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.     

Ionic medium effects on equilibrium constants Part I. Proton, copper(II), cadmium(II), lead(II) and acetate activity coefficients in aqueous solution

The molar single ion activity coefficients associated with hydrogen, copper(II), cadmium(II) and lead(II) ions were determined at 25 degrees C and ionic strengths between 0.100 and 3.00 M (NaClO4), whereas for acetate the ionic strengths were fixed between 0.300 and 2.00 M, held with the same inert electrolyte. The investigation was carried out potentiometrically by using proton-sensitive glass, copper, cadmium and lead ion-selective electrodes and a second-class Hg|Hg2(CH3COO)2 electrode. It was found that the activity coefficients of these ions (y(i)) can be assessed through the following empirical equations: log y(H) = -0.542I(0.5) + 0.451I; log y(Cu) = -1.249I(0.5) + 0.912I; log y(Cd) = -0.829I(0.5) + 0.448I(1.5); log y(Pb) = -0.404I(0.5) + 0.117I(2); and log y(Ac) = 0.0370I     

Iron(II) and nickel(II) mixed-ligand complexes containing 1,10-phenanthroline and 4,7-diphenyl-1,10-phenanthroline

Two types of mixed-ligand complexes, i.e. [M(phen)2 (dip)]2+ and [M(phen)(dip)2]2+ (M = iron(II) and nickel(II); phen = 1,10-phenanthroline and dip = 4,7-diphenyl-1,10-phenanthroline) have been prepared from their related tris-complexes, [M(phen)3]2+ by ligand substitution, and isolated by semi-preparative HPLC. Elemental and chromatographic analyses confirm the purity of the isolated complexes while u.v./vis and i.r. spectra were used to identify and characterize them. 1H-n.m.r. and room temperature Mössbauer spectra of the iron(III) complexes were also measured and the results are discussed. In addition, our preliminary results on hypochromicity in the MLCT band and circular dihroism (CD) emerging in the u.v./vis region upon addition of CT(calf thymus)-DNA to the racemic complexes indicated that the iron(II) mixed-ligand complexes interact with CT-DNA.     

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.     

Antiproliferative activity of chelating N,O- and N,N-ruthenium(II) arene functionalised poly(propyleneimine) dendrimer scaffolds

Chelating neutral (N,O) and cationic (N,N) first- and second-generation ruthenium(II) arene metallodendrimers based on poly(propyleneimine) dendrimer scaffolds were obtained from dinuclear arene ruthenium precursors by reactions with salicylaldimine and iminopyridyl dendritic ligands, respectively. The N,N cationic complexes were isolated as hexafluorophosphate salts and were characterised by NMR and IR spectroscopy, and MALDI-TOF mass spectrometry. Related mononuclear complexes were obtained in a similar manner and their molecular structures have been determined by X-ray diffraction analysis. The cytotoxicities of the mono- and multinuclear complexes were established using A2780 and A2780cisR human ovarian carcinoma cancer cell lines.     

The redox series [M(bpy)2(q)]n+, M = Ru or Os, Q = 3,5-di-tert-butyl-n-phenyl-1,2-benzoquinonemonoimine. Isolation and a complete X and W band EPR study of the semiquinone states (n = 1)

The complexes [M(bpy)(2)(Q)](PF(6)) (bpy = 2,2'-bipyridyl; M = Ru, Os; Q = 3,5-di-tert-butyl-N-phenyl-1,2-benzoquinonemonoimine) were isolated and studied by X and W band EPR in a dichloromethane solution at ambient temperatures and at 4 K. For M = Ru, the (14)N hyperfine splitting confirms the Ru(II)/semiquinone formulation, although at a > 1 mT, the (99,101)Ru satellite coupling is unusually high. W band EPR allowed us to determine the relatively small g anisotropy Delta g = g(1) - g(3) = 0.0665 for the ruthenium complex. The osmium analogue exhibits a much higher difference Delta g = 0.370, which is attributed not only to the larger spin-orbit coupling constant of Os versus that of Ru but also to a higher extent of metal contribution to the singly occupied molecular orbital. The difference Delta E between the oxidation and reduction potentials of the radical complexes is larger for the ruthenium compound (Delta E = 0.87 V) than for the osmium analogue (Delta E = 0.72), confirming the difference in metal/ligand interaction. The electrochemically generated states [M(bpy)(2)(Q)](n+), n = 0, 1, 2, and 3, were also characterized using UV-vis-near-infrared spectroelectrochemistry.     

