The first (<Superscript>31</Superscript>P, <Superscript>17</Superscript>O,and <Superscript>103</Superscript>Rh) NMR observation complex formation of rhodium(III) with phosphoric acid

³¹P, ¹⁷O, and ¹⁰³Rh NMR spectroscopy shows that rhodium(III) reacts with phosphoric acid to generate polynuclear aquaphosphate complexes in which phosphate ions mostly have a bridging function. Assignment of ¹⁰³Rh NMR signals in dominant rhodium complexes is suggested.     

<Superscript>103</Superscript>Rh, <Superscript>17</Superscript>O,and <Superscript>31</Superscript>P NMR study of Rh(III) complex formation in acidic sulfate-phosphate media

Rhodium(III) complex formation with phosphoric acid in strong acidic solutions has been studied by ¹⁰³Rh, ¹⁷O, and ³¹P NMR. Phosphoric acid is mainly coordinated to rhodium as a monodentate terminal HPO₄²⁻ ion, while the coordinated phosphate ion accounts for no more than 7%.     

Formation of mononuclear rhodium(III) sulfates: <Superscript>103</Superscript>Rh and <Superscript>17</Superscript>O NMR study

It was shown that the monomeric rhodium sulfate complexes [Rh(H₂O)₄(SO₄)]⁺, trans-[Rh(H₂O)₂(SO₄)₂]^?, cis-[Rh(H₂O)₂(SO₄)₂]^?, and [Rh(SO₄)₃]^3? were not predominant forms in aqueous solutions. The ¹⁰³Rh NMR chemical shifts of the complexes were assigned, and the conditions for their formation in solutions, concentration parameters, and acidity at which the fraction of the monomers was maximal were determined. The constants of formation of the complexes and ion pair (IP) were estimated: K _IP = 8 ± 3.5, K ₁ ≈ 8, K _2trans ≈ 1, K _2cis ≈ 1, and K ₃ ≈ 2.     

The stability of the <Superscript>105</Superscript>[Rh(16S<Subscript>4</Subscript>diol)Cl<Subscript>2</Subscript>]<Superscript>+</Superscript> radiopharmaceutical precursor in solutions containing human plasma thiols

¹⁰⁵Rh[1,5,9,13-tetrathiacyclohexadecane-3,11-diol] is a promising drug precursor for targeted radiotherapy. Nevertheless, the axial position of chloride ions in the complex structure and their weak binding to rhodium centre, due to HSAB concept, make such a complex subject to modifying action of certain sulphuric ligands, like human plasma thiol antioxidants: glutathione and cysteine. Experiments were performed with both radioactive ¹⁰⁵Rh and inactive rhodium. The complexation of rhodium with 1,5,9,13-tetrathiacyclohexadecane-3,11-diol (16S₄diol) resulted in three distinct peaks seen on UV, radiometric and MS chromatograms. The substitution of chlorides was noted in over 80% of ¹⁰⁵[Rh(16S₄diol)Cl₂]⁺ units after incubation with glutathione, and less than 10% of complex units after incubation with cysteine (24 h, 37 °C). Reaction of ¹⁰⁵[Rh(16S₄diol)Cl₂]⁺ with 1,8-octandithiol and 1,9-nonandithiol resulted in disappearance of the complex peak and occurrence of two new peaks. Product of RhCl₃ and 16S₄diol reaction is a mixture of three distinct forms having different number of chlorine atoms. Our in vitro experiments suggest that the substitution of axial chlorides with glutathione and cysteine might also occur in vivo in human plasma. Glutathione shows higher reactivity than cysteine in replacement reaction. Axial positions in precursor might be effectively blocked by 1,8-octandithiol and 1,9-nonandithiol.     

