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1.
Thermodynamic parameters (??G°, ??S°) of quasi-isoenthalpic coordination of (tetraphenylporphyrinato) zinc(II) with anilines (except for 4-halo derivatives) in chloroform at 273?C313 K in the absence of steric factors are linearly related to shifts of their absorption bands in the electronic spectra in reactions with anilines, as well as with logarithms of the stability constants of the complexes, pK a values of the ligands in water, and Hammett substituent constants ??+. Linear relations were also found between thermodynamic and kinetic parameters of some nucleophilic substitution reactions and complex formation of (tetraphenylporphyrinato) zinc(II) with anilines.  相似文献   

2.
Ionization constants of {(2-amino)-bicyclo[2.2.1]-hept-3-yl}anilines and {(2-aminomethyl)bicyclo [2.2.1]-hept-3-yl}anilines in nitromethane have been determined by potentiometric titration. Due to high values of pK a 1 BH+ and pK a 2 BH+ (close to known adamantane-containing diamines) the studied compounds are promising candidates for preparation of (co)polyimides with a complex of excellent utilitarian properties.  相似文献   

3.
The dibenzodioxatetraazamacrocycle [26]pbz2N4O2 was characterised by single crystal X-ray diffraction and the protonation constants of this compound and the stability constants of its copper(II) and lead(II) complexes were determined by potentiometry in water at 298.2 K in 0.10 mol dm−3 in KNO3. Mono- and dinuclear complexes were found for both metal ions, the dinuclear complexes being the main species in the 5–7.5 pH range for copper(II) and 7.5–8.5 for lead(II). As expected the values of the stability constants for the copper(II) complexes are lower than those for related macrocycles containing only nitrogen atoms. The presence of mono- and dinuclear copper complexes was also confirmed by electrospray ionization mass spectrometry. These results suggest that the symmetric macrocyclic cavity of [26]pbz2N4O2 has enough space for the coordination of two metal ions. Additionally, NMR spectroscopy showed that the dinuclear complex of lead(II) has high symmetry. The equilibrium constants of the dinuclear copper(II) complexes and dicarboxylate anions (oxalate, malonate and succinate) were also determined in 0.10 mol dm−3 aqueous KNO3 solution. Only species containing one anion, Cu2HhLA(2+h), were found, strongly suggesting that the anion bridges the two copper(II) ions. The binding constants of the cascade species formed by [Cu2[26]pbz2N4O2(H2O)x]4+ with dicarboxylate anions decrease with the increase in length of the alkyl chain of the anion, a fact which was attributed to a higher conformational energy necessary for the rearrangement of the macrocycle to accommodate the larger anions bridging the two copper(II) centres. The variation of the magnetic susceptibility with temperature of [Cu2(H2[26]pbz2N4O2)(oxa)3] · 4H2O and [Cu2([26]pbz2N4O2)(suc)Cl2] were measured and the two complexes showed different behaviour.  相似文献   

4.

Complex formation equilibria involving pyridine-2-carboxaldehyde oxime (1), 1-(2-pyridinyl)ethanone oxime (2) and 6-methylpyridine-2-carboxaldehyde oxime (3), HL, with zinc(II) and cadmium(II) ions were studied in aqueous 0.1 M NaCl solution at 25° C by potentiometric titrations with a glass electrode. Experimental data were analysed with the least-squares computer program SUPERQUAD to determine the complexes formed and their stability constants. With Ligands 1 and 2 the sets of complexes for Zn(II) and Cd(II) are essentially the same, mono- and dinuclear oxime complexes and their deprotonated/hydrolysed products HpMq(HL)2q+p r. Owing to the steric requirements of the 6-methyl group, sets of complexes formed with 3 are distinctly different. For zinc(II), only dinuclear oximato species HpZn2(HL)4q+p 2 ( p = ? 2, ? 3, ? 4) are found, while for the larger cadmium(II) ion mononuclear oximato species CdL+ and CdL2 are detected in addition to the dinuclear complex HpCd2(HL)4q+p 2 ( p = ? 3).  相似文献   

