Marek Duczmal

Syntheses, structure, and properties of a manganese-calcium cluster containing a Mn4Ca2 core.

We describe here a novel, simple, efficient self-assembly method for the in situ generation of [Mn4Cl4(micro-OCH2CH2OMe)4(EtOH)4] and [Mn4(micro-Cl)Cl3(micro-OCH2CH2OMe)4(HOCH2CH2OMe)3]2 cubane-type compounds which react readily with calcium species to form cluster [Mn4Ca2Cl4(micro-OCH2CH2OMe)8], the calcium atoms attached to the Mn4 unit of flatten out the cubane inducing significant conformational changes.

Synthesis and structure of the mixed ligand complex of copper(II), bis(9, 10-dihydro-9-oxo-10-acridineacetato)bis(imidazole)copper(II) tetrahydrate

Abstract The new ternary compound Cu(CMA)2(Him)2·4H2O (where CMA−=9,10-dihydro-9-oxo-10-acridineacetate ion) has been synthesized and investigated by X-ray analysis, UV–Vis, EPR, IR and Raman spectroscopy. Magnetic susceptibility was measured in the range 4–300 K. The crystal structure consists of neutral monomers Cu(CMA)2(Him)2 linked by intermolecular hydrogen bonds with water molecules. The copper(II) ion is in a tetragonally elongated octahedral O2N2O′2 environment. Magnetic and spectroscopic results support the X-ray data.

Magnetic properties of TiLnS2 compounds (Ln Nd, Gd, Dy, Er and Yb)

Abstract Magnetic properties of the thallium lanthanide disulphides (TlLnS 2 , Ln  Nd, Gd, Dy, Er and Yb) were investigated. They crystallize with the rhombohedral structure ( R 3 m , α-NaFeO 2 type). Parameters of the crystal field Hamiltonian were deduced from the high field magnetization assuming trigonally distorted octahedral symmetry of the coordination spheres of metal ions. The second-order crystal field parameter was correlated with the deformation of LnS 6 octahedra.

Structural, spectroscopic, magnetic behavior and DFT investigations of L-tyrosinato nickel(II) coordination polymer

New 1D-coordination polymer {[Ni(L-Tyr)2(μ-4,4′-bpy)]·4H2O}n (1) (L-Tyr = L-tyrosine, 4,4′-bpy = 4,4′-bipyridine) is composed of L-tyrosinate anions chelated nickel(II) centres via N amino and O carboxylate atoms, whereas the apices of the elongated octahedral coordination sphere are occupied by the N atoms of 4,4′-bipyridine. Its molecular structure was determined by single-crystal X-ray diffraction and characterized using vibrational (FT-IR), Raman spectroscopy (FT-Raman), electronic (NIR-Vis-UV) and high field electron paramagnetic resonance (HF-EPR) spectroscopy and thermal (TG-DTA, DSC) and magnetic methods. The tetragonality distortion parameter (T) equals 0.945. The gx, gy and gz parameters (HF-EPR spectra) are slightly temperature dependent and the set gx = 2.178(5), gy = 2.156(4), gz = 2.19(1), D = −5.76(2) cm−1, E = −0.41(1) cm−1 was found at 5 K. The analysis of the temperature and field dependent magnetization shows the weakness of magnetic interactions in 1.

Metal–organic framework in an L-arginine copper(II) ion polymer: structure, properties, theoretical studies and microbiological activity

A novel 1D polymeric copper(II) complex with L-arginine and a linear bridged 4,4′-bipyridine with a formula of {[Cu(L-Arg)2(μ-4,4′-bpy)]Cl2·3H2O}∞ (1) (where L-Arg = L-arginine, 4,4′-bpy = 4,4′-bipyridine) was synthesized. The crystal structure and properties of the product were characterized using X-ray diffraction, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), spectroscopic techniques (FT-IR, Raman, NIR-vis-UV electronic and EPR), magnetic methods, and microbiological examinations. The crystals of 1 crystallized in a trigonal system and a space group of P3221 was characterized with a = b = 12.31 A, c = 18.45 A, V = 2420 A3, Z = 3, α = β = 90° and γ = 120°. The N and O donor atoms of trans-chelated L-Arg zwitterions and two N atoms of the 4,4′-bpy molecule form a tetragonal distorted octahedral geometry around the copper(II) ions with static character (T = 0.748). The diffuse-reflectance electronic spectrum of 1 is characteristic of the [CuN2N′2O2] chromophore. The EPR spectrum of frozen 1 (at 77 K) dissolved in water is related to the N2O2 set (g⊥ = 2.057, g‖ = 2.258 and A‖ = 169 G). The structure of the [Cu(L-Arg)2(μ-4,4′-bpy)]2+ model complex was optimized at the B3LYP and B3LYP-D3 levels. The calculations of the atomic spin densities on the atoms in the doublet state of the model complex revealed that, with regard to the ligands, the spin population is distributed mainly over the oxygen and nitrogen atoms of L-arginine. The antimicrobial activities were examined against the Gram-positive and Gram-negative bacteria strains: Streptococcus mutans, Enterococcus hirae, Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Salmonella enterica, Shigella flexneri; and fungi: Saccharomyces cerevisiae, Candida albicans. Complex 1 exhibited strong antimicrobial activity against bacteria and fungi, both in their growth inhibition as well as in microbial killing.

