Potentiometric and Spectrophotometric Studies of Copper(II) Complexes of Some Ligands in Aqueous and Nonaqueous Solution

Stoichiometry and equilibrium study of copper‐ligands including mercaptobenzoxazole (MBO), 4‐propyl 2‐thiouracyl (PTU), methyl‐2‐pyridylketone oxime (MPKO), phenyl‐2‐pyridylketone oxime (PPKO), 4,6‐dihydroxy‐2‐mercaptopyrimidine (DHMP), N,N′‐phenylene bis(salicylaldimine) (PBS) and 1,2‐bis(2‐hydroxyphenyl)naphtaldiimine (BHNPDI) were conducted in aqueous and nonaqueous solution by potentiometry and spectrophotometry. Stability constants of the complexes are determined at 25 ± 1 °C and 0.1 or 0.05 M ionic strength in water or acetonitrile solvents. Oximes ligand protonation constants and copper‐ligands complexes' stability and hydrolysis constants were calculated using the BEST program in aqueous solution. The stability constants of copper‐ligands complexes were calculated using the KINFIT program in acetonitrile solution. The results of these two methods are made self‐consistent, then rationalized assuming an equilibrium model including the species, ML, MLH, MLOH and ML₂ (where the charges of the species have been ignored for the sake of simplicity) (L = MBO, PTU, MPKO, PPKO, DHMP, BHNPDI and PBS).     

Separation and spectroscopic characterization of new metal chelates of 8-arylazo-6-formyl-7-hydroxy-5-methoxy-2-methyl chromones

Transition metal chelates of the title compounds have been prepared and characterized by elemental analyses, i.r., 1H-n.m.r., electronic spectra, thermogravimetric analysis, conductometric and magnetic measurements. Chelates of general formulae MLjX · nH2O for 1:1 (M:L), where X=OH– or Cl–, j=1 or 2, n=1– 4 and M=VO2+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+ ions or ML2 for 1:2 (M:L) Ni-(1a), ML2·2H2O where M=Co2+, Ni2+ and Cu2+ or M2LjX·nH2O for 2:1 (M:L) Cr3+, Fe2+, Ni2+ and Cu2+, L=Ligand, have been prepared. I.r. and 1H-n.m.r. spectra indicate that the aldehydic group in position six and the hydroxylic group in position seven are involved in chelation in the 1:1 and 1:2 (M:L) chelates, whereas for 2:1 (M:L) chelates with (1c), the interaction of the metal ion takes place through CHO, OH, CO2H and NN groups. Tetrahedral, octahedral and square planar geometries are proposed for the chelates based on their electronic spectra and magnetic moments.     

Interaction of alkyltin(IV) compounds with ligands of interest in the speciation of natural fluids: carboxylate and hydroxycarboxylate complexes of monomethyltin(IV) trichloride

The formation and stability of some carboxylate and hydroxycarboxylate (acetate, 1,2,3-propanetricarboxylate, 1,2,3,4-butanetetracarboxylate, malate and citrate) complexes of monomethyltin trichloride was studied potentiometrically at 25 degrees C and at different ionic strengths in NaNO3 aqueous solution. The following quite stable species are formed in the different systems (M = CH3Sn3+): ML(OH)+, ML2(OH)0, ML(OH)2(0) and M2L(OH)5(0) for acetate; MLH+, ML0, ML(OH)- and ML(OH)2(2-) for propanetricarboxylate; MLH2+, MLH0, ML-, ML(OH)2- and ML(OH)2(3-) for butanetetracarboxylate; ML(OH)0, ML(OH)2- and ML(OH)3(2-) for malate; ML0, ML(OH)-, ML(OH)2(2-) and ML(OH)3(3-) for citrate. Hydroxycarboxylate complexes are significantly stronger than simple carboxylate ones and this is likely to be due to the interaction of the -OH group in citrate and malate with monomethyltin(IV), whose strength was also quantified. It was found that the stability of these complexes can be roughly expressed by the simple relationship log K = a zeta, where zeta is the product of the charges of reactants and log K is the equilibrium constant. For simple carboxylic ligands we have a = 1.8 +/- 0.4 and, for hydroxycarboxylic ligands, a = 3.7 +/- 0.9. Other useful empirical relationships are reported. Moreover, hydroxycarboxylic complexes also play a prominent role in the speciation of monomethyltin(IV) under the pH conditions of interest for natural fluids.     

