A μ(1,1)- or μ(1,3)-carboxylate bridge makes the difference in the magnetic properties of dinuclear Mn(II) compounds

Six new dinuclear Mn(II) compounds with carboxylate bridges have been synthesized and characterized by X-ray diffraction: [{Mn(phen)(2)}(2)(μ-RC(6)H(4)COO)(2)](ClO(4))(2) with R = 2-Cl (1), 2-CH(3) (2), 3-Cl (3), 3-CH(3) (4), 4-Cl (5) and 4-CH(3) (6). Compounds 1 and 2 show two μ(1,3)-carboxylate bridges in a syn-anti mode while compounds 3-6 present a very uncommon coordination mode of the carboxylate ligand: the μ(1,1)-bridge. The magnetic properties of these compounds are very sensitive to the bridging mode of the carboxylate ligands. While compounds 1 and 2 (μ(1,3)-bridge) display antiferromagnetic interactions, with J values of -1.41 and -1.66 cm(-1), respectively, compounds 3-6 (μ(1,1)-bridge) show ferromagnetic interactions, with J values of 1.01, 0.98, 1.04 and 1.06 cm(-1), respectively. It is worth noting that compounds 3-6 are the first of their class to be magnetically characterized. The EPR spectra at 4 K for compounds with antiferromagnetic coupling (1 and 2) are more complex than those for compounds with a ferromagnetic interaction (3-6). Quite good simulations can be obtained with the ZFS parameters of the Mn(II) ion D(Mn) ~ 0.095 cm(-1) and E(Mn) ~ 0.025 cm(-1) for compounds 1 and 2 and D(Mn) ~ 0.060 cm(-1) and E(Mn) ~ 0.004 cm(-1) for compounds 3-6.     

Synthesis and Structure of μ-Peroxo-bis(4-bromophenoxotri-p-tolylantimony)

-Peroxo-bis(4-bromophenoxotri-p-tolylantimony) was synthesized by reacting 4-bromophenol with tri-p-tolylstibine in the presence of hydrogen peroxide. According to X-ray diffraction data, the Sb atoms have trigonal bipyramidal coordination. In the centrosymmetric molecule, the two Sb atoms are joined via bridging peroxo group disordered over two sites. The Sb–O(1,2') bond lengths are equal to 1.999(6) and 2.03(1) Å, the Sb···O(2,1') distances are equal to 2.605(9) and 2.626(5) Å, respectively. The lengths of the terminal Sb–O(3) bonds are 2.093(3) Å.     

Theoretical Investigation of Transparent (3–5 μm) and High Reflective (1.3 μm) Filter by Sol-Gel Process

When designing a cut-off interference filter, extra layers are needed to add on each side of periodic symmetrical multilayer to match the incident medium and the substrate. In this paper, we use sol-gel film with adjustable refractive index as the match layer. The influence of the refractive index and thickness of the match layer on the film system is discussed in detail. As an example, a special filter which is transparent (>80%) at the wavelength 3–5 m and high reflective (>90%) at the wavelength 1.3 m is designed. Finally a series of optimized film parameters are presented. The whole design process is a good reference to the other multilayer special filter made by sol-gel process.     

Binuclear cationic μ-bromo complexes of vanadium(II)

The compounds [V₂(μ-Br)₃L₆]BPh₄, with L = 3-methyltetrahydrofuran (1) and tetrahydrofuran (2), have been prepared. The crystal and molecular structures of 1 have been determined. The compound crystallizes in space group Cc with unit cell dimensions a = 18.499(3), b = 10.923(3), c = 29.619(7) Å, β = 103.18(2)^o, V = 5827(5) ų and Z = 4. The [V₂(μ-Br)₃(CH₃C₄H₇O)₆]⁺ ion is analogous to the [V₂(μ-Cl)₃L₆]⁺ cations previously described, but has a longer V—V distance, viz. 3.146(4) A. The UV-vis spectrum shows a double spin-flip transition but it is extremely weak compared to that in the chloro analog. Qualitatively, this was expected because of the ca 0.16 Å increase in the V—V distance, but the magnitude of the decrease (∼ 5 fold) is of interest.     

