4-triazine (HL1), benzimidazolethione (H2L2) and 2-hydrazinobenzimidazole (H2L3). The mixed ligand complexes of oxorhenium(V) with the previous ligands and one of the following ligands: NH4SCN, 1,10-phenanthroline (1,10-phen), 8-hydroxyquinoline (8-OHquin) or glycine (Gly), were isolated. All the binary and mixed ligand complexes have monomeric structures and exist in the octahedral configuration. Thermal studies on these complexes showed the possibility of structural transformation from mononuclear into binuclear ones. The structures of all complexes and the corresponding thermal products were elucidated by elemental analyses, IR, electronic absorption and 1H NMR spectra, magnetic moments, conductance and TG-DSC measurements. The antifungal activities of the metal complexes towards Alternaria alternata and Aspergilus niger were tested and showed comparable behaviour with some well known antibiotics.     

多胺多羧酸双吡哆醇酯顺磁性金属螯合物及其弛豫性能研究

由二乙三胺五乙酸(DTPA)双酸酐和乙二胺四乙酸(EDTA)双酸酐与维生素B₆族化合物吡哆醇(PN)或其衍生物合成了一系列新型的多胺多羧酸双吡哆醇酯衍生物及其钆(Ⅲ)、锰(Ⅱ)、铁(Ⅲ)等顺磁性金属螯合物,研究了其中钆(Ⅲ)和锰(Ⅱ)螯合物在体外水溶液中对水质子的纵向弛豫性能(R₁).结果表明,所有配体和配合物均有很好的水溶性,且对光和空气稳定.螯合物的弛豫率(T₁)可与其母体螯合物相媲美,如钆-二乙三胺五乙酸二吡哆醇酯(GdDTPA-BPN)和锰-乙二胺四乙酸二吡哆醇酯(MnEDTA-BPN)的弛豫率R₁分别为5.5和3.1L·mmol^-1·s^-1,与其母体螯合物GdDTPA^2-和MnEDTA^2-的R₁值(5.2和2.8L·mmol^-1·s^-1)相当.     

Synthesis and photoluminescence properties of BF2 complexes with 1,3-diketone ligands

BF₂ complexes with 1,3-diketone ligands were synthesized, and their optical and electrochemical properties were studied. The colors of the complexes varied depending on the structures of the 1,3-diketone ligands. The absorption and emission maxima of the complexes with 1,3-diaryl-1,3-diketone ligands were considerably red shifted as compared to those of the complexes with 1-aryl-3-trifluoromethyl-1,3-diketone ligands, suggesting an extended π-conjugation of the 1,3-diaryl-1,3-diketone moieties. The molar absorption coefficients and quantum yields of the complexes with 1,3-diaryl-1,3-diketone ligands were larger than those of the complexes with 1-aryl-3-trifluoromethyl-1,3-diketone ligands. Cyclic voltammetry measurements revealed that the reduction potentials of the BF₂ complexes were higher than those of the free ligands. These complexes exhibited various emission colors in the solid states due to the intermolecular interactions.     

Synthesis and self-assembly of spin-labile and redox-active manganese(III) complexes

New amphiphilic and spin-labile Mn(III) complexes based on dianionic N(4)O(2)-hexadentate sal(2)trien or sal(2)bapen ligands, which contain OC(6)H(13), OC(12)H(25), or OC(18)H(37) alkoxy substituents at different positions of the salicylidene unit were prepared (H(2)sal(2)trien = N,N'-bis(salicylidene)-1,4,7,10-tetraazadecane, H(2)sal(2)bapen = N,N'-bis(salicylidene)-1,5,8,12-tetraazadodecane). According to electrochemical measurements, these complexes undergo two (quasi)reversible redox processes. Temperature-dependent magnetic measurements revealed a high-spin configuration for all sal(2)trien complexes (S = 2) and gradual spin crossover for sal(2)bapen complexes from high to low spin (S = 1). The chain length strongly influences the spin crossover, as C(18)-functionalization stabilizes the low spin state at much higher temperatures than shorter alkyl chains. Moreover, long alkyl chains allow for spontaneous self-assembly of the molecules, which was investigated in single crystals and in Langmuir-films at the air-water interface. Long alkyl chains (C(12) or C(18)) as well as a mutual syn-orientation of these molecular recognition sites were required for the Langmuir monolayers to be stable.     