Di-2-pyridyl ketone oxime in copper chemistry: di-, tri-, penta- and hexanuclear complexes

The use of di-2-pyridyl ketone oxime (Hpko)/X- "blends" (X- = OH-, Cl-, ClO4-) in copper chemistry has yielded neutral binuclear and cationic trinuclear, pentanuclear or hexanuclear complexes. Various synthetic procedures have led to the synthesis of compounds [Cu5(pko)7].[ClO4]3.2CH3OH.2H2O (1), [Cu3(pko)3(OH)(Cl)]2[Ph4B]2.4DMF.2H2O (2), [Cu2(pko)4] (3), {[Cu6(pko)6ClO4(CH3CN)6][Cu6(pko)6(ClO4)3(CH3CN)4]}.8ClO4.14CH3CN.H2O (4). The structures of the complexes have been determined by single-crystal X-ray crystallography.     

On the formation of iron(III) hydroxo acetate complexes

The formation of hydroxo acetate complexes of iron (III) ion has been studied at 25 degrees C in 3 M (Na)ClO4 ionic medium by measuring with a glass electrode the hydrogen ion concentration in Fe(ClO4)3-HClO4-NaAc mixtures (Ac = acetate ion). The acetate/metal ratio ranged from 0 to 6, the metal concentration varied from 0.005 to 0.06 M, whereas [H+] was stepwise decreased from 0.1 M to initial precipitation of hydroxo-acetates. This occurred, depending on the acetate/metal ratio, in the -log[H+] range 1.85-2.7. The potentiometric data are consistent with the presence of Fe3(OH)3Ac3(3+), Fe2(OH)2(4+), Fe3(OH)4(5+), Fe3(OH)5(4+) and, as minor species, of Fe3(OH)2Ac6+, FeAc2+, FeAc2+, FeOH2+ and Fe(OH)2+. Previously published EMF measurements with redox and glass half-cells were recalculated to refine the stability constants of FeAc2+, FeAc2+ and Fe3(OH)2Ac6+. Formation constants *beta pqr for pFe(3+)+(q-r)H2O + rHAc reversible Fep(OH)(q-r)(Ac)r3p-q + qH+ (in parenthesis the infinite dilution value): log*beta 111 = -1.85 +/- 0.02 (-0.67 +/- 0.15), log*beta 122 = -3.43 +/- 0.02 (-1.45 +/- 0.15); log*beta 363 = -5.66 +/- 0.03 (-2.85 +/- 0.40), log*beta 386 = -8.016 +/- 0.006 (-4.06 +/- 0.15), log*beta 220 = -2.88 +/- 0.02 (-2.84 +/- 0.05), log*beta 340 = -6.14 +/- 0.18 (-6.9 +/- 0.4), log*beta 350 = -8.44 +/- 0.09 (-7.65 +/- 0.15).     

Polarographic investigation of syn-phenyl 2-pyridyl ketone oxime

The polarographic reduction of syn-phenyl 2-pyridyl ketone oxime to -(2-pyridyl)benzylamine over the pH range 0.78–12.88 is reported. Two waves are observed, both of which are pH-dependent. The complex electrode reaction is discussed and a mechanism advanced to describe the reduction of the oxime group over the pH range considered.     

The chemistry of iron in biosystems-V Study of complex formation between iron(III) and tartaric acid in alkaline aqueous solutions

Complex formation between Fe(III) and tartaric acid (H(2)L) has been studied in O.5M NaNO(3) medium at 25 degrees by potentiometry at pH 4.5-11. The following complex species and corresponding values of the stability constants (charges omitted) are proposed: 2Fe + 2L + 5H(2)O --> Fe(2)(OH)(5)L(2) + 5H(+); log* beta(-522) = 4.95 Fe + L + 3H(2)O --> Fe(OH)(3)L + 3H(+); log* beta(-311) = -1.55 Fe + L + 5H(2)O --> Fe(OH)(5)L + 5H(+); log* beta(-511) = -21.2 These results are in good agreement with those reported for this system in acid. The results may be presented as the degeneration of the "core + link" mechanism observed in the acidic zone. Structures are suggested for the complex species formed.     