Syntheses,Structures and Vitro Anticancer Activities of μ_2-O-and μ_2-Dimethylglyoximato-bridged μ_3-O-Tris[di(m-fluorobenzyl)tin] Bis(dimethylglyoximate)

μ_2-O-and μ_2-dimethylglyoximato-bridged μ_3-O-tris[di(m-fluorobenzyl)tin] bis(dimethylglyoximate)(1) has been synthesized by the reaction of di(m-fluorobenzyl)tin dichloride with dimethylglyoxime. Complex 1 was characterized by means of IR,~1H NMR,elemental analysis and X-ray diffraction. It crystallizes in orthorhombic system,space group Pna21 with a = 2.22172(12),b = 1.05566(6),c = 2.15577(12) nm,V = 5.0561(5) nm~3,Z = 4,C_(50)H_(50)F_6N_4O_6Sn_3,Mr = 1273.01,Dc = 1. 6721 g/cm3,μ_(MoΚα) = 15.44 cm~(-1),F(000) = 2520,R = 0.0281 and wR = 0.0683. The stabilities,orbital energies and composition characteristics of some frontier molecular orbitals of 1 have been investigated with the quantum chemistry calculation. The properties of thermogravimetric and vitro anticancer activities of the compound have been discussed.     

New unsymmetrical μ-phenoxo bridged binuclear copper(II) complexes

A series of binuclear Cu^II complexes [Cu₂XL] ⁿ⁺ having two copper(II) ions bridged by different motifs (X = OH^–, MeCO₂ ^–, or Cl^–) have been prepared using the ligands: H₂L¹ = 4-methyl-2-[N-(2-{dimethylamino}ethyl-N-methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H₂L² = 4-nitro-2-[N-(2-{dimethylamino}ethyl-N-methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H₂L³ = 4-methyl-2-[N-(2-{diethylamino}ethyl-N-ethyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol and H₂L⁴ = 4-nitro-2-[N-(2-{diethylamino}ethyl-N-ethyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol. The complexes have been characterized by spectroscopic, analytical, magnetic and electrochemical measurements. Cryomagnetic investigations (80–300 K) revealed anti-ferromagnetic exchange between the Cu^II ions (–2J in the range –50 to –182 cm^–1). The strength of anti-ferromagnetic coupling lies in the order: OAc > OH > Cl. Cyclic voltammetry revealed the presence of two redox couples, assigned to Cu^II/Cu^II/Cu^II/Cu^I/Cu^I/Cu^I. The first reduction potential is sensitive to electronic effects from the aromatic ring substituents and steric effect on the donor nitrogens (side arm) of the ligand systems.     

Synthesis,structure and reactions of μ-oxobis(arenesulfonatotriarylbismuth)

Hydrolysis of triarylbismuth bis(arenesulfonates) in acetone gives bismuth derivatives of the general formula [Ar₃Bi(OSO₂Ar)]₂O (Ar = Ph, p-Tol; Ar = Ph, C₆H₄Me-4, C₆H₃Me₂-2,4, C₆H₃Me₂-3,4). The structure of -oxobis[(3,4-dimethylbenzenesulfonato)triphenylbismuth] was established by means of X-ray diffraction. The molecule has a linear centrosymmetric structure with the bridging oxygen atom in the inversion center. The bismuth atom has a distorted trigonal bipyramidal coordination with the bridging oxygen atom and the arenesulfonate group in axial positions. The Bi-C and Bi-O_term distances are 2.200(2), 2.204(3), and 2.442(2) Å, and the Bi-O_br distances are 2.067(1) Å.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1466–1471.Original Russian Text Copyright © 2004 by Sharutin, Egorova, Sharutina, Ivanenko, Pavlushkina, Gerasimenko, Pushilin.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis and Magnetism of μ-IsophthalatoOxovanadium(Ⅱ) Binuclear Complexes

INTRoDUCTIONThestudyoflong-rangemagneticinteractiotisofbinuclearcom-plexeswithextendedbridgedstructureareofcurrentinterestinrecentyears.Inviewoftheeffectivebridgingfunctionofisophthalatedianion(abbreviatedasIPHTA),thispa-perdealswiththesguthesis,characterizationandrnagnetismoftwonewp-IPHTAoxo-vanadium(ll)binuclearcomplexes.Synthesisof[(Vo),(IPHTA)(phen),]SO4(1)Asolutionofpiperidiniumisophthalate'(134.4mg,O.4mmol)andphen(l44.2mg,o.8mmol)inmethanol(1omL)wasaddedslow1ytoamethanolsolut…     