Mononuclear cyano- and hydroxo-complexes of iron(III)

A detailed investigation of the iron(III)-cyanide and iron(III)-hydroxide systems has been made in NaClO(4) media at 25 degrees C, using combined UV-vis spectrophotometric and pH-potentiometric titrations. For the Fe(III)/OH- system, use of low total Fe(III) concentrations (< or =10 microM) and a wide pH range (0 < or = pH < or = 12.7) enabled detection of six mononuclear complexes, corresponding to the following equilibria: Fe3+(aq)+rH2O<=>Fe(OH)r(3-r)+(aq) + rH(+)(aq), where r = 1-6 with stability constants (log *beta 1r) of -2.66, -7.0, -12.5, -20.7, -30.8, and -43.4, respectively, at I = 1 M (NaClO(4)). It was also found to be possible to measure, for the first time, stability constants for most of the following equilibria: Fe3+(aq)+qCN-(aq)<=>Fe(CN)q(3-q)+(aq), despite a plethora of complicating factors. Values of log beta(1q) = 8.5, 15.8, 23.1, and 38.8 were obtained at I = 1.0 M (NaClO(4)) for q = 1-3 and 6, respectively. No reliable evidence could be obtained for the intermediate (q = 4 or 5) complexes. Similar results were obtained for both systems at I = 0.5 M(NaClO(4)). Spectra for the individual mononuclear complexes detected for Fe(III) with OH- and CN- are reported. Attempted measurements on the Fe(II)/CN- system were unsuccessful, but values of log beta(16)(Fe(CN)(6)(4-)) = 31.8 and log beta(15)(Fe(CN)(5)(3-) approximately 24 were estimated from well established electrode potential and other data.     

Rigid MIIL2Gd2III (M = Fe, Ru) complexes of a terpyridine-based heteroditopic chelate: a class of candidates for MRI contrast agents

Rigid chelates of high-molecular weight, [M(tpy-DTTA)2]6- (M = Fe, Ru), are obtained upon self-assembly around one M(II) ion of two terpyridine-based molecules substituted in the 4'-position with the polyaminocarboxylate diethylenetriamine-N,N,N',N'-tetraacetate, tpy-DTTA4-. The protonation constants of tpy-DTTA4- (log K1 = 8.65(4), log K2 = 7.63(4), log K3 = 5.25(6), log K4 = 3.30(7)) and [Fe(tpy-DTTA)2]6- (log K1 = 8.40(4), log K2 = 7.26(4)) have been determined by potentiometry, 1H NMR and UV-vis titrations. The thermodynamic stability constant log K(GdL) of [Fe(tpy-DTTA)2Gd2(H2O)4] measured at 25 degrees C by potentiometry is 10.87. This relatively low value is due to the direct linkage of the polyaminocarboxylate part to the electron-withdrawing terpyridine. UV-vis absorbance spectra of [M(tpy-DTTA)2Gd2(H2O)4] and 1H NMR spectra of [M(tpy-DTTA)2Eu2(H2O)4] revealed similar solution behavior of the Fe and Ru complexes. An I(d) water-exchange mechanism (DeltaV++ = +6.8 +/- 1 cm3 mol(-1)) with a rate constant of k(ex)298 = (5.1 +/- 0.3) x 10(6) s(-1) has been found for [Fe(tpy-DTTA)2Gd2(H2O)4] by 17O NMR. A slow rotational correlation time (tau(RO) = 410 +/- 10 ps) and the presence of two water molecules (q = 2) in the coordination inner-sphere of each Gd(III) ion have also been determined for this complex. A remarkably high relaxivity has been observed for both [M(tpy-DTTA)2Gd2(H2O)4] complexes (at 20 MHz and 37 degrees C, r(1) = 15.7 mM(-1) s(-1) for the Fe complex, and r(1) = 15.6 mM(-1) s(-1) for the Ru complex).     

