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1.
Stability Constants of Complexes of Divalent and Rare Earth Metals with Substituted Salicynals 总被引:1,自引:0,他引:1
Summary. 5-Chloro-4-6-dimethyl-salicylaldehyde was synthesized from 4-chloro-3,5-dimethyl-phenol. A series of substituted salicynals
were obtained by condensation of 5-chloro-4,6-dimethyl-salicylaldehyde with several amines. The amines were chosen such as
to vary the basicity of salicynals by changing the substituents at one of the coordination sites. The stability constants
of complexes of bivalent (Mg2+, Ca2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+) and trivalent (Y3+, La3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Er3+, Yb3+) metal ions with these salicynals and the pK values corresponding to the dissociation of the phenolic proton and the association of a proton to the azomethine nitrogen
were determined potentiometrically using the Calvin-Bjerrum technique as adopted by Irving and Rossotti at 303 K and a constant ionic strength of 0.1 M in a 75:25 (v/v) dioxan-water mixture in an inert atmosphere. The influence of substituents on the proton affinity of the
ligands was examined on the basis of inductive and mesomeric effects. It is also shown that some of the complexes possess
antibacterial, antitubercular, antifungal, and anticoagulant activity.
Received August 5, 1999./Accepted November 11, 1999 相似文献
2.
Summary. tris-(Benzimidazol-2-yl-methyl)-amine, H3
ntb, was prepared and used in the synthesis of dinuclear Ru(II) polypyridyl and polynuclear Ru(II)–Co(III) complexes of the type
[Ru2(H2
ntb) (bpy)4]3+, [Ru2(Hntb)(phen)4]2+, [(Ru2(H2
ntb)(bpy)4)2Co(en)2]9+, and [(Ru2(Hntb)(phen)4)2 Co(en)2]7+ (bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, en = 1,2-diaminoethane). The complexes were characterized by elemental analysis as well as spectroscopic and redox data. The
luminescent properties of the complexes were also studied. The complexes showed significant antitumour and anti-HIV activities.
Received May 9, 2001. Accepted (revised) June 7, 2001 相似文献
3.
Tarek M. El-Gogary Mostafa A. Diab Shreen F. El-Tantawy 《Monatshefte für Chemie / Chemical Monthly》2006,38(12):1027-1042
Equilibrium constants and molar extinction coefficients for 1:1 charge-transfer complexes between 2-hydroxyaniline (HA), 5-chloro-2-hydroxyaniline (CHA), and 4-bromo-2,6-dimethylaniline (BMA) as donors and iodine, as a typical σ-acceptor were determined spectrophotometrically in chloroform, dichloromethane, and
carbontetrachloride solutions. Spectral characteristics and formation constants are discussed in terms of donor molecular
structure and solvent polarity. The stoichiometry of the complexes was established to be 1:1. For this purpose, optical data
were subjected to the form of the Rose-Drago equation for 1:1 equilibria. Electronic absorption spectra of the studied anilines were measured in different solvents. Spectral
data were reported and band maxima were assigned to the appropriate molecular orbital transitions (π–π* and n–π* electronic transition). Solvent effects on the electronic transitions were discussed. Optimized geometry of the studied anilines
was obtained at B3LYP/6-31 + G(d). The effect of the electronic factors of the substituents on the geometrical parameters
of the ring has been explored. Geometrical values of the ring deviate from the regular hexagonal ring. Intramolecular H-bonds
in HA and CHA have been computed at B3LYP/6-31 + G(d) and MP2/6-31 + G(d) levels. The H-bonding distance was calculated to be 2.105 ? in
HA and 2.127 ? in CHA. 相似文献
4.
