Unusual metal ion selectivities of the highly preorganized tetradentrate ligand 1,10-phenanthroline-2,9-dicarboxamide: a thermodynamic and fluorescence study

Some metal ion complexing properties of the ligand PDAM (1,10-phenanthroline-2,9-dicarboxamide) in aqueous solution are reported. Using UV-visible spectroscopy to follow the intense π-π* transitions of PDAM as a function of metal ion concentration, log K(1) values in 0.1 M NaClO(4) and at 25 °C are, for Cu(II), 3.56(5); Ni(II), 3.06(5); Zn(II), 3.77(5); Co(II), 3.8(1); Mg(II), 0.1(1); Ca(II), 1.94(4); and Ba(II), 0.7(1). For more strongly bound metal ions, competition reactions between PDAM and EDTA (ethylenedinitrilo-tetraacetic acid) or tetren (1,4,7,10,13-pentaazatridecane), monitored following the UV spectrum of PDAM, gave the following log K(1) values in 0.1 M NaClO(4) and at 25 °C: Cd(II), 7.1(1); Pb(II), 5.82(5); In(III), 9.4(1); and Bi(III), 9.4(1). The very low log K(1)(PDAM) values for small metal ions such as Cu(II) or Zn(II) are unprecedented for a phen-based ligand (phen = 1,10-phenanthroline), which is rationalized in terms of the low basicity of the N donors of the ligand (pK(a) = 0.6) and the fact that PDAM has a best-fit size corresponding to large metal ions of ionic radius ~1.0 ?. Large metal ions with ionic radius ≥1.0 ? show large increases in log K(1) relative to their phen complexes, which in turn produces unparalleled selectivities, such as a 3.5 log units greater log K(1)(PDAM) for Cd(II) than for Cu(II). PDAM shows strong fluorescence in aqueous solution, suggesting that its carboxamide groups do not produce a fluorescence-quenching photon-induced electron transfer (PET) effect. Only Ca(II) produces a weak CHEF (chelation enhanced fluorescence) effect with PDAM, while all other metal ions tested produce a decrease in fluorescence, a CHEQ (chelation enhanced quenching effect). The production of the CHEQ effect is rationalized in terms of the idea that coordination of metal ions to PDAM stabilizes a canonical form of the carboxamide groups that promotes a PET effect.     

The amide oxygen donor. Metal ion coordinating properties of the ligand nitrilotriacetamide. A thermodynamic and crystallographic study

The metal ion coordinating properties of ntam (nitrilotriacetamide) are reported. The protonation constant (pK) for ntam is 2.6 in 0.1 M NaClO(4) at 25 degrees C. Formation constants (log K(1)) in 0.1 M NaClO(4) at 25 degrees C, determined by (1)H NMR and UV-Vis spectroscopy are: Ca(II), 1.28; Mg(II), 0.4; La(III), 2.30; Pb(II), 3.69; Cd(II), 3.78; Ni(II), 2.38; Cu(II), 3.16. The measured log K(1) values for the ntam complexes are discussed in terms of the low basicity of the N-donor, as evidenced by the pK, and the effect of metal ion size on complex stability. The amide O-donors of ntam lead to the stabilization of complexes of large metal ions (Pb(II), Cd(II), La(III), Ca(II)) relative to log K1 for the NH3 complexes, while for small metal ions (Ni(II), Cu(II)) the amide O-donors lead to destabilization. This is discussed in terms of the role of chelate ring size in controlling metal ion size-based selectivity. The structures of [Pb(ntam)(NO3)2]2 (1) and [Ca2(ntam)3(H2O)2](ClO4)4.3H2O (2) are reported. For 1: triclinic, space group P1, a = 7.4411(16), b = 9.0455(19), c = 11.625(3) A, alpha = 69.976(4), beta = 79.591(4), gamma = 67.045(3) degrees, Z = 2, R = 0.0275. For 2: monoclinic, space group P2(1)/c, a = 10.485(2), b = 11.414(2), c = 38.059(8) A, beta = 92.05(3) degrees, Z = 4, R = 0.0634. Structure 1 is dimeric with two Pb atoms linked by bridging O-donors from the two ntam ligands. The coordination sphere consists of one N-donor and 3 O-donors from the ntam ligand, two O-donors from nitrates, and one bridging O-donor. The variation in bond length suggests a stereochemically active lone pair of electrons on the Pb. Structure 2 consists of two Ca(II) ions held together by 3 bridging O-donors from ntam groups. One Ca is 9-coordinate with two ntam ligands present, plus one bridging O-donor from the other Ca(II) ntam complex. The other Ca is 8-coordinate, with a single coordinated ntam, plus two coordinated H2O molecules, and two bridging O-donors from the other half of the complex. The role of M-O=C bond angles in controlling selectivity for metal ions on the basis of their size is discussed.     