Trinuclear Cu(II) and Zn(II) complexes bridged by μ3-carbonato anion

The trinuclear Cu(II) and Zn(II) complexes [(CuTPA),(μ₃-CO,)] (C10₄)₄(1) and [(ZnTPA),(μ₃-C0₃)](C10₄)₄ (2) (TPA = tri(pyridylmethy1)amine) have been synthesized. X-ray structure analysis of the two complexes proves that CO₃ ^2- anion has an unusual triply bridging ligand, bridging three CuTPA and ZnTPA units respectively, and assembles new trinuclear complexes. The CO₃ ²- comes from atmospheric CO₂. The structure of each trinuclear unit consists of three copper or zinc atoms in a five-coordinate triangular hipyramidal environment. The [(CuTPA)₃(μ₃-C0₃) ](C10₄), compound shows a very weak antifemmagnetic coupling. Project supported by the National Natural Science Foundation of China (Grant No.29771021).     

Darstellung und kristallstruktur von μ3-allyl-μ1-chlorobis(triphenylphosphin)dipalladium(I)

μ₃-Allyl-μ₁-chloro-bis(triphenylphosphine)dipalladium(I) was obtained by the reaction of (π-C₃H₅PdCl)₂ with P(C₆H₅)₃ and NaOCH₃. The X-ray structure analysis of the yellow air-stable crystals confirms the presence of a PdPd bond (2.623 Å) and a bridging μ₃-allyl group. The PdC distances to the terminal carbon atoms of the allyl group are 2.07(1) Å. The distances of the Pd atoms to the bridging chloride ion are 2.433(3) and 2.438(3) Å.     

PREPARATION AND CHARACTERIZATION OF BINUCLEAR μ-PHENOLATOCOPPER(II)CHELATES.

Two new water-soluble binuclear copper(II)chelates derived from the condensationof 2,6-diformyl-4-methylphenol with glycylglycine were characterized with spectral.magnetic and electrochemical techniques.     

Synthesis and magnetism of μ-isophthalato dinuclear lanthanide(Ⅲ) complexes

Seven new μ-isophthalato dinuclear lanthanide(Ⅲ) complexes, namely [Ln2(IPHTA)(Me2-phen)4-(ClO4)2](ClO4)2 (Ln = La, Nd, Sm, Eu, Gd, Ho, Er), where Me2-phen denotes 2,9-dimethyl-1, 10-phenanthroline (Me2-phen) , IPHTA represents isophthalate dianion, have been synthesized and characterized by elemental analyses, molar conductance measurements, IR, ESR and electronic spectra. The variable-temperature magnetic susceptibilities of [Gd2( IPHTA) (Mez-phen)4 (ClO4)2] (ClO4)2 complex were measured in the temperature range of 4-300 K and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, H = - 2JS1 · S2, giving the exchange parameter J =- 0.19 cm-1 . This result is commensurate with a weak antiferromagnetic spin-exchange interaction between Gd(Ⅲ)-Gd(Ⅲ) ions within the complex.     

Nucleotide hydrolysis in the presence of μ-hydroxo-bridged-cobalt(III) complexes

Abstract

Two cobalt(III) complexes with tridentate ligands, the acyclic diethylenetriamine and macrocyclic 1,4,7-triazacyclononane, were examined as potential catalysts for the hydrolysis of adenosine 5′-triphosphate (ATP). Studies were performed primarily at pH 4.5, where the two complexes were in the binuclear di-μ-hydroxo forms. For both complexes, a rapid initial hydrolysis with first order dependence on the concentration of ATP was observed, k_obs of approximately 0.20 min^?1, followed by very slow hydrolysis. Deuterium isotope studies done in D₂O showed a normal isotope effect with k_H/k_D = 1.8. Spectral investigations and ⁵⁹Co NMR studies indicated that the biphasic nature of the hydrolysis reaction may be due to the formation of a complex in which inorganic phosphate is coordinated to the cobalt, effectively poisoning the catalyst.     

