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1.
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 1.6 × 106, 1.8 × 106, 2.0 × 106 and 1.5 × 106 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 D2O, suggesting the formation of singlet oxygen as a reactive species in a type-II process.  相似文献   

2.
Equilibrium studies on the ternary complex systems involving ampicillin (amp) as ligand (A) and imidazole containing ligands viz., imidazole (Him), benzimidazole (Hbim), histamine (Hist) and histidine (His) as ligands (B) at 37 °C and I = 0.15 mol dm?3 (NaClO4) show the presence of CuABH, CuAB and CuAB2. The proton in the CuABH species is attached to ligand A. In the ternary complexes the ligand, amp(A) binds the metal ion via amino nitrogen and carbonyl oxygen atom. The CuAB (B = Hist/His)/CuAB2 (B = Him/Hbim) species have also been isolated and the analytical data confirmed its formation. Non-electrolytic behavior and monomeric type of chelates have been assessed from their low conductance and magnetic susceptibility values. The electronic and vibrational spectral results were interpreted to find the mode of binding of ligands to metal and geometry of the complexes. This is also supported by the g tensor values calculated from ESR spectra. The thermal behaviour of complexes were studied by TGA/DTA. The redox behavior of the complexes has been studied by cyclic voltammetry. The antimicrobial activity and CT DNA cleavage study of the complexes show higher activity for ternary complexes.  相似文献   

3.
The interaction of [Nd(bpy)2Cl3·OH2], where bipy is 2,2′-bipyridine, with DNA has been studied by absorption, emission, and viscosity measurements. [Nd(bpy)2Cl3·OH2] showed absorption decreasing in charge transfer band with increasing of DNA. The binding constant, Kb has been determined by absorption measurement and found to be (1.5 ± 0.1) × 105 M?1. The fluorescent of [Nd(bpy)2Cl3·OH2] has been investigated in detail. The interaction was also studied by fluorescence quenching technique. The results of fluorescence titration revealed that DNA had the strong ability to quenching the intrinsic fluorescence of Nd(III) complex at 327 nm. The binding site number n, apparent binding constant Kb and the Stern–Volmer quenching constant KSV have been determined. Thermodynamic parameters have been calculated according to relevant fluorescent data and Van’t Hoff equation. Characterization of bonding mode has been studied. The results suggested that the major interaction mode between [Nd(bpy)2Cl3·OH2] and DNA was groove binding.  相似文献   

4.
In an effort to develop new tripodal N-heterocyclic carbene (NHC) ligands for small molecule activation, two new classes of tripodal NHC ligands TIMER and TIMENR have been synthesized. The carbon-anchored tris(carbene) ligand system TIMER (R = Me, t-Bu) forms bi- or polynuclear metal complexes. While the methyl derivative exclusively forms trinuclear 3:2 complexes [(TIMEMe)2M3]3+ with group 11 metal ions, the tert-butyl derivative yields a dinuclear 2:2 complex [(TIMEt-Bu)2Cu2]2+ with copper(I). The latter complex shows both “normal” and “abnormal” carbene binding modes and accordingly, is best formulated as a bis(carbene)alkenyl complex. The nitrogen-anchored tris(carbene) ligands TIMENR (R = alkyl, aryl) bind to a variety of first-row transition metal ions in 1:1 stoichiometry, affording monomeric complexes with a protected reactivity cavity at the coordinated metal center. Complexes of TIMENR with Cu(I)/(II), Ni(0)/(I), and Co(I)/(II)/(III) have been synthesized. The cobalt(I) complexes with the aryl-substituted TIMENR (R = mesityl, xylyl) ligands show great potential for small molecule activation. These complexes activate for instance dioxygen to form cobalt(III) peroxo complexes that, upon reaction with electrophilic organic substrates, transfer an oxygen atom. The cobalt(I) complexes are also precursors for terminal cobalt(III) imido complexes. These imido complexes were found to undergo unprecedented intra-molecular imido insertion reactions to form cobalt(II) imine species. The molecular and electronic structures of some representative metal NHC complexes as well as the nature of the metal–carbene bond of these metal NHC complexes was elucidated by X-ray and DFT computational methods and are discussed briefly. In contrast to the common assumption that NHCs are pure σ-donors, our studies revealed non-negligible and even significant π-backbonding in electron-rich metal NHC complexes.  相似文献   

