EPR spectra and structures of dinuclear copper(<Emphasis Type="SmallCaps">II</Emphasis>) complexes with acyldihydrazones of benzenedicarboxylic acids

Spacer-armed dinuclear copper(II) complexes with condensation products of isophthalic and terephthalic acid dihydrazides with salicylaldehyde and 2-hydroxyacetophenone were synthesized and studied by EPR and X-ray diffraction. The compositions and structures of most of the complexes were determined by elemental analysis, thermogravimetric analysis, and IR spectroscopy. The structure of the copper(II) complex with acyldihydrazone of salicylaldehyde and 1,3-benzenedicarboxylic acid (H₄L) with the composition [Cu₂L¹·2morph·MeOH] (morph is morpholine) was established by X-ray diffraction. The Cu^II atoms are spaced by 10.29 Å and are structurally nonequivalent. One copper cation has a square-planar coordination formed by donor atoms (2 N + O) of the doubly deprotonated acylhydrazine fragment and the N atom of the morpholine molecule. The second copper atom is additionally coordinated by a methanol molecule through the oxygen atom, so that this copper atom is in a tetragonal-pyramidal coordination with the oxygen atom in the axial position. The EPR spectra of liquid solutions of the complexes based on 1,4-benzenedicarboxylic acid acyldihydrazones and 1,3-benzenedicarboxylic acid bis(salicylidene)hydrazone at room temperature show a four-line hyperfine structure with the constant a _Cu = 54.4–67.0·10⁻⁴ cm⁻¹ (g = 2.105–2.147), which is indicative of the independent behavior of the paramagnetic centers. The EPR spectrum of a solution of the complex based on isophthalic acid and 2-hydroxyacetophenone shows the seven-line hyperfine structure corresponding to two equivalent copper nuclei (g = 2.11, a _Cu = 36.5·10⁻⁴ cm⁻¹). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1898–1905, October, 2007.     

ESR spectra of spacered copper(II) dimers of 5-bromo-2-hydroxyacetophenone acyldihydrazones based on aliphatic dicarboxylic acids

Binuclear copper(II) complexes with 5-bromo-2-hydroxyacetophenone acyldihydrazones (H₄L) with the composition [Cu₂L·nPy] where the coordination polyhedra are linked by polymethylene chains with different lengths (from one to five units) have been synthesized and studied. The ESR spectrum of a polycrystalline sample of a complex based on malonyldihydrazone contains a major signal (g = 2.11) together with a weak signal corresponding to the forbidden transition (ΔM _S = 2, g = 4.18). At room temperature, ESR spectra of solutions of complexes of acyldihydrazones based on malonic, succinic, glutaric, and adipic acids contain seven HFS lines from two equivalent copper nuclei. These lines result from weak spin-spin exchange interaction between two unpaired electrons with the constant (36–38)·10⁻⁴ cm⁻¹. An increase in the polymethylene chain length to five units prevents the exchange interactions, and the ESR spectrum of a complex of the acyldihydrazone based on pimelic acid contains a signal of four HFS lines (a _Cu = 69.5·10⁻⁴ cm⁻¹), which is common to the monomeric copper(II) compounds. In the parallel orientation, the ESR spectrum of a frozen solution of the complex of malonyldihydrazone contained the superposition of signals due to fine and hyperfine structures with similar constants (D _∥ = 0.0074 cm⁻¹, A _∥ = 0.0070 cm⁻¹, g _∥ = 2.089, g _⊥ = 2.053). __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1752–1757, August, 2005.     

Synthesis and electrochemical characterization of CoII, NiII, and CuII complexes with organic N2S2-type ligands derived from 2-thio-substituted benzaldehydes and aromatic amines

Transition metal complexes (Ni^II, Co^II, and Cu^II) with tetradentate N₂S₂-type ligands (L), which are reaction products of 2-thio-substituted benzaldehydes with aromatic amines (3-aminopyridine or 2-aminothiophenol), were synthesized for the first time. The complexes have the composition L·MX₂ or L·2MX₂ (X = Cl or ClO₄). The electrochemical behavior of the ligands and complexes was studied by cyclic voltammetry and rotating disk electrode voltammetry. Depending on the structure of the complexes, the metal atom in the latter is initially reduced in a one-or two-electron process. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2115–2124, November, 2007.     