Extraction of metal ions (Fe<Superscript>3+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript>, Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript>) using immobilized-polysiloxane iminobis(n-2-aminophenylacetamide) ligand system

A new insoluble solid functionalized ligand system bearing chelating ligand group of the general formula P-(CH₂)₃-N[CH₂CONH(C₆H₄)NH₂]₂, where P represents [Si–O] _n polysiloxane network, was prepared by the reaction of the immobilized diethyliminodiacetate polysiloxane ligand system, P-(CH₂)₃N(CH₂CO₂Et)₂ with 1,2-diaminobenzene in toluene. ¹³C CP-MAS NMR, XPS and FTIR results showed that most ethylacetate groups (–COOEt) were converted into the amide groups (–N–C=O). The new functionalized ligand system exhibits high capacity for extraction and removal of the metal ions (Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) with efficiency of 95–97% after recovery from its primary metal complexes. This functionalized ligand system formed 1:1 metal to ligand complexes.     

Interaction energies of histidine with cations (H<Superscript>+</Superscript>, Li<Superscript>+</Superscript>, Na<Superscript>+</Superscript>, K<Superscript>+</Superscript>, Mg<Superscript>2+</Superscript>, Ca<Superscript>2+</Superscript>)

The imidazol side group of histidine has two nitrogen atoms capable of being protonated or participating in metal binding. Hence, histidine can take on various metal-bound and protonated forms in proteins. Because of its variable structural state, histidine often functions as a key amino acid residue in enzymatic reactions. Ab initio (HF and MP2) calculations were done in modeling the cation (H⁺, Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺) interaction with side chain of histidine. The region selectivity of metal ion complexation is controlled by the affinity of the side of attack. In the imidazol unite of histidine the ring nitrogen has much higher metal ion (as well as proton) affinity. The complexation energies with the model systems decrease in the following order: Mg²⁺ > Ca²⁺ > Li⁺ > Na⁺ > K⁺. The variation of the bond lengths and the extent of charge transfer upon complexation correlate well with the computed interaction energies.     

Electrodissolution system for rhodium fragmented electroplated targets used for the industrial cyclotron production of <Superscript>103</Superscript>Pd

The present paper discusses the development of a high current density (2 A cm⁻²) electrodissolution system of Rh targets that allows the solubility of rhodium fragments, powder and pieces of foils and wires in the presence of hydrochloric and chlorine gas for the production of ¹⁰³Pd.     

Structure of binuclear platinum(III) acetamidate complexes in solutions as probed by <Superscript>195</Superscript>Pt, <Superscript>13</Superscript>C,and <Superscript>1</Superscript>H NMR spectroscopy

¹⁹⁵Pt, ¹H, and ¹³C NMR spectroscopy was used to study the structure of binuclear platinum(III) acetamidate complexes with 1,10-phenanthroline and 2,2′-bipyridine ligands [Pt₂(phen)₂(acam)₄](NO₃)₂ (1) and [Pt₂(bipy)₂(acam)₄](NO₃)₂ (2) in aqueous solutions. The ¹⁹⁵Pt NMR spectra of solutions of complexes 1 and 2 in D₂O exhibit two signals with satellites due to the ¹⁹⁵Pt–¹⁹⁵Pt spin-spin coupling (¹ J(Pt–Pt) ≈ 6345 Hz), whereas their ¹H and ¹³C NMR spectra contain four sets of signals for the protons and the carbon atoms of the heterocyclic and acetamidate ligands. The signals were assigned using the COSY, NOESY, and HSQC/ HMBC experiments and comparing the coordination shifts of the signals for the protons of heterocycles. These data allowed us to draw a conclusion that binuclear complexes 1 and 2 in solution have a head-to-head structure with nonequivalent platinum(III) atoms (coordination cores PtN₅ and PtN₃O₂), the axial-equatorial coordination of the bidentate heterocyclic molecules, and two bridging and two terminal acetamidate ligands.     