Crystal structure of a μ-oxo-bridged dimeric iron(III) complex

A dimeric [{Fe(5-ClL1)}₂(μ-O)], [H₂-5-ClL1 = N,N′-bis(5-chloro-2-hydroxybenzylidene)-2-methylpropane-1,2-diamine] tetradentate Schiff-base complex, 1, has been synthesized and its crystal structure has been determined by single crystal X-ray diffraction analysis. Structural analysis of complex 1 shows that the complex is a centrosymmetric dimer. Each of the Fe(III) ions has a five-coordinate geometry and one oxygen atom bridges two Fe(III) ions to form a μ-oxo structure. The geometry around iron atom can be described as a square based pyramid with the FeN₂O₂ coordination plane and oxo ligand.     

Synthesis and Crystal Structure of catena-Poly[bis-(benzimidazole)cobalt(II) μ-Phthalato]

1 INTRODUCTION Chemists have recognized that intermolecular inter- actions are the basis of functional properties for most molecular assembles, and detailed understan- ding of non-covalent chemistry is therefore funda- mental to interpreting and predicting the relation- ship between structure and function. Among intermo- lecular interactions, the π-π stacking between aro- matic rings is correlated with the electron transfer process in some biological systems[1], and the nature of π-π s…     

A ferromagnetic methoxido-bridged Mn(III) dimer and a spin-canted metamagnetic μ(1,3)-azido-bridged chain

Two new Mn(III) complexes of formulas [MnL(1)(N(3))(OMe)](2) (1) and [MnL(2)(N(3))(2)](n) (2) have been synthesized by using two tridentate NNO-donor Schiff base ligands HL(1){(2-[(3-methylaminoethylimino)-methyl]-phenol)} and HL(2) {(2-[1-(2-dimethylaminoethylimino)methyl]phenol)}, respectively. Substitution of the H atom on the secondary amine group of the N-methyldiamine fragment of the Schiff base by a methyl group leads to a drastic structural change from a methoxido-bridged dimer (1) to a single μ(1,3)-azido-bridged 1D helical polymer (2). Both complexes were characterized by single-crystal X-ray structural analyses and variable-temperature magnetic susceptibility measurements. The magnetic properties of compound 1 show the presence of weak ferromagnetic exchange interactions mediated by double methoxido bridges (J = 0.95 cm(-1)). Compound 2 shows the existence of a weak antiferromangetic coupling along the chain (J = -8.5 cm(-1)) through the single μ(1,3)-N(3) bridge with a spin canting that leads to a long-range antiferromagnetic order at T(c) ≈ 9.3 K and a canting leading to a weak ferromagnetic long-range order at T(c) ≈ 8.5 K. It also exibits metamagnetic behavior at low temperatures with a critical field of ca.1.2 T due to the weak antiferromagnetic interchain interactions that appear in the canted ordered phase.     

Synthesis and Structure of μ-Oxobis[triphenyl(furfuraloximato)antimony(V)]

Reaction of triphenylstibine with furfuraloxime in the presence of hydrogen peroxide in water-ether solution forms -oxobis[triphenyl(furfuraloximato)antimony(V)] in 90% yield. This complex has a dimeric structure in which two antimony atoms are bound with the bridge oxygen atom and two bridge oxime groups coordinating the metal atom by the oxygen as well as by the nitrogen atoms to form bicyclo[2.2.1]heptane fragment. SbOSb angle is 125.5(3)°, the bonds between the antimony atom and the bridge oxygen atoms [1.957(6) and 1.946(5) Å] are shorter than with the oxygen atoms of oxime groups [2.146(6) and 2.148(6) Å].     

Expansion Reaction of μ-FcCCHCo_2(CO)_6 with Benzylideneacetonetricarbonyliron, and Molecular Structure of μ_3-FcCHCFeCo_2(CO)_9

Alkyne-andvinylidene-bridgedclusters0fgeneraltype(p3-L)FeCo2(C0)9havebeensh0wntobeimPortantprecursorsforthesynthesisofchiralskelet0nclusters.Thesecompoundscanbepreparedfromalkyne-bridgeddicobaltcomPlexesandmetalcarbonylssuchasFe2(CO)9orFe,(C0),,,"'buttheyieldswerepoorduetoeasydec0mP0siti0nofthestartingmaterialinreactionconditions.Moreover,inordertostudythecooperativeinteractionsaswellasinductive/mesomericeffectSbetweentheferr0ceneunitandtransitionmetalclusterframework,thep3-FcCHCFeCo2(…