Synthesis, characterizations and luminescent properties of three novel aryl amide type ligands and their lanthanide complexes

Three new aryl amide type ligands, N-(phenyl)-2-(quinolin-8-yloxy)acetamide (L(1)), N-(benzyl)-2-(quinolin-8-yloxy)acetamide (L(2)) and N-(naphthalene-1-yl)-2-(quinolin-8-yloxy)acetamide (L(3)) were synthesized. With these ligands, three series of lanthanide(III) complexes were prepared: [Ln(L(1))(2)(NO(3))(2)]NO(3), [Ln(L(2))(2)(NO(3))(2)(H(2)O)(2)]NO(3).H(2)O and [Ln(L(3))(2)(NO(3))(2)(H(2)O)(2)]NO(3).H(2)O (Ln=La, Sm, Eu, Gd). The complexes were characterized by the elemental analyses, molar conductivity, (1)H NMR spectra, IR spectra and TG-DTA. The fluorescence properties of complexes in the solid state and the triplet state energies of the ligands were studied in detail, respectively. It was found that the Eu(III) complexes have bright red fluorescence in solid state. The energies of excited triplet state for the three ligands are 20325 cm(-1) (L(3)), 21053 cm(-1) (L(2)) and 22831 cm(-1) (L(1)), respectively. All the three ligands sensitize Eu(III) strongly and the order of the emission intensity for the Eu(III) complexes with the three ligands is L(3)>L(2)>L(1). It can be explained by the relative energy gap between the lowest triplet energy level of the ligand (T) and (5)D(1) of Eu(III). This means that the triplet energy level of the ligand is the chief factor, which dominates Eu(III) complexes luminescence.     

Structural and Functional Models for the Dinuclear Copper Active Site in Catechol Oxidases: Syntheses, X-ray Crystal Structures, Magnetic and Spectral Properties, and X-ray Absorption Spectroscopic Studies in Solid State and in Solution

Two novel tridentate dinucleating ligands containing benzimidazole were prepared, 1,3-bis(2-benzimidazolyl)-2-propanol (Hbbp, 1) and 1,5-bis(2-benzimidazolyl)-3-pentanol (Hbbpen, 2). Their complexing properties toward copper were studied in order to obtain structural and functional models for catechol oxidases. Syntheses and crystal structures of dinuclear Cu(II) complexes derived from these ligands are reported. [Cu(2)bbp(2)](ClO(4))(2).2MeOH, 3, crystallizes in the triclinic space group P&onemacr; with the following unit cell parameters: a = 7.702(3) ?, b = 10.973(6) ?, c = 12.396(6) ?, alpha = 100.59(4) degrees, beta = 99.02(4) degrees, gamma = 98.90(4) degrees, V = 998.7(8) ?(3), and Z = 1. [Cu(2)bbpen(2)](ClO(4))(2).3MeOH, 4, crystallizes in the orthorhombic space group Pccn, with the following unit cell parameters: a = 17.478(9) ?, b = 18.795(8) ?, c = 13.888(6) ?, V = 4562.2(4) ?(3), and Z = 4. Magnetic susceptibility measurements in the temperature ranges 4.6-459 K (3) and 4.6-425 K (4) indicate an antiferromagnetic coupling between the Cu(II) centers of both complexes. In order to determine the structures of the complexes in solution, XAS spectra (EXAFS and XANES) were recorded in the solid state and in solution. The interpretation of these data, including multiple scattering calculations, together with UV-vis titrations, shows that the complexes have the same structure in the crystalline state as well as in methanolic solution. Complex 4 is able to oxidize 3,5-di-tert-butylcatechol (3,5-DTBC) to the quinone (catecholase activity). This reaction was also studied by XAS and UV-vis spectroscopy. These measurements reveal the reduction of Cu(II) to Cu(I) accompanied by a decrease of the coordination number.     

Syntheses and characterization of Ru(III) with chelating containing ONNO donor quadridentate Schiff bases

Complexes of ruthenium(III) with N,N'-disalicylidene-l,2-phenylenediamine (H2dsp), N,N'-disalicylidene-3,4-diaminotoluene (H2dst), 4-nitro-N,N'-disalicylidene-1,2-phenylenediamine (H2ndsp) and N,N'-disalicylidene ethylenediamine (H2salen) have been prepared and characterized by elemental analysis, molar conductivity, spectral methods (mid-infrared, 1H NMR and UV-vis spectra) and simultaneous thermal analysis (TG and DTG) techniques. The molar conductance measurements proved that all these complexes are non-electrolytes. The electronic spectra measurements were used to infer the structures. The IR spectra of the ligands and their complexes are used to identify the type of bonding. The kinetic thermodynamic parameters such as: E*, DeltaH*, DeltaS* and DeltaG* are estimated from the DTG curves. The four ligands and their complexes have been studied for their possible biological antifungal activity.     

