Bis[1,1'-N,N'-(2-picolyl)aminomethyl]ferrocene as a redox sensor for transition metal ions

The compound bis[1,1'-N,N'-(2-picolyl)aminomethyl]ferrocene, L(1), was synthesized. The protonation constants of this ligand and the stability constants of its complexes with Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Pb(2+) were determined in aqueous solution by potentiometric methods at 25 degrees C and at ionic strength 0.10 mol dm(-3) in KNO(3). The compound L(1) forms only 1:1 (M:L) complexes with Pb(2+) and Cd(2+) while with Ni(2+) and Cu(2+) species of 2 [ratio] 1 ratio were also found. The complexing behaviour of L(1) is regulated by the constraint imposed by the ferrocene in its backbone, leading to lower values of stability constants for complexes of the divalent first row transition metals when compared with related ligands. However, the differences in stability are smaller for the larger metal ions. The structure of the copper complex with L(1) was determined by single-crystal X-ray diffraction and shows that a species of 2:2 ratio is formed. The two copper centres display distorted octahedral geometries and are linked through the two L(1) bridges at a long distance of 8.781(10) Angstrom. The electrochemical behaviour of L(1) was studied in the presence of Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Pb(2+), showing that upon complexation the ferrocene-ferrocenium half-wave potential shifts anodically in relation to that of the free ligand. The maximum electrochemical shift ([capital Delta]E(1/2)) of 268 mV was found in the presence of Pb(2+), followed by Cu(2+)(218 mV), Ni(2+)(152 mV), Zn(2+)(111 mV) and Cd(2+)(110 mV). Moreover, L(1) is able to electrochemically and selectively sense Cu(2+) in the presence of a large excess of the other transition metal cations studied.     

Structural and electronic characterization of the complexes obtained by the interaction between bare and hydrated first-row transition-metal ions (Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+)) and glycine

The complexes formed by the simplest amino acid, glycine, with different bare and hydrated metal ions (Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+)) were studied in the gas phase and in solvent in order to give better insight into the field of the metal ion-biological ligand interactions. The effects of the size and charge of each cation on the organization of the surrounding water molecules were analyzed. Results in the gas phase showed that the zwitterion of glycine is the form present in the most stable complexes of all ions and that it usually gives rise to an eta(2)O,O coordination type. After the addition of solvation sphere, a resulting octahedral arrangement was found around Ni(2+), Co(2+), and Fe(2+), ions in their high-spin states, whereas the bipyramidal-trigonal (Mn(2+) and Zn(2+)) or square-pyramidal (Cu(2+)) geometries were observed for the other metal species, according to glycine behaves as bi- or monodentate ligand. Despite the fact that the zwitterionic structure is in the ground conformation in solution, its complexes in water are less stable than those obtained from the canonical form. Binding energy values decrease in the order Cu(2+) > Ni(2+) > Zn(2+) approximately Co(2+) > Fe(2+) > Mn(2+) and Cu(2+) > Ni(2+) > Mn(2+) approximately Zn(2+) > Fe(2+) > Co(2+) for M(2+)-Gly and Gly-M(2+) (H(2)O)(n) complexes, respectively. The nature of the metal ion-ligand bonds was examined by using natural bond order and charge decomposition analyses.     

Synthesis and ion-exchange properties of thermally stable stannic selenite

Stannic selenites have been synthesized under a variety of conditions. The most stable sample is prepared by mixing 0-0.5M solutions of stannic chloride and sodium selenite in the ratio of 1:1 at pH 1. It is a bifunctional amorphous material. A tentative structure has been proposed on the basis of chemical composition, pH titrations, infrared and thermogravimetric analyses. Its ion-exchange capacity is 0.75 and 0.73 meq g after drying at 50 degrees and 500 degrees respectively. Its analytical importance has been established by the following quantitative separations: Cu(2+) from Ni(2+), Co(2+), Fe(3+), Ga(3+) and In(3+), Fe(3+) from Pb(2+) and Sc(3+), and Sc(3+) from VO(2+).     

