Maciej Zubko

On the Role of Intermolecular Interactions on Structural and Spin‐Crossover Properties of 2D Coordination Networks [Fe(bbtr)3]A2 (bbtr=1,4‐bis(1,2,3‐triazol‐1‐yl)butane; A=ClO4−, BF4−)

A series of complexes [M(bbtr)(3)]A(2) (M=Fe(II), Zn(II); bbtr=1,4-bis(1,2,3-triazol-1-yl)butane; A=ClO(4)(-), BF(4)(-)) and [Fe(x)Zn(1-x)(bbtr)(3)](ClO(4))(2) (0<x<1) dilute systems was synthesized and characterized. Earlier studies on [Fe(bbtr)(3)](ClO(4))(2) (1⋅ClO(4)), which crystallizes in space group P3, revealed an abrupt spin transition with T(1/2)↓ ≈101 K and T(1/2)↑ ≈109 K. Variable-temperature measurements of the lattice parameters and change in Bragg peaks profiles of 1⋅ClO(4) showed a structural phase transition at 125 K leading to space group P1. Single-crystal X-ray diffraction studies allowed structures of the quenched high-spin phase and then a low-symmetry low-spin phase of 1⋅ClO(4) to be determined. We established that tetrafluoroborate analogue 1⋅BF(4) remains in the high-spin form in the temperature range 5-300 K. Contrary to 1⋅ClO(4), structural investigations did not reveal the presence of a structural phase transition in 1⋅BF(4). Analogous to 1⋅ClO(4), [Zn(bbtr)(3)](ClO(4))(2) (2⋅ClO(4)) undergoes a structural transition at 151 K, whereas at low-temperature [Zn(bbtr)(3)](BF(4))(2) (2⋅BF(4)) remains in space group P3. The structural phase transitions in both perchlorates are accompanied by similar reorganization of the intermolecular contacts, which leads to a shift of 2D layers. In effect, compression of the unit cell takes place, favouring the appearance of the spin transition in 1⋅ClO(4) in relation to 1⋅BF(4). The metal ion determines the temperature of the structural phase transition in 1⋅ClO(4) and 2⋅ClO(4). This property was exploited to separate the non-magnetic structural transformation and spin transition in 1⋅ClO(4). The spin and structural transitions in the [Fe(x)Zn(1-x)(bbtr)(3)](ClO(4))(2) systems take place at different temperatures, and the temperature difference between them increases with increasing zinc(II) content. This means that structural phase transition is necessary for appearance of the spin transition, but this transformation does not trigger directly the spin transition in 1⋅ClO(4).

Structural phase transition to disorder low-temperature phase in [Fe(ptz)6](BF4)2 spin-crossover compounds

In the spin-crossover compound [Fe(ptz)(6)](BF(4))(2) (where ptz=1-n-propyltetrazole) six different phases are observed. When a single crystal is slowly cooled from high temperatures to those below 125 K, the reflections broaden into diffuse maxima and split into two maxima along the c* direction [Kusz, Gütlich & Spiering (2004). Top. Curr. Chem. 234, 129-153]. As both maxima are broad along the c* direction, the short-range order exists only along the c direction and in the ab plane the structure remains long-range ordered. In this disordered phase additional satellite reflections appear. Upon heating above 135 K, the diffuse maxima return to their previous shape and this process is completely reversible. Rapidly cooled samples, on the other hand, do not show such splitting and the symmetry remains R\bar 3, despite a jump in lattice parameters. We use a special technique to analyse the disorder model of the slowly cooled samples, which consists of layered domains shifted in the hexagonal ab plane. The low-spin disordered phase was solved in a novel approach to accommodate the very unusual twinning and refined in the non-standard space group C\bar 1. In contrast to the ordered low-spin phase, the Fe ion is in a non-centrosymmetric coordination polyhedron and two of the six propyl groups change their conformation.

Isostructural phase transition in the spin crossover compound [Fe(dpp)2(NCS)2] · py

Abstract The spin crossover complex [Fe(dpp)2(NCS)2] · py crystallises in the monoclinic P2/n space group with one guest pyridine molecule per iron complex and undergoes an isostructural phase transition near 100 K on cooling and around 155 K on heating. The space group does not change upon spin transition despite the occurrence of hysteresis with ca. 55 K width, which is clearly seen in the temperature dependence of the lattice parameters. These are highly anisotropic upon spin transition, and surprisingly the unit cell volume reduces only little (0.1%) upon spin transition from high spin to low spin phase. The differences between the high- and low-spin structures are discussed.

Crystal structure of betulinic acid-DMSO solvate

Abstract The crystal structure of betulinic acid-DMSO (1:1) solvate has been determined. The betulinic acid, [3β-hydroxy-lup-20(29)-en-28-oic acid, C30H48O3] is considered as a promising natural agent for the clinical treatment for various types of cancer. Crystals of betulinic acid for X-ray structural analysis were grown from a DMSO-water (9:1, v/v) solution. Betulinic acid-DMSO (1:1) solvate crystallizes in the orthorhombic symmetry the P212121 space group, Z = 4. The unit cell parameters are as follows: cell lengths a = 6.9417(2) Å, b = 13.8559(5) Å, c = 31.6232(10) Å, V = 3041.63(17) Å3. Betulinic acid molecules are hydrogen bonded to DMSO molecules. The weak intermolecular hydrogen bonds and van der Waals interactions are present in the crystal structure. The crystal and molecular structures of betulinic acid-DMSO solvates are discussed with reference to betulin and betulinic acid derivatives.

