X-ray diffraction, magnetochemical, and quantum chemical study of the structure and properties of binuclear copper(II) complexes

The binuclear chelates of copper(II) based on the tridentate azomethine ligands were synthesized and characterized by elemental analysis, IR, ¹H NMR spectroscopy, X-ray absorption spectroscopy (XANES and EXAFS), and magnetic measurements. The quantum-chemical study of the structure and calculation of magnetic properties of the obtained metal-chelates was performed using the density functional theory with the broken symmetry technique. The performed magnetochemical studies in the temperature range 2?C300 K suggest the existence of antiferromagnetic exchange interaction in all obtained complexes. The parameters of the exchange interaction ?2J > 260 cm^?1 were determined experimentally for all compounds, the experimental data is in a good agreement with the results of quantum-chemical calculations.     

Structural analysis of the solid amorphous binuclear complexes of iron(III) and aluminum(III) with chromium(III)-DTPA chelator using energy dispersive X-ray diffraction

This paper is concerned with the structural data obtained for two amorphous binuclear complexes of iron(III) and aluminum(III) with chromium(III)-diethylentriaminepentaacetic acid (chromium(III)-DTPA, CrL(2)(-)) using the energy-dispersive X-ray diffraction technique. Fe(OH)CrL(H(2)O)(6) and Al(OH)CrL(H(2)O)(6) are binuclear complexes, the metals ions being bridged via oxygen atoms. The metal ions are all octahedrally coordinated.     

Synthesis and magnetic properties of new binuclear Cu(II) complexes with tridentate azomethine ligands

New binuclear copper complexes of tridentate azomethine ligands with various combinations of N, O, and S donor centers were prepared by various procedures, including template synthesis. The magnetochemical data obtained for the range 2-300 K suggest the occurrence of antiferromagnetic coupling in most of these chelates. The only exception is the complex containing N-tosyl and N-ethyl donor fragments, in which the ferromagnetic exchange is observed.     

Synthesis and catalytic activity of binuclear Mn(III,III)–BINOL complexes for epoxidation of olefins

The novel binuclear complexes [Mn₂^{(III, III)}(BINOL)₃L₂]2H₂O, where, L = 2, 2′‐bipyridine (Bpy) or 1,10‐phenanthroline (Phen) and BINOL = 1, 1′‐bi‐2‐naphthol were synthesized and characterized by elemental analyses, magnetic susceptibility and various spectral methods. The catalytic activity of these complexes was studied for the epoxidation reaction of unfunctionalized olefins like styrene, 1‐hexene, 1‐octene and 1‐decene. The products thus obtained were analyzed by GC. The epoxidation reactions were carried out, in the presence of catalyst with different oxidants, to study the effect of the nature of the oxidant on the reactions. The different oxidants used were the peroxide oxygen donor (e.g. TBHP and H₂O₂), mono oxygen donor (e.g. PhIO) and dioxygen donor (e.g. molecular O₂). TBHP was found to be the best oxidant for the epoxidation reaction. To study the effect of the solvent on the epoxidation, the reactions were carried out in different media, such as a polar media (e.g. with CH₃OH as solvent), non‐polar media (e.g. with CH₂Cl₂ and C₆H₆ as solvents) and coordinating solvent (e.g. CH₃CN). The maximum epoxide formation was observed in CH₂Cl₂ medium. The epoxidation reactions with optically active BINOL catalysts under optimum established conditions were carried out to examine the enantioselectivity of the catalysts. The complexes were, however, found not to be enantioselective. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis and magnetic properties of tetrabromophthalato-bridged manganese(II) binuclear complexes

Summary Four novel Mn^II binuclear complexes have been prepared and characterized, namely: [Mn₂(TBPHTA)(L)₄](ClO₄)₂ [L = 2,2-bipyridyl (bipy), 1,10-phenanthroline (phen), 4,4-dimethyl-2,2-bipyridyl (Me₂bipy) and 5-nitro-1,10-phenanthroline (NO₂-phen), respectively], and TBPHTA = the tetrabromophthalate dianion. Based on i.r. spectra, elemental analyses and conductivity measurements, extended tetrabromophthalato-bridged structures consisting of two Mn^II ions, in which each Mn^II ion has a distorted octahedral environment, are proposed for these complexes. The temperature dependence of the magnetic susceptibility for [Mn₂(TBPHTA)(phen)₄] (ClO₄)₂·H₂O was measured over the 4–300 K range and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator ( = -2J _{1 2}), giving the exchange integral J = -1.22 cm^–1. This result indicates a weak antiferromagnetic spin exchange interaction between the metal ions.     