Tarek M. El-Gogary Mostafa A. Diab Shreen F. El-Tantawy 《Monatshefte für Chemie / Chemical Monthly》2006,137(8):1027-1042
Summary. Equilibrium constants and molar extinction coefficients for 1:1 charge-transfer complexes between 2-hydroxyaniline (HA), 5-chloro-2-hydroxyaniline (CHA), and 4-bromo-2,6-dimethylaniline (BMA) as donors and iodine, as a typical σ-acceptor were determined spectrophotometrically in chloroform, dichloromethane, and
carbontetrachloride solutions. Spectral characteristics and formation constants are discussed in terms of donor molecular
structure and solvent polarity. The stoichiometry of the complexes was established to be 1:1. For this purpose, optical data
were subjected to the form of the Rose-Drago equation for 1:1 equilibria. Electronic absorption spectra of the studied anilines were measured in different solvents. Spectral
data were reported and band maxima were assigned to the appropriate molecular orbital transitions (π–π* and n–π* electronic transition). Solvent effects on the electronic transitions were discussed. Optimized geometry of the studied anilines
was obtained at B3LYP/6-31 + G(d). The effect of the electronic factors of the substituents on the geometrical parameters
of the ring has been explored. Geometrical values of the ring deviate from the regular hexagonal ring. Intramolecular H-bonds
in HA and CHA have been computed at B3LYP/6-31 + G(d) and MP2/6-31 + G(d) levels. The H-bonding distance was calculated to be 2.105 ? in
HA and 2.127 ? in CHA.
Abstracted from her M.Sc. thesis 相似文献
5.
Seyed Majid Hashemianzadeh Shirin Faraji Amir Hossein Amin Sepideh Ketabi 《Monatshefte für Chemie / Chemical Monthly》2008,13(7):89-100
Interactions of the DNA bases adenine (A), guanine (G), cytosine (C), and thymine (T) with various metal ions (M) of groups IA and IIA of the periodic table of the elements were studied at the HF, MP2, and DFT levels of theory. The structures and thermodynamic stabilities of these species were studied at the gas phase. The calculations
uphold that there exist two active sites in G and one in A, C, and T. The calculations also show that the O2 atom in T is a more active site for metal ion bindings than that in C. The stability energies for G … M complexes are larger than those for A … M complexes and the stability energies for T … M complexes are larger than those for C … M complexes. As z/r ratio for the metal ion increases, the interaction energy for the complex increases systematically. Thermodynamic quantities
such as ΔH, ΔG, ΔS, and ln K were determined for each complexation reaction, [Base+M
n+ →(Base … M)
n+]. A, G, and C complexation reactions except for C … Rb+ are exothermic. The situation is quite different for T complexation reactions and all except for T … Be2+ and T … Mg2+ are endothermic. 相似文献
6.
Seyed Majid Hashemianzadeh Shirin Faraji Amir Hossein Amin Sepideh Ketabi 《Monatshefte für Chemie / Chemical Monthly》2008,139(2):89-100
Summary. Interactions of the DNA bases adenine (A), guanine (G), cytosine (C), and thymine (T) with various metal ions (M) of groups IA and IIA of the periodic table of the elements were studied at the HF, MP2, and DFT levels of theory. The structures and thermodynamic stabilities of these species were studied at the gas phase. The calculations
uphold that there exist two active sites in G and one in A, C, and T. The calculations also show that the O2 atom in T is a more active site for metal ion bindings than that in C. The stability energies for G … M complexes are larger than those for A … M complexes and the stability energies for T … M complexes are larger than those for C … M complexes. As z/r ratio for the metal ion increases, the interaction energy for the complex increases systematically. Thermodynamic quantities
such as ΔH, ΔG, ΔS, and ln K were determined for each complexation reaction, [Base+M
n+ →(Base … M)
n+]. A, G, and C complexation reactions except for C … Rb+ are exothermic. The situation is quite different for T complexation reactions and all except for T … Be2+ and T … Mg2+ are endothermic. 相似文献
7.
