Jerzy Mrozinski

Synthesis, Structures, and Magnetic Properties of Face-Sharing Heterodinuclear Ni(II)−Ln(III) (Ln = Eu, Gd, Tb, Dy) Complexes

Heterodinuclear [(Ni (II)L)Ln (III)(hfac) 2(EtOH)] (H 3L = 1,1,1-tris[(salicylideneamino)methyl]ethane; Ln = Eu, Gd, Tb, and Dy; hfac = hexafluoroacetylacetonate) complexes ( 1.Ln) were prepared by treating [Ni(H 1.5L)]Cl 0.5 ( 1) with [Ln(hfac) 3(H 2O) 2] and triethylamine in ethanol (1:1:1). All 1.Ln complexes ( 1.Eu, 1.Gd, 1.Tb, and 1.Dy) crystallized in the triclinic space group P1 (No. 2) with Z = 2 with very similar structures. Each complex is a face-sharing dinuclear molecule. The Ni (II) ion is coordinated by the L (3-) ligand in a N 3O 3 coordination sphere, and the three phenolate oxygen atoms coordinate to an Ln (III) ion as bridging atoms. The Ln (III) ion is eight-coordinate, with four oxygen atoms of two hfac (-)s, three phenolate oxygen atoms of L (3-), and one ethanol oxygen atom coordinated. Temperature-dependent magnetic susceptibility and field-dependent magnetization measurements showed a ferromagnetic interaction between Ni (II) and Gd (III) in 1.Gd. The Ni (II)-Ln (III) magnetic interactions in 1.Eu, 1.Tb, and 1.Dy were evaluated by comparing their magnetic susceptibilities with those of the isostructural Zn (II)-Ln (III) complexes, [(ZnL)Ln(hfac) 2(EtOH)] ( 2.Ln) containing a diamagnetic Zn (II) ion. A ferromagnetic interaction was indicated in 1.Tb and 1.Dy, while the interaction between Ni (II) and Eu (III) was negligible in 1.Eu. The magnetic behaviors of 1.Dy and 2.Dy were analyzed theoretically to give insight into the sublevel structures of the Dy (III) ion and its coupling with Ni (II). Frequency dependence in the ac susceptibility signals was observed in 1.Dy.

Discrepancy between the structural and magnetic dimensionality in the (μ-terephthalato)bis[(diethylenetriamine)Cu(II)]perchlorate complex

Abstract The crystal structure of [(dien)Cu(μ-tp)Cu(dien)](ClO4)2, where tp is the dianion of terephthalic acid and dien is diethylenetriamine, has been determined by direct X-ray methods. The complex crystallizes in the monoclinic space group P21/c with a=8.911(6), b=8.002(5), c=19.61(2) A, β=90.2(1)°, Z=2 and V=1398.3 A3. Solution of the structure of a twin crystal of the compound led to final values of R=0.069 and Rw=0.079 with 174 least-squares parameters for 2263 unique reflections with I>2σ(I). The compound is a perchlorate salt of a dicationic centrosymmetric binuclear copper(II) complex, [(dien)Cu(μ-tp)Cu(dien)]2+ — the crystallographic inversion center being located at the center of the benzene ring of the tp bridging ligand. Within the binuclear unit the copper(II) ions are bridged by tp ligand in a bis-unidentate fashion, the coordination geometry about each Cu(II) ion is distorted octahedral; the CuCu distance in each binuclear entity is 11.006(5) A. Moreover, two Cu(II) centers of two different dimeric units are bridged by an oxygen atom of a carboxylate group. Thus, chains along the b direction and layers parallel to (100) are formed. The variable-temperature (4.2–290 K) magnetic susceptibility data of the complex, interpreted with a dimer law with a molecular field approximation, yielded to J, g and zJ′ values of −3.66 cm−1 2.07 and −0.03 cm−1, respectively. An orbital interpretation of the coupling is proposed.

