Montserrat Barquín

Coordination compounds of 4,2′-6′,4″-terpyridine, [MCl2(4,2′-6′,4″-terpyridine)], M = Mn(II), Co(II), Ni(II), Cu(II) or Zn(II). Crystal structure of catena-poly [(dichlorozinc)-μ-(4,2′-6′,4″-terpyridine)]

Abstract MCl2(4,2′-6′,4″-terpyridine) compounds, where M = Mn(II), Co(II), Ni(II), Cu(II) or Zn(II), have been synthesized and characterized by IR and electronic spectroscopy and susceptibility magnetic measurements. Crystalline structure of the Zn(II) complex has been determine by X-ray diffraction. The Zn(II) atom shows to be in a highly distorted tetrahedral environment, defined by two Cl atoms and two N atoms of two ligand molecules, that act as bridges bound through the N atoms of the external pyridine rings. The structure is made of chains that do not interact among them.

Acetato and formato copper(II) paddle-wheel complexes with nitrogen ligands

Compounds Cu(AcO)2(pydz) (1), Cu(HCOO)2(pymd)1/2 (2), Cu(AcO)2(pymd)1/2 (3), and Cu(AcO)2(4,4′-bipy)1/2 (4) were obtained by reactions of Cu(AcO)2⋅H2O and Cu(HCOO)2 ⋅ 4H2O with pyridazine, pyrimidine, or 4,4′-bipyridine. In all the studied structures, the paddle-wheel units [Cu2[µ-RCOO)4] are present. Coppers show a square pyramidal coordination determined by four oxygens in the equatorial positions and a nitrogen in the axial position. Compound 1 consists of centrosymmetric dimeric molecules. Compounds 2 and 3 instead consist of zig-zag chains of [Cu2[µ-RCOO)4] units linked by bridging pyrimidine molecules. The chains run in the (1 0 1) and (1 1 −2) directions in 2 and 3, respectively. By crystallization of a solution of 4 in chloroform, Cu(AcO)2(4,4′-bipy)1/2 ⋅ 1/2CHCl3 (5) was obtained. It consists of monodimensional chains of [Cu2(µ-CH3COO)4] units linked by bridging 4,4′-bipy molecules. The chains, of two different types, run parallel to the b-axis in the crystal. Two chlorines of each CHCl3 molecule are close to two oxygens of two parallel chains. The packing can be described as sheets parallel to the (1 0 −1) plane. Magnetic properties and electron paramagnetic resonance spectra have been studied.

Magnetic properties, infrared spectroscopy, thermal and theoretical studies of oxomolybdenum(V) complexes with 2,2′-bipyrimidine

Mono- and dinuclear complexes of oxomolybdenum(V) with 2,2′-bipyrimidine (bpym), MoOCl3(bpym) (1) as two geometric isomers (violet and brown), Mo2O3Cl4(bpym)2 (2), Mo2O4Cl2(bpym)2 (3), and Mo2O2Cl6(μ-bpym) (4), have been prepared and characterized by EPR, electronic, infrared and Raman spectroscopy, thermal analysis and theoretical calculations. Magnetic susceptibilities in the 4.6–290 K range show different magnetic behavior for the MoO3+, and Mo2O2 (μ-bpym)6+ units. The EPR spectra have also been registered. Theoretical calculations converged to two stable isomers named cis and trans for MoOCl3(bpym), Mo2O3Cl4(bpym)2 and for Mo2O4Cl2(bpym)2 but four isomers for Mo2O2Cl6(μ-bpym). Based on the theoretical and experimental results for the violet and brown 1, we assume that both cis and trans isomers are present in the solid state. This could also explain the existence of two isomers in Mo2O2Cl6(μ-bpym).

Homo- and heterodinuclear 2,2′-bipyrimidine-bridged complexes

Abstract[M′(hfacac)2(bpym)] complexes, where M′ = CoII, NiII or ZnII, hfacac = hexafluoroacetylacetonate and bpym = 2,2′bipyrimidine; and [Cl2M(μbpym)M′(hfacac)2] complexes, where M = CoII, NiII MnII or ZnII M′ = NiII; M = NiII or ZnII and M′ = ZnII; M = NiII and M′ = CoII have been prepared and characterized by chemical analysis, conductance measurements, IR and electronic spectroscopies and magnetic susceptibility measurements (4.2–292 K range). The dinuclear NiII–NiII, CoII–NiII and MnII–NiII complexes are antiferromagnetic, with an intramolecular exchange parameter, J, of −2.3–8.9 cm−1. CoII and MnII are in a high spin state. The low temperature effect observed in monomers and in NiII–ZnII dimers is considered a consequence of either an intermolecular antiferromagnetic interaction or the zero-field splitting in NiII.