Diamidodipyrrins: versatile bipyrrolic ligands with multiple metal binding modes

A straightforward, facile synthesis of diamidodipyrromethenes (diamidodipyrrins, DADP (R,R')) is presented. These tetradentate ligands readily form complexes with metal ions such as Ni (2+) and Cu (2+) and can adopt different binding modes with these metals. One version of the ligand (DADP (Ph, iPr )) has been structurally characterized in its "free base" form, as a HBr salt, and as the Ni (2+) and Cu (2+) complexes. A symmetric NNOO donor set is found for the Cu (2+) complex in the solid state, involving two carbonyl oxygen atoms and two dipyrrin nitrogen atoms, and this coordination mode has been confirmed in solution by electron paramagnetic resonance. An asymmetric NNNO binding mode found for the Ni (2+) complex in the solid state persists in solution as revealed by (1)H NMR. The HBr salt form of the ligand shows an intriguing hydrogen-bonded head-to-head dimer arrangement. Experiments show that Cu (2+), but not Ni (2+), can mediate the rapid oxidation of the diamidodipyrromethane precursors to the diamidodipyrromethene ligands in the presence of dioxygen. The work here shows that diamidodipyrrins are a versatile new class of ligands in the area of nonporphyrinic pyrrole-based compounds that merit further investigation.     

Study of metal ion labeling of the conformational and charge states of lysozyme by ion mobility mass spectrometry

The efficiency of Zn(2+), Cu(2+), Ni(2+), Co(2+), Fe(2+) or Mn(2+) labeling of the conformational and charge states of lysozyme was studied in H(2)O solvent at pH 2.5-6.8. Labeling of lysozyme was conducted with 50 M, 100 M and 500 M excess of the metal ion, resulting in the number of metal ions attached to lysozyme increasing two-fold over this range. At pH 6.2-6.8, Zn(2+), Cu(2+), Ni(2+), Co(2+) and Mn(2+) labeled the highly folded 7+ conformer and the 8+ and 9+ partially unfolded conformers of lysozyme with the same number of metal ion tags, with only Fe(2+) exhibiting no labeling. Lysozyme conserved its charge after metal ion labeling which shows at each charge state the divalent metal ion is replacing two protons. As the pH is lowered to 4.7-5.0 and 2.5-2.9, the labeling of lysozyme by Zn(2+), Cu(2+), Ni(2+), Co(2+) or Mn(2+) decreased in efficiency due to increased competition from protons for the aspartate and glutamate binding sites. The metal ions preferentially labeled the highly folded 7+ and partially unfolded 8+ conformers, but labeling decreased as the charge of lysozyme increased. In contrast to the other metal ions, Fe(2+) exhibited labeling of lysozyme only at the lowest pH of 2.8. At higher pH, the oxidation of Fe(2+) and formation of hydroxy-bridged complexes probably make the Fe(2+) unreactive towards lysozyme.     

Application of xylenol orange to the separation of metal ions on amberlyst A-26 macroreticular anion-exchange resin

The possibility of using a sulphonated aromatic organic complexing agent-Xylenol Orange-for separation of metal ions on the macroreticular anion-exchanger Amberlyst A-26 has been investigated. The dependence of retention on pH was determined by the batch method for Al(3+), Cr(3+), Mn(3+), Fe(3+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Ga(3+), Rh(3+) Cd(2+), In(3+), Ir(3+), and Pb(2+). The selectivity differences make possible the separation of some of these metal ions. The following mixtures, of practical importance, have been separated: Al(3+)-In(3+), Ga(3+)-In(3+) Zn(2+)-In(3+), Cu(2+)-Mn(2+), in various ratios. The method has been applied to analysis of Ga-In alloy.     

A naphthalene-based Al3+ selective fluorescent sensor for living cell imaging

An efficient fluorescent Al(3+) receptor, N-(2-hydroxy-1-naphthalene)-N'-(2-(2-hydroxy-1-naphthalene)amino-ethyl)-ethane-1,2-diamine (L) has been synthesized by the condensation reaction between 2-hydroxy naphthaldehyde and diethylenetriamine. High selectivity and affinity of L towards Al(3+) in ethanol (EtOH) as well as in HEPES buffer at pH 7.4, makes it suitable to detect intracellular Al(3+) with fluorescence microscopy. Metal ions, viz. Li(+), Na(+), K(+), Mg(2+), Ca(2+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Ag(+), Cd(2+), Hg(2+) and Pb(2+) do not interfere. The lowest detection limit for Al(3+) is 3.0 × 10(-7) M and 1.0 × 10(-7) M in EtOH and HEPES buffer respectively.     

