Synthesis,characterization and cytotoxicity evaluation of new cerium(III), lanthanum(III) and neodymium(III) complexes

Complexes of cerium(III), lanthanum(III) and neodymium(III) with coumarin‐3‐carboxylic acid (HCCA) were synthesized by mixing of equimolar amounts of the respective metal nitrates and coumarin‐3‐carboxylic acid in ethanol. The complexes were characterized and identified by elemental analysis, IR and Raman spectroscopy. DTA and TGA were applied to study the compositions of the compounds. The vibrational study showed bidentate coordination of CCA^? to Ln(III) ions through the carbonyl oxygen and the carboxylic oxygen atoms. The newly synthesized compounds were assayed for cytotoxicity against SKW‐3, HL‐60 and Reh cells. The complexes of cerium(III) and lanthanum(III) showed marginal cytotoxic activity against SKW‐3 and Reh cells as compared with the inorganic salts at concentration 200 µM . The complex of neodymium(III) induced approximately 50% reduction of the survival HL‐60 and SKW‐3 cells at concentration 200 µM . Copyright © 2007 John Wiley & Sons, Ltd.     

Investigations into the synthesis and fluorescence properties of Eu(III), Tb(III), Sm(III) and Gd(III) complexes of a novel bis-beta-diketone-type ligand

A novel bis-beta-diketon ligand, 1,1'-(2,6-bispyridyl)bis-3-phenyl-1,3-propane-dione (L), was designed and synthesized and its complexes with Eu(III), Tb(III), Sm(III) and Gd(III) ions were successfully prepared. The ligand and the corresponding metal complexes were characterized by elemental analysis, and infrared, mass and proton nuclear magnetic resonance spectroscopy. Analysis of the IR spectra suggested that each of the lanthanide metal ions coordinated to the ligand via the carbonyl oxygen atoms and the nitrogen atom of the pyridine ring. The fluorescence properties of these complexes in solid state were investigated and it was discovered that all of the lanthanide ions could be sensitized by the ligand (L) to some extent. In particular, the Tb(III) complex was an excellent green-emitter and would be a potential candidate material for applications in organic light-emitting devices (OLEDs) and medical diagnosis.     

Effect of Pyridyl Donors in the Chelation of Aluminum(III), Gallium(III), and Indium(III)

A new preparation of N,N'-bis(2-pyridylmethyl)ethylenediamine-N,N'-diacetic acid (H(2)bped) is reported, and its properties of complexation with Al(III), Ga(III), In(III), and Co(III) are investigated. The molecular structure of the cobalt(III) complex [Co(bped)]PF(6).CH(3)CN.H(2)O (C(20)H(25)CoF(6)N(5)O(5)P) has been solved by X-ray methods; the complex crystallizes in the triclinic space group P&onemacr;, with a = 10.611(2) ?, b = 12.720(2) ?, c = 9.868(1) ?, alpha = 102.70(1) degrees, beta =93.60(1) degrees, gamma = 106.96(1) degrees, and Z = 2. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.041 (R(w) = 0.038) for 4312 reflections with I > 3sigma(I). The Co(III) ion is coordinated in a distorted octahedral geometry with an N(4)O(2) donor atom set. The carboxylato oxygen atoms are coordinated trans, while the pyridyl nitrogen atoms are coordinated cis. The largest distortion from octahedral geometry is the N(pyridyl)-Co-N(pyridyl) angle of 107 degrees. Complex formation constants have been measured at 25 degrees C (&mgr; = 0.16 M (NaCl)). log K([M(bped)](+)) (log K([M(bped)(OH)])): M = Al, 10.85 (6.37); M = Ga, 19.89 (15.62); M = In, 22.6 (15.44). A protonated complex was also detected, [Ga(Hbped)](2+), log K = 21.79. The order of stability is In(III) > Ga(III) > Al(III) for the binary species, [M(bped)](+). The solution structures of the complexes have been probed in multinuclear NMR ((1)H, (13)C, (27)Al) studies, and these solution structures are compared with the solid state structure of the cobalt(III) complex. The complexes [In(bped)](+) and [In(bped)(OH)] are proposed to contain 7-coordinate In(III) with water and hydroxide completing the respective coordination spheres. The gallium complexes are proposed to be 6-coordinate: the [Ga(Hbped)](2+) complex contains a nondeprotonated carboxylic acid group which is not coordinated, and [Ga(bped)(OH)] contains a coordinated hydroxide which displaces a carboxylato donor. The [Al(bped)(OH)] complex may be 5-coordinate on the basis of its downfield (27)Al NMR chemical shift, 54 ppm.     

