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1.
Felipe S. Vilhena Letícia R. Teixeira Odivaldo Cambraia Alves Heloisa Beraldo Fabio da S. Miranda Judith Felcman 《Journal of solution chemistry》2013,42(3):555-565
The binary systems of iron(II) and iron(III) with 2-pyridineformamide thiosemicarbazone (H2Am4DH) and its N(4)-methyl (H2Am4Me), N(4)-ethyl (H2Am4Et) and N(4)-phenyl (H2Am4Ph) derivatives were studied in aqueous solution by pH-potentiometry, ultraviolet–visible spectroscopy and EPR spectra. The formation constants of the iron(II) and iron(III) complexes were calculated from potentiometric and electronic absorption data at 25 °C and ionic strength μ = 0.1 mol·L?1 using the HYPERQUAD program. The values of the formation constant of the FeL species decrease in the order Fe:H2Am4DH > Fe:H2Am4Me ≈ Fe:H2Am4Et > Fe:H2Am4Ph in the same way as the basicity of the ligands. The species distribution diagrams show that the species FeL2 predominates at physiological pH in the Fe:H2Am4DH, Fe:H2Am4Me and Fe:H2Am4Et systems. The similar EPR spectra of these iron(III) binary systems indicate the same coordination spheres around the metallic center and the EPR g values suggests that the unpaired electron is in the dxy orbital, indicating a d xz 2 d yz 2 d xy 1 ground state configuration for the complexes. For the Fe(III):H2Am4Ph system the EPR results indicated dimerization and antiferromagnetic interaction due to the presence of only one thiosemicarbazone ligand around the metallic center. 相似文献
2.
1H and 13C NMR chemical shifts of iron porphyrin complexes are determined mainly by the spin densities at the peripheral carbon and nitrogen atoms caused by the interaction between paramagnetic iron 3d and porphyrin molecular orbitals. This review describes how the half‐occupied iron 3d orbitals such as dπ(dxz, dyz), dxy, d, and d‐ interact with a specific porphyrin molecular orbital and affect the 1H and 13C NMR chemical shifts in planar, ruffled, saddled, and domed complexes. Revealing the relationship between the orbital interactions and NMR chemical shifts is quite important to determine the fine electronic structures of synthetic iron porphyrin complexes as well as naturally occurring heme proteins. 相似文献
3.
The phenol‐tailed porphyrin ligand, H3L was synthesized as a model compound for catalases. H3L and its corresponding iron complex [Fe(L)] were synthesized by using the precursor, 5‐(8‐ethoxycarbonyl‐1‐naphthyl)‐10, 15, 20‐triphenyl porphyrin (ENTPP). They were characterized by 1H NMR spectroscopy, mass spectrometry, X‐ray crystallography, and cyclic voltammetry. All the results have confirmed that the phenol group is covalently attached to the porphyrin. In the iron complex, phenolate oxygen is coordinated to iron(III) as the fifth ligand, leading to the five‐coordinate high‐spin iron(III) species. 相似文献
4.
Luce VanderElst Audrey Sessoye Sophie Laurent RobertN. Muller 《Helvetica chimica acta》2005,88(3):574-587
The self‐diffusion (Dc) coefficients of various lanthanum(III) diamagnetic analogues of open‐chain and macrocyclic complexes of gadolinium used as MRI contrast agents were determined in dilute aqueous solutions (3–31 mM ) by pulsed‐field‐gradient (PFG) high‐resolution 1H‐NMR spectroscopy. The self‐diffusion coefficient of H2O (Dw) was obtained for the same samples to derive the relative diffusion constant, a parameter involved in the outersphere paramagnetic‐relaxation mechanism. The results agree with an averaged relative diffusion constant of 2.5 (±0.1)×10?9 and of 3.3 (±0.1)×10?9 m2 s?1 at 25 and 37°, respectively, for 'small' contrast agents (Mr 500–750 g/mol), and with the value of bulk H2O (2.2×10?9 and 2.9×10?9 m2 s?1 at 25° and at 37°, respectively) for larger complexes. The use of the measured values of Dc for the theoretical fitting of proton NMRD curves of gadolinium complexes shows that the rotational correlation times (τR) are very close to those already reported. However, differences in the electronic relaxation time (τSO) at very low field and in the correlation time (τV) related to electronic relaxation were found. 相似文献
5.