Complexes of greatly enhanced thermodynamic stability and metal ion size-based selectivity, formed by the highly preorganized non-macrocyclic ligand 1,10-phenanthroline-2,9-dicarboxylic acid. A thermodynamic and crystallographic study

The metal ion-complexing properties of 1,10-phenanthroline-2,9-dicarboxylic acid (PDA) are reported. The protonation constants (pK1 = 4.75, pK2 = 2.53) and formation constants (log K(1)) for PDA with Mg(II) (3.53), Ca(II) (7.3), Sr(II) (5.61), Ba(II) (5.43), La(III) (13.5), Gd(III) (16.1), Zn(II) (11.0), Cd(II) (12.8), Pb(II) (11.4), and Cu(II) (12.8) were determined by UV-vis spectroscopy in 0.1 M NaClO4 at 25 degrees C. The log K(1) values for most of these metal ions were high enough that they were not displaced from their PDA complexes even at pH 2. The log K(1) values were determined using the UV spectra to monitor the competition with EDTA (or DTPA; EDTA = ethylendiamine tetraacetic acid, DTPA = diethylenetriamine pentaacetic acid) as a function of pH according to the equilibrium: M(EDTA) + PDA + nH+ = M(PDA) + EDTAHn. The log K1 values indicate that the rigid extended aromatic backbone of PDA leads to high levels of ligand preorganization and selectivity toward large metal ions (e.g., Ca(II), Cd(II), Gd(III)) with an ionic radius of about 1.0 A and greatly enhanced thermodynamic stability as compared to similar ligands without the reinforcing aromatic backbone. The structure of [Ca(PDA)(H2O)2].2H2O (1) is reported: orthorhombic, Fdd2, a = 44.007(9) A, b = 18.945(4) A, c = 7.2446(14) A, V = 6040(2) A(3), Z = 16, R = 0.0882. The Ca(II) ion has a coordination number of eight, lying in the plane of the tetradentate PDA, with Ca-N bonds averaging 2.55 A and Ca-O bonds to the two acetate groups of PDA averaging 2.45 A. These are very close to the normal Ca-L bonds of this type, supporting the idea that a metal ion the size of Ca(II) (ionic radius approximately 1.0 A) will fit into PDA in a low-strain manner. The remaining four coordination sites on Ca(II) in 1 come from two coordinated water molecules and a chelating carboxylate bridging from an adjacent [Ca(PDA)(H2O)2].2H2O complex. Potential applications of PDA as a ligand in biomedical applications such as Gd(III) contrast agents in MRI are discussed.     

Metal-ion-complexing properties of 2-(pyrid-2'-yl)-1,10-phenanthroline, a more preorganized analogue of terpyridyl. A crystallographic, fluorescence, and thermodynamic study

Some metal-ion-complexing properties of the ligand 2-(pyrid-2'-yl)-1,10-phenanthroline (MPP) are reported. MPP is of interest in that it is a more preorganized version of 2,2';6,2'-terpyridine (tpy). Protonation constants (pK(1) = 4.60; pK(2) = 3.35) for MPP were determined by monitoring the intense π-π* transitions of 2 × 10(-5) M solutions of the ligand as a function of the pH at an ionic strength of 0 and 25 °C. Formation constants (log K(1)) at an ionic strength of 0 and 25 °C were obtained by monitoring the π-π* transitions of MPP titrated with solutions of the metal ion, or 1:1 solutions of MPP and the metal ion were titrated with acid. Large metal ions such as Ca(II) or La(III) showed increases of log K(1) of about 1.5 log units compared to that of tpy. Small metal ions such as Zn(II) and Ni(II) showed little increase in log K(1) for MPP compared to the tpy complexes, which is attributed to the presence of five-membered chelate rings in the MPP complexes, which favor large metal ions. The structure of [Cd(MPP)(H(2)O)(NO(3))(2)] (1) is reported: monoclinic, P2(1)/c, a = 7.4940(13) ?, b = 12.165(2) ?, c = 20.557(4) ?, β = 96.271(7)°, V = 1864.67(9) ?(3), Z = 4, and final R = 0.0786. The Cd in 1 is seven-coordinate, comprising the three donor atoms of MPP, a coordinated water, a monodentate, and a bidentate NO(3)(-). Cd(II) is a fairly large metal ion, with r(+) = 0.96 ?, slightly too small for coordination with MPP. The effect of this size matching in terms of the structure is discussed. Fluorescence spectra of 2 × 10(-7) M MPP in aqueous solution are reported. The nonprotonated MPP ligand fluoresces only weakly, which is attributed to a photoinduced-electron-transfer effect. The chelation-enhanced-fluorescence (CHEF) effect induced by some metal ions is presented, and the trend of the CHEF effect, which is Ca(II) > Zn(II) > Cd(II) ~ La(III) > Hg(II), is discussed in terms of factors that control the CHEF effect, such as the heavy-atom effect.     