3- and 4-picolylamine complexes of bivalent metal halides and pseudohalides

Summary Coordination compounds formed by the interaction of some bivalent metal halides and pseudohalides with the potentially bidentate ligands, 3-picolylamine and 4-picolyl-amine, have been prepared and characterized by molecular conductance, magnetic susceptibility, electronic and i.r. spectral measurements in the solid state. The i.r. spectral studies indicate that, in addition to their monodentate bonding through pyridine ring nitrogens, these ligands also bond through their amino nitrogen and, in some cases, act as bidentate bridging or chelating ligands. Tentative stereochemistries of the complexes isolated in the solid state are discussed. The ligand field parameters 10 Dq, B, Dq/B, andv ₂/v ₁ are calculated for the cobalt(II) and nickel(II) complexes and are consistent with their proposed stereochemistries.     

Preparation and XAFS studies of organotin(IV) complexes with adenosine and related compounds and calf thymus DNA

Complexes of adenosine and related compounds (adenosine-5’-monophosphate, adenosine-5’-triphosphate and pyridoxal-5-phosphate) with Bu₂SnO and/or BuSnCl₂ were prepared in the solid state. The compositions of the complexes were determined by standard analytical methods. It was found that the complexes contain the organotin(IV) moiety and the ligand in a ratio of 1:1. The FT-IR spectra demonstrated that Bu₂SnO reacts with the D-ribose moiety of the ligands, while Bu₂SnCl₂ is coordinated to the deprotonated phosphate group. The basic part of the ligands does not participate directly in complex formation. Comparison of the experimental Mössbauer Δ (quadrupole splitting) values with those calculated on the basis of the pqs concept revealed that the organotin(IV) moiety has Tbp and in some cases also T_h geometry. The adenosine complex contains the organotin(IV) cation in two different surroundings (Tbp and T_h). The local structures of the complexes were determined by means of EXAFS measurements. At the same time a number of organotin(IV) complexes containing different organo moieties of calf thymus DNA were also prepared. Similarly as above, EXAFS data were obtained for these compounds and analyzed by using multishell models up to 300 pm. These results are the first structural data (bond lengths) on complexes formed with organotin(IV)-DNA and related compounds.     

Mono- and dinuclear ruthenium complexes of bridging ligands incorporating two di-2-pyridylamine motifs: Synthesis, spectroscopy and electrochemistry

Mono- and dinuclear ruthenium(II) complexes of six bridging ligands that contain a central arene (phenyl, naphthalenyl or biphenyl) core to which are attached two di-2-pyridylamine groups have been prepared. These complexes possess six-membered chelate rings. Full assignments of their ¹H NMR spectra are described which provides insight into the comformations of the ligands in these complexes. The extent of metal–metal communication in the dinuclear complexes was probed by electrochemical measurements and related to metal–metal distances.     

Syntheses, spectral, electrochemical and thermal studies of mononuclear manganese(III) complexes with ligands derived from 1,2-propanediamine and 2-hydroxy-3 or 5-methoxybenzaldehyde: self-assembled monolayer formation on nanostructure zinc oxide thin film

Mononuclear Mn(III) complexes have been prepared via the Mn(II) reaction of an equimolar of Schiff-bases derived from reaction of 2-hydroxy-3-methoxybenzaldehyde or 2-hydroxy-5-methoxybenzaldehyde with 1,2-diaminopropane. Axial ligands L include: pyridine (py) and H(2)O. The resulting complexes have been characterized by FT-IR and UV-vis spectroscopy. The crystal structures of the complexes were determined and indicate that in the solid state the complex adopts a slightly distorted octahedral environment of the imine N and hydroxo O with the two axial ligands. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Mn(III)-Mn(II) is electrochemically quasi-reversible. Thermal stability of these complexes was determined by TG and DTG. Layers of these complexes were formed on nanostructure zinc oxide thin film and a red shift was observed when zinc oxide thin film is modified by complex.     

Synthesis and characterization of some pyrimidine, purine, amino acid and mixed ligand complexes

Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes of barbital, thiouracil, adenine, amino acids (methionine, lysine and alanine) and some mixed ligands were prepared and characterized by elemental analyses, IR, electronic spectra, magnetic susceptibility and ESR spectra. Coordination of the metallic centre to the oxygen and nitrogen atoms of barbital, thiouracil, amino acids and coordinate to amino group and nitrogen atom of adenine occurred. Electronic spectra and magnetic susceptibility measurements were utilized to infer the structure of the complexes which are octahedral for Mn(II), Fe(III), Co(II), Ni(II) and Cd(II) and tetrahedral for Mn(II), Cu(II), Zn(II) complexes. ESR spectra were observed for copper complexes with a d(x2)-(y2) ground state with small g(||) values indicating strong interaction between the ligands and their metal ions.     

