Theodoros F. Zafiropoulos

Slow magnetization relaxation in unprecedented Mn(III)4Dy(III)3 and Mn(III)4Dy(III)5 clusters from the use of N-salicylidene-o-aminophenol.

The first use of N-salicylidene-o-aminophenol in 3d/4f chemistry has led to Mn(III)(4)Dy(III)(5) and Mn(III)(4)Dy(III)(3) clusters with unprecedented metal topologies and stoichiometries; both compounds exhibit out-of-phase signals indicative of the slow magnetization relaxation of a single-molecule magnet.

Preparation and properties of complexes of lanthanide(III) salts with n-(2-pyridyl) pyridine-2′-carboxamide

New complexes of the general formulae [Ln(LH)2(NCS)3(H2O)] (Ln = La-Eu), [Ln(LH)2(NCS)3] (Ln = Gd-Yb), [Ln(LH)3(OClO3)](ClO4)2 (Ln = La-Gd), [Ln(LH)3] (ClO4)3 (Ln = Tb-Yb), [Ln(LH)2(ONO2)2](NO3) (Ln = La-Yb) and [Ln(LH)(ONO2)3] (Ln = La, Pr, Nd, Sm, Eu), where LH = N-(2-pyridyl)pyridine-2′-carboxamide, have been isolated. The complexes were characterized by elemental analyses, conductivity measurements, X-ray powder patterns, thermal methods, magnetic susceptibilities and spectroscopic (IR, 1H NMR, electronic diffuse reflectance and solid state emission f-f spectra) studies. All the data are discussed in terms of the nature of the bonding and the possible structural types. The 1:2 and 1:3 complexes appear to be monomeric, while polymeric structures are assigned for the 1:1 nitrato compounds. The LH molecule behaves as a bidentate ligand in the monomeric complexes, bonding through the amide oxygen and N(l′). The amide oxygen and both pyridine residues are coordinated in the 1:1 nitrato complexes.

Synthetic and structural chemistry of nickel(II)/1-methylbenzotriazole complexes

Abstract A systematic investigation of the NiX2/Mebta (X = Cl, Br, NCS, NO3; Mebta = 1-methylbenzotriazole) reaction system in various solvents is described. Particular emphasis has been placed on determining the influence of the Mebta: Ni11 ratio on the identity of the reaction products. In the nitrate case, the influence of the water concentration in the reaction mixture on reaction products has also been investigated. These combined variations have led to the preparation of 14 discrete six-coordinate complexes with the formulae [Ni(NO)3)2(Mebta)2], [Ni(NO3)(H2O)2(Mebta)2]NO3, [Ni(H2O)4 (Mebta)2](NO3)2, [Ni(NO3)2(Mebta)3]·CH3COCH3, [NiX2(Mebta)4](X = ONO2, NCS, Cl, Br), [NiX2(Mebta)2]n (X = Cl, Br), [NiX2(MeOH)2(Mebta)2] (C = Br, NCS) and [NiX2 (Mebta)]n (X = Cl, Br). Four complexes have been structurally characterized by single-crystal X-ray studies: cis-[Ni(NO3)2(Mebta)2] (1), trans-[Ni(H2O)4)Mebta)2](NO3)2 (3), mer-[Ni(NO)3)2((Mebta)3]·CH3COCH3 )4) and trans-[Ni(NCS)2(MeOH)2(Mebta)2] (6). Mebta behaves as a monodentate ligand binding through N(3). The structures of 3and 6 are stabilized by intermolecular hydrogen bonds. The new complexes were studied by thermal techniques, conductivity measurements, magnetic susceptibilities and spectroscopic (IR, ligand field) methods. Monomeric, trans pseudo-octahedral structures are assigned for the complexes [NiX2(Mebta)4] and [NiBr2(MeOH)2(Mebta)2] in the solid state. Polymeric structures are suggested for [NiX2(Mebta)2]n and [NIX2(Mebta)]n with NiX4N2 and NiX5N coordination spheres, respectively.

Gallium(III) chloride-benzotriazole chemistry: variation of product as a function of metal-to-ligand reaction ratio; preparation, structure and properties of a tetrahedral adduct and the first example of a GaX3L2 trigonal-bipyramidal complex

Abstract The 1:1 and 1:3 reactions of GaCl3 with benzotriazole (Hbta) in toluencce-diethyl ether afforded the pseudotetrahedral adduct [GaCl3(Hbta)] (1) and the novel trigonal-bipyramidal species [GaCl3(Hbta)2] (2), respectively, crystal structures of which have been determined. Some spectroscopic properties of the prepared complexes are also discussed.

Synthesis, Structure, and Antiproliferative Activity of Three Gallium(III) Azole Complexes

As part of our interest into the bioinorganic chemistry of gallium, gallium(III) complexes of the azole ligands 2,1,3-benzothiadiazole (btd), 1,2,3-benzotriazole (btaH), and 1-methyl-4,5-diphenylimidazole (L) have been isolated. Reaction of btaH or btd with GaBr3 or GaCl3 resulted in the mononuclear complexes [GaBr3(btaH)2] (1) and [GaCl3(btd)2] (2), respectively, while treatment of GaCl3 with L resulted in the anionic complex (LH)2[GaCl4] (3). All three complexes were characterized by single-crystal X-ray crystallography and IR spectroscopy, while their antiproliferative activities were investigated against a series of human and mouse cancer cell lines.