Dioxouranium(VI)-carboxylate complexes. Speciation of UO2(2+)-1,2,3-propanetricarboxylate system in NaCl(aq) at different ionic strengths and at t=25 degrees C

The formation constants of dioxouranium(VI)-1,2,3-propanetricarboxylate [tricarballylate (3-), TCA] complexes were determined in NaCl aqueous solutions at 0 < or = I/mol L(-1) < or = 1.0 and t=25 degrees C, by potentiometry, ISE-[H+] glass electrode. The speciation model obtained at each ionic strength includes the following species: ML-, MLH0, ML2(4-) and ML2H3- (M = UO2(2+) and L = TCA). The dependence on ionic strength of protonation constants of 1,2,3-propanetricarboxylate and of the metal-ligand complexes was modeled by the SIT (Specific ion Interaction Theory) approach and by the Pitzer equations. The formation constants at infinite dilution are [for the generic equilibrium p UO22+ + q (L3-) + r H+ = (UO2(2+))p(L)qHr(2p-3q+r); betapqr]: log beta110 = 6.222 +/- 0.030, log beta111 = 11.251 +/- 0.009, log beta121 = 7.75 +/- 0.02, log beta121 = 14.33 +/- 0.06. The sequestering ability of 1,2,3-propanetricarboxylate towards UO2(2+) was quantified by using a sigmoid Boltzman type equation.     

Route to metallacrowns: the mechanism of formation of a dinuclear iron(III)-salicylhydroxamate complex

The equilibria and the kinetics of the binding of Iron(III) to salicylhydroxamic (SHA) and benzohydroxamic (BHA) acids have been investigated in aqueous solution (I = 1 M (HClO(4)/NaClO(4)), T = 298 K) using spectrophotometric and stopped-flow methods. Whereas Iron(III) forms a 1:1 complex (ML) with BHA, it forms both ML and M(2)L complexes with SHA. The presence of M(2)L in aqueous medium is corroborated by FTIR measurements. The reactive form of Iron(III) is the hydrolyzed species FeOH(2+), which binds to the O,O site in ML and to the O,O and O(P),N (P = phenolate) sites in M(2)L, inducing full deprotonation of the latter. The reaction pathway is discussed in terms of a multistep mechanistic scheme in which the metal-ligand interaction is coupled to hydrolysis and self-aggregation steps of Iron(III). The observation and characterization of M(2)L as a stable species is important because it contains the -Fe-O-N-Fe- sequence, which constitutes the repetitive motif of the SHA-based metallacrown ring and provides the rationale for 12-MC-4 metallacrowns. In the framework of this study, the kinetics of the Iron(III) dimerization and trimerization have also been investigated using the stopped-flow method to perform dilution jumps. The reaction scheme put forward involves two parallel steps (FeOH(2+) + FeOH(2+) and Fe(3+) + FeOH(2+)) that lead to formation of the Fe(2)(OH)(2)(4+) dimer and a slower step (FeOH(2+) + Fe(2)(OH)(2)(4+)) to form the trimer species. The kinetics of the last step have been investigated here for the first time, and the results deduced indicate that, of the two possible trimer structures reported in the literature, Fe(3)(OH)(3)(6+) and Fe(3)(OH)(4)(5+), the latter prevails by far.     

The first pyridyl N,N′-coordinated di-2-pyridyl ketone oxime,fac-tricarbonylchloro(di-2-pyridyl ketone oxime)rhenium(I) dimethyl sulfoxide solvate

The structure of the first metal compound of pyridyl N,N′-coordinated di-2-pyridyl ketone oxime (dpk-o), fac-tri­carbonyl­chloro­(di-2-pyridyl-κN ketone oxime)­rhenium(I) di­methyl sulfoxide solvate, [ReCl(C₁₁H₉N₂O)(CO)₃]·C₂H₆OS, (I), is reported. The coordinated atoms (two N atoms from the pyridyl rings, three C atoms from the carbonyl groups and one Cl atom) are in a distorted octahedral arrangement, with the major distortion being due to the constraints associated with the binding of dpk-o. The packing of the mol­ecules shows antiparallel tapes of (I), with a network of classical (O⃛H—O) and non-classical (O⃛H—C) hydrogen bonds between the di­methyl sulfoxide solvate molecule and the complexed metal moiety.     