Thermodynamic and biodistribution studies of Zn(II), Ca(II), Gd(III) and Cu(II) complexes of 3,3,9,9-tetramethyl-4,8-diazaundecane-2,10-dione dioxime

The thermodynamic equilibria of copper(II), zinc(II), calcium(II) and gadolinium(III) with 3,3,9,9-tetramethyl-4,8-diazaundecane-2,10-dione dioxime (L1) have been studied at 25 degrees C and an ionic strength of 0.15 mol dm(-3). Copper and gadolinium form stable complexes with the ligand while the corresponding zinc species are more than 9 log units less stable. No complexes between calcium and the ligand were detected. The low binding strength of L1 towards zinc is attributed to the square-planar coordination geometry forced on the metal ion by the ligand as revealed by molecular mechanics calculations and molecular dynamics simulations. Speciation calculations, using a computer model of blood plasma, indicate that, despite the high concentration of zinc(II) and calcium(II) in vivo, L1 is able to increase the low-molecular-mass fraction of copper in plasma. Octanol/water partition coefficient of [CuL1H(-1)] indicates that although this species is largely hydrophilic, approximately 6% of the complex goes into the octanol phase and hence may promote dermal absorption of copper by the same amount. The dermal penetration rate is calculated to be 4.0 x 10(-4) mm h(-1). The [CuL1H(-1)] complex, which predominates at pH 7.4, is a poor mimic of native copper-zinc superoxide dismutase. Biodistribution experiments using the 64Cu-labelled [CuL1H(-1)] complex indicate an initial high uptake of this species in the liver followed by redistribution into muscle. Only a small amount is excreted through the urine.     

Complex formation reactions of lanthanum(III), cerium(III), thorium(IV), dioxouranyl(IV) complexes with tricine

Equilibrium studies for the heavy metal ions La(III), Ce(III), Th(IV) and UO2(IV) (M) complexes of the zwitterionic buffer tricine (L) in aqueous solution are investigated. Stoichiometry and stability constants for the different complexes formed as well as hydrolysis products of the metal cations are determined at 25 degrees C and ionic strength 0.1 M NaNO3. The stability of the formed complexes are discussed in terms of the nature of the heavy metal cation. The solid complexes are synthesized and characterized by means of elemental analysis, FTIR, and TG analysis. The general molecular formulae of the obtained complexes is suggested to be [M(L)2](NO3)n-2(H2O)x, where n = the charge of the metal cation, x = no. of water molecules.     

2-[(8-Hydroxyquinolinyl)methylene]hydrazinecarboxamide: expanding the coordination sphere of 8-hydroxyquinoline for coordination of rare-earth metal(III) ions

The semicarbazone of 8-hydroxyquinoline-2-carbaldehyde can be easily synthesized and is an effective tetradentate ligand for the coordination of rare-earth(III) ions. Investigations with yttrium(III) and lanthanum(III) in solution and in the solid state show, that the small yttrium ion can form 2 : 2 (1 : 1 stoichiometry) and 2 : 1 ligand to metal complexes (X-ray structures: [LY(NO3)(DMF)2]2Cl2 x 2DMF and [LL'Y] x 3MeOH x Et2O). With the larger lanthanum(III) ion only a well defined 1 : 1 complex (X-ray structure: [LLa(NO3)(MeOH)2]2(NO3)2) can be observed but probably 2 : 1 complexes are also formed. The X-ray structure analyses of [(L-H)MCl3] x MeOH (M = Er, Ho) and Na[(micro-NO3){LEu(NO3)2}2] x 2DMF show different coordination modes of the ligand. It can coordinate in its deprotonated but also in the protonated form.     

Highly hydrated cations: deficiency, mobility, and coordination of water in crystalline nonahydrated scandium(III), yttrium(III), and lanthanoid(III) trifluoromethanesulfonates