Two multidentate ligands: N,N′-di-(propionic acid-2′-yl-)-2,9-di-aminomethylphenanthroline (L1) and N,N′-di-(3′-methylbutyric acid-2′-yl-)-2,9-di-amino-methylphenanthroline (L2) were synthesized and fully characterized by 1H NMR and elemental analysis. The binding ability of L1 and L2 to metal ions such as M(II) (M = Cu, Zn, Co and Ni) and Ln(III) (Ln = La, Nd, Sm, Eu, and Gd) has been investigated by potentiometric
titration in aqueous solution and 0.1 mol dm−3KNO3 at 25.0 ± °C. In view of the structure of L1 and L2, mononuclear metal complexes can be formed in solution. The stability constants of binary complexes of ligands L1 and L2
with metal ions M(II) and Ln(III) have been determined respectively and further discussed. 相似文献
6.
Two N‐2‐hydroxy‐1‐phenylethyl and N‐2‐hydroxy‐2‐phenylethyl derivatives of DTPA (3,6,9‐tri(carboxymethyl)‐3,6,9‐triazaundecanedioic acid), DTPA‐H1P = 3,9‐di(carboxymethyl)‐6‐2‐hydroxy‐1‐phenylethyl‐3,6,9‐triazaundecanedioic acid, and DTPA‐H2P = 3,9‐di(carboxymethyl)‐6‐2‐hydroxy‐2‐phenylethyl‐3,6,9‐triazaundecanedioic acid were synthesized. Their protonation constants were determined by Potentiometric titration in 0.10 M Me4NNO3 and by NMR pH titration at 25.0 ± 0.1°C. The formations of lanthanide(III), copper(II), zinc(II) and calcium(II) complexes were investigated quantitatively by potentiometry. The stability constant for Gd(III) complex is larger than those for Ca(II), Zn(II) and Cu(II) complexes with these two ligands. The selectivity constants and modified selectivity constants of the DTPA‐H1P and DTPA‐H2P for Gd(III) over endogenously available metal ions were calculated. Comparing pM values at physiological pH 7.4 assesses effectiveness of these two ligands in binding divalent and trivalent metal ions in biological media. The observed water proton relaxivity values of [Gd(DTPA‐H1P)]? and [Gd(DTPA‐H2P)]? became constant with respect to pH changes over the range of 4‐10. 17O NMR shifts showed that the [Dy(DTPA‐H1P)]? and [Dy(DTPA‐H2P)]? complexes at pH 6.30 had 1.91 and 2.28 inner‐sphere water molecules, respectively. Water proton spin‐lattice relaxation rates of [Gd(DTPA‐H1P)]? and [Gd(DTPA‐H2P)]? complexes were also consistent with the inner‐sphere Gd(III) coordination. 相似文献
7.
The dissociation constant values of glycylglycine were determined at 25 ± 0.1 °C (I = 0.1 mol L?1 KNO3) with Potentiometric pH titration in pure water and various mixture of water and organic solvents. The organic solvents used were methanol, ethanol, N, N-dimethylformamide, dimethylsulfoxide, acetonitrile and dioxane. Initial estimates of the dissociation constants of glycylglycine were refined with ESAP2M computer program. The results obtained are discussed in terms of average macroscopic properties of the mixed solvents and the possible variation in microheterogeneity of the solvation shells around the solute. 相似文献
8.
V. G. Alekseev 《Russian Journal of Inorganic Chemistry》2007,52(5):698-702
The interaction of Nd3+ ions with ampicillin, amoxicillin, and cephalexin anions (L) in aqueous solution at 20°C and ionic strength of 0.1 (KNO3) was studied by pH titration. The NdL and Nd(OH)L complexes are formed in weak alkaline solution. The distribution curves of neodymium(III) complex species depending on pH were constructed. The formation constants of the complexes were determined. 相似文献
9.