Chemometric analysis of voltammetric data on metal ion binding by selenocystine

The behavior of selenocystine (SeCyst) alone or in the presence of various metal ions (Bi(3+), Cd(2+), Co(2+), Cu(2+), Cr(3+), Ni(2+), Pb(2+), and Zn(2+)) was studied using differential pulse voltammetry (DPV) over a wide pH range. Voltammetric data matrices were analyzed using chemometric tools recently developed for nonlinear data: pHfit and Gaussian Peak Adjustment (GPA). Under the experimental conditions tested, no evidence was found for the formation of metal complexes with Bi(3+), Cu(2+), Cr(3+), and Pb(2+). In contrast, SeCyst formed electroinactive complexes with Co(2+) and Ni(2+) and kinetically inert but electroactive complexes with Cd(2+) and Zn(2+). Titrations with Cd(2+), Co(2+), Ni(2+), and Zn(2+) produced data that were reasonably consistent with the formation of stable 1:1 M(SeCyst) complexes.     

A novel fluorescent sensor for metal cations and protons based of bis-1,8-naphthalimide

A newly synthesized bis-1,8-naphthalimide aimed to increase its fluorescence intensity in the presence of protons or metal cations has been investigated. Its spectral photophysical characteristics in acetonitrile and chloroform solutions are described. The influence of metal cations (Zn(2+), Ni(2+), Ce(3+), Co(2+), Cu(2+) and Ag(+)) and protons on the fluorescence intensity has been investigate with regard to obtain fluorescence sensors for this ions in the environment.     

Catalytic activity for decomposition of hydrogen peroxide by metal complexes of water-soluble thiacalix[4]arenetetrasulfonate on the modified anion-exchangers

The catalytic activity for the decomposition of hydrogen peroxide by anion-exchangers modified with metal complexes of thiacalix[4]arenetetrasulfonate (Me(n+)-TCAS[4], Me(n+)=Mn(3+), Mn(2+), Fe(3+), Co(3+), Co(2+), Cu(2+), Zn(2+) and Ni(2+)) was investigated. As a reference, calix[4]arenetetrasulfonate, calix[6]arenehexasulfonate and calix[8]areneoctasulfonate were also examined. Mn(3+)- and Fe(3+)-TCAS[4] on the modified anion-exchangers showed high catalytic activity in alkaline buffer solutions among metal complexes tested. Mn(3+)- and Fe(3+)-TCAS[4] on the modified anion-exchangers exhibited high and constant levels of catalytic activity even after having been used 5 times, and showed catalytic activity in the presence of an excess of H(2)O(2) over Mn(3+)- and Fe(3+)-TCAS[4] on the modified anion-exchangers. Only Mn(3+)-TCAS[4] on the modified anion-exchangers exhibited high catalytic activity at around a neutral pH.     

Dansyl-anthracene dyads for ratiometric fluorescence recognition of Cu2+

Dansyl-anthracene dyads 1 and 2 in CH(3)CN-H(2)O (7:3) selectively recognize Cu(2+) ions amongst alkali, alkaline earth and other heavy metal ions using both absorbance and fluorescence spectroscopy. In absorbance, the addition of Cu(2+) to the solution of dyads 1 or 2 results in appearance of broad absorption band from 200 nm to 725 nm for dyad 1 and from 200 nm to 520 nm for dyad 2. This is associated with color change from colorless to blue (for 1) and fluorescent green (for 2). This bathochromic shift of the spectrum could be assigned to internal charge transfer from sulfonamide nitrogen to anthracene moiety. In fluorescence, under similar conditions dyads 1 and 2 on addition of Cu(2+) selectively quench fluorescence due to dansyl moiety between 520-570 nm (for 1)/555-650 nm (for 2) with simultaneous fluorescence enhancement at 470 nm and 505 nm for dyads 1 and 2, respectively. Hence these dyads provide opportunity for ratiometric analysis of 1-50 μM Cu(2+). The other metal ions viz. Fe(3+), Co(2+), Ni(2+), Cd(2+), Zn(2+), Hg(2+), Ag(+), Pb(2+), Li(+), Na(+), K(+), Mg(2+), Ca(2+), Ba(2+) do not interfere in the estimation of Cu(2+) except Cr(3+) in case of dyad 1. The coordination of dimethylamino group of dansyl unit with Cu(2+) causes quenching of fluorescence due to dansyl moiety between 520-600 nm and also restricts the photoinduced electron transfer from dimethylamino to anthracene moiety to release fluorescence between 450-510 nm. This simultaneous quenching and release of fluorescence respectively due to dansyl and anthracene moieties emulates into Cu(2+) induced ratiometric change.     