Trivalent lanthanide-like metal ions coordinate nine water oxygen atoms, which form a tricapped trigonal prism in a large number of crystalline hydrates. Water deficiency, randomly distributed over the capping positions, was found for the smallest metal ions in the isomorphous nonahydrated trifluoromethanesulfonates, [M(H2O)n](CF3SO3)3, in which M = Sc(III), Lu(III), Yb(III), Tm(III) or Er(III). The hydration number n increases (n = 8.0(1), 8.4(1), 8.7(1), 8.8(1) and 8.96(5), respectively) with increasing ionic size. Deuterium (2H) solid-state NMR spectroscopy revealed fast positional exchange between the coordinated capping and prism water molecules; this exchange started at temperatures higher than about 280 K for lutetium(III) and below 268 K for scandium(III). Similar positional exchange for the fully nonahydrated yttrium(III) and lanthanum(III) compounds started at higher temperatures, over about 330 and 360 K, respectively. An exchange mechanism is proposed that can exchange equatorial and capping water molecules within the restrictions of the crystal lattice, even for fully hydrated lanthanoid(III) ions. Phase transitions occurred for all the water-deficient compounds at approximately 185 K. The hydrated scandium(III) trifluoromethanesulfonate transforms reversibly (DeltaH degrees = -0.80(1) kJ mol(-1) on cooling) to a trigonal unit cell that is almost nine times larger, with the scandium ion surrounded by seven fully occupied and two partly occupied oxygen atom positions in a distorted capped trigonal prism. The hydrogen bonding to the trifluoromethanesulfonate anions stabilises the trigonal prism of water ligands, even for the crowded hydration sphere of the smallest metal ions in the series. Implications for the Lewis acid catalytic activity of the hydrated scandium(III) and lanthanoid(III) trifluoromethanesulfonates for organic syntheses performed in aqueous media are discussed.     

Synthesis and photophysical properties of new Ln(III) (Ln = Eu(III), Gd(III), or Tb(III)) complexes of 1-amidino-O-methylurea

Three new solid lanthanide(III) complexes, [Ln(1-AMUH)₃] · (NO₃)₃ (1-AMUH = 1-amidino-O-methylurea; Ln = Eu(III), Gd(III), or Tb(III)) were synthesised and characterised by elemental analysis, infrared spectra, magnetic moment measurement, and electron paramagnetic resonance (EPR) spectra for Gd(III) complex. The formation of lanthanide(III) complexes is confirmed by the spectroscopic studies. The photophysical properties of Gd(III), Eu(III), and Tb(III) complexes in solid state were investigated. The Tb(III) complex exhibits the strongest green emission at 543 nm and the Eu(III) complex shows a red emission at 615 nm while the Gd(III) complex shows a weak emission band at 303 nm. Under excitation with UV light, these complexes exhibited an emission characteristic of central metal ions. The powder EPR spectrum of the Gd(III) complex at 300 K exhibits a single broad band with g = 2.025. The bi-exponential nature of the decay lifetime curve is observed in the Eu(III) and Tb(III) complexes. The results reveal them to have potential as luminescent materials.     

Formation constants of chromium(III), scandium(III) and yttrium(III) complexes of some hydroxy naphthoic acids

The complexes of chromium(III), scandium(III) and yttrium(III) formed by 1-hydroxy-2-naphthoic acid (1,2-HNA: H2L) and 3-hydroxy-2-naphthoic acid (3,2-HNA: H2L) were investigated by potentiometry and spectroscopy at 25+/-0.1 degrees C and at an ionic strength of 0.1 M KNO3 in 50% ethanol-water (v/v) medium. The stoichiometries of these three M(III) complexes formed with these hydroxy-naphthoic acids and with hydroxo ion were defined and their formation constants were determined and compared. Thus, the removing capacities of these ligands could be examined by calculating the equilibrium concentration of Cr(III) that exists in the discharge water of various industries since Cr(III) ions are the main pollutants present during waste water treatment in our city, Bursa.     

Utility of 1-octanol/octane mixed solvents for the solvent extraction of aluminum(III), gallium(III), and indium(III) with 8-quinolinol.

Using 1-octanol/octane mixed solvents, the extraction of aluminum(III), gallium(III) and indium(III) with 8-quinolinol was carried out at 25 degrees C. The formation constants of the respective metal(III) 8-quinolinolates in the aqueous phase and their partition constants between the mixed solvents and water were determined based on an analysis of the extraction equilibria. The relationship between the partition constants of 8-quinolinol and its complexes was analyzed by the regular solution theory. The molar volumes of aluminum(III), gallium(III) and indium(III) 8-quinolinolates, calculated from the present results, suggest that the electrostriction effect functions in complex forming. It has been found that octane/1-octanol mixed solvents were available not only for the extraction of metal ions, but also for determining the formation constants of these metal 8-quinolinolates in the aqueous phase and their partition constants.     