Synthesis and magnetic properties of chloroanilato-bridged manganese(II) binuclear complexes

Five chloroanilato-bridged manganese(II) binuclear complexes, [Mn₂(CA)L₄](ClO₄)₂, where L = 4,4′-dimethyl-2,2′-bipyridine (Me₂-bpy), 5-methyl-1,10-phenanthroline (Me-phen), 5-chloro-1,10-phenanthroline (Cl-phen), 5-nitro-1,10-phenanthroline (NO₂-phen) and 2,9-dimethyl-1,10-phenanthroline (Me₂-phen), and CA represents the dianion of chloroanilic acid, have been synthesized and characterized by elemental analyses, molar conductivity and room temperature magnetic moment measurements, and by spectroscopy. It is proposed that these complexes have CA-bridged structures and consist of two manganese(II) ions in a distorted-octahedral environment. The complexes [Mn₂(CA)(Me₂-bpy)₄](ClO₄)₂ (1) and [Mn₂(CA)(Me-phen)₄](ClO₄)₂ (2) were characterized by variable temperature magnetic susceptibility measurements (4–300 K) and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator, Ĥ = −2JŜ ₁ Ŝ ₂, giving the exchange integral J = −1.98 cm⁻¹ for (1) and J = −2.41 cm⁻¹ for (2). This result indicates that there is a weak antiferromagnetic spin-exchange interaction between the two Mn^II ions within each molecule. This revised version was published online in June 2006 with corrections to the Cover Date.     

X-ray diffraction study of volatile complexes of dimethylgold(III) derived from symmetrical β-diketones

Crystal chemical investigation of volatile dimethylgold(III) β-diketonates of the general formula (CH₃)₂AuL [L = acetylacetone (acac), dipivalylmethane (dpm), dibenzoylmethane (dbm)] has been carried out for the first time. The synthetic procedure and structural data are reported; differential thermal analysis (DTA) data are given. The structure of the compounds includes monomeric complex molecules arranged as polymeric stack associates. The gold atom has a plane square environment AuO₂C₂ formed by two oxygen atoms of the bidentate (O,O) ligand and two methyl groups. The geometrical characteristics of the coordination units are the following: in all complexes, the Au-O and Au-C_Me bond lengths and O-Au-O chelate angles are 2.070–2.108 Å, 1.989–2.034 Å, and 89.7-93.7°, respectively. The shortest Au-Au distance (3.475 Å) in the stack is observed for the (CH₃)₂Au(dpm) complex.     

Electrochemical and luminescent properties of new mononuclear ruthenium(II) and binuclear iridium(III)-ruthenium(II) terpyridine complexes.

Hexafluorophosphate salts of mononuclear complexes [Ru(II)Cl(L)(terpy)]+ (L = dmbpy (1); dpbpy (2), sambpy (3), and dpp (7), and binuclear complexes [Ru(II)2Cl2(dpp)(terpy)2]2+ (8) and [Ir(III)Ru(II)Cl2(dpp)(terpy)2]3+ (9) were prepared and characterized. Abbreviations of the ligands are bpy = 2,2'-bipyridine, dmbpy = 4,4'-dimethyl-2,2'-bipyridine, dpbpy = 4,4'-diphenyl-2,2'-bipyridine, dpp = 2,3-bis(2-pyridyl)pyrazine, sambpy = 4,4'-bis((S)-(+)-alpha-1-phenylethylamido)-2,2'-bipyridine, and terpy = 2,2':6',2'-terpyridine. The absorption spectra of 8 and 9 are dominated by ligand-centered bands in the UV region and by metal-to-ligand charge-transfer bands in the visible region. The details of their spectroscopic and electrochemical properties were investigated. In both binuclear complexes, it has been found that the HOMO is based on the Ru metal, and LUMO is dpp-based. [Ir(III)Ru(II)Cl2(dpp)(terpy)2]3+, indicating intense emission at room temperature, and a lifetime of 154 ns. The long lifetime of this bimetallic chromophore makes it a useful component in the design of supramolecular complexes.     

X-ray photoelectron and X-ray emission study of the electronic structure of hexanuclear Mn(II,III) pivalate complexes

The electronic structure of hexanuclear Mn(II,III) pivalate complexes with tetrahydrofuran and isonicotinamide are studied by X-ray photoelectron spectroscopy and X-ray emission spectroscopy. It is shown that when isonicotinamide substitutes for tetrahydrofuran the spin state of manganese ions is retained; the electron density increases on the manganese and oxygen atoms of the [Mn₆(O)₂Piv₁₀] core.     