Complexation of metal ions, including alkali-earth and lanthanide(III) ions, in aqueous solution by the ligand 2,2',6',2'-terpyridyl

Some metal-ion-complexing properties of the ligand 2,2',6',2'-terpyridyl (terpy) in aqueous solution are determined by following the π-π* transitions of 2 × 10(-5) M terpy by UV-visible spectroscopy. It is found that terpy forms precipitates when present as the neutral ligand above pH ～5, in the presence of electrolytes such as NaClO(4) or NaCl added to control the ionic strength, as evidenced by large light-scattering peaks. The protonation constants of terpy are thus determined at the ionic strength (μ) = 0 to avoid precipitation and found to be 4.32(3) and 3.27(3). The log K(1) values were determined for terpy with alkali-earth metal ions Mg(II), Ca(II), Sr(II), and Ba(II) and Ln(III) (Ln = lanthanide) ions La(III), Gd(III), and Lu(III) by titration of 2 × 10(-5) M free terpy at pH >5.0 with solutions of the metal ion. Log K(1)(terpy) was determined for Zn(II), Cd(II), and Pb(II) by following the competition between the metal ions and protons as a function of the pH. Complex formation for all of these metal ions was accompanied by marked sharpening of the broad π-π* transitions of free terpy, which was attributed to complex formation affecting ligand vibrations, which in the free ligand are coupled to the π-π* transitions and thus broaden them. It is shown that log K(1)(terpy) for a wide variety of metal ions correlates well with log K(1)(NH(3)) values for the metal ions. The latter include both experimental log K(1)(NH(3)) values and log K(1)(NH(3)) values predicted previously by density functional theory calculation. The structure of [Ni(terpy)(2)][Ni(CN)(4)]·CH(3)CH(2)OH·H(2)O (1) is reported as follows: triclinic, P1, a = 8.644(3) ?, b = 9.840(3) ?, c = 20.162(6) ?, α = 97.355(5)°, β = 97.100(5)°, γ = 98.606(5)°, V = 1663.8(9) ?(3), Z = 4, and final R = 0.0319. The two Ni-N bonds to the central N donors of the terpy ligands in 1 average 1.990(2) ?, while the four peripheral Ni-N bonds average 2.107(10) ?. This difference in the M-N bond length for terpy complexes is typical of the complexes of smaller metal ions, while for larger metal ions, the difference is reversed. The significance of the metal-ion size dependence of the selectivity of polypyridyl ligands, and the greater rigidity of ligands based on aromatic groups such as pyridyl groups, is discussed.     

Factors controlling metal-ion selectivity in the binding sites of calcium-binding proteins. The metal-binding properties of amide donors. A crystallographic and thermodynamic study