J. M. Santana-Casiano M. González-Dávila F. J. Millero 《Journal of solution chemistry》2008,37(6):749-762
The stability constants for the hydrolysis of Cu(II) and formation of chloride complexes in NaClO4 solution, at 25 °C, have been examined using the Pitzer equations. The calculated activity coefficients of CuOH+, Cu(OH)2, Cu2(OH)3+, Cu2(OH)22+, CuCl+ and CuCl2 have been used to determine the Pitzer parameter (β
i
(0), β
i
(1), and C
i
) for these complexes. These parameters yield values for the hydrolysis constants (log 10
β
1*, log 10
β
2*, log 10
β
2,1* and log 10
β
2,2*) and the formation of the chloride complexes (log 10
β
CuCl* and
that agree with the experimental measurements, respectively to ±0.01,±0.02,±0.03,±0.06,±0.03 and ±0.07.
The stability constants for the hydrolysis and chloride complexes of Cu(II) were found to be related to those of other divalent
metals over a wide range of ionic strength. This has allowed us to use the calculated Pitzer parameters for copper complexes
to model the stability constants and activity coefficients of hydroxide and chloride complexes of other divalent metals. The
applicability of the Pitzer Cu(II) model to the ionic strength dependence of hydrolysis of zinc and cadmium is presented.
The resulting thermodynamic hydroxide and chloride constants for zinc are
and
. For cadmium the thermodynamic hydrolysis constants are
and
. The Cu(II) model allows one to determine the stability of other divalent metal complexes over a wide range of concentration
when little experimental data are available. More reliable stepwise stability constants for divalent metals are needed to
test the linearity found for the chloro complexes. 相似文献
8.
Summary. Two novel Er-Cr ion-pair complexes ([Er(DMA)3(H2O)4][Cr(CN)6] and [Er(MPL)4(H2O)3][Cr(CN)6]·2H2O; DMA = dimethylacetamide, MPL = 1-methyl-2-pyrrolidinone) have been synthesized. [Er(DMA)3(H2O)4][Cr(CN)6] crystallizes in the monoclinic system (space group P
c
) with a = 9.789(2), b = 11.263(2), c = 13.997(3)?, β = 105.66(3)°, V = 1485.9(5)?3, Z = 2; [Er(MPL)4(H2O)3][Cr(CN)6]·2H2O crystallizes in the monoclinic system (space group P21) with a = 9.447(2), b = 13.881(3), c = 14.673(3)?, β = 101.85(3), V = 1883.1(7)?3, Z = 2. X-Ray crystal diffraction analyses reveal that the two complexes form a hydrogen bonding network structure through the
CN group and H2O molecules. Variable temperature susceptibilities for the two complexes indicate that weak antiferromagnetic interactions
exist between cation and anion pairs through this hydrogen bonding network. 相似文献
9.
T. M. El‐Gogary A. El‐Dissouky A. S. Hilali 《International journal of quantum chemistry》2003,91(6):685-694
The geometry of metal ions (La3+, Ce3+, UO, and Th4+) complexes with 5‐azorhodanine derivatives was optimized at the level of molecular mechanics. Two stoichiometric ratios of metal to ligand (i.e., 1:1 and 1:2) were investigated. Tetracoordinate and hexacoordinate of each stoichiometric ratio have been studied. Effect of substitution in the ligand on the geometry of the complexes was discussed in the light of electron donating–accepting properties of these substituents. The influence of the nuclear effective charge of the central metal ions on the metal–ligand (M–L) bonding was discussed and the effect of the number of ligands on the M–L bond length was also discussed and correlated to the experimental results. The total energies of the different metal complexes were computed using the extended Huckel method. The effect of substituents in ligand, metal type, and stoichiometry of the complexes on the complex total energies were discussed. Stability constant of (La3+, Ce3+, UO, and Th4+) metal ions with 5‐azorhodanine derivaties have been determined potentiometrically in 0.1 M KCl and 50% (v/v) ethanol–water mixture. The order of the stability constants of the formed complexes was found to be La3+ < Ce3+ < UO < Th4+. The influence of substituents on the stability of the complexes was examined on the basis of electron‐repelling property of the substituent. The effect of temperature on the stability of the complexes formed was studied and the corresponding thermodynamic parameters (ΔG, ΔH, and ΔS) were derived and discussed. The stoichiometries of these complexes were determined conductometrically and indicated the formation of 1:1 and 1:2 (metal:ligand) complexes. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 相似文献
10.