氯冉酸阴离子桥联的Nd(III)-Nd(III), Dy(III)-Dy(III)和 Ho(III)-Ho(III)双 核配合物的合成与磁性

本文合成了三个以氯冉酸阴离子为桥基的稀土双核配合物,Ln~2(Phen)~4(CA)(NCS)~4(Ln=Nd,Dy,Ho;Phen=菲咯啉;CA=氯冉酸二价阴离子)。通过元素分析,红外光谱,电导,电子吸收光谱及变温(4-300K)磁化率表征了配合物,并由变温磁化率观察到的数据和理论方程通过最小二乘法拟合,得出分子内稀土离子间的相互作用参数:Z'J'=-0.79(Nd),-0.67(Dy),-0.63cm^-^1(Ho);表明稀土离子间存在极弱的反铁磁性交换相互作用。零场分裂参数Δ=-0.16(Nd),-0.76(Dy),-2.55cm^-^1(Ho);g=0.618(Nd),1.739(Dy),1.601(Ho),拟合因子≈10^-^4。     

Chemistry of iron complexes—III. X-ray diffraction,ESR and other spectral studies of new iron(II) and iron(III) complexes with tri-p-tolylarsine oxide

Reactions of iron(II) and iron(III) salts with tri-p-tolylarsine oxide(L) in suitable organic solvents yield complexes of formulas: (i) [FeL₂Cl₂(OH₂)₂] [FeCl₄].2H₂O, [FeL₂Br₂] [FeBr₄].2H₂O; (ii) [Fe(NCS)₃L₂].H₂O; (iii) [FeL(O₂ClO₂)₂(OH₂)] (ClO₄).0.25C₆H₆; (iv) [FeL₃I] [FeI₃].H₂O and (v) [Fe(CO)₃LI]I. Characterization has been done through elemental analyses, IR, far IR, ESR, and reflectance spectra, molar conductance, magnetic moments, t.g.a. and X-ray diffraction (powder) data. The species [FeL₂Cl₂(OH₂)₂]⁺, [FeL₂Br₂]⁺, [Fe(NCS)₃L₂], [FeL(O₂ClO₂)₂OH₂]⁺, [FeL₃I]⁺ and [Fe(CO)₃LI]⁺ have been assigned trans-octahedral, trans-square planar, trans-trigonal bipyramid, trans-octahedral, tetrahedral and cis-trigonal bipyramid structures respectively.     

Spectroscopic,magnetic and X-ray powder diffraction studies on U(III) and Np(III) formates

The synthesis of the new Np(III) compound Np(HCOO)₃ is reported and its lattice data, spectroscopic and magnetochemical properties are compared with the refined properties of U(HCOO)₃. Both compounds are isotypic and crystallize in the rhombohedral lattice of Gd(III) formate. The electronic reflectance and IR spectra have been measured and discussed. Low temperature magnetic susceptibilities indicate an antiferromagnetic transition for U(HCOO)₃ at T_N = 12 K. The magnetic moments of 3.70 B.M. (140–300 K) for U(HCOO)₃ and 2.69 B.M. (80–300 K) for Np(HCOO)₃ closely approach the corresponding free ion values.     

X-ray diffraction study of scanium(III) and indium(III) tris(dipivaloylmethanates)

Conclusions An x-ray diffraction study was carried out for scandium(III) and indium(III) tris(di pivaloylmethanates). The similarity of the unit cell parameters, the reflection indices and analogous ratios of the intensities of the major lines in the diffraction patterns indicate the isostructural nature of Sc(DPM)₃ and In(DPM)₃ with Fe(DPM)₃.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2098–2099, September, 1987.     

A high-frequency and high-field EPR study of new azide and fluoride mononuclear Mn(III) complexes

The isolation, structural characterization and electronic properties of three new six-coordinated Mn(III) complexes, [Mn(bpea)(F)(3)] (1), [Mn(bpea)(N(3))(3)] (2), and [Mn(terpy)(F)(3)] (3) are reported (bpea = N,N-bis(2-pyridylmethyl)-ethylamine; terpy = 2,2':6',2' '-terpyridine). As for [Mn(terpy)(N(3))(3)] (4) (previously described by Limburg J.; Vrettos J. S.; Crabtree R. H.; Brudvig G. W.; de Paula J. C.; Hassan A.; Barra A-L.; Duboc-Toia C.; Collomb M-N. Inorg. Chem. 2001, 40, 1698), all these complexes exhibit a Jahn-Teller distortion of the octahedron characteristic of high-spin Mn(III) (S = 2). The analysis of the crystallographic data shows an elongation along the tetragonal axis of the octahedron for complexes 1 and 3, while complex 2 presents an unexpected compression. The electronic properties were investigated using a high-field and high-frequency EPR study performed between 5 and 15 K (190-575 GHz). The spin Hamiltonian parameters determined in solid state are in agreement with the geometry of the complexes observed in the crystal structures. A negative D value found for 1 and 3 is related to the elongated tetragonal distortion, whereas the positive D value determined for 2 is in accordance with a compressed octahedron. The high E/D values, in the range of 0.103 to 0.230 for all complexes, are correlated with the highly distorted geometry present around the Mn(III) ion. HF-EPR experiments were also performed on complex 1 in solution and show that the D value is the only spin Hamiltonian parameter which is slightly modified compared to the solid state (D = -3.67 cm(-1) in solid state; D = -3.95 cm(-1) in solution).     