The metal-ion complexing properties of the ligand EDTAM (ethylenediamine-N,N,N',N'-tetraacetamide) are investigated as a model for the role of amide oxygen donors in the binding sites of Ca-binding proteins. The structures of the complexes [Ca(EDTAM)NO3]NO3 (1), [La(EDTAM)(H2O)4](NO3)3.H2O (2), and [Cd(EDTAM)(NO3)]NO3 (3) are reported: 1 monoclinic, P2(1)/c, a = 10.853(2) angstroms, b = 12.893(3) angstroms, c = 13.407(3) angstroms, beta = 103.28(3) degrees, Z = 4, R = 0.0281; 2 triclinic, P, a = 8.695(2) angstroms, b = 9.960(2) angstroms, c = 16.136(3) angstroms, alpha = 95.57(3) degrees, beta = 94.84(3) degrees, gamma = 98.72(3) degrees, Z = 2, R = 0.0394; 3 monoclinic, P2(1)/c, a = 10.767(2) angstroms, b = 12.952(2) angstroms, c = 13.273(2) angstroms, beta = 103.572(3) degrees, Z = 4, R = 0.0167. Compounds 1 and 3 are isostructural, and the EDTAM binds to the metal ion through its two N-donors and four O-donors from the amide groups. Ca(II) in 1 is 8-coordinate with a chelating NO3- group, while Cd(II) in 3 may possibly be 7-coordinate, with an asymmetrically coordinated NO3- that is best regarded as unidentate. The La(III) in 2 is coordinated to the EDTAM in a manner similar to that of 1 and 3, but it is 10-coordinate with four water molecules coordinated to the La(III). The formation constants (log K1) for complexes of a variety of metal ions with EDTAM are reported in 0.1 M NaNO3 at 25.0 +/- 0.1 degrees C. These are compared to the log K1 values for en (ethylenediamine) and THPED (N,N,N',N'-tetrakis(2-hydroxypropyl)-ethylenediamine). For large metal ions, such as Ca2+ or La3+, log K1 increases strongly when the four acetamide groups are added to en to give EDTAM, whereas for a small metal ion, such as Mg2+, this increase is small. The log K1 values for EDTAM compared to THPED suggest that the amide oxygen is a much stronger base than the alcoholic oxygen. Structures of binding sites in 40 Ca-binding proteins are examined. It is shown that the Ca-O=C bond angles involving coordinated amides in these sites are large, commonly being in the 150-180 degrees range. This is discussed in terms of the idea that for purely ionic bonding the M-O=C bond angle will approach 180 degrees, while for covalent bonding the angle should be closer to 120 degrees. How this fact might be used by the proteins to control selectivity for different metal ions is discussed.     

Preparation, characterization and application of an cellulose ion-exchanger with acetoacetamide functional groups

Summary A method is described for functionalizing acetoacetamide chelating groups onto microcrystalline cellulose (Cell-AcAc). This material shows a significant affinity for Fe(III), Cu(II) and U(VI) and no or very less affinity for the M(I) ions (M=Na, K), M(II) ions (M= Mg, Ca; Fe, Co, Ni, Zn), La(III) and Y(III) including Th(IV). The obtained K _d values offer a column separation method for U(VI) ions from the rest of above-mentioned metal ions except Fe(III). Cell-AcAc and its Cu(II) complexes are characterized by means of FT-IR spectra.

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Darstellung, Charakterisierung und Anwendung von Ionenaustauschmaterial aus Cellulose mit chemisch gebundener Acetoacetamid-Gruppe

Zusammenfassung Die Darstellung von immobilisiertem Acetoacetamid auf mikrokristallinem Cellulosepulver (Cell-AcAc) wird beschrieben. Der Ionenaustauscher Cell-AcAc hat eine ausgeprägte Affinität für Fe(III), Cu(II) and U(VI), aber nahezu keine für die M(I)-Ionen (M=Na, K) M(II)-Ionen (M=Mg, Ca; Fe, Co, Ni, Zn), La(III), Y(III) sowie Th(IV). Die erhaltenen K _d-Werte ermöglichen für U(VI)-Ionen eine quantitative säulen-chromatographische Trennung von den anderen genannten Kationen mit Ausnahme von Fe(III). Das Ionenaustauschmaterial Cell-AcAc und sein Cu(II)-Komplex wurden durch FT-IR-Spektren charakterisiert.

     

Crystal structures and magnetic and luminescent properties of a series of homodinuclear lanthanide complexes with 4-cyanobenzoic ligand

A series of homodinuclear lanthanide(III) complexes with the 4-cba ligand, [La2(4-cba)6(phen)2(H2O)6] (1) and [Ln2(4-cba)6(phen)2(H2O)2] (Ln = Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), and Dy (7); 4-Hcba = 4-cyanobenzoic acid; phen = 1,10-phenanthroline), have been synthesized and structurally characterized by single-crystal X-ray diffraction. In 1, two water molecules bridge two nine-coordinated La ions, and six 4-cba ligands coordinate to the two La ions in terminal mode. In the isostructural complexes 2-7, two eight-coordinated Ln ions are connected by four bidentate 4-cba ligands, and another two 4-cba ligands terminate the two Ln ions. The variable-temperature magnetic properties of 2-7 have been investigated. Complex 7 shows a significant ferromagnetic interaction between Dy(III), while no magnetic interaction exists between Gd(III) ions in 6. In 2-5, the value of chi(M)T decreases with decreasing temperature, but the magnetic interactions between the Ln(III) ions cannot definitely be concluded. Notably, the spin-orbit coupling parameters, lambda, for Sm(III) (216(2) cm(-1)) and Eu(III) (404(2) cm(-1)) have been obtained in 4 and 5, respectively. The strong fluorescent emissions of 4, 5, and 7 demonstrate that ligand-to-Ln(III) energy transfer is efficient and that the coordinated water molecules do not quench their luminescence by the nonradiative dissipation of energy.     