ESR study of weak exchange interactions in binuclear copper(ii) complexes with acyldihydrazones of fluorinated β-diketones

A series of binuclear copper(ii) complexes with acyldihydrazones of aliphatic dicarboxylic acids (from malonic to adipic) and fluorinated -diketones (trifluoro- and hexafluoroacetylacetone) of composition Cu₂L·2Py (H₄L is acyldihydrazone) were studied by ESR spectroscopy. The ESR spectra of solutions of complexes with trifluoroacetylacetone acyldihydrazones have an isotropic signal with a seven-line hyperfine structure from two equivalent copper nuclei (g = 2.112, a _Cu = (39—40)·10^–4 cm^–1), which is indicative of weak exchange interactions between the paramagnetic centers due to spin density delocalization through a chain of the -bonds of the polymethylene bridge. On going to hexafluoroacetylacetone derivatives, the coupling is suppressed and the ESR spectra of solutions of such complexes show a signal with a four-line hyperfine structure (g = 2.121—2.131, a _Cu = (55—63)·10^–4 cm^–1) typical of mononuclear copper complexes.     

ESR spectra of copper(ii) complexes with 2-hydroxy-5-methyl- and 5-chloro-2-hydroxyacetophenone acyldihydrazones

ESR spectra of binuclear copper(ii) complexes with 2-hydroxy-5-methyl- and 5-chloro-2-hydroxyacetophenone acyldihydrazones (H₄L) [Cu₂L·2Py], in which the coordination polyhedra are linked by the polymethylene chain with different lengths (from one to five units), were studied. The spectra of the complexes based on acyldihydrazones of malonic, succinic, glutaric, and adipic acids exhibit weak exchange interactions between the paramagnetic sites. These interactions induce seven HFS lines from two equivalent copper nuclei with the constant 40·10^–4 cm^–1 in the ESR spectra of liquid solutions. An increase in the polymethylene chain length to five units prevents the exchange interactions, and the ESR spectrum of the complex based on heptadioic acyldihydrazone contains the signal of four HFS lines with the constant 72·10^–4 cm^–1, which is common for the copper(ii) monomeric compounds.     

Critical phenomena in ethylbenzene oxidation in acetic acid solution at high cobalt(<Emphasis Type="SmallCaps">II</Emphasis>) concentrations

Critical phenomena in ethylbenzene oxidation in an acetic acid solution at high cobalt(III) concentrations (from 0.01 to 0.2 mol L⁻¹) were studied at 60–90 °C by the gasometric (O₂ absorption), spectrophotometric (Co^III accumulation), and chemiluminescence (relative concentration of radical RO₂ ^·) methods. These phenomena are as follows: (1) increase in the oxidation rate above the theoretical limiting rate of radical autooxidation (k ₃ ²[RH]²/2k ₆); (2) achievement of a maximum and a sharp decrease in the oxidation rate and concentration of radical RO₂ ^· with the further increase in the Co^II concentration (existence of critical concentrations). The oxidation rate increases due to the reaction RO₂ ^· + Co^II + H⁺ → → ROOH + Co^III, while the inhibition effect is caused by the decay of RO₂ ^· radical involving two cobalt(II) atoms: RO₂ ^· + 2 Co^II → R′CO + Co^III + Co^II (k(70 °C) ≈ 300 L² mol⁻² s⁻¹). The detailed scheme (through the formation of the complex RO₂ ^·Co^II) describing the conjugation of these reactions was proposed. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1823–1827, August, 2005.     

Ionic mobility in the antimony(<Emphasis Type="SmallCaps">iii</Emphasis>) fluorochloride complexes

Ionic mobility in the NaSbClF₃ · H₂O, KSbClF₃, and NH₄SbClF₃ fluorochloride complexes was studied by ¹H and ¹⁹F NMR spectroscopy in the temperature interval from 150 to 480 K. The types of ionic motions in the compounds were determined. Their physicochemical characteristics were compared with those of the earlier studied sodium, potassium, and ammonium tetrafluoroantimonates(iii). The replacement of one F atom by the Cl atom in MSbF₄ (M = Na, K, NH₄) changes both the structure of the Sb polyhedra forming the structure of the antimony(iii) fluorochloride complex and the character of ionic motions in the compounds. The ionic conductivity in the 324–436 K range was determined for NH₄SbClF₃: σ = 1.07 · 10⁻⁴ S cm⁻¹ at T = 423 K. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1353–1357, July, 2008.     