5.
The first use of dipyridocarbenes as Arduengo–Wanzlick type carbene ligands for transition metal complexes is reported. The complexes M(CO)5L (L = dipyridoimidazolinylidene, di-tert-butyldipyridoimidazolinylidene, M = Cr, W) were synthesized and their spectroscopic and structural properties compared with the literature known N-heterocyclic carbene (NHC) group 6 metal pentacarbonyl complexes. This reveals that the 13C NMR carbene signals of theses complexes with dipyrido carbene ligands show the strongest high-field shift ever observed for M(CO)5(NHC) (M = Cr, W) complexes. The structural characterization shows alternating single and double bonds in the conjugated dipyrido moiety of the ligand.  相似文献   

6.
New luminescent mononuclear and dinuclear copper(II) (S = 1/2) complexes [Cu(HL)(H2O)2](ClO4)2 (1a) and [Cu2(HL)2(μ-SO4)2]·2H2O (1b) were synthesized with the acyclic tridentate pyridine-2-carboxaldehyde-2-pyridylhydrazone ligand, HL (1). Interestingly, the mononuclear complex 1a can be converted into the disulfate bridged dimeric copper(II) complex 1b by passing freshly prepared SO2 through the basic medium. On excitation at 290 nm, the ligand fluoresces at 364 nm due to an intraligand 1(π–π1) transition. Upon complexation with copper(II), the emission peak is slightly blue shifted (356 nm, F/F0 0.76 for 1a and 354 nm, F/F0 0.89 for 1b) with a little quenching in the emission intensity. The association constants (Kass (5.06 ± 0.004) × 104 for 1a and Kass (5.46 ± 0.006) × 104 for 1b at 298 K) and the thermodynamic parameters have been determined by UV–Vis spectroscopy. The molecular structure of the complex 1b (Cu?Cu 4.456 Å) has been determined by single crystal X-ray diffraction studies. The complex 1b exhibits a strong interaction towards DNA as revealed from the Kb (intrinsic binding constant) 6.3 × 104 M?1 and Ksv (Stern–Volmer quenching constant) 2.93 values.  相似文献   

7.
Binding of copper to three peptide fragments of prion (Cu2+ binding sites: 60–91, 92–96 and 180–193 amino acid residues) was investigated by anodic stripping voltammetry to determine the stoichiometries of Cu2+-prion peptide interactions. The method relies on the synthesis of N-terminally acetylated/C-terminally amidated peptide fragments of prion by solid-phase synthesis and direct monitoring of the oxidation current of copper in the absence and presence of each prion fragment. Titration curves of Cu2+ with Ac-PHGGGWGQ-NH2, Ac-GGGTH-NH2 and Ac-VNITKQHTVTTTT-NH2 were obtained in concentrations ranging from 8.52 × 10?7 to 5.08 × 10?6, 3.95 × 10?7 to 1.94 × 10?6 and 7.82 × 10?8 to 4.51 × 10?7 M, respectively. The acquired data were used to calculate the stoichiometries (one peptide per Cu2+ ion for all the three studied systems) and apparent dissociation constants (Kd = 4.37 × 10?8–3.50 × 10?10 M) for the three complexes.  相似文献   

8.
A novel helical peptide containing β-(3-pyirdyl)-l-alanine (Pal) and l-glutamic acid (Glu) residues has been designed and successfully prepared as a model ligand of metalloenzyme active sites. The helical peptide, Boc-Leu-Aib-Glu-Leu-Leu-Pal-Aib-Leu-OEt (1) (Boc = tert-butoxycarbonyl, Aib = 2-aminoisobutylic acid) yields fine crystals as an acetnitrile solvate. The metal ion binding affinities of 1 were tested for CoCl2 using UV/vis, CD, Raman, and 1H NMR spectroscopies. The non-linear fitting calculations have revealed the 1:1 complex for CoCl2 with the binding constant 3.6 (±0.7) × 102 M−1.  相似文献   