Thermodynamic behavior of complexation of 18-crown-6 with Tl<Superscript>+</Superscript>, Pb<Superscript>2+</Superscript>, Hg<Superscript>2+</Superscript>, and Zn<Superscript>2+</Superscript> metal cations in methanol-water binary media

The equilibrium constants and thermodynamic parameters for complex formation of 18-Crown-6 (18C6) with Tl⁺, Pb²⁺, Hg²⁺, and Zn²⁺ metal cations have been determined by conductivity measurements in methanol (MeOH)-water (H₂O) binary solutions. 18-Crown-6 forms 1:1 complexes with Hg²⁺ and Zn²⁺ cations, but in the case of Tl⁺ and Pb²⁺ cations, in addition to 1:1 stoichiometry, 1:2 (ML₂) complexes are formed in some binary solvents. The thermodynamic parameters (ΔH _c⁰ and ΔS _c⁰), which were obtained from the temperature dependences of equilibrium constants, show that in most cases the complexes are enthalpy destabilized but entropy stabilized. Non-linear behavior is observed between the equilibrium constants (log K _f ) of complexes and the composition of the mixed solvent. The selectivity of the ligand for these metal cations is sensitive to the solvent composition, and, in some cases, the selectivity order is reversed in certain compositions of the mixed solvent. The results also show that the mechanism of complexation reactions and the stoichiometry of complexes of some metal cations change with the nature and even with the composition of the mixed solvent. The article was submitted by the authors in English.     

Study of Complex Formation between Kryptofix 21 with La<Superscript>3+</Superscript>, Y<Superscript>3+</Superscript> and Ce<Superscript>3+</Superscript> Cations in Some Binary Mixed Non-Aqueous Solvents Using the Conductometric Method

The complexation reactions between La³⁺, Y³⁺ and Ce³⁺ cations with the macrocyclic ligand, kryptofix 21, were studied in methanol-acetonitrile (MeOH-AN) and methanol-methylacetate (MeOHMeOAc) binary mixed solvent solutions at different temperatures using the conductometric method. The conductance data show that in most solvent systems, the kryptofix 21 forms a 1: 1 [M: L] complex with La³⁺, Y³⁺ and Ce³⁺ metal cations, but in the case of Y³⁺ cation in pure methylacetate, in addition of formation of a 1: 1 [ML] complex, 1: 2 [ML₂] and 1: 3 [ML₃] complexes are formed in solution. In the case of Ce³⁺cation, a 1: 1 [ML] and also a 1: 2 [ML₂] complexes are formed in this solvent system at all studied temperatures. The electrical conductance data in acetonitrile, show that a 1: 1 [ML] and also a 1: 2 [ML₂] complexes are formed between the ligand and La³⁺ and Ce³⁺ metal cations at different temperatures. The stability constants of the 1: 1 [ML] complexes were determined using the conductometric data and a computer program, GENPLOT. A non-monotonic relationship was observed between log_{K f} of the 1: 1 complexes with the composition of the binary solvent solutions which was discussed in term of solvent-solvent interactions and also preferential solvation of the metal cations and the ligand in solutions. The selectivity order of the ligand for the metal cations in MeOH–AN and MeOH–MeOAc binary solvent solutions, at 25°C was found to be: Y³⁺ > La³⁺ > Ce³⁺ and La³⁺ > Y³⁺ > Ce³⁺, respectively. The values of the standard thermodynamic quantities (ΔH _c ^° and ΔS _c ^° ) for formation of the 1: 1 complexes were obtained from temperature dependence of the stability constans of the complexes and the results show that the thermodynamics of the complexation reactions between kryptofix 21 and La³⁺, Y³⁺ and Ce³⁺ cations, is affected by the nature and composition of the mixed solvents systems.     

<Superscript>103</Superscript>Ru/<Superscript>103m</Superscript>Rh generator

^103mRh is a very promising radionuclide for Auger electron therapy due to its very low photon/electron ratio. The goal of the present work was the elaboration a method for production of large quantities of ^103mRh for generator system. It was found that the combination of solvent extraction with evaporation of ¹⁰³RuO₄ followed by decomposition of H₅IO₆ makes it possible to produce ^103mRh of high radionuclidic and chemical purity.     