The effect of ring size variation on the structure and stability of lanthanide(III) complexes with crown ethers containing picolinate pendants

The coordination properties of the macrocyclic receptor N,N'-bis[(6-carboxy-2-pyridyl)methylene]-1,10-diaza-15-crown-5 (H(2)bp15c5) towards the lanthanide ions are reported. Thermodynamic stability constants were determined by pH-potentiometric titration at 25 °C in 0.1 M KCl. A smooth decrease in complex stability is observed upon decreasing the ionic radius of the Ln(III) ion from La [log K(LaL) = 12.52(2)] to Lu [log K(LuL) = 10.03(6)]. Luminescence lifetime measurements recorded on solutions of the Eu(III) and Tb(III) complexes confirm the absence of inner-sphere water molecules in these complexes. (1)H and (13)C NMR spectra of the complexes formed with the diamagnetic La(III) metal ion were obtained in D(2)O solution and assigned with the aid of HSQC and HMBC 2D heteronuclear experiments, as well as standard 2D homonuclear COSY and NOESY spectra. The (1)H NMR spectra of the paramagnetic Ce(III), Eu(III) and Yb(III) complex suggest nonadentate binding of the ligand to the metal ion. The syn conformation of the ligand in [Ln(bp15c5)](+) complexes implies the occurrence of two helicities, one associated with the layout of the picolinate pendant arms (absolute configuration Δ or Λ), and the other to the five five-membered chelate rings formed by the binding of the crown moiety (absolute configuration δ or λ). A detailed conformational analysis performed with the aid of DFT calculations (B3LYP model) indicates that the complexes adopt a Λ(λδ)(δδλ) [or Δ(δλ)(λλδ)] conformation in aqueous solution. Our calculations show that the interaction between the Ln(III) ion and several donor atoms of the crown moiety is weakened as the ionic radius of the metal ion decreases, in line with the decrease of complex stability observed on proceeding to the right across the lanthanide series.     

Effects of Metal Ions on the Micellization of Ionic Surfactants

The effect of metal ions (Cu(II), Zn(II), Co(II), Ni(II), La(III), Fe(III)) on the critical micelle concentration (CMC) of ionic surfactants (sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (CTAB)) were investigated at 25±0.1°C, μ = 0.1 M (KNO₃), using conductivity method in this paper. A series of general empirical expressions about the relationship between the CMC values for SDS and CTAB and the concentrations of metal ions have been derived. The results showed that the CMC values for both SDS and CTAB decreased with increasing the concentrations of metal ions. This can be interpreted by the counterion effect and the entropy driving effect.     

Potentiometric and conductometric studies on the binary and mixed ligand complexes in solution: M(II)-dipicolinic acid-glycine systems

The binary and mixed ligand complexes of some alkaline earth and transition metal (II) ions with dipicolinic acid (DPA) as a primary ligand and the biologically important secondary ligand (glycine), were studied using potentiometric technique. The acidity constants of the ligands were determined and used for determining the stability constants of the complexes formed in aqueous solutions under the experimental conditions (t=25 degrees C, mu=0.1 M NaNO(3) ). The dissociation constants of DPA were also determined in various water+dioxane mixtures under the same experimental conditions. It is concluded that a pronounced change in the pK values is observed as the solvent is enriched in dioxane. The values of DeltalogK have been evaluated and discussed. In addition, the chelation mode of ternary complexes was ascertained by conductivity measurements.     

Cooperative binding of phosphate anion and a neutral nitrogen donor to alkaline-Earth metal ions. Investigation of group 2 metal-organophosphate interaction in the absence and presence of 1,10-phenanthroline