9.
A series of new unsymmetrical perylene diimides have been synthesized to investigate their binding selectivities to G-quadruplex DNA structure, a unique four-stranded DNA motif, which is significant to the regulation of telomerase activity. The structures of the perylene diimides have been characterized by IR spectrophotometer, 1H NMR, 13C NMR, MS, TGA and time-resolved instruments. Spectrochemical behaviors have been investigated by visible absorption and fluorescence emission spectra. The spectral characterization of the compounds has been investigated in five common organic solvents of different polarity and in water (in 170 mM phosphate buffer at pH 6). Marked red shifts of absorbance and fluorescence emission bands of the compounds in aqueous solution are compared with the other organic solutions. The fluorescence quantum yields are determined low in more polar solvents and also calculated to be about less than about 0.05 in aqueous solution because of the aggregation effects. Photodegradation rate constants (kp) of the synthesized compounds have been compared under xenon lamp irradiation in acetonitrile solution.Binding abilities of the synthesized perylene diimides to different form of DNA strands have been investigated by visible absorption and fluorescence spectroscopy in the phosphate buffer solutions. Also, pH-dependent aggregation and G-quadruplex DNA binding selectivity of these ligands have been compared. Among these ligands, N-(2,6-diisopropylphenyl)-N′-(4-pyridyl)-perylene-3,4,9,10-tetracarboxylic diimide (PYPER) has been found to be the most selective interactive ligand for G-quadruplex formed in the G4′-DNA structure. PYPER has shown a significant selectivity to G4′-DNA which is comprised of d(TTAGGG) repeats, known as human telomeres, in the phosphate buffer at pH 6. The absorption maximum of the PYPER/G4′-DNA complex has given bathochromic shift of 7 nm with respect to the absorption maximum of DNA-free solution of PYPER in phosphate buffer at pH 6. Fluorescence quenching experiments between PYPER and G4′-DNA show that PYPER demonstrates about a 9.3-fold selectivity for binding to G4′-DNA versus ds-DNA base pairs with the bimolecular rate constant of 0.95 × 1012 M−1 s−1.  相似文献   

10.
A simple, sensitive and accurate spectrophotometric method has been described for the assay of diphenhydramine hydrochloride (DPH) in raw material and in biological samples. The method is based on extraction of DPH into dichloromethane as ion-pair complexes with patent blue (PB), eriochrome black T (EBT), methyl orange (MO) and bromocresol purple (BCP) in acidic medium. The coloured species exhibited absorption maxima at 632, 514, 428 and 414 nm for PB, EBT, MO and BCP, with molar absorptivity values of 1.32 × 105, 2.36 × 104, 3.68 × 104 and 3.07 × 104 l mol?1 cm?1, respectively. The reaction conditions were optimized to obtain the maximum colour intensity. Beer’s law was obeyed with a good correlation coefficient (0.9982–0.9993) in the concentration ranges 0.5–3, 2.0–16, 2.0–10 and 1.0–10 μg ml?1 for PB, EBT, MO and BCP methods, respectively. The composition ratio of the ion-association complexes was found to be 1:1 in all cases as established by Job’s method. The conditional stability constant (Kf) and the free energy changes (ΔG°) were determined for all complexes formed. The proposed method was successfully applied for the determination of DPH in tablets and human urine with good accuracy and precision. Statistical comparison of the results with those obtained by the official method showed good agreement and indicated no significant difference in accuracy and precision.  相似文献   

11.
Multiple equilibrium studies by pH-metric measurements in the ternary copper(II) complexes with ampicillin(amp) as ligand A and glycine(gly), dl-2-aminobutanoic acid(2aba), dl-3-aminobutanoic acid(3aba), 1,2-diaminopropane(dp), 1,3-diaminopropane(tp), dl-2,3-diaminopropanoic acid(dapa), dl-2,4-diaminobutanoic acid(daba) & dl-2,5-diaminopentanoic acid(ornithine)(orn) as ligands B show the presence of CuABH, CuAB or CuAH?1 B ternary complex species. In the CuAB species the binding of the ligands A and B is similar to their binding in their respective binary complexes. In CuABH?1 species the deprotonation occurs with amp(A) ligand. The Δlog K values indicate higher stabilities for the ternary complexes than the binary species. The CuAB species with B = gly, 2aba, dapa & orn have been isolated and characterized. The conductivity measurements indicate that the complexes are non-electrolytes. Magnetic susceptibility and electronic spectral data suggest a square pyramidal geometry for CuAB with B = gly/2aba complexes and distorted octahedral geometry for CuAB with B = dapa/orn. The vibrational spectra are interpreted to find the mode of binding of ligand to metal. The TG/DTA studies reveal that the complexes decompose in three steps, indicating non-involvement of hydrated or coordinated water molecules in the complex. The cyclic voltammograms indicate a quasi reversible Cu2+/Cu+ couple. The antimicrobial activity and CT-DNA cleavage ability of the complexes show higher activity for ternary complexes.  相似文献   