Structural characterization and formation kinetics of sitting-atop (SAT) complexes of some porphyrins with copper(II) ion in aqueous acetonitrile relevant to porphyrin metalation mechanism. Structures of aquacopper(II) and cu(II)-SAT complexes as determined by XAFS spectroscopy

The formation of the sitting-atop (SAT) complexes of 5,10,15,20-tetraphenylporphyrin (H(2)tpp), 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin (H(2)t(4-Clp)p), 5,10,15,20-tetramesitylporphyrin (H(2)tmp), and 2,3,7,8,12,13,17,18-octaethylporphyrin (H(2)oep) with the Cu(II) ion was spectrophotometrically confirmed in aqueous acetonitrile (AN), and the formation rates were determined as a function of the water concentration (C(W)). The decrease in the conditional first-order rate constants with the increasing C(W) was reproduced by taking into consideration the contribution of [Cu(H(2)O)(an)(5)](2+) in addition to [Cu(an)(6)](2+) to form the Cu(II)-SAT complexes. The second-order rate constants for the reaction of [Cu(an)(6)](2+) and [Cu(H(2)O)(an)(5)](2+) at 298 K were respectively determined as follows: (4.1 +/- 0.2) x 10(5) and (3.6 +/- 0.2) x 10(4) M(-1) s(-1) for H(2)tpp, (1.15 +/- 0.06) x 10(5) M(-1) s(-1) and negligible for H(2)t(4-Clp)p, and (4.8 +/- 0.3) x 10(3) and (1.3 +/- 0.3) x 10(2) M(-1) s(-1) for H(2)tmp. Since the reaction of H(2)oep was too fast to observe the reaction trace due to the dead time of 2 ms for the present stopped-flow technique, the rate constant was estimated to be greater than 1.5 x 10(6) M(-1) s(-1). According to the structure of the Cu(II)-SAT complexes determined by the fluorescent XAFS measurements, two pyrrolenine nitrogens of the meso-substituted porphyrins (H(2)tpp and H(2)tmp) bind to the Cu(II) ion with a Cu-N(pyr) distance of ca. 2.04 A, while those of the beta-pyrrole-substituted porphyrin (H(2)oep) coordinate with the corresponding bond distance of 1.97 A. The shorter distance of H(2)oep is ascribed to the flexibility of the porphyrin ring, and the much greater rate for the formation of the Cu(II)-SAT complex of H(2)oep than those for the meso-substituted porphyrins is interpreted as due to a small energetic loss at the porphyrin deformation step during the formation of the Cu(II)-SAT complex. The overall formation constants, beta(n), of [Cu(H(2)O)(n)()(an)(6)(-)(n)](2+) for the water addition in aqueous AN were spectrophotometrically determined at 298 K as follows: log(beta(1)/M(-1)) = 1.19 +/- 0.18, log(beta(2)/M(-2)) = 1.86 +/- 0.35, and log(beta(3)/M(-3)) = 2.12 +/- 0.57. The structure parameters around the Cu(II) ion in [Cu(H(2)O)(n)(an)(6-n)](2+) were determined using XAFS spectroscopy.     

Hydrogen-atom transfer in open-shell organometallic chemistry: the reactivity of Rh(II)(cod) and Ir(II)(cod) radicals