Alkaline-earth metal phosphates containing nitrogen-donor ligands have been prepared by the reaction of alkaline-earth metal acetates M(OAc) 2. xH 2O (M = Mg, Ca, Sr, Ba) with 2,6-diisopropylphenyl phosphate (dippH 2) in the absence and presence of 1,10-phenanthroline (phen). Interaction of strontium or barium acetate with dippH 2 in methanol at room temperature leads to the isolation of ionic phosphates [{M 2(mu-H 2O) 4(H 2O) 10}{dipp} 2].4L [M = Sr, L = CH 3OH ( 1); M = Ba, L = H 2O ( 2)]. The addition of a bidentate nitrogen-donor phen to these reactions leads to the isolation of dinuclear metal phosphates [Mg(dipp)(phen)(CH 3OH) 2] 2 ( 3) and [M(dippH) 2(phen) 2(H 2O)] 2 [M = Ca ( 4), Sr ( 5), Ba ( 6)]. While ionic phosphates 1 and 2 are soluble in water, the predominately covalent dimeric compounds 3- 6 are insoluble in all common solvents including water. The new compounds have been characterized in the solid state by elemental analysis, IR, UV-vis, and emission spectroscopy, and single-crystal X-ray diffraction studies. The cationic part in 1 and 2 is a {M 2(mu-H 2O) 4(H 2O) 10} unit, where each metal ion is surrounded by four bridging and five terminal water molecules as ligands. The dipp anion does not directly bind to the metal ions but is extensively hydrogen-bonded to the cationic unit through the phosphate oxygen and water hydrogen atoms to result in an infinitely layered structure where the hydrophobic aryl group protrudes out of the hydrophilic layer formed by the cationic part and -PO 3 (2-) units. In contrast, compounds 3- 6 are discrete dimeric molecules built around a central M 2O 4P 2 eight-membered ring. While the dippH 2 ligand exists in a doubly deprotonated form in 3, two monodeprotonated dippH 2 ligands are present per metal ion in compounds 4- 6. While 3 prefers only one phen ligand in the metal coordination sphere, two phen ligands chelate each metal ion in 4- 6. The conformations of the eight-membered rings in 3- 6 vary significantly from each other depending on the size of the cation and the coordination number around the metal. Further, intermolecular hydrogen bonding involving the phenanthroline C-H linkages result, in a gridlike structure in 1, one-dimensional chains in isostructural 2 and 3, and a two-dimensional layer arrangement in 4. Compounds 3- 6 are the only examples of alkaline-earth metal phosphate complexes with neutral M-N donor bonds. The thermal behavior of compounds 1- 6 has been examined with the help of thermogravimetric analysis and differential scanning calorimetry and also by bulk thermolysis followed by powder X-ray diffraction measurements. While compounds 1 and 2 yield M 2P 2O 7, decomposition of 4- 6 results in the formation of M(PO 3) 2, consistent with the M-P ratio in the precursor complexes.     

A photometric study of the complexation reaction between Alizarin complexan and zinc(II), nickel(II), lead(II), cobalt(II) and copper(II)

The complexation reaction between Alizarin complexan ([3-N,N-di(carboxymethyl)aminomethyl]-1,2-dihydroxyanthraquinone; H(4)L) and zinc(II), nickel(II), lead(II), cobalt(II) and copper(II) has been studied by a spectrophotometric method. All these metal ions form 1:1 complexes with HL; 2:1 metal:ligand complex were found only for Pb(II) and Cu(II). The stability constants are (ionic strength I = 0.1, 20 degrees C): Zn(2+) + HL(3-) right harpoon over left harpoon ZnHL(-) log K +/- 3sigma(log K) = 12.19 +/- 0.09 (I = 0.5) Ni(2+) + HL(3-) right harpoon over left harpoon NiHL(-) log K +/- 3sigma(log K) = 12.23 +/- 0.21 Pb(2+) + HL(3-) right harpoon over left harpoon PbHL(-) log K +/- 3sigma(log K) = 11.69 +/- 0.06 PbHL(-) + Pb(2+) right harpoon over left harpoon Pb(2)L + H(+) log K approximately -0.8 Co(2+) + HL(3-) right harpoon over left harpoon CoHL(-) log K 3sigma(log K) = 12.25 + 0.13 Cu(2+) + HL(3-) right harpoon over left harpoon CuHL(-) log K 3sigma(log K) = 14.75 +/- 0.07 Cu(2+) + CuHL(-) right harpoon over left harpoon Cu(2)L + H(+) log K approximately 3.5 The solubility and stability of both the reagent and the complexes and the closenes of the values of the stability constants make this reagent suitable for the photometric detection of several metal ions in the eluate from an ion-exchange column.     