The complexes of 4-chloro-2-methoxybenzoic acid anion with Mn2+,
Co2+, Ni2+, Cu2+
and Zn2+ were obtained as polycrystalline solids
with general formula M(C8H6ClO3)2·nH2O and colours typical for M(II) ions (Mn – slightly pink, Co –
pink, Ni – slightly green, Cu – turquoise and Zn – white).
The results of elemental, thermal and spectral analyses suggest that compounds
of Mn(II), Cu(II) and Zn(II) are tetrahydrates whereas those of Co(II) and
Ni(II) are pentahydrates. The carboxylate groups in these complexes are monodentate.
The hydrates of 4-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II), Cu(II)
and Zn(II) heated in air to 1273 K are dehydrated in one step in the range
of 323–411 K and form anhydrous salts which next in the range of 433–1212
K are decomposed to the following oxides: Mn3O4,
CoO, NiO and ZnO. The final products of decomposition of Cu(II) complex are
CuO and Cu. The solubility value in water at 293 K for all complexes is in
the order of 10–3 mol dm–3.
The plots of χM
vs.
temperature of 4-chloro-2-methoxybenzoates of Mn(II), Co(II), Ni(II) and Cu(II)
follow the Curie–Weiss law. The magnetic moment values of Mn2+,
Co2+, Ni2+ and Cu2+
ions in these complexes were determined in the range of 76−303 K and
they change from: 5.88–6.04 μB for Mn(C8H6ClO3)2·4H2O, 3.96–4.75
μB for Co(C8H6ClO3)2·5H2O, 2.32–3.02 μB for Ni(C8H6ClO3)2·5H2O and 1.77–1.94
μB for Cu(C8H6ClO3)2·4H2O. 相似文献
11.
A. M. Radalla 《Journal of solution chemistry》2010,39(9):1394-1407
The binary and ternary complexes of Cu2+, Ni2+, Co2+ and Zn2+ metal ions with resorcinol (R) as primary ligand and some biologically important aliphatic dicarboxylic acids (adipic, succinic,
malic, malonic, maleic, tartaric and oxalic acids) as secondary ligands were studied in aqueous solution at 25 °C and I=0.1 mol⋅dm−3 NaNO3 using the potentiometric technique. The formation of different 1:1 and 1:2 binary complexes and 1:1:1 ternary complexes is
inferred from the corresponding potentiometric pH-titration curves. The ternary complex formation was found to take place
in a stepwise manner. The protonation constants of the ligands were determined and used for determining the stability constants
of the different complexes formed in aqueous solutions. The lower stability of the 1:2 binary complexes compared to the corresponding
1:1 systems of all ligands studied were in accordance with statistical considerations. The order of stability of the complexes
formed in solution was investigated in terms of the nature of the resorcinol, carboxylic acid, and metal ion used. The values
of Δlog 10
K, percentage of relative stabilization (% R.S.), and log 10
X for mixed-ligand complexes studied have been evaluated and discussed. The concentration distribution of the various species
formed in solution was evaluated. The mode of chelation of the ternary complexes was ascertained by conductivity measurements. 相似文献
12.