Amphiphilic Schiff base organogels: metal-ion-mediated chiral twists and chiral recognition

New amphiphilic gelators that contained both Schiff base and L-glutamide moieties, abbreviated as o-SLG and p-SLG, were synthesized and their self-assembly in various organic solvents in the absence and presence of metal ions was investigated. Gelation test revealed that o-SLG formed a thermotropic gel in many organic solvents, whilst p-SLG did not. When metal ions, such as Cu(2+), Zn(2+), Mg(2+), Ni(2+), were added, different behaviors were observed. The addition of Cu(2+) induced p-SLG to from an organogel. In the case of o-SLG, the addition of Cu(2+) and Mg(2+) ions maintained the gelating ability of the compound, whilst Zn(2+) and Ni(2+) ions destroyed the gel. In addition, the introduction of Cu(2+) ions caused the nanofiber gel to perform a chiral twist, whilst the Mg(2+) ions enhanced the fluorescence of the gel. More interestingly, the Mg(2+)-ion-mediated organogel showed differences in the fluorescence quenching by D- and L-tartaric acid, thus showing a chiral recognition ability.     

A comparative study on textural characterization: cation-exchange and sorption properties of crystalline alpha-zirconium(IV), tin(IV), and titanium(IV) phosphates

Tetravalent metal phosphates (M=Zr, Ti, and Sn) were prepared and characterized by XRD, surface properties, and TG-DTA. The cation exchange and sorption behavior of these metal phosphates toward transition metal ions such as Cu(2+), Co(2+), and Ni(2+) have been studied comparatively as a function of temperature and concentration. The adsorption process was found to increases with increase in temperature and concentration. The selectivity order for alpha-titanium and alpha-tin phosphates is Cu(2+)>Co(2+)>Ni(2+), whereas for alpha-zirconium phosphate it is Cu(2+)>Ni(2+)>Co(2+). The ion exchange capacity of alpha-titanium phosphate is greater than those of other phosphates, which is explained on the basis of the surface behavior, disorderness of the system, degree of hydrolysis of incoming guest adsorbate metal ions, and structural steric hindrance of the exchangers during adsorption and sorption. The distribution coefficient, Gibbs free energy, enthalpy, and entropy values indicate that the ion-exchange processes are spontaneous.     

Oxidative cyclization of thiosemicarbazone: an optical and turn-on fluorescent chemodosimeter for Cu(II)

A weakly fluorescent thiosemicabazone (L(1)H) was found to be a selective optical and "turn-on" fluorescent chemodosimeter for Cu(2+) ion in aqueous medium. A significant fluorescence enhancement along with change in color was only observed for Cu(2+) ion; among the other tested metal ions (viz. Na(+), K(+), Mg(2+), Ca(2+), Cr(3+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), Ag(+), Ni(2+), Co(2+), Fe(3+) and Mn(2+)). The Cu(2+) selectivity resulted from an oxidative cyclization of the weak fluorescent L(1)H into highly fluorescent rigid 4,5-dihydro-5,5-dimethyl-4-(naphthalen-5-yl)-1,2,4-triazole-3-thione (L(2)). The signaling mechanism has been confirmed by independent synthesis with detail characterization of L(2).     