Qiao Deng Yongdong Jin Qinggui Wang Rongxin Zhao Ning Pan Fuwan Zhai Meiming Luo Chuanqin Xia 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(1):125-133
A new N-containing ligand, 1,4,7,10-tetra-(4-nitrobenzyl)-1,4,7,10-tetraazacyclo-dodecane (L), was synthesized, and its structure was determined by 1H NMR, high resolution mass spectrometry and X-ray diffraction. L crystallized in the monoclinic system (P21/n space group; a = 7.7895(2) Å, b = 22.9592(5) Å, c = 9.9204(2) Å; α = 90.00°, β = 105.481(3)°, γ = 90.00°; Z = 2). Slope analysis and the continuous variation method demonstrated that 1:2 complexes between Th(IV) and L are formed; furthermore, the XPS analysis suggested that two oxygen atoms might be provided by two water molecules and that eight nitrogen atoms might be provided by two L molecules to form a ten-coordinate compound with Th(IV). The extraction equilibrium constant for the complex formation between Th(IV) and L was logK ex = 6.95 ± 0.15 (25 °C), and the Gibbs free energy, ΔG o (25 °C), of the 1:2 Th–L complex in dichloromethane was ?39.56 kJ/mol. The L ligand in dichloromethane only slightly extracted Th(IV) from HNO3 solution at pH = 1–3; however, an extraction efficiency of E = 94.9 ± 0.3 % was observed at pH = 4.63. The selectivity of L for the Th(IV) cation over other cations (i.e., Cs(I), Sr(II), Y(III), La(III), Sm(III), Eu(III), U(VI), and 241Am(III)) was evaluated. Furthermore, the stripping experiments showed that the stripping agent (0.5 mol/L Na2CO3 + 0.1 mol/L EDTA) could provide an optimal condition for stripping thorium, and thorium recovery was up to 91.6 ± 0.1 %. 相似文献
10.
Hermas R. Jimnez Esther Ruiz de Sola Jos M. Moratal Maria Arbona 《无机化学与普通化学杂志》2005,631(11):2020-2025
Electronic transfer protein cytochrome c‐550 from horse heart is studied in the unfolded state by means of paramagnetic 1H NMR. The protein contains 104 aminoacid residues and a heme group with low spin FeIII ion in the oxidized form of protein. The global secondary structure is of the α‐helix type as occurs in the case of very other cytochromes c investigated such as cyt c‐550 from Thiobacillus versutus or cyt c‐551 from Pseudomonas aeruginosa. We have studied the coordination characteristic and electronic properties of heme iron horse heart ferricytochrome c‐550 at increasing denaturing conditions (up to 3.1 M GuHCl and 288‐323 K). The 1H T1 values of the signals were measured and some resonance assignments made based on EXSY experiments. The electronic structure of the iron(III) is discussed on the basis of the temperature dependence of the isotropic shifts and relaxation times. These results show that it is produced a change of spin, from low‐spin iron(III) (2T2, S=1/2) in the folded state to high‐spin iron(III) (6A1, S=5/2) in the unfolded state. It seems to be possible that in the opened structure the ferricyt c‐550 loses one axial ligand (His/‐) appearing the spin transition. 相似文献
11.
V. G. Alekseev E. N. Myasnikova V. M. Nikol’skii 《Russian Journal of Inorganic Chemistry》2013,58(12):1593-1596
The hydrolysis constants of Al3+, Ga3+, and In3+ cations are determined by potentiometric titration at 25°C against the background of 0.1 M KNO3. 相似文献
12.
The acid dissociation constants of N-carboxymethyl-N-(p-hydroxy phenyl carbamoyl-methyl)-2,3-dihydroxy-5-carbomethoxy benzylamine (CHDCB) and the stability constants of its 1:1 complexes with alkaline earth, Cd(II), Co(II), Ni(II), Cu(II), Zn(II), Fe(III), Th(IV) and U(VI) ions have been determined at 25.0 ± 0.1 °C and at an ionic strength of 0.1 (KNO3) by pH titration method. The probable coordination sites have also been discussed. 相似文献
13.