Nuclear magnetic resonance investigation of intramolecular processes in metal polyaminepolycarboxylates Ethylenebis(oxyethyleneamino)tetraacetic acid complexes

The kinetics of the acetate scrambling processes occurring in some diamagnetic complexes formed by ethylenebis(oxyethyleneamino)tetraacetic acid (EGTA) has been investigated in D₂O solutions by performing computer line shape analysis of the NMR spectra recorded at different temperatures in the working range 0–100°C. The NMR patterns obtained suggest ether oxygen coordination in the scandium(III) and lutetium(III) complexes, but not in those formed with the magnesium(II), calcium(II), strontium(II), barium(II), yttrium(III), lanthanum(III), zinc(II) and lead(II) ions, and allow one to calculate the activation parameters for the LuEGTA and LaEGTA systems. But only qualitative conclusions can be drawn for the other chelates. Twist mechanisms and water assisted displacements are discussed in reaching a suitable reaction pathway for the intramolecular rearrangements in both groups of complexes. The possibility of acetate scrambling occurring either by only breaking MO bonds (Δ⇌Λ conversion) or also by rupture of MN ones (N inversion) seems valid since nitrogen atoms and acetate arms are the only coordinating groups. An intramolecular change not involving MN bond breaking can be ruled out when the ether oxygen atoms behave as donor units as well.     

Complexation of trivalent cations (Al(III), Cr(III), Fe(III)) with two phosphonic acids in the pH range of fresh waters

The complex formation constants of two phosphonic acids, HEDP and ATMP, with three trivalent metallic cations, Al(III), Cr(III) and Fe(III), have been determined by acid-base titration at 25 degrees C and constant ionic strength (0.1 mol l(-1), KNO(3)), using Martell and Motekaitis' computer programs. Species distribution curves showed that all three cations are in complex form in the pH range of fresh waters (5-9). The study of different cation/ligand ratios proved that both ligands mainly form anionic soluble complexes for systems having an excess of ligand-as protonated and unprotonated forms and especially ternary complexes with HEDP. For higher metal concentrations (excess of cation), weakly soluble species of HEDP and ATMP were formed with Al(III) and Cr(III). Two insoluble complexes with ATMP have been identified by SEM/EDAX as AlH(3)X((s)) and Cr(2)X((s)). Regarding Fe(III) species, Fe(OH)(3(s)) precipitate seems to predominate in solution.     

Synthesis and molecular structure of the dihydrobis(thioxotriazolinyl)borato complexes of zinc(II), bismuth(III), and nickel(II). M...H-B interaction studied by Ab initio calculations

Reacting the heterocycle 5-thioxo-1,4-dihydro-4-ethyl-3-methyl-1,2,4-triazole (thioxotriazoline) with sodium tetrahydroborate in the molar ratio of approximately 2:1 at 130 degrees C provides the new ligand dihydrobis(thioxotriazolinyl)borato, [Bt(Et,Me)](-), as its sodium salt. The neutral complexes of this anionic ligand with zinc(II), bismuth(III), and nickel(II) have been synthesized and characterized by X-ray crystallography. In every complex, the ligand is coordinated to the metal in the S(2) mode, generating eight-membered chelate rings. The bismuth and nickel complexes exhibit two M.H-B interactions responsible for the dodecahedral and octahedral geometries, respectively. For the zinc complex, the trigonal-bipyramidal coordination is achieved with an apical Zn.H-B interaction. The crystal structures for the three complexes are described, and ab initio calculations on Bi(III), Ni(II), and Zn(II) compounds have been performed in order to assess the nature of the M.H-B interaction and its role for the definition of the molecular geometries.     

In vitro and in vivo stability investigations of Cu(II), Zn(II), Ca(II) and Gd(III) complexes with N,N'-bis(2-hydroxyiminopropionyl) propane-1,3-diamine

Formation constants of copper(II), zinc(II), calcium(II) and gadolinium(III) with N,N'-bis(2-hydroxyiminopropionyl) propane-1,3-diamine (L2) have been studied at 25 degrees C and an ionic strength of 0.15 mol dm(-3). The reasonably high formation constants of the copper with this ligand are due to the ease with which the metal ion deprotonates the amide moieties. The square-planar coordination of L2 towards copper as predicted from UV-visible data may also account for the high selectivity of L2 towards the metal ion. Octanol/water partition coefficients of Cu(II)-L2 complexes indicate that although these complexes are largely hydrophilic, approximately 1.86% of the [CuL2H(-1)] species goes into the octanol layer and hence may promote dermal absorption of copper with a calculated penetration rate of 1.24 x 10(-5) cm h(-1). The [CuL2H(-1)] complex which predominates at pH 7.4 is a poor mimic of native copper-zinc superoxide dismutase. Blood-plasma simulation studies predict that, despite the high concentration of zinc and calcium in vivo, L2 is able to increase the low-molecular-mass fraction of copper. Biodistribution experiments using 64Cu-labelled [CuL2H(-1)] indicate an initial high uptake of this species in the liver, but it is predominantly excreted through the renal system.     