Synthesis, structure and magnetic properties of a new chloro-bridged dimeric copper complex, bis(μ-chloro)bis(8-amino-5-aza-4-methyl-3-octene-2-onato)dicopper(II)

Abstract The synthesis, structure and important properties of the title compound are reported. The complex, formulated as Cu2L2Cl2 (L=singly deprotonated 8-amino-5-aza-4-methyl-3-octene-2-one ligand), has a dimeric structure composed of two CuLCl subunits linked via bridging chlorine atoms. Each copper atom is five-coordinate in a distorted square-pyramidal coordination environment. The Cu2Cl2 structural core is characterized by an acute Cu-Cl-Cu′ angle of 82.9° and a short Cu-Cu′ separation of 3.418 A. Crystallographic data: monoclinic space group P21/c (No. 14), a=6.150(1), b=11.224(2), c=15.057(3) A; β=99.08(1)°; R=0.0222, Rw=0.0291. Magnetic susceptibility and magnetization measurements indicate ferromagnetic coupling of the copper(II) centers within the dimer, contrary to the predictions of a previously reported empirical correlation between the exchange energy, 2J, and structural factors.

A linkage isomeric pair of bis(dicyanamido)-bis(imidazole)copper(II) complexes with considerably different magnetic properties

Abstract Two isomeric compounds (α and β) of the composition Cu{N(CN)2}2(imidazole)2 were prepared and studied by IR, far-IR, electronic and ESR spectra, as well as by temperature-dependent (down to 4.2 K) magnetic susceptibility measurements. A sixcoordinate polymeric chain structure is assumed with different bridging functions of the N(CN)2group, viz. through both cyanide nitrogens and through amide and cyanide nitrogens in the α- and β-isomers, respectively. The temperat

Synthesis, Spectroscopy, and Magnetic Properties of Transition-Metal Complexes with the Diethyl 2-Quinolylmethylphosphonate (2-qmpe) Ligand − Crystal Structures of [Ni(2-qmpe)4(H2O)2](ClO4)2 and [Mn(2-qmpe)4(H2O)2](ClO4)2 Showing Unexpected O-Binding of the qmpe Ligands

The synthesis and characterization of transition-metal coordination compounds containing the ligand diethyl 2-quinolylmethylphosphonate (2-qmpe) is described. Complexes of CoII, MnII, NiII, CdII, and ZnII were found to be mutually isomorphous according to their X-ray powder diffraction patterns and IR spectra. The new coordination compounds were identified and characterized by elemental analysis, magnetic measurements, infrared and ligand-field spectra. The crystal structures of the complexes [M(2-qmpe)4(H2O)2](ClO4)2 (M = Ni, 1; Mn, 2) reveal six-coordinate [M(2-qmpe)4(H2O)2] cations with the qmpe ligand coordinating via the oxygen rather than via the nitrogen atom, as well as lattice perchlorate anions. The metal ion is octahedrally surrounded by the four oxygen atoms of the four organic ligands. The non-participation of the pyridine nitrogen atom is unusual. The two water molecules occupy the fifth and the sixth coordination sites in a trans configuration. The coordinated water molecules are strongly hydrogen-bonded to the pyridine nitrogen atom of the 2-qmpe, further stabilizing the solid-state structure. The geometry of the metal ion can be described as distorted octahedral. For the CuII complex, a hydroxo-bridged dinuclear structure of the type [Cu(2-qmpe)2(OH)(H2O)2]2(ClO4)2 is proposed, based on its spectroscopic and magnetic properties. Ligand-field spectra of the Co and Ni compounds were found to be in agreement with the tetragonally distorted octahedral geometry.

Spectral and magnetic characterization of amine adducts of copper(II) valproate

Abstract The copper(II) complex of valproic acid and its corresponding pyridine and aniline adducts have been prepared and studied. The complexes were characterized on the basis of elemental analyses, molecular weight determinations, IR, electronic and EPR spectra, as well as variable temperature magnetic susceptibility measurements. All data are consistent with a binuclear structure for the complexes with four valproates as bridges and one donor amine ligand per copper atom in the case of adducts. Singlet— triplet energy separation values were found equal to 320, 344 and 300 cm−1 for the copper(II) valproate complex and its pyridine and aniline adducts, respectively.