5‐(8‐Carboxy‐1‐naphthyl)‐10, 5, 20‐tritolyl porphyrin (H3CNTTP) and its iron(III) complexes, [Fe(CNTTP)]2 and [Fe(CNTTP)(N‐MeIm)2], were synthesized and characterized. X‐ray crystallography revealed that the carboxylate group is “hanging” over the porphyrin plane. The rigid framework makes the distance between the carboxylate oxygen and iron in the same porphyrin too long to form a coordination bond. On the other hand, the carboxylate group is not bulky enough to block the axial binding site. In the presence of OH–, the carboxylate oxygen is coordinated to iron in the symmetry‐related unit, which led to the dimeric structure, [Fe(CNTTP)]2. In the presence of excess N‐methylimidazole, a six‐coordinate species, [Fe(CNTTP)(N‐MeIm)2], was obtained. In such a structure, CH ··· O interactions between the carboxylate group and imidazole probably play an important role to determine the orientation of imidazole plane. Two imidazole planes have relative parallel orientation. For [Fe(CNTTP)(N‐MeIm)2], 1H NMR shows pyrrole protons at the region –10 to –25 ppm. EPR shows rhombic spectrum. Those suggest [Fe(CNTTP)(N‐MeIm)2] is a type II low‐spin iron(III) porphyrinate. 相似文献
14.
15.
Coordination of sigma-aryl carbanions by chloroiron(II) 5,20-ditolyl-10,15-diphenyl-21-oxaporphyrin (ODTDPP)Fe(II)Cl has been followed by (1)H NMR spectroscopy. Addition of pentafluorophenyl Grignard reagent (C(6)F(5))MgBr to the toluene solution of (ODTDPP)Fe(II)Cl in the absence of dioxygen at 205 K resulted in the formation of the high-spin (ODTDPP)Fe(II)(C(6)F(5)). The titration of (ODTDPP)Fe(II)Cl with a solution of (C(6)H(5))MgBr carried at 205 K yields a rare six-coordinate species which binds two sigma-aryl ligands [(ODTDPP)Fe(II)(C(6)H(5))(2)](-). Warming of the [(ODTDPP)Fe(II)(C(6)H(5))(2)](-) solution above 270 K results in the decomposition to mono-sigma-phenyliron species (ODTDPP)Fe(II)(C(6)H(5)). Controlled oxidation of [(ODTDPP)Fe(II)(C(6)H(5))(2)](-) with Br(2) affords (ODTDPP)Fe(III)(C(6)H(5))Br, which demonstrates a typical (1)H NMR pattern of low-spin sigma-aryl iron(III) porphyrin. The considered oxidation mechanism involves the (ODTDPP)Fe(III)(C(6)H(5))(2) species, which is readily reduced to the iron(I) 21-oxaporphyrin, followed by oxidation with Br(2) and replacement of one bromide anion by aryl substituent. The (1)H NMR spectra of paramagnetic iron complexes have been examined in detail. Functional group assignments have been made with the use of selective deuteration. The peculiar (1)H NMR spectral features of [(ODTDPP)Fe(II)(p-CH(3)C(6)H(4))(2)](-) (sigma-p-tolyl: ortho, 30.8; meta, 53.6; para-CH(3), 42.1; furan: -16.0; beta-H pyrrole: -27.5, -34.3, -41.8 ppm, at 205 K) are without a parallel to any iron(II) porphyrin or heteroporphyrin and indicate a profound alteration of the electronic structure of iron(II) porphyrin upon the coordination of two sigma-aryls. 相似文献
16.
《Journal of Coordination Chemistry》2012,65(23):4130-4142
Eight new (porphyrinato)(naphthalocyaninato) rare earth(III) double-decker complexes MIII(TONPP)[Nc(PhS)8] [M = La, Pr, Nd, Sm, Eu, Gd, Tb, and Dy; TONPP = 5,10,15,20-tetrakis(4-octyloxynaphthyl) porphyrin; Nc(PhS)8 = 3,4,12,13,21,22,30,31-octa(phenylthio)-2,3-naphthalocyanine] have been prepared and characterized by spectroscopic methods. The UV–vis absorption spectra depend on the central rare earth ionic size, suggesting that all the transitions involve molecular orbitals with contribution from both porphyrin and naphthalocyanine ligands. The IR and Raman spectra of these double-decker compounds were systemically investigated, showing that the electron hole in these mixed double-deckers is mainly localized at the naphthalocyanine ring. Their sandwich nature was also characterized by MS, EA, and 1H NMR techniques. 相似文献
17.