Synthesis and structure investigation of the antibiotic amoxicillin complexes of d-block elements

The study of some transition metals (M) and amoxicillin trihydrate (ACT) ligand complexes (M-ACT) that formed in solution involved the spectrophotometric determination of stoichiometric ratios and their stability constants and these ratios were found to be M:ACT = 1:1, 1:2 and 2:1 in some instances. The calculated stability constants of these chelates, under selected optimum conditions, using molar ratio method have values ranging from K(f) = 10(7) to 10(14). These data were confirmed by calculations of their free energy of formation deltaG, which corresponded to their high stabilities. The separated solid complexes were studied using elemental analyses, IR, reflectance spectra, magnetic measurements, mass spectra and thermal analyses (TGA and DTA). The proposed general formulae of these complexes were found to be ML(H2O)w(H2O)x(OH)y(Cl)2, where M = Fe(II), Co(III), w = 0, x = 2, y = 1, z = 0; M = Co(II), w = 0, x = 1, y = 0, z = 1; M = Fe(III), w = 0, x = 1, y = 2, z = 0; M = Ni(II), Cu(II) and Zn(II), w = 2, x = 0, y = 1, z = 0, where w = water of crystallization, x = coordinated water, y = coordinated OH(-) and z = Cl- in the outer sphere of the complex. The IR spectra show a shift of nu(NH) (2968 cm(-1)) to 2984-2999 cm(-1) of imino group of the ligand ACT and the absence of nu(CO) (beta-lactame) band at 1774 cm(-1) and the appearance of the band at 1605-1523 cm(-1) in all complexes suggest that 6,7-enolization takes place before coordination of the ligand to the metal ions. The bands of M-N (at 625-520 cm(-1)) and of M-O (at 889-7550 cm(-1)) proved the bond of N (of amino and imino groups) and O of C-O group of the ligand to the metal ions. The reflectance spectra and room temperature magnetic measurements refer to octahedral complexes of Fe(II) and Fe(III); square planner form of Co(II), reduced Co(III), Ni(II) and Cu(II)-ACT complexes but tetrahedral form of Zn-ACT complex. The thermal degradation of these complexes is confirmed by their mass spectral fragmentation. These data confirmed the proposed structural and general formulae of these complexes.     

Kinetic study of the Ce(III)‐, Mn(II)‐, or ferroin‐catalyzed Belousov‐Zhabotinsky reaction with pyruvic acid

The Ce(III)‐, Mn(II)‐, or ferroin (Fe(phen)₃²⁺)‐catalyzed reaction of bromate ion and pyruvic acid (PA) or its dimer exhibits oscillatory behavior. Both the open‐chain dimer (parapyruvic acid, γ‐methyl‐γ‐hydroxyl‐α‐keto‐glutaric acid, DPA1) and the cyclic‐form dimer (α‐keto‐γ‐valerolactone‐γ‐carboxylic acid, DPA2) show more sustained oscillations than PA monomer. Ferroin behaves differently from Ce(III) or Mn(II) ion in catalyzing these oscillating systems. The kinetics of reactions of PA, 3‐brompyruvic acid (BrPA), DPA1, or DPA2 with Ce(IV), Mn(III), Fe(phen)₃³⁺ ion were investigated. The order of relative reactivity of pyruvic acids toward reaction with Ce(IV), Mn(III), or Fe(phen)₃³⁺ ion is DPA2 > DPA1 > BrPA > PA and that of metal ions toward reaction with pyruvic acids is Mn(III) > Ce(IV) > Fe(phen)₃³⁺. The rates of bromination reactions of pyruvic acids are independent of the concentration of bromine and the order of reactivity toward bromination is (DPA1, DPA2) > BrPA > PA. Experimental results are rationalized. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 408–418, 2000     

N,N'-乙二水杨酰胺合铜(II)酸根和N,N'-1,2-丙二水杨酰胺全铜(II)酸根的双核Cu(II)-Fe(III)配合物的合成和磁性

本文合成了四个新型双核配合物、[Cu(samen)Fe(L)Cl]和[Cu(sampn)Fe(L)Cl]。经元素分析、IR, 电导、磁性测量等手段推定配合物具有酚氧桥结构, Cu(II)及Fe(III)的配位环境分别为平面四方及四角锥的构型, Fe(III)离子的自旋态S=3/2。测定了配合物[Cu(samen)Fe(L)Cl]的变温磁化率(4-300K), 参数J和θ值表明两个双核配合物中金属离子之间有中等程度的反铁磁性超交换作用和双核单元之间有弱的分子间相互作用。     