Thermodynamics of citrate complexation with Mn<Superscript>2+</Superscript>, Co<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> ions

Isothermal titration calorimetry has been used to determine the stoichiometry, formation constants and thermodynamic parameters (ΔG ^o, ΔH, ΔS) for the formation of the citrate complexes with the Mn²⁺, Co²⁺, Ni²⁺ and Zn²⁺ ions. The measurements were run in Cacodylate, Pipes and Mes buffer solutions with a pH of 6, at 298.15 K. A constant ionic strength of 100 mM was maintained with NaClO₄. The influence of a metal ion on its interaction energy with the citrate ions and the stability of the resulting complexes have been discussed.     

Synthesis and properties of potassium salts of per-<Emphasis Type="Italic">O</Emphasis>-carboxymethyl-calix[4]pyrogallols and their complexes with Cu<Superscript>2+</Superscript>, Fe<Superscript>3+</Superscript>, and La<Superscript>3+</Superscript>

Synthesis of water-soluble potassium salts of carboxymethyl derivatives of calix[4]pyrogallols and dodeca(carboxylatomethyl)tetramethylcalix[4]pyrogallol (L) complexes with transition metal ions (Cu²⁺, Fe³⁺, La³⁺) is described. Their structures in the solid state and in solution were characterized by NMR spectroscopy, ESR, and IR spectroscopy. Calix[4]pyrogallol dodecacarboxylates exist in the rccc-configuration. Calix[4]pyrogallol with methyl substituents at the lower rim in a wide range concentrations exists in water predominantly in the dimeric form. The obtained polynuclear transition metal complexes possess less symmetric structure than potassium salt of calix[4]pyrogallol (K₁₂L). All studied complexes contain water molecules bound by rather strong hydrogen bonds. At room temperature the Fe₄L complex is characterized by the environment of the Fe³⁺ ions close to octahedral. The absence of signals in the ESR spectrum of the Cu₆L complex indicates the strong antiferromagnetic interaction Cu²⁺-Cu²⁺.     

Synthesis,Structure, and Magnetic Properties of a Twist Linear Tetranuclear Co<Stack><Subscript>2</Subscript><Superscript>III</Superscript></Stack>Ln<Stack><Subscript>2</Subscript><Superscript>III</Superscript></Stack> Complexes

A series of twist linear tetranuclear 3d–4f Co ₂ ^III Ln ₂ ^III [Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5)] complexes have been prepared under solvothermal conditions and structurally characterized with Schiff-base ligand 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H₄L). The two central Co ions are linked by two alkoxyl oxygen atoms, and one Ln ion lying above and the other below the Co–Co dimer, form a twist linear array. The magnetic susceptibility studies reveal antiferromagnetic or ferromagnetic behaviour, whilst dynamic magnetic studies indicate no slow magnetic relaxation for these complexes.     

Thermodynamics of Complex Formation of Ce<Superscript>3+</Superscript> and La<Superscript>3+</Superscript> Ions with Glycylglycine in Aqueous Solution

Enthalpy of the complex formation between diglycine (HL^±) and Ce³⁺ or La³⁺ at 308.15 K and ionic strength of 0.5 mol/L (KNO₃) has been determined by means of calorimetry. Thermodynamic parameters of the diglycine complexes formation with Ce³⁺ and La³⁺ at different metal to ligand molar ratios have been determined.     

Sorption of Cu<Superscript>2+</Superscript> and Zn<Superscript>2+</Superscript> by Natural Biomaterial: Duck Feather

Feather fibers were modified by treatment with 5% tannic acid (TA) solution. Kinetics of the modification was investigated as a function of the reaction time. The maximum loading of TA on feather reached 8.3% after being treated by TA for 9 h. The adsorption of metal cations (Cu²⁺, Zn²⁺) by unmodified and TA-modified feather fibers was investigated as a function of fiber weight gain, temperature, and pH of the metal solution. The adsorption was enhanced at alkaline pH and ambient temperature and increased with the weight gain of TA. The maximum uptake of metal cations (Cu²⁺, 0.77 mmol/g; Zn²⁺, 0.95 mmol/g) was obtained by TA-modified feather at weight gain: 8.3%, pH 11, while at the acidic pH, the adsorption of metal cations by either unmodified or TA-modified feather was negligible. The influence of anions on the adsorption of metal cations was also studied. The uptake of Cu²⁺ from chloride was higher and faster than that from nitrate. Desorption of the metals was performed at acidic pH 2.5 for 48 h. The feather–TA–metal complexes exhibited higher stability for metal cations than the feather–metal complexes. All these experiments reveal that TA-modified feather fibers have good adsorption to metal cations and can be used as metal adsorbent in wastewater treatment.     

