Alina Bieńko

Trinuclear thiocyanate-bridged compounds of the type [ML]2[Mn(NCS)4](ClO4)2 (where M = Cu(II), Ni(II); L = N-dl-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene)

The complexes of general formula [ML]2[Mn(NCS)4](ClO4)2 (where M = Cu(II), Ni(II); L = N-dl-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) were obtained and the crystal structures of both heteronuclear compounds were determined at 173 K. Complex [CuL]2[Mn(NCS)4](ClO4)2 (1) crystallizes in a monoclinic space group, C2/c, with a = 41.297(9) A, b = 7.571(2) A, c = 16.417(4) A, beta = 96.97(15) degrees, Z = 8, whereas complex [NiL]2[Mn(NCS)4](ClO4)2.H2O (2) crystallizes in a monoclinic space group, P2/c, with a = 21.018(5) A, b = 7.627(2) A, c = 16.295(4) A, beta = 104.47(1) degrees, Z = 4. The magnetic behaviour of (1) and (2) has been investigated over the temperature range 1.8-300 K. Complex (1) displays ferromagnetic coupling inside the trinuclear core of CuMnCu and compound (2) behaves like a mononuclear Mn(II) system. The magnetic properties of the second compound (2) with a similar trinuclear structure shows that Ni(II) ions have a diamagnetic character and a rather weak zero-field splitting at the central Mn(II) ion occurs. Finally, the magnitudes of the Cu(II)-M(II) interactions with M = Ni and Mn have been compared and qualitatively justified.

Thiocyanate copper complexes with pyrazole-derived ligands – synthesis, crystal structures, DFT calculations and magnetic properties

This paper presents the synthesis, X-ray studies, spectroscopic characterization and variable temperature magnetic investigations and DFT calculation of four novel thiocyanato Cu(II) compounds [Cu(mpz)2(NCS)2]n·nH2O (1), {[Cu2(dmpz)4(NCS)4][Cu(dmpz)(NCS)2]}n·2nMeOH (2) [(bdmpzm)CuII(SCN)2(μ1,3-SCN)CuI(bdmpzm)]n (3) and [Cu(bpzpy)(NCS)2] (4). Three of them (1, 2 and 3) display one-dimensional coordination structures while complex (4), incorporating a tridentate N-donor ligand, possesses a 0D molecular structure. Complex 3 belongs to a relatively rare group of mixed-valence CuII/CuI coordination polymers.

Interchain relay of antiferromagnetic ordering in 1D Co(II) coordination polymers via π–π interactions

Two new Phen-Co(II) complexes bridged by a hydroxyl isophthalate ligand, {[Co(dimphen)(HIA)]·H2O}n (1) and {[Co(phen)(HIA)]·H2O}n (2) (dimphen = 2,9-dimethyl-1,10-phenanthroline, phen = 1,10-phenanthroline, HIA = 5-hydroxyisophthalic acid), have been synthesized by carefully tuning the basicity of the reaction medium. In addition to single-crystal X-ray crystallography, the complexes were also characterized by IR spectroscopy, thermogravimetric and elemental analyses. Structurally, both complexes are 1D zigzag polymers with different metal nuclearities. Variable-temperature magnetic susceptibility measurements revealed ferromagnetic coupling within the chain while antiferromagnetic ordering is propagated in parallel running interchain via π–π interactions at low temperature.

Physical and Structural Characterization of Imidazolium-Based Organic–Inorganic Hybrid: (C3N2H5)2[CoCl4]

(C3N2H5)2[CoCl4] (ICC) was characterized in a wide temperature range by the single-crystal X-ray diffraction method. Differential scanning calorimetry revealed two structural phase transitions: continuous at 245.5 K (from phase I to II) and a discontinuous one at 234/237 K (cooling/heating) (II → III). ICC adopts monoclinic space groups C2/c and P21/c in phase (I) and (III), respectively. The intermediate phase (II) appears to be incommensurately modulated. Dynamic properties of polycrystalline ICC were studied by means of dielectric spectroscopy and proton magnetic resonance ((1)H NMR). The presence of a low frequency dielectric relaxation process in phase III reflects libration motion of the imidazolium cations. The temperature dependence of the (1)H spin-lattice relaxation time indicated two motional processes with similar activation energies that are by about an order of magnitude smaller than the activation energy obtained from dielectric studies. There are no abrupt changes in the (1)H relaxation time at the phase transitions indicating that the dynamics of the imidazolium rings gradually varies with temperature; that is, it does not change suddenly at the phase transition. Negative values of the Weiss constant and the intermolecular exchange parameter were obtained, confirming the presence of a weak antiferromagnetic interaction between the nearest cobalt centers. Moreover, the magnitude of zero field splitting was determined. The AC susceptibility measurements show that a slow magnetic relaxation is induced by small external magnetic field.