Syntheses, structures, and magnetic properties of dinuclear/1-D copper(II) acetato and formato derivatives with methylpyrazine and dimethylpyrazine

In this study, {[Cu2(µ-HCO2)4](µ-Mepyrz)} n (1), [Cu2(µ-HCO2)4(Mepyrz)2] (2), {[Cu2(µ-AcO)4](µ-Mepyrz)} n (3), [Cu2(µ-AcO)4(Mepyrz)2] (4), [Cu2(µ-AcO)4(2,3-Me2pyrz)2] (5), [Cu2(µ-AcO)4(2,6-Me2pyrz)2] (6), and {[Cu2(µ-AcO)4](µ-2,5-Me2pyrz)} n (7) have been synthesized and characterized by chemical analysis and electronic spectroscopy. Compounds 2, 4, 5, and 6, characterized by single-crystal X-ray diffraction, are composed of molecular dimers based on a paddle-wheel motif with two coppers, four syn–syn carboxylates, and two ligands coordinated to copper in the axial positions. In 7, chains of [Cu2(µ-AcO)4] dimers with 2,5-Me2pyrz as bridging ligands are formed. Magnetic properties and electron paramagnetic resonance results of the compounds are also described.

Synthesis and characterization of complexes of the first transition series cations with 2,2′-biimidazole and 2,2′-biimidazolate

Mononuclear [M(hfacac)2(H2biim)] complexes, where M = MnII, FeII, CoII, NiII, CuII or ZnII, hfacac = hexafluoroacetylacetonate, H2biim = 2,2′-biimidazole; dinuclear K2[M2(acac)4(μ-biim)] (M = CuII or ZnII) and tetranuclear K2[M4(acac)8(μ4-biim)] (M = CoII or NiII) complexes have been prepared and characterized by chemical analysis, conductance measurements, i.r., electronic and e.p.r. spectroscopies and by magnetic susceptibility measurements (in the 2–300 K range). MnII, FeII and CoII are in a high spin state. The e.p.r. spectra of CuII and MnII compounds have been recorded.

Synthesis, spectroscopic studies and magnetic properties of binuclear complexes of the first transition series cations bridged by 2,2′-bipyrimidine

Binuclear complexes [M2Cl4(μ-bpym)], where M = VO2+, FeII, CoII or CuII and bpym = 2,2′-bipyrimidine, and [M2(hfacac)4(μ-bpym)] complexes, where hfacac = hexafluoroacetylacetonate and M = FeII, NiII or CoII have been synthesized and characterized by chemical analysis, conductance measurements, i.r., electronic and e.p.r spectroscopies and by magnetic susceptibility measurements (in the 4.2–291 K range). CoII and FeII are in a high spin state. [(VO)2Cl4(μ-bpym)] is paramagnetic, without significant interactions. [Fe2Cl4(μ-bpym)] shows a singular behaviour explained by an antiferromagnetic intradimer exchange and a ferromagnetic interdimer interaction. All other complexes are antiferromagnetic, with an intramolecular exchange parameter, J, varying from −3.3  cm−1 for CoII/math> to −109  cm−1 for CuII.

Synthesis and characterization of biacetyldihydrazone complexes of cobalt(II), copper(II), nickel(II) and iron(III)

SummaryBiacetyldihydrazone (BdH) complexes [M(BdH)3](ClO4)2 (M=CoIIor CuII) and [M(BdH)3](NO3)2,3 (M = NiIIor FeIII) have been prepared and characterized by chemical analysis, conductance measurements, electronic, i.r. and e.p.r. spectral studies and magnetic subsceptibilities measurements. A mononuclear octahedral configuration is proposed for all complexes studied.

Magnetic properties of biacetyldihydrazone complexes

SummaryMagnetic susceptibilities of the biacetyldihydrazone (BdH) complexes [M(BdH)3](NO3)2 (M = CoII, NiII, CuII or ZnII), [Fe(BdH)3](NO3)3, [M(BdH)3](Ni(dto)2] (M = CoII, NiII or ZnII; dto = dithiooxalate), [(BdH)2Cu(dto)Ni(dto)] and [Fe(BdH)3]2[Ni(dto)2]3 have been studied in the 4.2–295 K range. ZnII complexes are diamagnetic, and complexes of NiII, CuII and FeIII obey the Curie-Weiss law. The CoII complexes behave anomalously and the results are interpreted in terms of a high spin↔low spin equilibrium.

Nitrates and bis(dithiooxalato)nickelates(II) of biacetyldihydrazone complexes

SummaryBiacetyldihydrazone (BdH) complexes [M(BdH)3](NO3)2 (M=CoII, NiII, CuII or ZnII); [Fe(BdH)3](NO3)3; [M(BdH)3][Ni(dto)2] (M=CoII, NiII or ZnII; dto=dithiooxalate); [Cu(BdH)2][Ni(dto)2] and [Fe(BdH)3]2[Ni(dto)2]3 have been prepared and characterized by chemical analysis, conductance measurements, electronic and i.r. spectral studies and cyclic voltammetry.A mononuclear octahedral configuration is proposed for all cationic complexes, excepting [Cu(BdH)2][Ni(dto)2, which is probably a dithiooxalate bridged dimer.