Lutz Preu Wolfgang Kliegel Steven J. Rettig James Trotter 《Monatshefte für Chemie / Chemical Monthly》2001,132(10):1213-1224
Summary. The structure of the dehydrogenation product 1′,3a′-dihydro-3′-((1,3-dioxoindan-2-ylidene)-phenyl-methyl)-5′-phenyl-spiro-(indan-2,1′-pyrrolo[3,4-c]pyrrole)-1,3,4′,6′-(5′H, 6a′H)-tetrone derived from the cycloadducts (±)-(3a′S,6a′R)-1′,3a′-dihydro-3′-((R)-α-(1,3-dioxoindanyl)-benzyl)-5′-phenyl-spiro-(indan-2,1′-pyrrolo[3,4-c]pyrrole)-1,3,4′,6′(5H,6a′H)-tetrone and/or (±)-(3a′S,6a′R)-1′,3a′-dihydro-3′-((S)-α-(1,3-dioxoindanyl)-benzyl)-5′-phenyl-spiro-(indan-2,1′-pyrrolo[3,4-c]pyrrole)-1,3,4′,6′(5H,6a′H)-tetrone, which were synthesized by 1,3-dipolar cycloaddition of N-phenylmaleimide to 2-((2-(1,3-dioxoindan-2-yl)-2-phenyl-ethenyl)-imino)-indan-1,3-dione,
was determined by X-ray analysis. Crystal data (CCD, 180 K): rhombohedral, R&3macr;;, a = 34.0871(7), c = 13.9358(5) ?, Z = 18; the structure was solved by direct methods and refined by full-matrix least-squares procedures to R(F, I ≥ 3σ(I)) = 0.053. The molecule contains a central folded ring system of two cis-fused 5-membered heterocyclic rings; each ring is nearly planar, and the angle between the rings amounts to 59.0°. Dynamic
1H NMR spectroscopy of the product revealed an exchange process caused by restricted rotation of the double bonded 1,3-indandione
moiety and the phenyl group about the Csp2-Csp2 single-bonds. Molecular modeling and complete lineshape analysis indicated a four site exchange process for which free energies
of activation and free energies could be established. ΔG
‡ values for the barriers of rotation are in the range of 57–59 kJ · mol − 1 at 273 K, which is unusually high for an unsubstituted phenyl group.
Received May 3, 2001. Accepted (revised) June 8, 2001 相似文献
13.
Predrag Djurdjević Ratomir Jelić Ljubinka Joksović Mirjana Cvijović 《Monatshefte für Chemie / Chemical Monthly》2006,137(6):717-735
Summary. Solution equilibria between aluminium(III) ion and L-aspartic acid were studied by potentiometric, 27Al, 13C, and 1H NMR measurements. Glass electrode equilibrium potentiometric studies were performed on solutions with ligand to metal concentration
ratios 1:1, 3:1, and 5:1 with the total metal concentration ranging from 0.5 to 5.0 mmol/dm3 in 0.1 mol/dm3 LiCl ionic medium, at 298 K. The pH of the solutions was varied from ca. 2.0 to 5.0. The non-linear least squares treatment of the data performed with the aid of the Hyperquad program, indicated
the formation of the following complexes with the respective stability constants log βp,q,r given in parenthesis (p, q, r are stoichiometric indices for metal, ligand, and proton, respectively): Al(HAsp)2+ (log β1,1,1 = 11.90 ± 0.02); Al(Asp)+ (log β1,1,0 = 7.90 ± 0.03); Al(OH)Asp0 (log β1,1,−1 = 3.32 ± 0.04); Al(OH)2Asp− (log β1,1−2 = −1.74 ± 0.08), and Al2(OH) Asp3+ (log β2,1,−1 = 6.30 ± 0.04). 27Al NMR spectra of Al3+ + aspartic acid solutions (pH 3.85) indicate that sharp symmetric resonance at δ∼10 ppm can be assigned to (1, 1, 0) complex. This resonance increases
in intensity and slightly broadens upon further increasing the pH. In Al(Asp)+ complex the aspartate is bound tridentately to aluminum. The 1H and 13C NMR spectra of aluminium + aspartic acid solutions at pH 2.5 and 3.0 indicate that β-methylene group undergoes the most pronounced changes upon coordination of aluminum as well as
α-carboxylate group in 13C NMR spectrum. Thus, in Al(HAsp)2+ which is the main complex in this pH interval the aspartic acid acts as a bidentate ligand with –COO− and –NH2 donors closing a five-membered ring. 相似文献
14.