5.
Stability constants of 46 complexes of zinc(II) tetraphenylporphyrin with primary, secondary, and tertiary amines and thermodynamic parameters of their formation (ΔG 0, ΔH 0, ΔS 0) in chloroform at 283–308 K have been analyzed. Probable factors responsible for enhanced stability of the complexes with ligands containing n-octyl groups are discussed. The X-ray diffraction data for the 1: 1 complex of zinc(II) tetraphenylporphyrin with di-n-octylamine are given.  相似文献   

6.
The estimation of the overall stability constants β1 of copper(II) and nickel(II) chelates with dipeptides was performed by using the model with the valence connectivity index of the 3rd order (3χv). It was done by dividing β1 to its constituting constants K1 and Ka, and subsequently by dividing the basic set into subsets or treating the chelate rings as separate units. Altogether 15 copper(II) and eight nickel(II) chelates with dipeptides were investigated. Six models for the estimation of log K1 and pKa were checked, most of them by usage of indicator variables (for differentiation of copper(II) and nickel(II) complexes or subclasses of ligands). Estimates of log β1 gave the range of rms values from 0.19 to 0.27. For the best model, errors of estimates were less than 0.34.  相似文献   

7.
Cobalt(II), nickel(II), copper(II) and zinc(II) complexes of 2-thiophenecarbonyl hydrazone of 3-isatin (H2L1) and 2-furoic hydrazones of 3-isatin (H2L2) and 3-(N-methyl)isatin (HL3), with general composition [M(L)2] · nX, where X is ethanol or/and water, were synthesised and characterised. The molecular structure of HL3 showed that it crystallised in the keto form, which is also the more abundant tautomer for the three hydrazone ligands in solution. The three ligands behave as κ2-O,N donors in the cobalt(II) and zinc(II) complexes. The X-ray crystal structure of pseudotetrahedral [Zn(HL1)2] · 1.75MeOH confirmed the O,N coordination mode of the two monodeprotonated ligands in their keto forms. Secondary interactions of zinc ions with the O atoms of each isatin keto residue provoke a substantial distortion towards a square pyramidal form. The interaction of the isatin keto residues is stronger in the three nickel(II) complexes where the three acylhydrazones can be considered as κ3-O,N,O donors.  相似文献   

8.
Complex formation of primary dipeptide hydroxamic acids, L-Ala-L-AlaNHOH and L-Ala-L-SerNHOH, as well as the corresponding Z-protected ones, Z-L-Ala-L-AlaNHOH and Z-L-Ala-L-SerNHOH (Z = benzyloxycarbonyl), with iron(III), aluminium(III), nickel(II), copper(II) and zinc(II) was studied in aqueous solution by pH-potentiometric and spectroscopic (UV–Vis, EPR, CD, 1H NMR) methods. The exclusive formation of [O,O] chelated hydroxamate complexes was found with iron(III) and aluminium(III) with all the ligands. Formation of linkage isomers with the involvement of either [O,O] hydroxamate or [NH2,CO] chelates was detected both in the zinc(II)-L-Ala-L-AlaNHOH and -L-Ala-L-SerNHOH systems. Upon increasing the pH, none of these chelating sets are capable of preventing the hydrolysis of the metal ion. The formation of stable complexes was found in the nickel(II) and copper(II) systems above pH ∼ 6 with a [NH2, Namide, Nhydrox.] binding mode after deprotonation and coordination of the peptide amide and the hydroxamate group. With an excess of copper(II), the formation of trinuclear [Cu3HxL2]x+4 type (x = −4 to −6) complexes as the major species was also detected. Blocking the terminal amino group in the Z-protected ligands results in a dramatic decrease of the nickel(II) and zinc(II) binding strengths, and insoluble complexes with copper(II). No indication was found for the role of the hydroxyl group of the serine moiety in metal ion binding.  相似文献   