Attempted syntheses of lanthanide(III) complexes of the anisole- and anilinosquarate ligands

The polymeric lanthanide complexes (Ln(mu-CH3OC6H5C4O3)(CH3OC6H5C4O3)2 (H2O)4.xH2O)n [Ln=La (1), Eu (2), Gd (3)], formed from the reaction of aqueous solutions of anisolesquarate and Ln(NO3)3.xH2O, are all structurally similar with only subtle differences between the lanthanum complex and the isomorphous pair of europium and gadolinium analogues. The lanthanum atom in 1 has a square antiprismatic coordination geometry comprising two pendant and two mu-1,3-bridging anisolesquarate groups and four aqua ligands. Complexes 2 and 3 have two independent metal atoms in their asymmetric units compared to one for the lanthanum complex. However, the gross structures of 1-3 are essentially the same. The asymmetric unit of the terbium complex ((CH3OC6H5C4O3)3Tb(H2O)4(mu-CH3OC6H5C4O3)(CH3OC6H5C4O3)2Tb(H2O)5).H2O (4) contains two independent binuclear units which hydrogen bond to form an extended structure very similar to those of 1-3. The ionic polymers ([Ln(mu2-C4O4)(H2O)6][C6H5NHC4O3].4H2O)n [Ln=Eu (5), Gd (6), Tb (7)] result from the incomplete hydrolysis of the anilinosquarate ion during the attempted synthesis of Eu(III), Gd(III), and Tb(III) anilinosquarate complexes. However, complete hydrolysis of the substituent is accomplished by La(III) ions, and the neutral polymer (La2(mu2-C4O4)2(mu3-C4O4)(H2O)11.2H2O)n (8) is formed. In complexes 5-7, the central lanthanide atom has a square antiprismatic geometry, being bonded to two mu-1,2-bridging squarate and six aqua ligands. Two anilinosquarate counteranions participate in second-sphere coordination via direct hydrogen bonding to aqua ligands on each metal center. These counteranions, and the included waters of crystallization, serve to link neighboring cationic polymer chains via an extensive array of O-H...O hydrogen bonds to form a 3-dimensional network. The polymeric lanthanum complex 8 contains two different metal environments, each having distorted monocapped square antiprismatic geometry. For one lanthanum atom the coordination polyhedron comprises five aqua and four squarate ligands, while for the other the polyhedron consists of six aqua and three squarate ligands; in each case one of the aqua ligands occupies the capping position. The squarate ligand exhibits two coordination modes in 8 (mu-1,2- and mu-1,3-bridging), and neighboring polymer chains are cross-linked by hydrogen bonds to form a 3-dimensional network.     

Synthesis,characterization, density functional theory,thermal, antimicrobial efficacy,and DNA binding/cleavage studies of Cu(II), Cr(III), Fe(III), Ni(II), Co(II), Zn(II), and Pt(IV) complexes with a derivative of 2-hydroxyphenoxymethylfuran-5-carbaldehyde

In this study, Seven new complexes incorporating (E)-2-(((5-([2-hydroxyphenoxy]methyl)furan-2-yl)methylene)amino)phenol derived from 2-hydroxyphenoxymethylfuran-5-carbaldehyde and 2-aminophenol have been synthesized using Cu(II), Cr(III), Fe(III), Ni(II), Co(II), Zn(II), and Pt(IV) metal salts. Thermal measurements, molar conductance, magnetic moment, elemental analyses, spectral (IR, UV–Vis, ¹H nuclear magnetic resonance (NMR), ESR, Mass), were used to characterize insulated solid complexes. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the complexes were carried out in the range of 30–900°C. Magnetic susceptibility and electronic spectral data, as well as quantum chemical calculations, reveal the square planar geometry for Ni (II) complex, square planar/octahedral geometry for Cu (II) complex, while Co(II), Zn(II), Cr(III), Fe(III), and Pt (IV) complexes are octahedral geometry. Density functional theory (DFT) studies revealed that geometries of metal complexes and Schiff base were entirely optimized in relation to use energy by 6–31 + g (d,p) basis set. The complexes show a well-defined crystal system indicated by a powder-X-ray diffraction pattern. The scanning electron microscope showed complexes were nanocrystalline in nature, in addition to the interaction of the complexes with calf thymus CT-DNA, which was investigated via the UV–visible absorption method. Therefore, the DNA cleavage activity by the H₂L ligand and its metal complexes was performed. Finally, the synthesized complexes were tested for their in-vitro antimicrobial efficacy.     