Ferromagnetic exchange coupling in a two-dimensional copper(II) compound: Cu(pyridine-2-carboxylate)Cl

Abstract Magnetic properties of the compound chloro(pyridine-2-carboxylate)copper(II) were studied. The crystal structure revealed a unique two-dimensional (2D) polymer. The framework of the structure is a 16-membered (–O–C–O–Cu)4 ring involving carboxylate group in a syn–anti conformation. Each copper ion of an individual tetrameric ring is connected to others through a dichlorobridge. The copper ions within a given layer are ferromagnetically coupled. The variable-temperature (1.9–300 K) magnetic susceptibility data of the complex were interpreted with the dimer law with molecular field approximation, yielding J, zJ′ and g values of 15.0, 1.5 and 2.07 cm−1, respectively. The magnitude of the magnetic interaction is discussed on the basis of known structural data.

Crystal structure and magnetic properties of two heteronuclear thiocyanate bridged compounds: (CuL)[Co(NCS)4] (L=N-meso-(5,12-Me2-7,14-Et2-[14]-4,11-dieneN4) and N-rac-(5,12-Me2-7,14-Et2-[14]-4,11-dieneN4))

Abstract Complexes of general formula [CuL][Co(NCS)4] (where L=N-meso-(5,12-Me2-7,14-Et2-[14]-4,11-dieneN4) (1); N-rac-(5,12-Me2-7,14-Et2-[14]-4,11-dieneN4) (2)) were obtained and characterised by X-ray diffraction, magnetic measurements and by infrared spectroscopy. For both compounds the crystal and molecular structures have been determined. We observed two different environments of copper(II) ions in the cell for both complexes. Complex 1 formed 1-D polymeric chains where copper(II) is square bipyramidal, while complex 2 has a binuclear structure with square pyramidal environments of copper(II) ions. The magnetic susceptibility of both complexes was measured over a temperature range 1.9–300 K by the SQUID method. The magnetic behaviour of complexes 1 and 2 is characteristic for compounds with ferromagnetic interactions.

2-(2′-pyridyl)quinoxaline (L) as a bidentate ligand: crystal structure, magnetic properties and quantum chemical study of [Cu2Cl4L2]

Abstract The X-ray crystal structure of the complex [Cu2Cl4L2], where L is 2-(2′-pyridyl)quinoxaline, has been determined. The structure consists of dimeric molecules [Cu2Cl4L2], in which copper ions are bridged by two chloride ligands. The geometry at copper can be described as either a distorted square-pyramidal or a distorted trigonalbipyramidal. Magnetic susceptibility and EPR data give evidence for exchange coupling with the best fit to the data of the dimeric expression for a pair of exchange-coupled S = 1 2 ions yielding g = 2.134, 2J = −10 cm−1 and zJ′ = −2 cm−1. The investigations of the ground-state electronic structure of the complex and its precursor ligand L, along with an orbital interpretation of the magnetic coupling based upon extended Huckel molecular orbital calculations, are also presented.

Crystal structure, magnetism and spectroscopy of bis(tetraphenylphosphonium)tetrakis(dicyanamido)cobaltate(II) with bridging and pendant dicyanamide ligands ☆

Abstract The synthesis, structure and magnetic properties of the cobalt(II) complex, (Ph 4 P) 2 [Co(NCNCN) 4 ] ( 1 ) is reported. The compound crystallises in the monoclinic system, space group C 2/ c , with cell constants: a=23.430(6) A , b=7.589(1) A , c=28.534(4) A , β =105.65(2)°, Z =4 and V=4886(2) A 3 . The structure of 1 consists of octahedral CoN 6 chromophores with uni- and bidentate N(CN) 2 ligands. Cobalt atoms are doubly bridged by bidentate NCNCN groups forming infinite ribbons along the crystallographic b -axis. As first representative of an anionic dicyanamide complex 1 behaves as a weak ferromagnet at low temperatures.