Studies on some oxovanadium(IV) complexes of acyl pyrazolone analogues

A series of novel bidentate pyrazolone based Schiff base ligands were synthesized by interaction of 4-benzoyl-3-methyl-1-(4′-methylphenyl)-2-pyrazolin-5-one with various aromatic amines like aniline, o-,m-,p-chloroaniline and o-,m-,p-toluidine in a ethanolic medium. All of these ligands have been characterized on the basis of elemental analysis, IR and ¹H NMR data. The molecular geometries of five of these ligands have been determined by single crystal X-ray study. Crystallographic study reveals that these ligands exist in the amine-one tautomeric form in the solid state. NMR study also suggests the existence of the amine-one form in solution at room temperature. Ab initio calculations for representative ligand HL¹ has been carried out to know the coordination site of the ligand. Novel vanadium Schiff base complexes of these ligands with general formula [OV(L^1–7)₂(H₂O)] have been prepared by interaction of aqueous solution of vanadyl sulfate pentahydrate with DMF solution of the appropriate ligands. The resulting complexes have been characterized on the basis of elemental analysis, vanadium determination, molar conductance and magnetic measurements, thermo gravimetric analysis, infrared and electronic spectral studies. Suitable distorted octahedral structures have been proposed for these complexes.     

Synthesis,characterization, electrochemical behaviour and catalytic activity of manganese(II) complexes with linear and tripodal tetradentate ligands derived from Schiff bases

New manganese(II) complexes, [Mn(H₂L)(H₂O)₂]Cl₂· xH₂O, with linear and tripodal tetradentate ligands have been synthesized and characterized by elemental analysis, molar conductance, i.r. spectra, magnetic measurements and electronic and e.s.r. spectra. The data show that the ligands are neutral and coordinate to manganese in a tetradentate manner; the other axial sites are occupied by the water molecules. Magnetic and e.s.r. data show that manganese(II) adopts a high-spin configuration in the complexes. The electrochemical behaviour of the complexes, determined by cyclic voltammetry, shows that the chelate structure, ligand geometry and electron donating effect of the ligand substituents are among the factors influencing the redox potentials of the complexes. In addition, we note that linear ligands stabilize the manganese(III) state to a greater extent than tripodal ligands and their complexes vigorously catalyse the disproportionation of hydrogen peroxide in the presence of added imidazole.     

Synthesis and characterization of 4-(alkylaminoisonitrosoacetyl)biphenyls and their complexes

Three new substituted 4-(alkylaminoisonitrosoacetyl)biphenyls (ligands) derived from 4-biphenylhydroxymoyl chloride and corresponding amines were synthesized. The following aromatic and aliphatic amines were used for ligands: ethanolamine, 2-amino-4-methylphenol, and 2-(aminomethyl)pyridine. Mononuclear or binuclear cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), and lead(II) complexes with these ligands were synthesized. These compounds were characterized by elemental analyses, AAS, infrared spectra, and magnetic susceptibility measurements. The ligands were additionally characterized by ¹H NMR. The results suggest that the ligands act as tridentate ligands. The text was submitted by the authors in English.     

Spectroscopic and Biochemical Studies of Some Manganese(II), Oxovanadium(V) and Dioxomolybdenum(VI) Complexes S/O and N Donor Agents Synthesized under Microwave Conditions

The synthesis of some new manganese(II), oxovanadium(V) and dioxomolybdenum(VI) complexes with 5-chloro-1,3-dihydro-3-[2-(phenyl)-ethylidene]-2H-indol-2-one-hydrazinecarbothioamide (L¹H) and 5-chloro-1,3-dihydro-3-[2-(phenyl)-ethylidene]-2H-indol-2-one-hydrazinecarboxamide (L²H) were carried out in unimolar and bimolar ratios. All the new derivatives have been characterized by elemental analyses, molecular weight determinations, molar conductance, magnetic measurements, i.r., ¹H-n.m.r. and e.s.r. studies. The i.r. and n.m.r. spectral data suggest the involvement of sulphur/oxygen and azomethine nitrogen in coordination to the central metal ion. The magnetic moment values of the manganese(II) complexes are in the 5.85–6.13 B.M. range, suggesting a high spin state in these complexes. Based on these spectral studies tetrahedral geometry for the manganese(II) complexes and octahedral geometry for the molybdenum complexes has been proposed. In the case of the oxovanadium complexes vanadium is in the penta and hexa coordinated environments. Compounds have been synthesized in an open vessel under microwave irradiation (MWI) using a domestic microwave oven. The reaction time decreases from hours to minutes with improved yield as compared to conventional heating. The free ligands and their metal complexes have been tested in vitro against a number of microorganisms in order to assess their antimicrobial properties. The results indicate that the ligands and their respective metal derivatives possess antimicrobial properties.