A series of new metalloradical rhodium and iridium complexes [M(II)(cod)(N-ligand)](2+) in the uncommon oxidation state +II were synthesized by one-electron oxidation of their [M(I)(cod)(N-ligand)](+) precursors (M=Rh, Ir; cod=(Z,Z)-1,5-cyclooctadiene; and N-ligand is a podal bis(pyridyl)amine ligand: N,N-bis(2-pyridylmethyl)amine (dpa), N-(2-pyridylmethyl)-N-(6-methyl-2-pyridylmethyl)amine (pla), or N-benzyl-N,N-bis(6-methyl-2-pyridylmethyl)amine (Bn-dla). EPR spectroscopy, X-ray diffraction, and DFT calculations reveal that each of these [M(II)(cod)(N-ligand)](2+) species adopts a square-pyramidal geometry with the two cod double bonds and the two pyridine fragments in the basal plane and the N(amine) donor at the apical position. The unpaired electron of these species mainly resides at the metal center, but the apical N(amine) donor also carries a considerable fraction of the total spin density (15-18 %). Density functional calculations proved a valuable tool for the analysis and simulation of the experimental EPR spectra. Whereas the M(II)(olefin) complexes are quite stable as solids, in solution they spontaneously transform into a 1:1 mixture of M(III)(allyl) species and protonated M(I)(olefin) complexes (in the forms [M(I)(olefin)(protonated N-ligand)](2+) for M=Rh and [M(III)(H)(olefin)(N-ligand)](2+) for M=Ir). Similar reactions were observed for the related propene complex [M(II)(propene)(Me(2)tpa)](2+) (Me(2)tpa=N,N,N-tris(6-methyl-2-pyridylmethyl)amine). The decomposition rate of the [M(II)(cod)(N-ligand)](2+) species decreases with increasing N-ligand bulk in the following order: dpa>pla>Bn-dla. Decomposition of the most hindered [M(II)(cod)(Bn-dla)](2+) complexes proceeds by a second-order process. The kinetic rate expression v=k(obs)[M(II)](2) in acetone with k(obs)=k'[H(+)][S], where [S] is the concentration of additional coordinating reagents (MeCN), is in agreement with ligand-assisted dissociation of one of the pyridine donors. Solvent coordination results in formation of more open, reactive species. Protonation of the noncoordinating pyridyl group increases the concentration of this species, and thus [H(+)] appears in the kinetic rate expression. The kinetic data are in agreement with bimolecular hydrogen-atom transfer from M(II)(cod) to another M(II) species (DeltaH( not equal)=11.5+/-2 kcal mol(-1), DeltaS( not equal)=-27+/-10 cal K(-1) mol(-1), and DeltaG( not equal)(298 K)=19.5+/-5 kcal mol(-1)).     

Formation,structure and reactivity of boryloxycarbyne complexes of group 6 metals

Reaction of the diborane(4) B(2)(NMe(2))(2)I(2) with two equivalents of K[(eta(5)-C(5)H(5))M(CO)(3)] (M=Cr, Mo, W) yielded the dinuclear boryloxycarbyne complexes [[(eta(5)-C(5)H(5))(OC)(2)M(triple bond)CO](2)B(2)(NMe(2))(2)] (4 a, M=Mo; b, M=W; c, M=Cr), which were fully characterised in solution by multinuclear NMR methods. The Mo and W complexes 4 a, b proved to be kinetically favoured products of this reaction and underwent quantitative rearrangement in solution to afford the complexes [[(eta(5)-C(5)H(5))(OC)(2)M(triple bond)CO]B(NMe(2))B(NMe(2))[M(CO)(3)(eta(5)-C(5)H(5))]] (5 a, M=Mo; b, M=W); 5 a was characterised by X-ray crystallography in the solid state. Corresponding reactions of B(2)(NMe(2))(2)I(2) with only one equivalent of K[(eta(5)-C(5)H(5))M(CO)(3)] (M=Mo, W) initially afforded 1:1 mixtures of the boryloxycarbyne complexes 4 a, b and unconsumed B(2)(NMe(2))(2)I(2). This mixture, however, yielded finally the diborane(4)yl complexes [(eta(5)-C(5)H(5))(OC)(3)M[B(NMe(2))B(NMe(2))I]] (6 a, M=Mo; b, M=W) by [(eta(5)-C(5)H(5))(OC)(3)M] transfer and rearrangement. Density functional calculations were carried out for 4 c and 5 a, b.     

Complexation of Nickel(II) with Guanosine 5'-Monophosphate and Inosine 5'-Monophosphate: A Potentiometric and Calorimetric Study