PSEUDOTETRAHEDRAL COBALT(II) COMPLEXES OF C3v and Cs SYMMETRIES

Abstract New complexes of the general types HCoX3 ·nL and HCo Y2X·nL (X=Br, I; Y=Cl, Br, I; L=diethyl ether, pyridine, aniline; n=1, 2, 3 and 4) have been prepared and characterized by elemental analyses, molar conductance measurements, magnetic measurements, spectral (UV, visible, IR and far-IR) data and X-ray powder patterns. All the magnetic and spectroscopic results indicate that pseudotetrahedral [CoX3L]− and [CoY2XL]− anions are present in the solid pyridine and aniline complexes. The data for the solid compounds are compatible with, and lend support to, outer spheres comprising (N[sbnd]H[sbnd]N)+ groups.

Mononuclear anionic octahedral cobalt(III) complexes based on N-salicylidene-o-aminophenol and its derivatives: Synthetic, structural and spectroscopic studies

The reactions of Co(II) sources with N-salicylidene-o-aminophenol (H2saph), N-salicylidene-o-amino-4-methylphenol (H2saph-4Me) and N-salicylidene-o-amino-4-chlorophenol (H2saph-4Cl) were studied in MeOH. The new solid complexes (Bu4(n)N)[Co(III)(saph)2] (1), (Et3NH)[Co(III)(saph-4Me)2]⋅MeOH⋅MeCO2H (2⋅MeOH⋅MeCO2H) and (Et3NH)[Co(III)(saph-4Cl)2]⋅MeOH⋅MeCO2H (3⋅MeOH⋅MeCO2H) have been isolated and their structures determined by single-crystal, X-ray crystallography. The three compounds contain the mononuclear, low- spin octahedral anion [Co(III)L2](-) (H2L=H2saph, H2saph-4Me, H2saph-4Cl), in which both L(2)(-) ligands act as tridentate chelating, meridional ONO donors. The crystal structures of 2⋅MeOH⋅MeCO2H and 3⋅MeOH⋅MeCO2H are built through H-bonding and π-π stacking interactions. The new complexes were characterized by elemental analyses and spectroscopic (IR, Raman, UV/VIS, (1)H NMR) data. All data are discussed in terms of the nature of bonding and known structures.

Bis(1-methylbenzotriazole)dinitratocobalt(II): A pseudo-octahedral complex with pseudo-tetrahedral magnetochemical and ligand field characteristics

SummaryThe reaction between cobalt(II) nitrate and 1-methylbenzotriazole (MeBTA) leads to a complex with unusual magnetochemical and ligand field characteristics. The synthesis and the physical and spectroscopic properties of the pseudo-octahedral complex [Co(MeBTA)2(NO3)2] are described.ZusammenfassungDie Reaktion zwischen Kobalt(II)nitrat und 1-Methylbenzotriazol (MeBTA) führt zu einem Komplex mit ungewöhnlichen magnetochemischen und Ligandenfeld-Eigenschaften. Die Synthese und die spektroskopischen Eigenschaften des pseudo-octaedrischen Komplexes [Co(MeBTA)2(NO3)2] werden beschrieben.

Benzotriazolate-mediated assembly of the discrete asymmetric pentanuclear nickel complex [Ni5(OH)(bta)5(acac)4(H2O)4](Hbta = benzotriazole, Hacac = pentane-2,4-dione)

Reaction of [Ni(acac)2(H2O)2] with benzotriazole (Hbta) in acetone–n-hexane yields the pentanuclear nickel complex [Ni5(OH)(bta)5(acac)4(H2O)4]1; the novel structure of this compound is described, together with the results of magnetic susceptibility studies which indicate antiferromagnetic coupling between the nickel(II) ions within the complex.

Synthesis and characterization of the complexes of lanthanide(III) chlorides and nitrates with the tetradentate schiff base diethyl(ethylenebis-β-aminocrotonate)

SummaryThe Schiff base ligand diethyl(ethylenebis-β-aminocrotonate) (LH2) reacts with lanthanide(III) chlorides and nitrates in various solvents to give solid complexes of the stoichiometriesLn(LH2)Cl3 (Ln=La−Yb),Ln(LH2)2Cl3 (Ln=La−Sm),Ln2(LH2)3Cl6(Ln=Eu−Yb) andLn(LH2)(NO3)3 (Ln=La−Yb). Properties, conductivity measurements, X-ray powder patterns, thermal data, magnetic moments and spectroscopic (IR,1H-NMR, electronic diffuse reflectance and solid state emission f-f spectra) are discussed in terms of the nature of the bonding and the possible structural types.ZusammenfassungDer Schiffbasen-Ligand Diethyl(ethylenbis-β-aminocrotonat) reagiert mit Lanthanid(III)chloriden und -nitraten in verschiedenen Lösungsmitteln unter der Bildung von festen Komplexen der StöchiometrienLn(LH2)Cl3 (Ln = La − Yb),Ln(LH2)2Cl3 (Ln = La − Sm),Ln(LH2)3Cl6 (Ln = Eu − Yb) undLn(LH2)(NO3)3 (Ln = La − Yb). Die allgemeinen Eigenschaften, Leitfähigkeitsmessungen, Röntgen-Pulverdiagramme, thermische Daten, magnetische Momente und spektroskopische Daten (IR,1H-NMR, Elektronenreflexionsspektren und Festkörperemissions-f-f-Spektren) werden im Hinblick auf die Bildungsverhältnisse im Komplex und strukturelle Möglichkeiten diskutiert.