Trace metal speciation in sea water — a paper electrophoretic approach

Stability constants of individual trace metal complexes form the basis for calculations predicting the distribution of trace metal species in complexing media, such as sea water. In this study, the electrophoretic mobility of radiotracer ²¹⁰Pb is measured as a function of ligand concentration in chloride and sulfate solutions of constant ionic strength and temperature. A theoretically-derived expression, relating mobility to ligand concentration and complex stability constants, is fitted by the method of least squares to the experimental data to obtain estimates of the conditional stability constants of lead(II) chloro and sulfato complexes at 23°C and ionic strength 0.7 i.e., under conditions resembling those of ocean water. The values obtained are: log β₁ = 0.999 ± 0.014, log β₂ = 1.037± 0.032, log β₃ = 1.250 ± 0.015 for lead(II) chloro complexes, and log β₁ = 1.048 ± 0.015 and log β₂ = 1.183 ± 0.025 for lead(II) sulfato complexes. Experiments with eight other metal ions [Au(III), Bi(III), Cd(II), Co(II), Cu(II), Hg(II), Ni(II), and Po(IV)] and with sea water as electrolyte indicate the general applicability of the method.     

Structural and density functional studies of uranium(III) and lanthanum(III) complexes with a neutral tripodal N-donor ligand suggesting the presence of a U-N back-bonding interaction

The crystal structures of two trisiodide octacoordinated uranium(III) complexes of tris[(2-pyrazinyl)methyl]amine (tpza), which differ only by the ligand occupying the eighth coordination site (thf or MeCN), and of their lanthanum(III) analogues have been determined. In the acetonitrile adducts the M-N(pyrazine) distances are very similar for U(III) and La(III), while the U-N(acetonitrile) distance is 0.05 A shorter than the La-N(acetonitrile) distance. In the [M(tpza)I(3)(thf)] complexes in which the monodentate acetonitrile ligand, a weak pi-acceptor ligand, is replaced by a thf molecule, a sigma-donor only, the mean value of the distance U-N(pyrazine) is 0.05 A shorter than the mean value of the La-N(pyrazine) distance. Since we are comparing isostructural compounds of ions with very similar ionic radii, these differences indicate the presence of a stronger M-N interaction in the U(III) complexes and therefore suggest the presence of a covalent contribution to the U-N bonding. The selectivity of the tpza ligand toward U(III) complexation (with respect to that of La(III)) in the presence of sigma-donor-only ligands has been quantified by the value of K(U(tpza))/K(La(tpza)) measured to be 3.3 +/- 0.5. The analysis of the metal-N-donor ligand bonding was carried out by a quasi-relativistic density functional theory study on small model compounds, of formula I(3)M-L (M = La, Nd, U; L = acetonitrile, pyrazine) and I(3)M-(pyrazine)(3) (M = La, U). The structural data obtained from geometry optimizations on these systems reproduce experimental trends, i.e., a decrease in the M-N distance from La to U, combined with an increase of the C-N distance in the acetonitrile derivatives. A detailed orbital analysis carried out on the resulting optimized complexes did not reveal any orbital interaction between the trivalent lanthanide cations (Ln(3+)) and the N-donor ligands. In contrast, a back-donation electron transfer from 5f U(3+) orbitals to the pi* virtual orbital of the ligand was observed for both acetonitrile and pyrazine. Evaluation of the total bonding energy between the MI(3) and L fragments shows that this orbital interaction leads to a stabilization of the uranium(III) system compared to the lanthanide species.     

Study on adsorption behavior of cesium using ammonium tungstophosphate (AWP)-calcium alginate microcapsules

A functional microcapsule was prepared by encapsulating the fine crystalline ammonium tungstophosphate(AWP) in calcium alginate polymer(CaALG).The characterization of AWP-CaALG microcapsule was examined by SEM and EPMA.The adsorption behavior of Cs(I),Rb(I),Sr(II),Pd(II),Ru(III),Rh(III),La(III),Ce(III),Dy(III) and Zr(IV) was investigated by the batch method.The batch experiments were carried out by varying the shaking times,HNO 3 concentration,and initial concentration of metal ions.Relatively large K d values above 10 5 cm 3 /g for Cs(I) were obtained in the range of 0.1-5 M HNO 3,resulting in a separation factor of Cs/Rb exceeding 10 2.In contrast,the K d values of Sr(II),Pd(II),Ru(III),La(III),Dy(III),Ce(III) and Zr(IV) were considerably lower than 50 cm 3 /g.The K d value of Cs(I) decreased in the order of the coexisting ions,H + > Na + >> NH 4 +,and a linear relationship with a slop of about 1 was obtained between log K d and log [NH 4 + ]([NH 4 + ] > 0.01 M).The adsorption of Cs(I) was found to be controlled by chemisorption mechanism,and followed a Langmuir-type adsorption equation.A high uptake percentage of 99.4% for Cs(I) was obtained by using the dissolved solutions of spent fuel from FBR-JOYO(JAEA).