The constants (K(s)) and enthalpies (DeltaH(s)) for stacking interactions between purine nucleoside monophosphates were determined by calorimetry; the values thus obtained were guanosine as follows: K(s) = 2.1 +/- 0.3 M(-)(1) and DeltaH(s) = -41.8 +/- 0.8 kJ/mol for adenosine 5'-monophosphate (5'AMP); K(s) = 1.5 +/- 0.3 M(-1) and DeltaH(s) = -42.0 +/- 1.5 kJ/mol for guanosine 5'-monophosphate (5'GMP); and K(s) = 1.0 +/- 0.2 M(-1) and DeltaH(s) = -42.3 +/- 1.1 kJ/mol for inosine 5'-monophosphate (5'IMP). The interaction of nickel(II) with purine nucleoside monophosphates was studied using potentiometric and calorimetric methods, with 0.1 M tetramethylammonium bromide as the background electrolyte, at 25 degrees C. The presence in solution of the complexes [Ni(5'GMP)(2)](2)(-) and [Ni(5'IMP)(2)](2)(-) was observed. The thermodynamic parameters obtained were log K(ML) = 3.04 +/- 0.02, log K(ML2) = 2.33 +/- 0.02, DeltaH(ML) = -18.4 +/- 0.9 kJ/mol and DeltaH(ML2) = -9.0 +/- 1.9 kJ/mol for 5'GMP; and log K(ML) = 2.91 +/- 0.01, log K(ML2) = 1.92 +/- 0.01, DeltaH(ML) = -16.2 +/- 0.9 kJ/mol and DeltaH(ML2) = -0.1 +/- 2.3 kJ/mol for 5'IMP. The relationships between complex enthalpies and the degree of macrochelation, as well as the stacking interaction between purine bases in the complexes are discussed in relation to previously reported calorimetric data.     

Exploring the interaction of ruthenium(II) polypyridyl complexes with DNA using single-molecule techniques

Here we explore DNA binding by a family of ruthenium(II) polypyridyl complexes using an atomic force microscope (AFM) and optical tweezers. We demonstrate using AFM that Ru(bpy)2dppz2+ intercalates into DNA (K(b) = 1.5 x 10(5) M(-1)), as does its close relative Ru(bpy)2dppx2+ (K(b) = 1.5 x 10(5) M(-1)). However, intercalation by Ru(phen)3(2+) and other Ru(II) complexes with K(b) values lower than that of Ru(bpy)2dppz2+ is difficult to determine using AFM because of competing aggregation and surface-binding phenomena. At the high Ru(II) concentrations required to evaluate intercalation, most of the DNA strands acquire a twisted, curled conformation that is impossible to measure accurately. The condensation of DNA on mica in the presence of polycations is well known, but it clearly precludes the accurate assessment by AFM of DNA intercalation by most Ru(II) complexes, though not by ethidium bromide and other monovalent intercalators. When stretching individual DNA molecules using optical tweezers, the same limitation on high metal concentration does not exist. Using optical tweezers, we show that Ru(phen)2dppz2+ intercalates avidly (K(b) = 3.2 x 10(6) M(-1)) whereas Ru(bpy)3(2+) does not intercalate, even at micromolar ruthenium concentrations. Ru(phen)3(2+) is shown to intercalate weakly (i.e., at micromolar concentrations (K(b) = 8.8 x 10(3) M(-1))). The distinct differences in DNA stretching behavior between Ru(phen)3(2+) and Ru(bpy)3(2+) clearly illustrate that intercalation can be distinguished from groove binding by pulling the DNA with optical tweezers. Our results demonstrate both the benefits and challenges of two single-molecule methods of exploring DNA binding and help to elucidate the mode of binding of Ru(phen)3(2+).     

Cationic sigma-phenylplatinum(II) complexes with carboxylic acid functionality: pK(a) determinations and x-ray structures

The preparation and characterization of a novel series of cationic sigma-phenylplatinum(II) complexes of the type trans-[Pt(sigma-C(6)H(5))(L)(2)A]OTf (A = picolinic acid, L = PPh(3) (4) and PMePh(2) (7); A = nicotinic acid, L = PPh(3) (5) and PMePh(2) (8); A = isonicotinic acid, L = PPh(3) (6), PMePh(2) (9), and PEt(3) (10)) are described. The pK(a) value for the carboxylic acid functionality in selected complexes was found to follow the order 7 (pK(a) = 5.23 +/- 0.09) > 8 (4.85 +/- 0.10) > 9 (3.51 +/- 0.08) > 6 (3.26 +/- 0.07) approximately 10 (3.21 +/- 0.08) by means of potentiometric titration experiments in 50% (v/v) EtOH/H(2)O solution at 295 K. The X-ray crystal structures of 9 and 10 were also determined. The asymmetric unit of each of 9 and 10 comprises a univalent complex cation, a triflate anion, and a solvent CH(2)Cl(2) molecule of crystallization. Centrosymmetrically related pairs of complex cations in 9 associate via the familiar carboxylic acid dimer motif, whereas with 10, the carboxylic acid dimer motif is absent. Instead, the carboxylic acid residue forms both donor and acceptor interactions to the triflate anion and CH(2)Cl(2) solvent of crystallization, respectively, to afford a 10-membered ring structure. Possible reasons for the observed differences in the solid-state structures of 9 and 10 are presented.     