Synthesis and electrochemical study of 2-(2-pyridyl)benzothiazole complexes with transition metals (CoII, NiII, and CuII). Molecular structure of aquabis[2-(2-pyridyl)benzothiazole]copper(II) diperchlorate

The reactions of 2-(2-pyridyl)benzothiazole (1) with MX₂·nH₂O salts (M = Ni^II, Co^II, or Cu^II; X = Cl or ClO₄; n = 0–2) in EtOH afforded the corresponding complexes. Depending on the nature of the counterion in the starting metal salt, the reactions give compounds of composition M(1)Cl₂·nH₂O or Cu(1)₂(ClO₄)₂·H₂O. The molecular and crystal structure of the Cu^II(1)₂(ClO₄)₂·H₂O complex was established by X-ray diffraction. The copper atom in this complex has a distorted tetragonal-pyramidal ligand environment and is coordinated by four nitrogen atoms of two ligand molecules and one water molecule. Electrochemical study of the ligand and the resulting complexes by cyclic voltammetry and at a rotating disk electrode demonstrated that ligand 1 stabilizes reduced forms of complexes containing Ni, Co, or Cu atoms in the oxidation state +1. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1738–1744, October, 2006.     

5-[2-(Methylthio)ethyl]-3-phenyl-2-thioxoimidazolidin-4-one and its complexes with transition metals (Co<Superscript>II</Superscript>, Ni<Superscript>II</Superscript>, and Cu<Superscript>II</Superscript>). Synthesis and electrochemical investigation

The reaction of 5-[2-(methylthio)ethyl]-3-phenyl-2-thioxoimidazolidin-4-one (LH) with salts MCl₂· xH₂O (M = Co, Ni, Cu; x = 2, 6) afforded the [M(L)Cl]_n complexes of Ni^II, Co^II, and Cu^II. The electrochemical behavior of the LH ligand and its complexes was studied using the cyclic voltammetry and rotating disk electrode techniques. The structures of the synthesized compounds were determined by the data of UV—Vis and IR spectroscopy, mass spectrometry, and electrochemical characteristics. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 339–343, February, 2007.     

Synthesis and electrochemical characterization of complexes of 1,2-bis[2-(pyridylmethylideneamino)phenylthio]ethanes with transition metals (CoII, NiII, CuII)

Transition metal (Ni^II, Co^II, and Cu^II) complexes with 1,2-bis[2-(3-pyridylmethylideneamino)phenylthio]ethane (1) and 1,2-bis[2-(4-pyridylmethylideneamino)phenylthio]ethane (2) were synthesized for the first time by slow diffusion of solutions of compounds 1 or 2 in CH₂Cl₂ into solutions of MX₂ · nH₂O (M = Ni, Co, or Cu; X = Cl or NO₃; n = 2 or 6) in ethanol. The reactions with Co^II and Cu^II chlorides afford complexes of composition M(L)Cl₂ (L = 1 or 2). The reactions of compound 1 with Ni^II salts produce complexes with 1,2-bis(2-aminophenylthio)ethane. The molecular structure of dinitrato[1,2-bis(2-aminophenylthio)ethane]nickel(ii) was confirmed by X-ray diffraction. The ligands and the complexes were investigated by cyclic voltammetry and rotating disk electrode voltammetry. The initial reduction of the complexes proceeds at the metal atom. The oxidation of the chlorine-containing complexes proceeds at the coordinated chloride anion. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 350–355, February, 2008.     

Molecular structures and ESR spectra of copper(ii) complexes with 2-hydroxypropiophenone acyldihydrazones

The dinuclear copper(ii) complexes with 2-hydroxypropiophenone acyldihydrazones (H₄L) having the composition [Cu₂L·mPy], where the L ligand contains the polymethylene chain with different lengths (from two to five units), were synthesized and studied. The crystal and molecular structures of the 2-hydroxypropiophenone adipoylhydrazone complex [Cu₂L·4Py]·Py were established by X-ray diffraction analysis. Copper atoms are 8.212 distant from each other, and their nearest environment has the tetragonal pyramidal geometry. The ESR spectra of solutions of the complexes based on acyldihydrazones of succinic, glutaric, and adipic acids contain seven HFS lines with the constant 40·10^–4 cm^–1 from two equivalent copper atoms. The spectra were interpreted as a result of the spin-spin exchange interaction of two unpaired electrons. An increase in the polymethylene chain length to five units prevents exchange interactions. The ESR spectrum of the complex with acyldihydrazone of pimelic acid contains a signal of four HFS lines with a _Cu = 73.4·10^–4 cm^–1, which is typical of mononuclear copper(ii) complexes.     