Predrag Djurdjevi? Ratomir Jeli? Ljubinka Joksovi? Mirjana Cvijovi? 《Monatshefte für Chemie / Chemical Monthly》2006,12(2):717-735
Solution equilibria between aluminium(III) ion and L-aspartic acid were studied by potentiometric, 27Al, 13C, and 1H NMR measurements. Glass electrode equilibrium potentiometric studies were performed on solutions with ligand to metal concentration
ratios 1:1, 3:1, and 5:1 with the total metal concentration ranging from 0.5 to 5.0 mmol/dm3 in 0.1 mol/dm3 LiCl ionic medium, at 298 K. The pH of the solutions was varied from ca. 2.0 to 5.0. The non-linear least squares treatment of the data performed with the aid of the Hyperquad program, indicated
the formation of the following complexes with the respective stability constants log βp,q,r given in parenthesis (p, q, r are stoichiometric indices for metal, ligand, and proton, respectively): Al(HAsp)2+ (log β1,1,1 = 11.90 ± 0.02); Al(Asp)+ (log β1,1,0 = 7.90 ± 0.03); Al(OH)Asp0 (log β1,1,−1 = 3.32 ± 0.04); Al(OH)2Asp− (log β1,1−2 = −1.74 ± 0.08), and Al2(OH) Asp3+ (log β2,1,−1 = 6.30 ± 0.04). 27Al NMR spectra of Al3+ + aspartic acid solutions (pH 3.85) indicate that sharp symmetric resonance at δ∼10 ppm can be assigned to (1, 1, 0) complex. This resonance increases
in intensity and slightly broadens upon further increasing the pH. In Al(Asp)+ complex the aspartate is bound tridentately to aluminum. The 1H and 13C NMR spectra of aluminium + aspartic acid solutions at pH 2.5 and 3.0 indicate that β-methylene group undergoes the most pronounced changes upon coordination of aluminum as well as
α-carboxylate group in 13C NMR spectrum. Thus, in Al(HAsp)2+ which is the main complex in this pH interval the aspartic acid acts as a bidentate ligand with –COO− and –NH2 donors closing a five-membered ring. 相似文献
15.
Summary. A new simple, rapid, sensitive, and selective method is proposed for the microdetermination of mercury. Mercury(II) forms
insoluble complexes with 2,3-dichloro-6-(2-hydroxy-3,5-dinitrophenylazo)-quinoxaline (1), 2,3-dichloro-6-(5-amino-3-carboxy-2-hydroxy-phenylazo)-quinoxaline (2), 2,3-dichloro-6-(2,7-dihydroxynaphth-1-ylazo)-quinoxaline (3), and 2,3-dichloro-6-(3-carboxy-2-hydroxy-naphth-1-ylazo)-quinoxaline (4) in aqueous acidic medium; the complexes can be made soluble by the action of an anionic surfactant. The solution of the
pink coloured compounds is stable for at least 24 h. Beer’s law is obeyed over the concentration range from 0.1 to 2.8 μg · cm−3 of mercury. For a more accurate analysis, Ringbom optimum concentration ranges were found to be 0.25–2.5 μg · cm−3. The molar absorpitivity, Sandell sensitivity, and relative standard deviations were also calculated. A slight interference from Pd2+ and Cd2+ is exhibited by the first three ligands, whereas the last one is only negligibly affected by these metal ions. Strong interference
from Ag(I) is evident for all ligands, whereas alkali, alkaline earth, and other transition metals tested posed negligible
interference. 15 μg · cm−3 of Cd2+ and Pd2+ or 10 μg · cm−3 of Ag+ can be tolerated if 1.0 mg of potassium bromide and 2.0 mg of citrate as masking agents are added for the determination of
1.5 μg · cm−3 of mercury(II). The method was applied to the determination of methyl- and ethylmercury chloride and the analysis of environmental
water samples.