Preparation, spectrochemical, and computational analysis of L-carnosine (2-[(3-aminopropanoyl)amino]-3-(1H-imidazol-5-yl)propanoic acid) and its ruthenium (II) coordination complexes in aqueous solution

This study reports the synthesis and characterization of novel ruthenium (II) complexes with the polydentate dipeptide, L-carnosine (2-[(3-aminopropanoyl)amino]-3-(1H-imidazol-5-yl)propanoic acid). Mixed-ligand complexes with the general composition [ML(p)(Cl)(q)(H?O)(r)]·xH?O (M = Ru(II); L = L-carnosine; p = 3 - q; r = 0-1; and x = 1-3) were prepared by refluxing aqueous solutions of the ligand with equimolar amounts of ruthenium chloride (black-alpha form) at 60 °C for 36 h. Physical properties of the complexes were characterized by elemental analysis, DSC/TGA, and cyclic voltammetry. The molecular structures of the complexes were elucidated using UV-Vis, ATR-IR, and heteronuclear NMR spectroscopy, then confirmed by density function theory (DFT) calculations at the B3LYP/LANL2DZ level. Two-dimensional NMR experiments (1H COSY, 13C gHMBC, and 1?N gHMBC) were also conducted for the assignment of chemical shifts and calculation of relative coordination-induced shifts (RCIS) by the complex formed. According to our results, the most probable coordination geometries of ruthenium in these compounds involve nitrogen (N1) from the imidazole ring and an oxygen atom from the carboxylic acid group of the ligand as donor atoms. Additional thermogravimetric and electrochemical data suggest that while the tetrahedral-monomer or octahedral-dimer are both possible structures of the formed complexes, the metal in either structure occurs in the 2? oxidation state. Resulting RCIS values indicate that the amide-carbonyl, and the amino-terminus of the dipeptide are not involved in chelation and these observations correlate well with theoretical shift predictions by DFT.     

Stabilities of the aqueous complexes Cm(CO3)33- and Am(CO3)33- in the temperature range 10-70 degrees C

The carbonate complexation of curium(III) in aqueous solutions with high ionic strength was investigated below solubility limits in the 10-70 degrees C temperature range using time-resolved laser-induced fluorescence spectroscopy (TRLFS). The equilibrium constant, K(3), for the Cm(CO(3))(2-) + CO(3)(2-) right harpoon over left harpoon Cm(CO(3))(3)(3-) reaction was determined (log K(3) = 2.01 +/- 0.05 at 25 degrees C, I = 3 M (NaClO(4))) and compared to scattered previously published values. The log K(3) value for Cm(III) was found to increase linearly with 1/T, reflecting a negligible temperature influence on the corresponding molar enthalpy change, Delta(r)H(3) = 12.2 +/- 4.4 kJ mol(-1), and molar entropy change, Delta(r)S(3) = 79 +/- 16 J mol(-1) K(-1). These values were extrapolated to I = 0 with the SIT formula (Delta(r)H(3) degrees = 9.4 +/- 4.8 kJ mol(-1), Delta(r)S(3) degrees = 48 +/- 23 J mol(-1) K(-1), log K(3) degrees = 0.88 +/- 0.05 at 25 degrees C). Virtually the same values were obtained from the solubility data for the analogous Am(III) complexes, which were reinterpreted considering the transformation of the solubility-controlling solid. The reaction studied was found to be driven by the entropy. This was interpreted as a result of hydration changes. As expected, excess energy changes of the reaction showed that the ionic strength had a greater influence on Delta(r)S(3) than it did on Delta(r)H(3).     

