Bogumiła Żurowska

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.

Study of the mutual influence of ligands in cobalt(II) complexes containing thiocyanate and imidazole derivatives

Abstract The cobalt(II) complexes of formula [Co(NCS)2L2] and [Co(NCS)2L′4] (L = imidazole (iz) derivatives, I-Meiz (1), Z-Meiz (2), 2-Etiz (3), 2-Isopropiz (4), 2-Pheniz (5), 1,2-Me2iz (6), Biz (7), 2-Mebiz (8), 2-Etbiz (9); L′ = iz (10), 1-Meiz (11)) have been synthesized and characterized by spectroscopic methods and magnetic measurements. The crystal and molecular structures of complexes 6 and 11 have been determined by X-ray diffraction methods. Complex 6 crystallizes inthe orthorhombic space group Pnma with cell constants a=9.209 (3), b = 12.462 (5), c = 14.851(3) A ; V = 1704.3(9) A 3 , D ( calc ., Z = 4) = 1.43 g cm −3 , M r =367.35, F(000)=640 , λ( Mo K α)=0.71079 A , μ=11.2 cm−1 and T=293 K. Complex 11 crystalizes in the monoclinic space group P21/nwith cell constants a=7.689(2), b=11.095(1), c=14.156(2) A , β=93.46(2)°; V=1205.4(3) A 3 , D ( calc ., Z=2)=1.39 g cm −3 , M r =503.51, F(000)=534, λ( Mo K α)=0.71079 A , μ=8.56 cm−1 and T=293 K. 2553 (6) and 2485 (12)reflections were collected over the range 1≤θ≤25; from these, 1571 (6) and 1977 (11) (independent with I≥3σ(I)) were used in the structural analysis. The final value of the Rw residual was 0.077 and 0.042 for (6) and 11, respectively. The structure of 6 is built up by [Co(NCS)2(1,2-Me2iz)2] mononuclear units where the metal atom exhibits an approximately tetrahedral configuration: the CoN bond distances and NCoN bond angles vary in the range 1.958(8)−1.922(8) A and 114.7(3)−108.3(3)°, respectively. The structure of 11 consists of [Co(NCS)2(1-Meiz)4] monomeric units where two N-coordinated thiocyanate groups in trans position and four 1-methylimidazole ligands build a slightly distorted CoN6 octahedral environment. The CoN bond lengths lie i the range 2.158(2)–2.135(3) A being significantly longer than the related ones observed in 6.

Spectrochemical properties of cobalt(II) complex with bidentate Schiff base in various solvents

As a continuation of our previous studies on copper(II) complexes with a bidentate Schiff base derived from 5-bromosalicylaldehyde and α-aminopyridine, we have investigated the electronic spectra of the cobalt(II) complex with this ligand. The complex is a red crystalline compound soluble in common solvents, such as chloroform, dioxane, dimethyl formamide, dimethyl sulfoxide, and methanol. The time-elapsed spectral measurements of the complex and ligand, as well as conductivities of the complex in chloroform and dioxane solutions, are presented and discussed. Molar conductivities indicate that the complex exists as a nonelectrolyte in nonpolar solvents and as a 1:1 or 1:2 electrolyte in polar solvents. The ligand-field parameters (CFM/AOM) for the complex in chloroform solution are estimated and discussed.

Synthesis, spectroscopy and magnetic properties of transition-metal complexes with aminophosphonate derivatives of pyridine

The compounds of general formula [ML2](ClO4)2 [M = Cu(II), Ni(II), Co(II)]; L = diethyl 3-pyridylmethyl[N-(butyl)amino]phosphonate (3-pmape) or diethyl 4-pyridylmethyl[N-(butyl)amino]phosphonate (4-pmape) were prepared. The new complexes were identified and characterized by elemental analysis, infrared, electronic spectral studies and magnetic measurements. The complexes are sixcoordinate. Metal ions are octahedrally surrounded by two pyridine and two amine nitrogens, and two oxygens of the phosphoryl groups. The results of the magnetic studies suggest polymeric chain structure of the above complexes and indicate weak antiferromagnetic interaction between the magnetic centers. The magnetic behavior of Co(II) complexes is characteristic for cobalt(II) system with an important orbital contribution via spin-orbit coupling.

Spectroscopic and magnetic evidence of coordination properties of bioactive diethyl (pyridin-4-ylmethyl)phosphate ligand with chloride transition-metal ions

A series of five chloride coordination compounds of diethyl (pyridin-4-ylmethyl)phosphate (4-pmOpe) ligand, i.e. [CuCl2(4-pmOpe)2], [NiCl2(4-pmOpe)4], [CoCl2(4-pmOpe)], [ZnCl2(4-pmOpe)2], and [CdCl2(4-pmOpe)2], was prepared and studied. Stoichiometry and stereochemistry of the compounds was confirmed by spectroscopic and magnetic studies as well as by elemental analyses. The 4-pmOpe ligand has a capacity to coordinate to metal ions by means of phosphoryl oxygen and/or nitrogen of pyridine atoms. In Cu(II), Ni(II), and Zn(II) compounds, 4-pmOpe adopts the monodentate coordination mode, bonding metal centers through the pyridine nitrogen atom only. On the contrary, in Co(II) and Cd(II) compounds, 4-pmOpe acts as N,O-bridging ligand forming polynuclear structures. Magnetic studies (1.8–300 K) indicate mononuclear structure of the Co(II) and Ni(II) compounds and suggest existence of a very weak exchange coupling between metal centers in crystal lattice.

Spectroscopic studies and crystal structure of a dimeric Zn(II) complex with diethyl (pyridin-2-ylmethyl)phosphate

The crystal structure of [Zn2(2-pmOpe)2Cl4] (2-pmOpe = diethyl (pyridin-2-ylmethyl)phosphate) was determined by X-ray-diffraction method. The compound was also characterized by IR, far-IR, 1H, and 31P NMR spectroscopy. In this compound, 2-pmOpe is a bidentate N,O-bridging ligand and Zn(II) are slightly distorted tetrahedral ZnNOCl2. Zn(II) ions are doubly bridged by the 2-pmOpe ligands, resulting in a dinuclear species. The structure is stabilized by intermolecular C–H ··· O and C–H ··· Cl hydrogen bonds. The spectral properties are in agreement with the structural data.