Photochromic transformations in solutions of 8,8′-diquinolyl disulfide and di(mercaptoquinolinato)nickel(<Emphasis Type="SmallCaps">II</Emphasis>)

The nature of intermediate species and their reactions were studied by laser pulse photolysis for a photochromic system consisting of 8,8′-diquinolyl disulfide (RSSR) and a planar Ni^II complex di(mercaptoquinolinato)nickel(II) (Ni(SR)₂) in toluene and benzene solutions. Under exposure to laser radiation, disulfide RSSR dissociates to two RS^· radicals, whose spectrum has an intense absorption band with a maximum at λ = 400 nm (ε = 8400 L mol⁻¹ cm⁻¹). The radicals disappear by recombination (2k _rec = 4.6 · 10⁹ L mol⁻¹ s⁻¹). In the presence of the Ni(SR)₂ complex, coordination of the radical (k _coord = 4.4 · 10⁹ L mol⁻¹ s⁻¹) competes with recombination to form a radical complex RS^· Ni(SR)₂ having an intense absorption band with a maximum at 460 nm (ε = 16 600 L mol⁻¹ cm⁻¹). This species decays in the second-order reaction (2k = 4.6 · 10⁴ L mol⁻¹ s⁻¹). Since the photochromic system returns to the initial state, the reaction of two radical complexes is assumed to produce radical recombination and reduction of the disulfide and Ni(SR)₂ complex. Analysis of the kinetic data showed that some RS^· radicals decay in the microsecond time interval due to the reaction with the RS^· Ni(SR)₂ radical complex (k = 3.1 · 10⁹ L mol⁻¹ s⁻¹). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2291–2300, October, 2005.     

Synthesis and studies of spectroscopic and electrochemical properties of dinuclear ruthenium(<Emphasis Type="SmallCaps">II</Emphasis>) and manganese(<Emphasis Type="SmallCaps">II</Emphasis>) complexes

New dinuclear ruthenium manganese complexes of general composition (bpy)₂Ru(L)MnCl_x(H₂O)₂ (L is 1,10-phenanthroline-5,6-dione, 3,3′-dicarboxy-2,2′-bipyridyl, or bis(pyrazolyl); x = 2 or 4) were synthesized by the reaction of (bpy)₂Ru(L) with MnCl₂ · 4H₂O. These compounds and the starting mononuclear ruthenium complexes were studied by spectrophotometric and electrochemical methods in MeCN. The position of the charge-transfer band Ru^II → L in the spectra depends on the donor-acceptor characteristics of the ligand L. For the dinuclear complex under study, the formal potentials of reversible one-electron oxidation of Ru^II are in the range of 0.9–1.2 V (vs. the standard hydrogen electrode), whereas oxidation of Mn^II occurs at more positive (by 0.1–0.2 V) potentials. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2281–2285, October, 2005.     

Fullerene complexes with divalent metal dithiocarbamates: structures,magnetic properties,and photoconductivity