Ni(II), Cu(II), and Zn(II) dinuclear metal complexes with an aza-phenolic ligand: crystal structures,magnetic properties,and solution studies

The basicity behavior and ligational properties of the ligand 2-((bis(aminoethyl)amino)methyl)phenol (L) toward Ni(II), Cu(II), and Zn(II) ions were studied by means of potentiometric measurements in aqueous solution (298.1 +/- 0.1 K, l = 0.15 mol dm-3). The anionic L-H- species can be obtained in strong alkaline solution; this species behaves as tetraprotic base (log K1 = 11.06, log K2 = 9.85, log K3 = 8.46, log K4 = 2.38). L forms mono- and dinuclear complexes in aqueous solution with all the transition metal ions examined; the dinuclear species show a [M2(L-H)2]2+ stoichiometry in which the ligand/metal ratio is 2:2. The studies revealed that two mononuclear [ML-H]+ species self-assemble, giving the dinuclear complexes, which can be easily isolated from the aqueous solution due to their low solubility. This behavior is ascribed to the fact that L does not fulfill the coordination requirement of the ion in the mononuclear species and to the capacity of the phenolic oxygen, as phenolate, to bridge two metal ions. All three dinuclear species were characterized by determining their crystal structures, which showed similar coordination patterns, where all the single metal ions are substantially coordinated by three amine functions and two oxygen atoms of the phenolate moieties. The two metals in the dinuclear complexes are at short distance interacting together as shown by magnetic measurements performed with Ni(II) and Cu(II) complexes, which revealed an antiferromagnetic coupling between the two metal ions. The [Cu2(L-H)2]2+ cation shows a phase transition occurring by the temperature between 100 and 90 K; the characterization of the compounds existing at different temperatures was investigated using X-ray single-crystal diffraction, EPR, and magnetic measurements.     

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).     

Transition metal(II) complexes of (E)-cinnamoylferrocene (S)-methylcarbodithioylhydrazone

A new organometallic ligand, (E)-cinnamoylferrocene (S)-methylcarbodithioylhydrazone (HCfmc) and six transition metal(II) complexes thereof M(Cfmc)2·nH2O (M=Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Hg2+; n=0–2) have been prepared and characterized by elemetal analyses, i.r., u.v., 1H-n.m.r. spectra, electrochemical properties, fluorescence spectra and molar conductances. The HCfmc ligand acts as a bidentate donor, coordinating to the metal ions via nitrogen and sulfur atoms with a trans-configuration.     

Transition metal complexes coordinated by an NAD(P)H model compound and their enhanced hydride-donating abilities in the presence of a base

The ruthenium(II) and rhenium(I) complexes containing an NAD(P)H model compound, 1-benzyl-1,4-dihydronicotinamide (BNAH), as ligand, [Ru(tpy)(bpy)(BNAH)]2+ (1 a) and [Re(bpy)(CO)3(BNAH)]+ (1 b), were quantitatively produced by the reaction of the corresponding metal hydrido complexes with BNA(+) (1-benzylnicotinamidium cation). In the presence of base with pK(a) = 8.9, 1 a and 1 b have much greater reducing power than "free" BNAH. The oxidation potentials of 1 a in the absence and the presence of triethylamine were 0.55 V and -0.04 V, respectively, versus Ag/AgNO(3), whereas that of "free" BNAH was 0.30 V. Spectroscopic results clearly showed that the base extracts a proton from the carbamoyl group on 1 a and 1 b to give the deprotonated BNAH coordinating to the transition-metal complexes [Ru(tpy)(bpy)(BNAH-H+)]+ (3 a) and [Re(bpy)(CO)3(BNAH-H+)] (3 b); this deprotonation underlies the enhancement in reducing ability. The deprotonated forms 3 a and 3 b can efficiently reduce other NAD(P) models to give the corresponding 1,4-dihydro form, resulting in the deprotonated BNA+ being coordinated to the metal complexes [Ru(tpy)(bpy)(BNA(+)-H+)]2+ (2 a) and [Re(bpy)(CO)3(BNA+-H+)]+ (2 b); "free" BNAH and the protonated adducts 1 a and 1 b cannot act in this way. X-ray crystallography was performed on the PF6- salt of 2 a, and showed that the deprotonated nitrogen atom on the carbamoyl group coordinates to the ruthenium(II) metal center with a bond length of 2.086(3) Angstroms. Infrared spectral data suggested that the deprotonated carbamoyl group on the reduced forms 3 a and 3 b is converted to the imido group, and that the oxygen atom coordinates to the metal center.