Crystal structure of two polymorphs of molybdenyl salicylidene-2-furfuriliminate (HL<Superscript>1</Superscript>) [MoO<Subscript>2</Subscript>(L<Superscript>1</Superscript>)<Subscript>2</Subscript>]

The crystal structures of two polymorphs of molybdenyl salicylidene-2-furfuryliminate [MoO₂(L¹)₂] have been solved by X-ray diffraction. Both complexes crystallize in centrosymmetric and non-centrosymmetric space groups (P2₁/c and Р2₁, respectively) of monoclinic system and have similar structures and close geometric parameters. The Мо atoms have a distorted octahedral coordination to two terminal oxo ligands in cis-positions to each other and two pairs of the oxygen atoms (cis- to О(oxo)) and the nitrogen atoms (trans- to О(oxo)) of two bidentate chelate ligands (L¹)^–.     

Kinetics of catalytic oxidation of carbon black in the presence of [Cu(L<Superscript>1</Superscript>/L<Superscript>2</Superscript>)][MCl<Subscript>4</Subscript>] complexes deposited on its surface

We have studied the kinetics of oxidation of carbon black by atmospheric oxygen in the presence of heterogenized heterobimetallic complexes [Cu(L¹/L²)][MCl₄] (M = Zn, Mn; L¹ = 4,6,6-trimethyl-1,9-diamino-3,7-diazanona-3-ene; L² = 1,15-dihydroxy-7,9,9-trimethyl-3,6,10,13-tetraazapentadeca-6-ene). We have established that deposition of the complexes considerably increases the oxidation rate for carbon black compared with deposition of the salts. Complexes containing the metal pair Cu–Mn and more hydrophobic ligands have the highest catalytic activity. We have obtained the kinetic parameters of the carbon black oxidation process in the presence of the complexes. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 3, pp. 190-195, May-June, 2009.     

Interaction of copper(II) halides with 4-azafluorene derivatives in neutral and acid media. Crystal and molecular structure of 4-aza-9-oxofluorenium tetrabromocuprate hydrate (HL<Superscript>4</Superscript>)<Subscript>2</Subscript>CuB<Subscript>4</Subscript> · H<Subscript>2</Subscript>O

Complexes of copper(II) halides (chlorides and bromides) with some 4-azafluorene derivatives have been synthesized and studied by X-ray crystallography and IR and UV spectroscopy. In neutral media, Cu(L)₂X₂ (X = Cl, Br) complexes are formed in which the ligands are coordinated to the metal atoms though the lone pair of the endocyclic nitrogen atom and through the oxygen atoms of substituents. In acid media at pH 2, (HL²)₂CuX₄ complexes are formed in which the 4-azafluorene molecules protonated at the endocyclic nitrogen atom act as an outer-sphere cation. The molecule and crystal structure of 4-aza-9-oxofluorenium tetrabromocuprate hydrate (HL⁴)₂CuBr₄·H₂O has been determined.     

Thermodynamics of reactions of complex formation for Ce<Superscript>3+</Superscript> and Er<Superscript>3+</Superscript> ions with glycine in an aqueous solution

Enthalpies of complex formation for glycine (HL^±) with Ce³⁺ and Er³⁺ ions at 298.15 K and the value of the ionic strength of 0.5 (KNO₃) are determined by calorimetric means using two independent procedures. Thermodynamic characteristics of the reactions of formation for complexes of glycine with Ce³⁺ and Er³⁺ ions at various [metal]: [ligand] molar ratios are calculated.