Received August 7, 2000. Accepted (revised) October 18, 2000 相似文献
16.
Fursemide is the chemical compound 4-chloro-2-(furan-2-ylmethylamino)-5-(aminosulfonyl) benzoic acid. It was oxidized by diperiodatocuprate(III)
in alkali solutions, and the oxidation products were identified as furfuraldehyde and 2-amino-4-chloro-5-(aminosulfonyl) benzoic
acid. The reaction kinetics were studied spectrophotometrically. The reaction was observed to be first order in [oxidant]
and fractional order each in [fursemide] and [periodate], whereas added alkali retarded the rate of reaction. The reactive
form of the oxidant was inferred to be [Cu(H3IO6)2]−. A mechanism consistent with the experimental results was proposed, in which oxidant interacts with the substrate to give
a complex as a pre-equilibrium state. This complex decomposed in a slow step to give a free radical that was further oxidized
by reaction with another molecule of DPC to yield 2-amino-4-chloro-5-(aminosulfonyl) benzoic acid and furfuraldehyde in a
fast step. This reaction was studied at 25, 30, 35, 40 and 45 °C, and the activation parameters E
a,ΔH
#,ΔS
# and ΔG
# were determined to be 51 kJ⋅mol−1,48.5 kJ⋅mol−1,−63.5 J⋅K−1⋅mol−1 and 67 kJ⋅mol−1, respectively. The value of log 10
A was calculated to be 6.8. 相似文献
17.
Fatemeh Hesami Gholam Hossein Rounaghi Massoumeh Mohajeri Somayeh Tarahomi 《Journal of solution chemistry》2011,40(8):1408-1417
The complexation reactions of 4′-nitrobenzo-15-crown-5 (4′NB15C5) with Zn2+, Mn2+, Cr3+ and Sn4+ cations were studied in acetonitrile–ethanol (AN–EtOH) binary solvent mixtures at different temperatures by the electrical
conductometry method. The stability constants of the resulting 1:1 complexes were determined from computer fitting of the
conductance versus mole ratio data. The results show that the selectivity order of 4′NB15C5 for the metal cations in the AN–EtOH
(mol-%AN=76) binary solvent at 298.15 K is: Cr3+>Mn2+≈Zn2+>Sn4+, but the selectivity order changes with the composition of the mixed solvents. A nonlinear relationship was observed between
the stability constants (log 10
K
f) of these complexes and the composition of the AN–EtOH binary solvents. The corresponding thermodynamic parameters (DHco, DSco)(\Delta H_{\mathrm{c}}^{\mathrm{o}}, \Delta S_{\mathrm{c}}^{\mathrm{o}}) were obtained from the temperature dependence of the stability constants using van’t Hoff plots. The results show that the
values and also the sign of these parameters are influenced by the nature and composition of the mixed solvents. 相似文献
18.
Ulrich Englich Ingo Prass Karin Ruhlandt-Senge Thorsten Schollmeier Frank Uhlig 《Monatshefte für Chemie / Chemical Monthly》2002,133(7):931-943
Summary. Hydrido substituted stannasilanes of the type or (Z = H, Me, Ph; R, R′ = alkyl, Ph) are accessible by reaction of either alkali metal stannides (MSn(Z)R
2; M = Li, Na) with halogen substituted silanes (; X = F, Cl) or chlorostannanes (R
2SnCl2, Ph3SnCl) and fluorosilanes in the presence of magnesium. Stannasilanes with halogen substituents at the silicon as well as the tin atom are formed by
treatment of the hydrido substituted stannasilanes with CHCl3 or CCl4. The hydrido substituted stannasilanes decompose in contact with air to distannanes and siloxanes or to the linear (
t
Bu2Sn(–O–
t
Bu2Si–OH)2) and cyclic ((–
t
Bu2Sn–O–
i
Pr2Si–O–)2) stannasiloxanes.