9.
The supramolecular self-assembly of para-substituted tetraphenylporphyrin complexes of zinc(II), Zn(p-X)TPP, with imidazolyl-linked porphyrinatomanganese(III), Mn(p-lmBPTPP)Cl, driven by coordinative bonding has been investigated by fluorescence spectra, electrospray mass spectrometry, 1H-n.m.r. and u.v.–vis. spectra. The association constants of the supramolecular complexes, Kc, were calculated using fluorescence spectroscopic titration data at suitable dilute concentration ranges in which the fluorescent quenching of Zn(p-X)TPP by Mn(p-ImBPTPP)Cl is a static process. The electronic effect in the supramolecular self-assembly of para-substituted . porphyrinatozinc(II) with imidazolyl-linked porphyrinatomanganese(III) is discussed. The non-linear dependence of log Kc on the Hammett constants was found, which suggested that the electronic effect in para-substituents of tetraphenylporphyrin complexes of zinc(II) is an important, but not a sole factor effecting the association constants of the Zn(p-X)TPP–Mn(p-ImBPTPP)Cl supramolecular complexes. The results indicate that the closed conformation of the Zn(p-X)TPP–Mn(p-ImBPTPP)Cl supramolecular complex is another important factor effecting the association constants of the Zn(p-X)TPP–Mn(p-ImBPTPP)Cl supramolecular complexes.  相似文献   

10.
Well-resolved ESR spectra of a series of α-hydro p-substituted phenyl nitroxides were obtained in the fast ET reactions of p-substituted anilines with perfluoroacyl peroxides in F113 (CCl2FCClF2) solutions and one parameter (σ or σ·) as well as dual-parameter (σ, σ·) correlation analyses of their hyperfine splitting constants were conducted.  相似文献   

11.
2,2′-Dipyridyl-2-furancarbothiohydrazone (DPFTH) was used for the spectrophotometric determination of trace amount of iron(II) after the extraction process. Iron(II) can be quantitatively extracted with DPFTH in benzene from aqueous solution buffered to 3.0–8.0. The extracted species has absorption maxima at 440, 477, and 738 nm and obeyed Beer's law over the range 0–40 μg of iron in 10 ml at 738 nm. The molar absorptivity at this wave length is 1.17 × 104 liters mole?1 cm?1. The proposed method is relatively selective for iron(II) and is satisfactorily applied to the determination of the total iron in natural waters. The proton dissociation constants of the ligand determined spectrophotometrically were pKa1 = 2.88 and pKa1 = 6.70 at 25 °C and μ = 0.1.  相似文献   

12.
Kinetics of the incorporation of mercury(II) ion in tetra (p-trimethylammoniumphenyl)porphine have been investigated in aqueous solution at 30.0°C and 0.2 M (NaNO3) ionic strength. The reaction was found to be first order each in mercury(II) and the porphyrin. The forward (formation) and the reverse (dissociation) rate constants were found to be 1.9 ± 0.2 × 103 M?1 s?1 and 7 ± 2 × 106 M?1 s?1, respectively. Kinetics of zinc(II) incorporation in tetra(p-trimethylammoniumphenyl)porphine catalyzed by mercury(II) were also investigated. This catalysis is explained in terms of steady-state formation of mono mercury(II) porphyrin followed by zinc(II) displacement of mercury(II) ion from the porphyrin. Such a mechanism also illustrates the importance of porphyrin core deformation to metal incorporation.  相似文献   

13.
Copper catalyzed modification of Gomberg-Bachmann-Hey reaction to synthesize symmetrical/unsymmetrical biaryls via diazotization of anilines with p-TSA and NaNO2 system at 50 °C, in aromatic liquids as solvents and second partners was successfully developed. Aniline and 3-nitronaniline gave biphenyl and 3-nitrobiphenyl, respectively, with moderate yields. All para-substituted anilines gave comparatively higher yields while in the other cases including ortho-substituted anilines yields were lower. Except anilines with o-NHCOCH3 and o-CONH2 which gave symmetrical biaryls, all others gave selectively unsymmetrical biaryls.  相似文献   