A series of complexes of fullerenes C₆₀ and C₇₀ with metal dithiocarbamates {M^II(R₂dtc)₂}·C_m (m = 60 or 70) and metal dithiocarbamates coordinated to nitrogen-containing ligands (L), {M^II(R₂dtc)₂)_x·L}·C₆₀ (x = 1 or 2), where M = Cu, Zn, Cd, Hg, Mn, or Fe, R = Me, Et, Prⁿ, Prⁱ, or Buⁿ, L is 1,4-diazabicyclo[2.2.2]octane (DABCO), N,N′-dimethylpiperazine, or hexamethylenetetramine, were synthesized. The shape of dithiocarbamate molecules is sterically compatible with the spherical shape of C₆₀, resulting in an efficient interaction between their π systems. The resulting compounds are characterized by a layered or three-dimensional packing of the fullerene molecules. In the C₆₀ complexes, iron(II) and manganese(II) dithiocarbamates exist in the high-spin states (S = 2 and 5/2). The magnetic susceptibility of {M^II(Et₂dtc)₂}₂·C_m (M = Fe or Mn, m = 60 or 70) in the temperature range of 200–300 K is described by the Curie-Weiss law with Θ = −250 and −96 K and with maxima at 110 and 46 K, respectively, which is indicative of a strong antiferromagnetic spin coupling between M^II. The Weiss constants for the [{M^II(Et₂dtc)₂}₂·DABCO]·C₆₀·(DABCO)₂ complexes (M = Fe or Mn) are 1.7 and 0.3 K, respectively. The magnetic moments of the complexes containing Fe and Mn dithiocarbamates slightly increase at temperatures below 50 and 35 K, respectively, which is evidence of the ferromagnetic spin coupling between M^II in {M^II(Et₂dtc)₂}₂·DABCO. Single crystals of the complexes exhibit low dark conductivity (10⁻¹⁰–10⁻¹¹ S cm⁻¹). The visible light irradiation of these crystals leads to an increase in the photocurrent by two–three orders of magnitude. The photogeneration of free charge carriers in the complexes occurs both due to the photoexcitation of metal dithiocarbamate (Cu^II(Et₂dtc)₂) and through the charge transfer from metal dithiocarbamate (M^II(Et₂dtc)₂, M = Zn or Cd) to C₆₀. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2072–2087, November, 2007.     

Heterospin complexes based on dinuclear CuII triketonate and nitroxides

Heterospin complexes of bis(μ₂-1,1,2,2,8,8,9,9-octafluorononane-3,5,7-trionato)dicopper(II) ([Cu₂L₂]) with nitronyl nitroxides 2-(1-methyl-1H-pyrazol-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl 3-oxide (2) and 4,4,5,5-tetramethyl-2-(3-pyridinyl)-4,5-dihydro-1H-imidazole-1-oxyl 3-oxide (1) were synthesized and structurally characterized. Crystals of the complexes are formed by the discrete bis[1-methyl-4-(4,4,5,5-tetramethyl-3-oxide-1-oxyl-4,5-dihydro-1H-imidazol-2-yl)-1H-pyrazole]-bis (μ₂-1,1,2,2,8,8,9,9-octafluorononane-3,5,7-trionato)dicopper(II) etherate (3) and bis[3-(4,4,5,5-tetramethyl-3-oxide-1-oxyl-4,5-dihydro-1H-imidazol-2-yl)pyridine]-bis (μ₂-1,1,2,2,8,8,9,9-octafluorononane-3,5,7-trionato)dicopper(II) (4) molecules. Each Cu atom of the dinuclear chelate fragment coordinates one paramagnetic ligand through the N atom of the pyrazole or pyridine fragment, respectively. In complex 3, the paramagnetic ligands are located on one side of the plane of the chelate fragment, whereas the ligands in complex 4 are located above and below the plane of the chelate fragment. The magnetic properties of complexes 3 and 4 are determined by dominant antiferromagnetic exchange interactions between the unpaired electrons of the Cu^II atoms in the dinuclear Cu₂L₂ moiety. Dedicated to Academician O. M. Nefedov on the occasion of his 75th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1836–1840, November, 2006.     

Shift of stereochemical nonrigidity from coordination units to polymethylene fragments in heterospin copper(<Emphasis Type="SmallCaps">II</Emphasis>) hexafluoroacetylacetonate complexes with nitronyl nitroxide biradicals

The reactions of bis(hexafluoroacetylacetonato)copper(II) [Cu(hfac)₂] with the nitronyl nitroxide biradicals bis[4-(4,4,5,5-tetramethyl-3-oxide-1-oxyl-4,5-dihydro-1H-imidazol-2-yl)pyrazol-1-yl]alkanes (L⁶, L¹⁰, and L¹²) produced the framework heterospin complex [Cu(hfac)₂]₂L⁶ and the layer-polymeric heterospin complexes [Cu(hfac)₂]₂L¹⁰ and {[Cu(hfac)₂]₂L¹²} [Cu(hfac)₂(PrⁱOH)₂], respectively. In the solid state of these compounds, the stereochemical nonrigidity is manifested as a deformation of the polymethylene fragments-(CH₂)_n-. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1732–1741, September, 2007.     