Interactions of metal ions with monoaza crown ethers A15C5 and A18C6 carrying dansyl fluorophore as pendant in acetonitrile solution

The influence of metal cations Li(+), Na(+), K(+), Cs(+), Mg(2+), Ca(2+), Sr(2+), Ba(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Pb(2+) and Al(3+) on the spectroscopic properties of the dansyl (1-dimethylaminonaphthalene-5-sulfonyl) group covalently linked to monoaza crown ethers 1-aza-15-crown-5 (1,4,7,10,-tetraoxa-13-azacyclopentadecane) (A15C5) and 1-aza-crown-6 (1,4,7,10,13-pentaoxa-16-azacyclooctadecane) (A18C6) was investigated by means of absorption and emission spectrophotometry. Interaction of the alkali metal ions with both fluoroionophores is weak, while alkaline earth metal ions interact strongly causing 50 and 85% quenching of dansyl fluorescence of N-(5-dimethylamine-1-naphthalenesulfonylo)-1,4,7,10,-tetraoxa-13-azacyclopentadecane (A15C5-Dns) and N-(5-dimethylamine-1-naphthalenesulfonylo)-1,4,7,10,13-pentaoxa-16-azacyclooctadecane (A18C6-Dns), respectively. The Cu(2+), Pb(2+) and Al(3+) cations interact very strongly with dansyl chromophore, causing a major change in absorption spectrum of the chromophore and forming non-fluorescent complexes. The Co(2+), Ni(2+), Zn(2+), Mg(2+) cations interact moderately with both fluoroionophores causing quenching of dansyl fluorescence by several percent only.     

Separation study of cadmium through an emulsion liquid membrane using triisooctylamine as mobile carrier

A study of the transport of Cd(2+) ions through a triisooctylamine (TIOA)-sorbitan monooleate (Span 80)-dimethylbenzene liquid membrane has been performed with varying concentrations of HCl, KI, TIOA, Span 80 and NaOH in the feed, membrane and stripping solutions. Maximum transport was observed with 0.025 M HCl, 0.01 M KI, 0.02 M TIOA, 3% (w/v) Span 80 and 0.05 M NaOH. With this system cadmium could be completely separated with Cu(2+), Zn(2+), Fe(2+), Co(2+), Ni(2+), Mn(2+), Cr(3+) and Al(3+). The transport mechanism of this metal ions through the membrane has been discussed.     

Novel adsorbent based on silkworm chrysalides for removal of heavy metals from wastewaters

In this contribution, maximum capacity for adsorption of Pb(2+), Ni(2+), and Cu(2+) by silkworm chrysalides (SC) was determined. The raw silkworm chrysalides (SC(r)) and chrysalides after acidic washing (SC(w)) were used. Chitin (CT), extracted from SC, and chitosan (CS), with 85% deacetylation, were employed as reference samples. Adsorption tests showed that all the studied adsorbents exhibited excellent performance in removal of metals. The choice of a more appropriate adsorbent is related to its efficiency for removal of a specific metal. The studied materials presented different intensities for metal adsorption as follows: (i) Ni(2+)>Cu(2+)>Pb(2+) for SC(r); (ii) Pb(2+)>Cu(2+)>Ni(2+) for SC(w); (iii) Ni(2+)>Cu(2+)>Pb(2+) for CT; and (iv) Cu(2+)>Pb(2+)>Ni(2+) for CS. Metal adsorption onto SC(r) and CS was analyzed by Freundlich and Langmuir isotherm equations. Adsorption values for CS-Pb and SC(r)-Ni were provided by the Freundlich model, while the adsorption values for CS-Cu, CS-Ni, SC(r)-Pb, and SC(r)-Cu were provided by the Langmuir model. The studied adsorbents are suitable for use in treatment of wastewater. From the economic point of view, the use of SC(r) as an adsorbent of heavy metals (mainly Ni(2+)) on the large industrial scale would be more appropriate.     