14.
The electronic absorption spectra of the oximic quinolinyl hydrazone (MHQ; H2L) and its Co(II) and Cu(II)-complexes have been studied in Britton–Rhobinson buffer solutions of varying pH's in 75% dioxane-water. The dissociation constant of the hydrazone (pKH) as well as the stability constants (log K) of its chelates were determined spectrophotometrically and pH-metrically. The obtained data are in good agreement. Beer's law is valid in the ranges (0.64–6.99) and (2.36–6.48) μg/mL for Cu(II) and Co(II)-ions, respectively. On the other hand, the pKH and log K were determined pH-metrically in 75% solvent-water; (solvent = dioxane, ethanol, methanol and isopropanol). The variation of pKH or log K as a function of solvent parameters viz. 1/D, ET, AN and π* was used to evaluate the dissociation and stability constants in the aqueous medium. Furthermore, the reaction of the oximic hydrazone (H2L) with copper(II)-nitrate and chloride in addition to copper(I)-iodide afforded square planar mononuclear and binuclear complexes in which the oximic hydrazone showed three different modes of bonding. The obtained complexes reflect the strong bridging ability of the oximato group as well as its ambidentate and flexidentate characters.  相似文献   

15.
Absolute frequencies of hyperfine components of the 230.6 nm (5s 2 1 S 0?5s5p 3 P 1 0 ), 193.6 nm (5s5p 3 P 0 0 ?5s6s 3 S 1), 197.7 nm (5s5p 3 P 1 0 ?5s6s 3 S 1) and 207.9 nm (5s5p 3 P 2 0 ?5s6s 3 S 1) transitions in In II emitted from a hollow-cathode source have been measured using a high-resolution, scanning échelle monochromator. The measured frequencies of these four transitions have been used to determine the energies and hyperfine interaction constants of the 5s5p 3 P 0 0 ,3 P 1 0 ,3 P 2 0 and 5s6s 3 S 1 levels in In II. The hyperfine interaction constants for the dominant isotope115In are found to be: 5s5p 3 P 1 0 A=0.2322(2) cm?1,B=?0.0159(9) cm?1 5s5p 3 P 2 0 A=0.1699(4) cm?1,B= 0.021 (6) cm?1 5s6s 3 S 1 A=0.4022(4) cm?1,B= 0.002 (2) cm?1. The absolute frequency of the very narrow, strongly forbidden In II 236.5 nm (5s 2 1 S 0?5s5p 3 P 0 0 ) transition, which has been proposed as a candidate for a new optical frequency standard, is found to be 42275.986(7) cm?1.  相似文献   

16.
Syntheses and solid-state structures of zinc and tin(II) compounds, containing the N-silyl-amide ligands (OtBu)(NR)SiMe2, R = tBu (LtBu), or R = p-tolyl (LpTol), are reported. The N-silyl amines were synthesized by modified published procedures from commercially available Me2SiCl2, tBuOH, and tBuNH2, or p-Me-C6H4NH2, respectively. Treatment of SnCl2 with LiLpTol furnished Sn(LpTol)2, which was X-ray structurally characterized and shown to contain two covalent Sn-N bonds and two asymmetrical O → Sn donor bonds. The single-crystal X-ray structure of Sn(LtBu)2 revealed a much more symmetrically-coordinated, pseudo-trigonal-bipyramidal tin atom. Aminolysis of diethylzinc with HLpTol produced [EtZn(LpTol)]2, which crystallized as a centrosymmetric dimer, containing four-coordinate zinc atoms connected by bridging amides. Zinc dichloride, by contrast, reacted with two equivalents of LiLtBu to produce the homoleptic, pseudo-spirocyclic Zn(LtBu)2.  相似文献   

17.
Carina M.M. Machado 《Talanta》2007,71(3):1352-1363
This work describes the application of polarography, a technique scarcely used for modelling and optimisation of stability constants, in the study of copper complexes with [(2-hydroxy-1,1-bis(hydroxymethyl)ethyl)amino]-1-propanesulfonic acid (TAPS). Direct current polarography (DCP), using low total copper ion and large total ligand to total copper concentration, enabled the full characterization of Cu-(TAPS)x-(OH)y system, whose complexation occurs in the pH range of copper hydrolysis and Cu(OH)2 precipitation. Cu-(TAPS)x-(OH)y system was studied by DCP and glass electrode potentiometry (GEP) in aqueous solution at fixed total ligand to total metal concentrations ratios and varied pH values (25.0 °C; I = 0.1 M, KNO3). The predicted model, as well as the overall stability constants values, are (as log β): CuL+ = 4.2, CuL2 = 7.8, CuL2(OH) = 13.9 and CuL2(OH)22− = 18.94. GEP only allowed confirming the stability constants for CuL+ and CuL2 and was used to determine the pKa of TAPS, 8.342.Finally, a briefly comparative analysis between TAPS and other structural related buffers was done. Evaluation based on log βCuL versus pKa revealed that TES, TRIS, TAPS and AMPSO coordinated via amino and hydroxymethylgroups forming a five-membered chelate ring. For BIS-TRIS and TAPSO, and possibly DIPSO, one or more five-membered chelate rings involving additional hydroxyl groups are also likely formed.  相似文献   