A macrocyclic ligand able to bind gallium(III) by preorganized pendant arms; coordination and kinetic studies

The equilibria and kinetics of the binding of gallium(III) to 4-(N),10-(N)-bis[2-(3-hydroxo-2-oxo-2-H-pyridine-1-y1)acetamido]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane (L) were investigated in acidic medium at ionic strength 1 M (NaClO4). Spectrophotometric titrations in the UV region revealed that L is able to bind Ga3+ also at high H+ concentration. The kinetic (stopped-flow) experiments are interpreted on the basis of three parallel reaction paths (i) M3+ + H2L2+ = M(H2L)5+ where M(H2L)5+ is in a steady state, (ii) M(OH)2+ + H2L2+ = M(HL)4+ + H2O and (iii) M(OH)2+ + HL+ = ML3+ + H2O. The first-order rate constants for conversion of the outer-sphere into the inner-sphere complexes are similar to those of the Ga(III)/tropolone system which is known to react according to the dissociative Id mechanism and to the relevant rate constants for water exchange at the metal ion. The effects of pH on the UV-Vis absorption, fluorescence emission properties and NMR spectral features on the Ga(III)/L system were also investigated. Spectrophotometric titrations in the UV region reveal that, in acid medium the prevailing species is M(HL)4+ whereas the chelate ML3+ prevails for [H+] < 0.01 M. The results indicate metal coordination at the oxygen atoms of the 3-hydroxo-2-oxopyridine residues.     

Highly selective and sensitized spectrophotometric determination of iron (III) following potentiometric study

A simple, selective and sensitized spectrophotometric method for determination of trace amounts of Fe3+ ion in tap and waste water solutions has been described. The spectrophotometric determination of Fe3+ ion using Ferron in the presence of N,N-Dodecytrimethylammonium bromide (DTAB) has been carried out. The Beer's law is obeyed over the concentration range of 0.05-2.6 microg mL(-1) of Fe3+ ion with the relative standard deviation (RSD %) <0.2% and the molar absorptivity of complexes in pH 3.5 is 3.8 x 10(3) L mol(-1) cm(-1). Potentiometric pH titration has been used for prediction of protonation constants of ferron, and evaluating its stoichiometry and respective stability constant with Fe3+ ion. As it is obvious the most likely species of ferron alone and its complexes are LH (log = 7.64), LH2 (logK = 10.52), LH3 (logK = 11.74) and ML2 (logbeta = 23.68), ML3 (logbeta = 23.68), ML3H (logbeta = 23.68), ML3H2 (logbta = 23.68) and ML(OH)2 (logbeta = 23.68) respectively.     

Two chiral metal clusters derived from nucleophilic addition of L-proline to di-2-pyridyl ketone

In the presence of cobalt (nickel) acetate, a chiral tetrahedral intermediate ligand of (S)-(C5NH4)2C(OH)(C4NH7CO2H) was first formed from the nucleophilic addition of l-proline as a secondary amine to ketone (di-2-pyridyl ketone). Based on the ligand synthesized in situ, two chiral tetranuclear isomorphous complexes 1 and 2 with the formula {Na[M4L3(OAc)3](ClO4)(1.5)(H2O)(1.5)}(ClO4)(OH)(0.5).3H2O (M = Co, Ni) have been achieved. The Co4 cluster (1) behaves as a ferromagnet.     