Study on the interaction of lanthanum(III) with adrenaline

Lanthanum(III) equilibria in the presence of adrenaline have been investigated by potentiometric titration under physiological conditions (37°C and an ionic strength of 0.15?M NaCl). The interaction of lanthanum(III) with adrenaline has also been studied using an ab initio method. The complex species in the lanthanum(III)–adrenaline system have been ascertained and the protonation constants for adrenaline and the stability constants for lanthanum(III) complexes with adrenaline have been obtained. Adrenaline can form stable lanthanum(III) complexes with the phenolic hydroxyl group of adrenaline as the binding site of lanthanum(III).     

Lanthanum(III) and praseodymium(III) complexes with isatin thiosemicarbazones

Ten new lanthanum(III) and praseodymium(III) complexes of the general formula Na[La(L)2H2O] (Ln=La(III) or Pr(III); LH2=thiosemicarbazones) derived from the condensation of isatin with 4-phenyl thiosemicarbazide, 4-(4-chlorophenyl) thiosemicarbazide, 4-(2-nitrophenyl) thiosemicarbazide, 4-(2-bromophenyl) thiosemicarbazide and 4-(2-methylphenyl) thiosemicarbazide, have been synthesized in methanol in presence of sodium hydroxide. The XRD spectra of the complexes were monitored to verify complex formation. The complexes have also been characterized by elemental analysis, molar conductance, electronic absorption and fluorescence, infrared, far infrared, 1H and 13C NMR spectral studies. Thermal studies of these complexes have been carried out in the temperature range 25-800 degrees C using TG, DTG and DTA techniques. All these complexes decompose gradually with the formation of Ln2O3 as the end product. The Judd-ofelt intensity parameter, oscillator strength, transition probability, stimulated emission cross section for different transitions of Pr3+ for 4-phenyl thiosemicarbazones have been calculated.     

Syntheses, spectral, electrochemical and thermal studies of mononuclear manganese(III) complexes with ligands derived from 1,2-propanediamine and 2-hydroxy-3 or 5-methoxybenzaldehyde: self-assembled monolayer formation on nanostructure zinc oxide thin film

Mononuclear Mn(III) complexes have been prepared via the Mn(II) reaction of an equimolar of Schiff-bases derived from reaction of 2-hydroxy-3-methoxybenzaldehyde or 2-hydroxy-5-methoxybenzaldehyde with 1,2-diaminopropane. Axial ligands L include: pyridine (py) and H(2)O. The resulting complexes have been characterized by FT-IR and UV-vis spectroscopy. The crystal structures of the complexes were determined and indicate that in the solid state the complex adopts a slightly distorted octahedral environment of the imine N and hydroxo O with the two axial ligands. The electrochemical reduction of these complexes at a glassy carbon electrode in acetonitrile solution indicates that the first reduction process corresponding to Mn(III)-Mn(II) is electrochemically quasi-reversible. Thermal stability of these complexes was determined by TG and DTG. Layers of these complexes were formed on nanostructure zinc oxide thin film and a red shift was observed when zinc oxide thin film is modified by complex.     

Exchange and magnetic dipole-dipole interactions in bi- and triradical complexes of Al(III), Ga(III), In(III), and Sn(IV) witho-semiquinones. PM3 calculation

Semiempirical (PM3 with CI) calculations of exchange interactions for the triradical complexes of Al(III), Ga(III), and In(III) and the biradical complex of Sn (IV) with o-semiquinones are carried out. The results are in agreement with both qualitative theoretical assumptions and experimental data. The calculations indicate that the superexchange via the unoccupied porbitals of the central metal ion predominantly determines the multiplicity of the ground states of the complexes. Zero-field splitting constants D are calculated; they also agree well with experimental data. Deceased. Translated fromZhumal Struktumoi Khimii, Vol. 38, No. 6, pp. 1053–1060, November–December, 1997.