18.
The extraction of In(III) from HCl, H2SO4, and HNO3 media using a 0.20 mol l−1 Cyanex 923 solution in toluene is investigated. In(III) is quantitatively extracted over a fairly wide range of HCl molarity while from H2SO4 and HNO3 media the extraction is quantitative at low acid concentration. The extracted metal ion has been recovered by stripping with 1.0 mol l−1 H2SO4. The stoichiometry of the In(III): Cyanex 923 complex is observed to be 1:2. The extraction of In(III) is insignificantly changed in diluents namely toluene, n-hexane, kerosene (160-200 °C), cyclohexane, and xylene having more or less the same dielectric constants, whereas, it decreases with increasing polarity of diluents such as cyclohexanone and chloroform. The extractant is stable towards prolonged acid contact and there is a negligible loss in its extraction efficiency even after recycling for 20 times. The extraction behavior of some commonly associated metal ions namely V(IV), Ti(IV), Al(III), Cr(III), Fe(III), Ga(III), Sb(III), Tl(III), Mn(II), Fe(II), Cu(II), Zn(II), Cd(II), Pb(II), and Tl(I) has also been investigated. Based on the partition data the conditions have been identified for attaining some binary separations of In(III). These conditions are extended for the recovery of pure indium from zinc blend, zinc plating mud, and galena. The recovery of the metal ions is around 95% with purity approximately 99%.  相似文献   

19.
The imidazolium fluorochromate (IFC) oxidation of meta‐ and para‐substituted anilines, in seven organic solvents, in the presence of p‐toluenesulfonic acid (TsOH) is first order in IFC and TsOH and is zero order with respect to substrate. The IFC oxidation of 15 meta‐ and para‐substituted anilines at 299–322 K complies with the isokinetic relationship but not to any of the linear free energy relationships; the isokinetic temperature lies within the experimental range. The specific rate of oxidizing species‐anilines reaction (k2) correlates with substituent constants affording negative reaction constants. The rate data failed to correlate with macroscopic solvent parameters such as εr and ENT. A correlation of rate data with Kamlet–Taft solvatochromic parameters (α, β, π*) suggests that the specific solute–solvent interactions play a major role in governing the reactivity, and the observed solvent effects have been explained on the basis of solute–solvent complexation. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 166–175, 2006  相似文献   

20.
Preparations, crystal structures, electronic and CD spectra are reported for new chiral Schiff base complexes, bis(N-R-1-naphthylethyl-3,5-dichlorosalicydenaminato)nickel(II), copper(II), and zinc(II). Nickel(II) and copper(II) complexes adopt a square planar trans-[MN2O2] coordination geometry with Δ(R,R) configuration. While zinc(II) complex adopts a compressed tetrahedral trans-[MN2O2] one with Δ(R,R) configuration and exhibits an emission band around 21 000 cm−1 (λex = 27 000 cm−1). Absorption and CD spectra were recorded in N,N′-dimethylformamide, acetone, methanol, chloroform, and toluene solutions to discuss relationships between spectral shifts of d–d and π–π bands by structural changes of the complexes and physical properties of the solvents. Moreover, we have attempted to investigate conformational changes of the complexes induced by photoisomerization of azobenzene, 4-hydroxyazobenzene, or 4-aminoazobenzene, in various solutions under different conditions. Weak intermolecular interactions between complexes and azobenzenes are important for the phenomenon by conformational changes of bulky π-conjugated moieties of the ligands.  相似文献   

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