Hydroxo sulfate complexes of iron (III) in solution

The ternary Fe (III)-OH(-)-SO4(2-) complexes have been investigated at 25 degrees C in 3 M NaClO4 by potentiometric titration with glass electrode. The metal and sulfate concentrations ranged from 2.5 x 10(-3) to 0.03 M and from 5.10(-3) to 0.060 M, respectively. [H+] was decreased from 0.05 M to incipient precipitation of basic sulfate which occured at log[H+] between -2.3 and -2.5 depending on the concentration of the metal. For the interpretation of the data stability constants of HSO4(-), of binary hydroxo complexes (FeOH2+, Fe(OH)2+, Fe2(OH)2(4+), Fe3(OH)4(5+), Fe3(OH)5(4+)) and of sulfate complexes (FeSO4+, FeHSO4(2+), Fe(SO4)2-) were assumed from independent sources. The data are consistent with the presence of FeOHSO4, log beta 1-11 = -0.49 +/- 0.03. Equilibrium constants are defined as beta pqr for pFe3+ +qH+ +rSO4(2-) [symbol: see text] FepHq(SO4)r3p+q-2r. No substantial better fit could be found by adding a second mixed complex. Only a slightly smaller agreement factor resulted introducing as minor ternary complex Fe3(OH)6(SO4)3(3-) with log beta 3-63 = -5.8 +/- 0.5. Its evidence, however, cannot be considered conclusive.     

Transition metal complexes of 2-formylthiophene S-methyldithiocarbazate

Transition metal complexes of 2-formylthiophene S-methyldithiocarbazate have been synthesized and characterized. Analytical data show that the complexes are of the type [ML3], where M = Fe3+, and [ML2], where M=Ni2+, Cu2+ or Zn2+. The i.r. spectra suggest coordination to the metal through the azomethine nitrogen and thiolate sulfur. The magnetic and spectroscopic data indicate a square planar geometry for the complexes, except for the Fe3+ complex, which is octahedral. The e.s.r. parameters are indicative of a square planar N2S2 system for the Cu2+ complex.     

P204萃取色谱法对Co~(2+)的分离研究

对萃取色谱法分离钴与铜、镉、锰、锌、铁等金属离子进行了研究。用含Ｐ２０４萃取剂的萃淋树脂,经过ｐＨ４．０的ＮａＡｃ溶液转型后,只需用ｐＨ２．５的氯乙酸－氯乙酸钠缓冲溶液作为流动相淋洗,就可将钴与其它金属离子分离。方法分离效果好,操作简单方便,是分离分析钴的一种新方法。     

Potentiometric determination of aminal stability constants

Potentiometric titration was used to determine the logarithms of the stepwise equilibrium constants for the species formed between morpholine and formaldehyde in aqueous solution, ionic strength 0.5 and 2.5M (KCl) at 25 degrees C. The instrumental and computational techniques developed for metal-ligand stability constant determination were applied. Formaldehyde is equivalent to the metal-ion and is represented by M while neutral morpholine is equivalent to the ligand and is represented by L. The stability constants of the following equilibria were determined by non-linear regression (figures in parentheses are at ionic strength 2.5 M KCl): M + L left arrow over right arrow ML (hemi-aminal) logK(1) = 2.90 +/- 0.02 (2.980 +/- 0.004); ML + L left arrow over right arrow ML(2) (bis-aminal); log K(2) = 1.3 +/- 0.2 (1.41 +/- 0.07); MLH left arrow over right arrow ML + H(+) (protonated hemi-aminal) pK(a) = 5.87 +/- 0.01 (6.411 +/- 0.005); ML(2)H left arrow over right arrow ML(2) + H(+) (protonated bis-aminal) pK(a) = (7.6 +/- 0.2). the pK(a) of the protonated bis-aminal could only be determined at the higher ionic strength. The results are in good agreement with reported values determined using the classic formol titration. The automated titration system acquired the full time course of the pH change upon each titrant addition allowing a kinetic analysis to be performed as well as an equilibrium analysis. The forward and reverse rate constants for M + L left arrow over right arrow ML were 0.77M(-1) sec(-1) and 8.1 x 10(-4) sec(-1). respectively.     