ESR study of weak exchange interactions in binuclear copper(ii) complexes with 2-hydroxyacetophenone acyldihydrazones

The binuclear copper(ii) complexes with 2-hydroxyacetophenone acyldihydrazones (H₄L) Cu₂L·2Py were studied by ESR spectroscopy. In these complexes, the coordination polyhedra are linked via the polymethylene chain containing from one to five units. In the complexes based on acyldihydrazones of malonic, succinic, glutaric, and adipic acids, weak spin-spin exchange interactions occur between the paramagnetic centers. An increase in the length of the polymethylene chain to five units hinders exchange interactions, and the ESR spectrum of the corresponding complex has a signal typical of monomeric copper(ii) complexes.     

Magnetic properties of fullerene salts containing d- and f-metal cations (Co2+, Ni2+, Fe2+, Mn2+, Eu2+, Cd2+). Specific features of the interaction between C60·? and the metal cations

The interaction between the radical anions C₆₀ ^·− and divalent d- and f-metal (Co, Fe, Ni, Mn, Eu, Cd) cations in DMF and acetonitrile-benzonitrile (AN-BN) mixture was studied. Black solid polycrystalline salts (C₆₀ ^·−)₂{(M²⁺)(DMF) _x } (x = 2.4–4, 1–6) containing the radical anions C₆₀ ^·− and metal(ii) cations solvated by DMF were prepared for the first time and their optical and magnetic properties were studied. The salts containing Co²⁺, Fe²⁺, and Ni²⁺ are characterized by antiferromagnetic interactions between the radical anions C₆₀ ^·−, which result in unusually large broadening of the EPR signal of C₆₀ ^·− upon lowering the temperature (from 5.55–12.6 mT at room temperature to 35–40 mT at 6 K for Co²⁺ and Ni²⁺). The salts containing Mn²⁺ and Eu²⁺ form diamagnetic dimers (C₆₀ ⁻)₂, which causes a jumpwise decrease in the magnetic moment of the complexes and disappearance of the EPR signal of C₆₀ ^·− in the temperature range 210–130 K. A feature of salt 6 is magnetic isolation of the radical anions C₆₀ ^·− due to the presence of diamagnetic cation Cd²⁺. The salts prepared are unstable in air and decompose in o-dichlorobenzene or AN. Reactions of C₆₀ ^·− with metal(ii) cations in AN-BN mixture result in decomposition products of the salts that contain neutral fullerene dimers and metals solvated by BN. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1909–1919, September, 2008.     

IR and <Superscript>31</Superscript>P NMR spectroscopic study of complexation of carbamoyl methyl phosphinates with U<Superscript>VI</Superscript> and Th<Superscript>IV</Superscript> in nitric acid solutions

The composition of complexes formed upon the extraction of U^VI and Th^IV nitrates with O-n-nonyl(N,N-dibutylcarbamoylmethyl) methyl phosphinate (L) from solutions of nitric acid without additional solvent was determined by ³¹P NMR spectroscopy. The structures of the complexes formed were studied by IR spectroscopy. Uranium(VI) is extracted from 3 and 5 M solutions of HNO₃ as the [UO₂(L)₂(NO₃)₂] complex, while thorium(IV) is extracted from 5 M HNO₃ as the [Th(L)₃(NO₃)₃]⁺·NO ₃ ⁻ complex. In both cases, ligand L has bidentate coordination. Ligand L contacts with 3 and 5 M nitric acid to form adducts L·HNO₃ and L· (HNO₃)₂, respectively. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2460–2464, November, 2005.     

EPR study of weak exchange interactions in binuclear copper(ii) complexes with salicylaldehyde acyldihydrazones

The binuclear Cu^II complexes with bis(salicylidene)hydrazones of dicarboxylic acids and their analogs (H₄L) of composition [Cu₂L·2Py] in which the coordination polyhedra are linked by a polymethylene chain containing from one to eight CH₂ units were studied by EPR spectroscopy. Weak antiferromagnetic spin-spin exchange interactions between two Cu^II atoms were found in the complexes based on hydrazones of malonic, succinic, glutaric, and adipic acids. These exchange interactions are manifested in the EPR spectra of liquid solutions as seven-line hyperfine signals from two equivalent Cu^II atoms with the hyperfine coupling constant a _Cu 40·10^–4 cm^–1. The exchange ceases as the length of the polymetylene chain increases to five-eight units and the EPR spectra show a four-line signal with a _Cu 80·10^–4 cm^–1 typical of mononuclear complexes.