Complex X-ray diffraction study of yttrium(III) dipivaloyl methanate

Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 3, pp. 163–165, May–June 1993.     

Catalytic activity of Mn(III) and Co(III) complexes: evaluation of catechol oxidase enzymatic and photodegradation properties

We have synthesized two mononuclear complexes, Mn-hq and Co-hq, to serve as sustainable catalysts (for degrading dyes from organic pollutant) and as biocatalysts (for promoting oxidation of catechol to quinone). The two complexes have been characterized by various spectroscopic tools, and with the assistance of single-crystal X-ray diffraction data, their molecular structures were established. The present complexes were exploited for the catalytic activity, i.e., enzymatic activity and photocatalytic property. In methanolic solution, Mn-hq and Co-hq were examined for catecholase-like activity and Mn-hq particularly catalyzes the oxidation of 3,5-di-tert-butyl catechol to analogous quinone with a K_cat value of 835.2 h^?1. Additionally, Mn-hq and Co-hq demonstrated remarkable photocatalytic activity for the degradation of methylene blue (MB) in the aqueous medium beneath visible light. Co-hq shows excellent stability and recyclability toward MB. Further, trapping experiment along with degradation pathways is also explored. Thus, the present research throws light on the excellent catalytic properties of simply designed complexes and this activity can be tuned for desired efficiencies in future prospects.

     

Synthesis and magnetic properties of new mono- and binuclear iron complexes with salicyloylhydrazono dithiolane ligand

We report here experimental evidence for the formation in the solid state of a new binuclear Fe (III) 2(mu-OMe) 2(HL) 4 complex (H 2L is 2-salicyloylhydrazono-1,3-dithiolane). The isostructural Mn (III) 2(mu-OMe) 2(HL) 4 complex has provided the strongest ferromagnetic interaction value (J approximately 20 cm (-1)) between Mn (III) ions to date. The new iron binuclear compound presented in this study shows antiferromagnetic intramolecular coupling, which agrees with the theoretical study that we previously proposed. During our synthetic work, we also observed an unexpected spontaneous reduction of the new Fe (III)(HL) 2Cl,S complex to the new Fe (II)(H 2L) 2Cl 2 high-spin mononuclear complex. This process has been checked by cyclo-voltammetry as well as pseudosteady voltammetry.     

Thermal study of some new quinolone ruthenium(III) complexes with potential cytostatic activity

A series of new complexes with mixed ligands of the type RuL _m (DMSO) _n Cl₃·xH₂O ((1) L: oxolinic acid (oxo), m = 1, n = 0, x = 4; (2) L: pipemidic acid (pip), m = 2, n = 1, x = 2; (3) L: enoxacin (enx), m = 2, n = 1, x = 0; (4) L: levofloxacin (levofx), m = 2, n = 2, x = 8; DMSO: dimethylsulfoxide) were synthesized and characterized by chemical analysis, IR and electronic data. Except oxolinic acid that behaves as bidentate, the other ligands (quinolone derivatives and DMSO) act as unidentate. Electronic spectra are in accordance with an octahedral stereochemistry. The thermal analysis (TG, DTA) in synthetic air flow elucidated the composition and also the number and nature of both water and DMSO molecules. The TG curves show 3–5 well-separated thermal steps. The first corresponds to the water and/or DMSO loss at lower temperatures followed either by quinolone thermal decomposition or pyrolisys at higher temperatures. The final product is ruthenium(IV) oxide.     

Cyano-bridged Mn(III)3M(III) (M(III) = Fe, Cr) complexes: synthesis, structure, and magnetic properties

Two cyano-bridged tetranuclear complexes composed of Mn(III) salen (salen = N,N'-ethylene bis(salicylideneiminate)) and hexacyanometalate(III) (M = Fe, Cr) in a stoichiometry of 3:1 have been selectively synthesized using {NH2(n-C12H25)2}3[M(III)(CN)6] (M(III) = Fe, Cr) starting materials: [{Mn(salen)(EtOH)}3{M(CN)6}] (M = Fe, 1; Cr, 2). Compounds 1 and 2 are isostructural with a T-shaped structure, in which [M(CN)6]3- assumes a meridional-tridentate building block to bind three [Mn(salen)(EtOH)]+ units. The strong frequency dependence and observation of hysteresis on the field dependence of the magnetization indicate that 1 is a single-molecule magnet.