Aqueous solution speciation of Fe(III) complexes with dihydroxamate siderophores alcaligin and rhodotorulic acid and synthetic analogues using electrospray ionization mass spectrometry

Aqueous solutions of Fe3+ complexes of cyclic (alcaligin) and linear (rhodotorulic acid) dihydroxamate siderophores and synthetic linear eight-carbon-chain and two-carbon-chain dihydroxamic acids ([CH3N(OH)C=O)]2(CH2)n; H2Ln; n = 2 and 8) were investigated by electrospray ionization mass spectrometry (ESI-MS). Information was obtained relevant to the structure and the speciation of various Fe(III)-dihydroxamate complexes present in aqueous solution by (1) comparing different ionization techniques (ESI and FAB), (2) altering the experimental parameters (Fe3+/ligand ratio, pH, cone voltage), (3) using high-stability hexacoordinated Fe(III) siderophore complex mixtures (ferrioxamine B/ferrioxamine E) as a calibrant to quantify intrinsically neutral (H+ clustered or protonated) and intrinsically charged complexes, and (4) using mixed-metal complexes containing Fe3+, Ga3+, and Al3+. These results illustrate that for all dihydroxamic acid ligands investigated multiple tris- and bis-chelated mono- and di-Fe(III) species are present in relative concentrations that depend on the pH and Fe/L ratio.     

Mononuclear versus dinuclear complex formation in nickel(II) sulfate/phenyl(2-pyridyl)ketone oxime chemistry depending on the ligand to metal reaction ratio: synthetic, spectral and structural studies

The reactions of phenyl(2-pyridyl)ketone oxime (py)C(ph)NOH, with nickel(II) sulfate hexahydrate under reflux, in the absence of an external base, have been investigated. The reaction of NiSO(4).6H(2)O with two equivalents of (py)C(ph)NOH in H(2)O/MeOH leads to the dinuclear complex [Ni(2)(SO(4))(2){(py)C(ph)NOH}(4)] (1), while an excess of the organic ligand affords the 1:3 cationic complex [Ni{(py)C(ph)NOH}(3)](SO(4)) (2). Compound 1 is transformed into 2 by a reaction with an excess of ligand in refluxing H(2)O/MeOH. Reactions of 1 and 2 with a limited amount of LiOH give the known cluster [Ni(6)(SO(4))(4)(OH){(py)C(ph)NO}(3){(py)C(ph)NOH}(3)(H(2)O)(3)]. The structures of 1 and 2 have been determined by single-crystal X-ray crystallography. In both complexes the organic ligand chelates through its 2-pyridyl and oxime nitrogen atoms. The metal centers of 1 are bridged by two eta(1):eta(1):mu sulfato ligands; each metal ion has the cis-cis-trans deposition of the coordinated sulfato oxygen, pyridyl nitrogen and oxime nitrogen atoms, respectively. The cation of 2 is the fac isomer considering the positions of the coordinated pyridyl and oxime nitrogen atoms. The crystal structures of both complexes are stabilized by hydrogen bonds. Compounds 1 and 2 join a small family of structurally characterized metal complexes containing the neutral or anionic forms of phenyl(2-pyridyl)ketone oxime as ligands. The IR spectra of the two complexes are discussed in terms of the nature of bonding and their structures. From the vibrational spectroscopy viewpoint, the SO(4)(2-) groups in 1 and 2 appear to have lower symmetries compared with those deduced from X-ray crystallography; this is attributed to the participation of sulfates in hydrogen bonding interactions.     

硫酸铵-溴化钾铵-正丙醇体系萃取分离和富集锗的研究

研究了硫酸铵-溴化钾铵-正丙醇体系萃取分离和富集锗的行为及与一些金属离子分离的条件.硫酸铵能使正丙醇的水溶液分成两相,在分相过程中,Ge4+与KBr生成(GeBr62-),并与质子化正丙醇(C3H7OH2+)形成缔合物[GeBr62-][C3H7OH2+]2,此缔合物能被正丙醇相完全萃取.当正丙醇、KBr和硫酸铵的浓度分别为30％(V/V)、7.0×10-3mol/L、0.20g/mL时,(GeBr62-)的萃取率达到97.7％以上,而Ni2,Pb2,Cr3+,Co2,Fe3+,Al3+,Mg2+,Ag+,Bi3+,CH2,W(Ⅵ)和V(Ⅴ)基本不被萃取,实现了Ge4+与上述金属离子的分离.