The complex formation equilibria of [Pd(FLX)(H2O)2]2+, where FLX = the drug fluoxetine, with the bio-ligands (L), glycine, serine, cysteine, histidine, glycylglycine and glycylvaline, were studied and their formation constants were determined. Stoichiometries and stability constants of the complexes were determined at 25 °C and at constant 0.10 mol·dm?3 NaNO3 ionic strength. The concentration distribution of the complexes in solution was evaluated. Palladium(II) complexes were synthesized and characterized by the 1H NMR and electronic spectral studies. The structures consist of monomeric units in which the Pd(II) atoms exhibit square planar geometry. 相似文献
18.
Melanie A. Short Roger D. Sommer Alec J. Falzone Tao Huang Walter W. Weare Jennifer L. Roizen 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(6):717-722
While six‐coordinate iron(III) porphyrin complexes with pyridine N‐oxides as axial ligands have been studied as they exhibit rare spin‐crossover behavior, studies of five‐coordinate iron(III) porphyrin complexes including neutral axial ligands are rare. A five‐coordinate pyridine N‐oxide–5,10,15,20‐tetraphenylporphyrinate–iron(III) complex, namely (pyridine N‐oxide‐κO)(5,10,15,20‐tetraphenylporphinato‐κ4N,N′,N′′,N′′′)iron(III) hexafluoroantimonate(V) dichloromethane disolvate, [Fe(C44H28N4)(C5H5NO)][SbF6]·2CH2Cl2, was isolated and its crystal structure determined in the space group P. The porphyrin core is moderately saddled and the Fe—O—N bond angle is 122.08 (13)°. The average Fe—N bond length is 2.03 Å and the Fe—ONC5H5 bond length is 1.9500 (14) Å. This complex provides a rare example of a five‐coordinate iron(III) porphyrin complex that is coordinated to a neutral organic ligand through an O‐monodentate binding mode. 相似文献
19.
Ana Gabriela Arvízu-Santamaría Yedith Soberanes Enrique F. Velázquez Hisila Santacruz Motomichi Inoue 《Supramolecular chemistry》2017,29(9):658-667
The 1H NMR signals of the titled neurotransmitters undergo up-field shift accompanied by line-broadening in NMR titration with the DTPA-based cyclophane at pD 7.3; the cyclophane consists of a 4,4′-bis(1,1′-biphenyl-4,4′-dihydroxy)dianiline unit cyclised by a DTPA (diethylenetriaminepentaacetate) group through two amide linkages. Changes in chemical shifts of dopamine indicate the formation of a 1:1 complex with the formation constant K1 400 M?1; the complex of serotonin is likely to form a 2:1 host?guest complex with β2 ≈ 105 M?2; melatonin does not form a complex with definite stoichiometry. The primary binding forces in the dopamine and serotonin complexes are electrostatic interaction between cationic neurotransmitter and anionic cyclophane molecules, and the resulting ionic pairs are stabilised by encapsulation. The electrostatic interaction is weakened by electrolytes; in 0.1 M Trizma buffer, dopamine does not yield a definite complex, and serotonin forms a 1:1 complex with K1 80 M?1. Extreme line-broadening of neurotransmitter signals suggests that the molecular motion of the guest molecule is slowed in the complex by interactions with the receptor molecule whose internal molecular motion is quenched partially. The high rigidity of the cyclophane enhances intermolecular interaction in the hydrophobic regions to prolong the lifetime of the complex. 相似文献
20.
《Journal of Coordination Chemistry》2012,65(1-4):299-304
Abstract A series of highly lipophilic bis-pocket porphyrins, 5,10,15,20-tetrakis(3′, 5′-di-t-butylphenyl)porphyrin with five metals (copper(II), nickel(II), zinc(II), cobalt(II), and iron(III)), have been prepared and characterized on the basis of electronic, infrared and 1H NMR spectra. Although electronic spectra of these porphyrins are substantially the same as their prototype tetraphenylporphyrin complexes of the respective metals, their solubility in common organic solvents such as chloroform, benzene, and hexane is dramatically enhanced. 相似文献