Synthesis, structural characterization and computational studies of layered metal phosphonates: [M(HO3P–C5H4N–PO3H)2(H2O)2]n [MII = Co, Zn, Cd]

Three novel isomorphous coordination polymers with a general formula [M(HO3P–C5H4N–PO3H)2(H2O)2]n [MII = Co (1), Zn (2) and Cd (3)] have been synthesized and characterized by powder and single-crystal X-ray diffraction, vibrational spectroscopy (IR and Raman) and simultaneous thermal analysis (TG-DTA-MS). Crystal structure analyses of compounds 1–3 have revealed that both phosphonate groups of (pyridin-1-ium-3,5-diyl)diphosphonate ligands serve to extend the metal cations into a strongly undulated grid structure parallel to the (101) plane. The adjacent monolayers are held together via multiple hydrogen bonds and offset face-to-face π–π interactions. The interlayer interaction energy values, estimated using the CRYSTAL code, have revealed that the stabilization energies of compounds 1–3 are quite similar, where 1 is least and 3 most advantageous. Computational studies have been further related to the results of thermal analyses. In the case of compound 1, which has unpaired electrons at the metal centre, the investigation has been supplemented by magnetic measurements. The magnetic properties of 1 (1.7–300 K) have been analyzed assuming that any possible exchange interactions are very weak. The obtained best-fit parameters are: Δ (axial splitting of 4T1g term) = −478 cm−1, λ (spin–orbit coupling) = −103 cm−1, α (orbital reduction factor) = 1.38, and zJ′ (mean-field exchange parameter) = −0.11 cm−1. The negative value of Δ implies that the ground state is the orbital doublet, which cannot be treated within the spin-Hamiltonian approach.

Magnetic and structural properties of iron and manganese lanthanide spinels

Six compounds with the spinel structure were obtained for the system (Fe, Mn)(Yb, Lu)2(S1 Se)4. The manganese spinels are normal and do not order magnetically in the applied temperature range. In the iron thiospinels some of the iron ions occupy the tetrahedral 16d and 16c sites and some of the lanthanide ions are partially transferred from 16d to 16c sites (but not to the tetrahedral positions as in inverted spinels). FeLu2S4, containing about 20% Fe at 16d positions, undergoes a magnetic transition at 8 K; FeYb2S4, with a smaller occupancy factor, remains paramagnetic down to 4.2 K. This suggests that the growing occupation of the 16d sites increases the ordering temperature. Measurements of high field magnetization for FeLu2S4 rule out a non-zero magnetic moment in the ordered phase and strongly support the hypothesis assuming antiferromagnetism.

Structural, spectroscopic and magnetic properties of a novel copper(II) L-tyrosinato complex

The complex [Cu(L-Tyr)2(H2O)]·H2O (1) (L-Tyr = L-tyrosine) was obtained as crystals and characterized by X-ray, spectroscopic (FT-IR, FT-Raman, NIR-vis-UV, and EPR) and magnetic methods. The monomeric complex crystallized in the monoclinic P21 symmetry with a = 11.967 (1) A, b = 5.9986 (4) A, c = 14.936 (1) A. The amino N and carboxylate O atoms of chelating L-tyrosinate anions together with the O atom of water molecules create a slightly distorted square pyramidal environment around the Cu(II) ions (τ = 0.11). The distance of about 5.998(1) A [Cu(L-Tyr)2(H2O)] units is involved in a polymeric chain based on N(1)–H⋯O(4)vi and N(2)–H⋯O(5)vi hydrogen bonds. The d–d band found in the polycrystalline-reflectance spectrum at 15 700 cm−1 is composed of three 2B1(dx2–y2) → 2A1 (dz2), 2B1 → 2B2(dxy) and 2B1 → 2E (dxz ≈ dyz) transitions with energies 14 880, 15 800 and 19 950 cm−1, respectively. In DMSO solution the complex preserves its square pyramidal geometry as evidenced by an intensive band at ca. 16 400 cm−1. The EPR spectral parameters for powder (g‖ = 2.236 and g⊥ = 2.063) and DMSO frozen solution (g‖ = 2.250, g⊥ = 2.055, and A‖ = 180 G) correspond to an axial symmetry of the Cu(II) coordination geometry with the dx2–y2 orbital as a ground state of the unpaired electron. Furthermore, the frozen solution spectrum revealed signals corresponding to S = 1 spin states of Cu(II) ions coupled by dipole–dipole interactions with distinctly resolved hyperfine splitting due to two copper nuclei (|D| = 0.0468 cm−1, g‖ = 2.238, g⊥ = 2.06 and A‖ = 85 G). The variable-temperature magnetic susceptibility measurements revealed the existence of a weak ferromagnetic interaction between neighboring copper(II) ions through the N–H⋯O hydrogen bonds.

Magnetic properties of AgLnSe2 compounds (Ln=Ho, Er, Tm and Yb)

Abstract The heavy lanthanide selenides AgLnSe 2 (Ln=Ho–Yb) crystallize in the orthorhombic AgErSe 2 type structure ( P2 1 2 1 2 1 ). The lanthanide ions are placed in the centres of slightly distorted octahedra, whereas each of the silver ions is surrounded by four selenide ions forming a strongly distorted tetrahedron. The high field magnetization (up to 14 T) and the magnetic susceptibility were measured on the polycrystalline samples. The crystal field parameters were estimated from the field dependences of the magnetizations, assuming a rhombic distortion of LnSe 6 octahedra. The magnetic susceptibilities were also calculated using the same set of the crystal field parameters. None of the compounds described here undergoes a magnetic transition above 4.2 K.

Magnetic properties of TlLnS2 compounds (Ln ≡ Tb, Ho and Tm)

Abstract TlLnS 2 compounds (Ln ≡ Tb, Ho and Tm) crystallize in the rhombohedral structure of α-NaFeO 2 type. The point symmetry of the lanthanide ions is 3 m . The parameters of the crystal field Hamiltonian were estimated from the high field magnetization (up to 14 T), assuming a trigonally distorted octahedral symmetry of the magnetic ions surrounding. The results were compared with data for other TlLnS 2 compounds. The second-order crystal field parameter B 2 changes similarly to the lanthanide environment deformation.