Received November 29, 2001. Accepted (revised) January 16, 2002 相似文献
19.
Wen-J. Mei Yu-Z. Ma Jie Liu Jin-C. Chen Kang-C. Zheng Liang-N. Ji Jun-H. Yao 《Transition Metal Chemistry》2006,31(3):277-285
A series of ruthenium(II) complexes with electron-donor or electron-acceptor groups in intercalative ligands, [Ru(phen)2(o-MOP)]2+ (1), [Ru(phen)2(o-MP)]2+ (2), [Ru(phen)2(o-CP)]2+ (3) and [Ru(phen)2(o-NP)]2+ (4), have been synthesized and characterized by elementary analysis, ES-MS, 1H NMR, electronic absorption and emission spectra. The binding properties of these complexes to CT-DNA have been investigated
by spectroscopy and viscosity experiments. The results showed that these complexes bind to DNA in intercalation mode and their
intrinsic binding constants (Kb) are 1.1, 0.35, 0.53 and 1.7 × 105 M−1, respectively. The subtle but detectable differences occurred in the DNA-binding properties of these complexes are mainly
ascribed to the electron-withdrawing abilities of substituents (–OCH3 < –CH3 < –Cl < –NO2) on the intercalative ligands as well as the intramolecular H-bond (for substituent –OCH3) which increase the planarity area of the intercalative ligand to some extent. The density functional theory (DFT) calculations
were also performed and used to further discuss the trend in the DNA-binding affinities of these complexes. 相似文献
20.
Silvia Berto Francesco Crea Pier Giuseppe Daniele Concetta De Stefano Enrico Prenesti Silvio Sammartano 《Journal of solution chemistry》2009,38(10):1343-1356
The formation constants of dioxouranium(VI)-2,2′-oxydiacetic acid (diglycolic acid, ODA) and 3,6,9-trioxaundecanedioic acid
(diethylenetrioxydiacetic acid, TODA) complexes were determined in NaCl (0.1≤I≤1.0 mol⋅L−1) and KNO3 (I=0.1 mol⋅L−1) aqueous solutions at T=298.15 K by ISE-[H+] glass electrode potentiometry and visible spectrophotometry. Quite different speciation models were obtained for the systems
investigated, namely: ML0, MLOH−, ML22−, M2L2(OH)−, and M2L2(OH)22−, for the dioxouranium(VI)–ODA system, and ML0, MLH+, and MLOH− for the dioxouranium(VI)–TODA system (M=UO22+ and L = ODA or TODA), respectively. The dependence on ionic strength of the protonation constants of ODA and TODA and of
both metal-ligand complexes was investigated using the SIT (Specific Ion Interaction Theory) approach. Formation constants
at infinite dilution are [for the generic equilibrium pUO22++q(L2−)+rH+
⇌(UO22+)
p
(L)
q
H
r
(2p−2q+r);β
pqr
]: log 10
β
110=6.146, log 10
β
11−1=0.196, log 10
β
120=8.360, log 10
β
22−1=8.966, log 10
β
22−2=3.529, for the dioxouranium(VI)–ODA system and log β
110=3.636, log 10
β
111=6.650, log 10
β
11−1=−1.242 for dioxouranium(VI)–TODA system. The influence of etheric oxygen(s) on the interaction towards the metal ion was
discussed, and this effect was quantified by means of a sigmoid Boltzman type equation that allows definition of a quantitative
parameter (pL
50) that expresses the sequestering capacity of ODA and TODA towards UO22+; a comparison with other dicarboxylates was made. A visible absorption spectrum for each complex reaching a significant percentage
of formation in solution (KNO3 medium) has been calculated to better characterize the compounds found by pH-metric refinement. 相似文献