Electron transfer reactions between copper(II) porphyrin complexes and various oxidizing reagents in acetonitrile

Homogeneous electron transfer reactions of the Cu(II) complexes of 5,10,15,20-tetraphenylporphyrin (TPP) and 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) with various oxidizing reagents were spectrophotometrically investigated in acetonitrile. The reaction products were confirmed to be the pi-cation radicals of the corresponding Cu(II)-porphyrin complexes on the basis of the electronic spectra and the redox potentials of the complexes. The rate of the electron transfer reaction between the Cu(II)-porphyrin complex and solvated Cu(2+) was determined as a function of the water concentration under the pseudo first-order conditions where Cu(2+) is in large excess over the Cu(II)-porphyrin complex. The decrease in the pseudo first-order rate constant with increasing the water concentration was attributed to the stepwise displacement of acetonitrile in [Cu(AN)(6)](2+)(AN = acetonitrile) by water, and it was concluded that only the Cu(2+) species fully solvated by acetonitrile, [Cu(AN)(6)](2+), possesses sufficiently high redox potential for the oxidation of Cu(ii)-OEP and Cu(ii)-TPP. The reactions of the Cu(II)-porphyrin complexes with other oxidizing reagents such as [Ni(tacn)(2)](3+)(tacn = 1,4,7-triazacyclononane) and [Ru(bpy)(3)](3+)(bpy = 2,2'-bipyridine) were too fast to be followed by a conventional stopped-flow technique. Marcus cross relation for the outer-sphere electron transfer reaction was used to estimate the rate constants of the electron self-exchange reaction between Cu(II)-porphyrin and its pi-cation radical: log(k/M(-1) s(-1))= 9.5 +/- 0.5 for TPP and log(k/M(-1) s(-1))= 11.1 +/- 0.5 for OEP at 25.0 degrees C. Such large electron self-exchange rate constants are typical for the porphyrin-centered redox reactions for which very small inner- and outer-sphere reorganization energies are required.     

Metal ion-binding properties of 1-methyl-4-aminobenzimidazole (=9-methyl-1,3-dideazaadenine) and 1,4-dimethylbenzimidazole (=6,9-dimethyl-1,3-dideazapurine). quantification of the steric effect of the 6-amino group on metal ion binding at the N7 site of the adenine residue

The stability constants of the 1:1 complexes formed between Mg(2+), Ca(2+), Sr(2+), Ba(2+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), or Cd(2+) (=M(2+)) and 1-methyl-4-aminobenzimidazole (MABI) or 1,4-dimethylbenzimidazole (DMBI) were determined by potentiometric pH titrations in aqueous solution (25 degrees C; I = 0.5 M, NaNO(3)). Some of the stability constants were also measured by UV spectrophotometry. The acidity constants of the species H(2)(MABI)(2+) and H(DMBI)(+) were determined by the same methods, some twice. Comparison of the stability constants of the M(MABI)(2+) and M(DMBI)(2+) complexes with those calculated from log versus p straight-line plots, which were established previously for sterically unhindered benzimidazole-type ligands (=L), reveals that the stabilities of the M(MABI)(2+) and M(DMBI)(2+) complexes are significantly reduced due to steric effects of the C4 substituents on metal ion binding at N3. This effect is more pronounced in the M(DMBI)(2+) complexes. Considering the steric equivalence of methyl and (noncoordinating) amino groups (as they occur in adenines), it is concluded that the same extent of steric inhibition by the (C6)NH(2) group is to be expected on metal ion binding at N7 with adenine derivatives. The basicity of the amino group in MABI is significantly higher than in its corresponding adenine derivative. Indeed, it is concluded that in the M(MABI)(2+) complexes chelate formation involving the amino group occurs to some extent. The formation degrees of these "closed" species are calculated; they vary for the complexes of Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), or Cd(2+) between about 50 and 90%. The stability of the M(MABI)(2+) and M(DMBI)(2+) complexes with the alkaline earth ions is very low but unaffected by the C4 substituent; this probably indicates that in these instances outersphere complexes (with a water molecule between N3 and the metal ion) are formed.     

Spectrophotometric and conductometric study of complexation of salophen and some transition metal ions in nonaqueous polar solvents

The complexation reaction between Cu(2+), Co(2+) and Ni(2+) metal cations with N,N'-bis(salicylidene)-1,2-phenylenediamine (salophen), in three nonaqueous polar solvents such as: acetonitrile (AN), dimethyl sulfoxide (DMSO), methanol (MeOH) and two binary mixtures of AN:DMSO and AN:MeOH at 25 degrees C were studied by spectrophotometric and conductometric methods. All investigated metal ions form 1:1 ML complex which their stability constants were determined and increase as Irving-Williams stability order of Co(2+)相似文献