Iron(III) bis(pyrazol-1-yl)acetate based decanuclear metallacycles: synthesis, structure, magnetic properties and DFT calculations

The synthesis, structural aspects, magnetic interpretation and theoretical rationalizations for a new member of the ferric wheel family, a decanuclear iron(iii) complex with the formula [Fe10(bdtbpza)10(μ2-OCH3)20] (1), featuring the N,N,O tridentate bis(3,5-di-tert-butylpyrazol-1-yl)acetate ligand, are reported. The influence of the steric effect on both the core geometry and coordination mode is observed. Temperature dependent (2.0-300 K range) magnetic susceptibility studies carried out on complexes 1 established unequivocally antiferromagnetic (AF) interactions between high-spin iron(iii) centers (S = 5/2), leading to a ground state S = 0. The mechanism of AF intramolecular coupling was proved using a broken-symmetry approach within the density functional method at the B3LYP/def2-TZVP(-f)/def2-SVP level of theory.

The effects of protonated heterocyclic cations on the structural and magnetic properties of tetrachlorocuprate(II) anions; X-ray, magnetochemical and EPR studies

The crystal and molecular structures and magnetic properties of two new complexes (HMepy)2[CuCl4]·2H2O, 2, and (H2Me2ppz)[CuCl4], 3, formed by tetrachlorocuprate(II) anions and organic heterocyclic cations, bis(3-amino-2-chloro-5-methylpyridinium) (HMepy) and trans-2,5-dimethylpiperazinium (H2Me2ppz), respectively, have been determined by the analysis of their X-ray diffraction data, magnetic susceptibility behaviour and EPR spectral parameters. These characteristics differentiate the [CuCl4]2− anions in 2 and 3 as well as that previously reported in (H2bipip)[CuCl4]·H2O, 1, (bipip = 4,4′-bipiperidine) (Tuikka et al., CrystEngComm, 2013, 15, 6177; Wikaira et al., J. Coord. Chem., 2016, 69(1), 57). The present study reveals a significant effect of the organic cations on the geometry and magnetic properties of the [CuCl4]2− anions caused evidently by the changes in the crystal packing structure. A characteristic relationship was observed between the average cis-angles around the Cu(II) ions in [CuCl4]2− for 1–3, affected by the Cu(II) coordination geometry, and g-tensor components derived from the EPR spectra, a measure of interaction of copper(II) unpaired electrons in the [CuCl4]2− anions with an external magnetic field. The magneto-structural correlations revealed weak antiferromagnetic exchange interactions between the [CuCl4]2− anions transmitted by different pathways.

Slow Magnetic Relaxation in Cobalt(II) Field-Induced Single-Ion Magnets with Positive Large Anisotropy

Three pentacoordinate complexes of the type [Co( pypz)X2], where pypz is a tridentate ligand 2,6-bis(pyrazol-1-yl)pyridine and X = Cl- (1), NCS- (2), and NCO- (3), have been synthesized, and their structures have been determined by X-ray analysis. The DC magnetic data show a sizable magnetic anisotropy, which was confirmed by high-field high-frequency electron paramagnetic resonance (HF EPR) measurements. Well-resolved HF EPR spectra of high spin cobalt (II) were observed over the microwave frequency range 100-650 GHz. The experimental spectra of both complexes were simulated with axial g tensor components, a very large positive D value, and different E/ D ratios. To determine the exact D value for 2 (38.4 cm-1) and 3 (40.92 cm-1), the far-infrared magnetic spectroscopy method was used. Knowledge of the zero field splitting parameters and their signs is crucial in interpreting the single-molecule magnet or single chain magnet behavior. The AC susceptibility data confirm that these complexes exhibit a slow magnetic relaxation under small applied DC field with two (1 and 3) or three (2) relaxation modes.

A blue luminescent binuclear cadmium-orotate coordination polymer: synthesis, crystal structure, and thermogravimetric analysis

Abstract Assembly of orotic acid (H3Or, 1,2,3,6-tetrahydro-2,6-dioxo-4-pyrimidinecarboxylic) and Cd(NO3)·6H2O yielded a coordination polymer, [(Cd(Hor)·2.5H2O)2]n (1), which has been characterized by X-ray single-crystal diffraction, TGA, and fluorescence spectra. Single-crystal X-ray structural analyses reveal that 1 is a hydrogen-bonded binuclear Cd-orotate coordination polymer in which both Cd2+ ions have different coordination environments with identical distorted octahedral geometry. Crystal data for 1: monoclinic, space group P21/n, a = 7.0209(10) Å, b = 13.974(2) Å, c = 17.541(3) Å, β = 98.842(2)°, V = 1700.5(4) Å, Z = 4, R1 = 0.0269, wR2 = 0.0612, θmax = 25.960. The emission spectrum of the Cd-complex recorded with 265 nm excitation wavelength reveals the complex has strong blue luminescence with the peak maximum 420 nm (2.95 eV) as a result of the n–π* and π–π* transitions on the H3Or ligand.

A strategy for new macrocycle magnetic materials synthesis

A study of a series of new types of copper(II) and rhenium(IV) macrocyclic complexes, important macrocyclic molecular magnets, is reported. A detailed description of crystal structure and magnetic behavior of mononuclear copper(II) macrocyclic compounds: CuL1(ClO4)2 (L1 = N-d-2,4,4,9,11,11-hexamethyl-1,5,8,12-tetraazacyclotetradeca-2,9-diene), CuL2(ClO4)2 (L2 = N-d-7,14-diisopropyl-5,12-dimethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) and of heteropolynuclear complexes: [CuL1][ReCl4(ox)] · DMF and [(CuL2)(ox)ReCl4] is presented. The results indicate that all compounds behave as weak interacting magnets.