12.
2,4,6-Tri(2′-pyridyl)-s-triazine (TPTZ) complexes with iron(II) and ruthenium(III) were prepared. Their sorption and desorption features on silica gel have been investigated. Both complexes were strongly adsorbed. This has been utilized for separating and preconcentrating iron(II) and ruthenium(III) using TPTZ-impregnated silica gel. The chromatographic behavior of TPTZ on silica gel column was examined and found to be effective modifier for silica gel surface. The sorption capacity of silica gel for those metal-triazine complexes has been determined under static conditions and was found to be 5.28 × 10–3 mM (Fe(TPTZ)22+) and 2.9 × 10–3 mM (Ru(TPTZ)23+). Saturated methanolic solutions of KI or 25% NaClO4 solutions desorbed both complexes quantitatively from the silica gel surface.  相似文献   

13.
A kinetic spectrophotometric method for the determination of thiocyanate, based on its inhibitory effect on silver(I) catalyzed substitution of cyanide ion, by phenylhydrazine in hexacyanoferrate(II) is described. Thiocyanate ions form strong complexes with silver(I) catalyst which is used as the basis for its determination at trace level. The progress of reaction was monitored, spectrophotometrically, at 488 nm (λmax of [Fe(CN)5PhNHNH2]3?, complex) under the optimum reaction conditions at: 2.5 × 10?3 M [Fe(CN)6]4?, 1.0 × 10?3 M [PhNHNH2], 8.0 × 10?7 M [Ag+], pH 2.8 ± 0.02, ionic strength (μ) 0.02 M (KNO3) and temperature 30 ± 0.1 °C. A linear relationship obtained between absorbance (measured at 488 nm at different times) and inhibitor concentration, under specified conditions, has been used for the determination of [thiocyanate] in the range of 0.8–8.0 × 10?8 M with a detection limit of 2 × 10?9 M. The standard deviation and percentage error have been calculated and reported with each datum. A most plausible mechanistic scheme has been proposed for the reaction. The values of equilibrium constants for complex formation between catalyst–inhibitor (KCI), catalyst–substrate (Ks) and Michaelis–Menten constant (Km) have been computed from the kinetic data. The influence of possible interference by major cations and anions on the determination of thiocyanate and their limits has been investigated.  相似文献   

14.
The photostabilization of poly(methyl methacrylate) (PMMA) films by Schiff bases of 2,5-dimercapto-1,3,4-thiadiazole compounds was investigated. The PMMA films containing concentration of complexes 0.5% by weight were produced by the casting method from chloroform solvent. The photostabilization activities of these compounds were determined by monitoring the hydroxyl index with irradiation time. The changes in viscosity average molecular weight of PMMA with irradiation time were also tracked (using benzene as a solvent). The quantum yield of the chain scission (Φcs) of these complexes in PMMA films was evaluated and found to range between 4.19 × 10?5 and 8.75 × 10?5. Results obtained showed that the rate of photostabilization of PMMA in the presence of the additive followed the trend:[1] > [2] > [3] > [4] > [5].According to the experimental results obtained, several mechanisms were suggested depending on the structure of the additive. Among them, UV absorption, peroxide decomposer, and radical scavenger for photostabilizer mechanisms were suggested.  相似文献   

15.
The diffusion of ferrocene methanol in super-cooled aqueous solutions containing sucrose has been studied, using disk and cylindrical microelectrodes, over a wide viscosity range. The solution viscosity and the reduced temperature T/Tg (Tg being the glass transition temperature) were varied by changing the sucrose concentration and the temperature of the system. The voltammetric limiting current obtained with a disk microelectrode and the i(t) response on a cylindrical microelectrode after a potential step were used to determine diffusion coefficients from 7 × 10−6 cm2 s−1 down to 2 × 10−11 cm2 s−1. The electrochemical procedure described in this work allows a simple and accurate measurement of the dynamics of electroactive solutes in glass-forming liquids.  相似文献   

16.
Novel Cu(II) (1) and Zn(II) (2) complexes with 4-(1-(4-morpholinophenyl)ethylideneamino)pyrimidine-5-carbonitrile) (L) have been synthesized and characterized by various spectroscopic and analytical techniques. DFT (density functional theory) studies result confirms that, LMCT mechanism have been done between L and M(II) ions. The antimicrobial studies indicate that the ligand L and complexes 1 & 2 exhibit higher activity against the E. coli bacteria and C. albicans fungi. The groove binding mode of ligand L and complexes 1 & 2 with CT-DNA have been confirmed by electronic absorption, competitive binding, viscometric and cyclic voltammetric studies. The electronic absorption titration of ligand L and complexes 1 & 2 with DNA have been carried out in different buffer solutions (pH 4.0, 7.0 & 10.0). The Kb values of ligand L and complexes 1 & 2 are higher in acidic buffer at pH 4.0 (Kb = 2.42 × 105, L; 2.8 × 105, 1; 2.65 × 105, 2) and the results revealed that, the interaction of synthesized compounds with DNA were higher in the acidic medium than basic and neutral medium. Furthermore, CT-DNA cleavage studies of ligand L and complexes 1 & 2 have been studied. The in vitro anticancer activities results show that complexes 1 & 2 have moderate cytotoxicity against cancer cell lines and low toxicity on normal cell line than ligand L.  相似文献   

17.
With the exception of metallocenes, transition metal complexes with hydrocarbon ligands only are rare. However, complexes of this type containing Group 10 metals are known and have been shown to be quite stable. These complexes are versatile precursors for many organometallic compounds. In addition, such compounds can play an important role in many reactions including C–H or C–C activation reactions and have useful applications in the thermal and photochemical production of metal films by chemical vapour deposition (CVD). The present review summarizes the synthesis, properties and chemistry of hydrocarbon complexes of Group 10 metals of the type LnM or LnMR1R2 (where Ln = σ- or π-hydrocarbon ligands; M = Ni, Pd and Pt; R1, R2 = σ-hydrocarbon ligands) without the involvement of any hetero donor ligands such as N, P, O and S in the metal coordination spheres.  相似文献   

18.
《Comptes Rendus Chimie》2007,10(7):568-572
A series of new ligands derived from N,N′-O-phenylenebis(salicylideneimine) have been synthesized and characterized by spectrometric methods. Their protonation constants and the stability constants of their complexes with Mn2+, Co2+, Ni2+ et Cu2+ have been determined by potentiometric methods in a water–ethanol (90:10 v/v) mixture at a 0.2 mol l−1 ionic strength (NaCl) and at 25.0 ± 0.1 °C. The Sirko program was used to determine the protonation constants as well as the binding constants of both species [M(HL)]+ and [ML]. The stability order obtained is in agreement with Irving–Williams series.  相似文献   

19.
The reaction of salicylaldoxime (H2salox) with Mn(ClO4)2 · 6H2O, NaN(CN)2 and NEt3 in MeOH affords a MnIII6 hexanuclear complex of [Mn6O2(salox)6(MeOH)6(NCNCONH2)2] (1), while reaction of H2salox with MnCl2 · 4H2O and NEt4OH in EtOH affords a MnIII6 hexanuclear complex of [Mn6O2(salox)6(EtOH)4(H2O)2Cl2] (2). Both complexes 1 and 2 contain a [MnIII63-O)2]14+ core, which is a known structural type in the family of Mn6 complexes. Variable temperature magnetic susceptibilities and magnetization measurement of complexes 1 and 2 have been carried out. Exchange interactions of metal centers for complexes 1 and 2 are fitted by a full diagonalization matrix method. The fitting results indicate that both complexes 1 and 2 have the ground-state spin value of S = 4, and the ground state of complex 1 has the much closer energy to low-lying spin states than that of complex 2. Magnetization measurements at 2.0–4.0 K and 10–70 kG confirm that the ground state is S = 4, with significant magnetoanisotropy as gauged by the D value of ?0.82 cm?1 and ?1.18 cm?1, for 1 and 2, respectively. The frequency dependence of the out-of-phase component in alternating current magnetic susceptibilities for both complexes 1 and 2 indicates the slow magnetic relaxation of superparamagnetic behaviour with a Ueff of 27.0(1) K and τ0 = 3.8(2) × 10?9 s for complex 1, and Ueff of 25.1(6) K and τ0 = 4.6(1) × 10?8 s for complex 2.  相似文献   

20.
The viscosity B-coefficients of mono-, di-, tri-saccharides and the derivatives (methyl glycosides) in mB = (0.5, 1.0, 2.0, and 3.0) mol · kg−1 aqueous solutions of magnesium chloride have been determined from viscosity data using the Jones–Dole equation at T = (288.15, 298.15, 308.15, and 318.15) K. The viscosity B-coefficients of transfer (ΔtB), the temperature derivatives of B-coefficients (dB/dT), pair and triplet viscometric interaction coefficients (ηAB, ηABB) have been determined. The viscosity B-coefficients data of systems studied in water have been reported earlier. The results have been interpreted in light of the solute–solute and solute–solvent interactions occurring in these systems. The comparison of results has been made with those reported in the presence of potassium chloride, ammonium sulphate, and sodium sulphate.  相似文献   

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