X-Ray Diffraction and Infrared Spectroscopy of N,N- Dimethylformamide and Dimethyl Sulfoxide Solvatomorphs of Betulonic Acid

X-ray diffraction and infrared spectroscopy measurements for the N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) solvatomorphs of betulonic acid (BA) were investigated. BA [3-oxolup-20(29)-en-28-oic acid, C(30)H(46)O(3)] exhibits a wide spectrum of biological activities and is considered to be a promising natural agent for the treatment of various cancer diseases. BA as a noncrystalline substance was obtained by oxidation of betulin. Crystal structures and the spectral data allowed analysis of hydrogen bonding (H-bonding), molecular conformation, and crystal packing differences in the solvatomorphs. Crystals of BA solvates were grown from the DMF-acetone (1:10, v/v) and DMSO-water (9:1, v/v) solutions. BA-DMF (1:1) solvate crystallizes in the monoclinic P2(1) space group, Z = 2. The unit cell parameters are as follows: cell lengths a = 13.2458(5) Å, b = 6.6501(2) Å, c = 17.9766(7) Å, and β = 110.513(4)°. BA-DMSO (1:1) solvate crystallizes in the orthorhombic P2(1)2(1)2(1) (Z = 4) space group with the following unit cell parameters: a = 6.6484(4) Å, b = 13.3279(8) Å, and c = 32.6821(19) Å. Conformational analysis of the six-membered rings, cyclopentane ring, and isopropenyl group showed differences in comparison with other betulin derivatives examined earlier. For both solvates, the intermolecular packing arrangement was governed mainly by H-bonds. The shortest H-bonds with D···A distances of 2.604 and 2.657 Å, and almost linear DH···A connection occurred between OH of carboxylic group of BA and oxygen atoms from O=C and O=S groups of DMF and DMSO, respectively.

Unique properties of silver and copper silica-based nanocomposites as antimicrobial agents

The paper reports a new route for the fabrication and determination of physicochemical properties and biological activity, of metallic silica-based nanostructure (Ag/SiO2, Cu/SiO2). A research studies shows mono-dispersed nanoparticles in silica matrix with an average size of 12 nm for silver, as well as 12 nm and 4 nm, respectively for copper in hydrophobic and hydrophilic silica composites. The chemical analysis highlights metallic silver and copper ions heterogeneously distributed in the composite as well as metallic oxides such as Ag2O, Cu2O and CuO in hydrophobic system, and CuO in hydrophilic one. Structural research evidences the presence of amorphous, stoichiometric and non-stoichiometric crystalline phase of silica. Biological studies reveal potentially inhibition of growth gram-positive and gram-negative bacteria as well as microscopic fungi. The size of metal nanoparticles and level of silica hydrophobicity show the highest inhibition bacterial growth for hydrophilic system with embedding inside them, 4 nm in size copper nanoparticles. Finally, cytotoxic interaction against human cells with respect to silver and copper silica-based nanocomposites was not found.

Characterization of the μ and P phase precipitates in the CMSX‐4 single crystal superalloy

A combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and scanning‐transmission electron microscopy (STEM) using high‐angle annular‐dark‐field (HAADF) imaging, focussed ion beam‐ scanning electron microscopy (FIB‐SEM) tomography, selected area electron diffraction with beam precession (PED), as well as spatially resolved energy‐dispersive X‐ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), was used to investigate topologically close‐packed (TCP) phases, occurring in the CMSX‐4 superalloy subjected to high temperature annealing and creep deformation. Structural and chemical analyses were performed to identify the TCP phases and provide information concerning the compositional partitioning of elements between them. The results of SEM and FIB‐SEM tomography revealed the presence of merged TCP particles, which were identified by TEM and PED analysis as coprecipitates of the μ and P phases. Inside the TCP particles that were several micrometres in size, platelets of alternating μ and P phases of nanometric width were found. The combination of STEM‐HAADF imaging with spatially resolved EDS and EELS microanalysis allowed determination of the significant partitioning of the constituent elements between the μ and P phases.

Low-Temperature XRD Study of Phase Transformations in NiTi and TiNiCo Shape Memory Alloys Used for the Preparation of the Prototypes of Medical Implants

The NiTi shape memory alloys with ternary additions of Co are being considered for future applications in the construction of medical products. In this study the commercially available Ni50.8Ti49.2 medical alloy and Ti50Ni48.7Co1.3 alloy obtained by the conventional VIM technique, were used to prepare shape memory and superelastic staples. The phase transformations in the wires of those alloys after various thermo-mechanical and thermal treatments have been defined by the differential scanning calorimetry (DSC) method and three-point bending and free recovery ASTM F2082-06 tests. In this work the courses of phase transformations in the studied alloys were investigated by means of the low-temperature X-ray powder diffraction method. In both alloys after cold working and annealing during cooling two phase transformations occur: from parent B2-phase to rhombohedral R-phase and monoclinic B19’ martensite phase. Such phase transformations are fully reversible during heating and the obtained characteristic temperatures from DSC and X-ray powder diffraction measurements are in good agreement.

Fate of neutral-charged gold nanoparticles in the roots of the Hordeum vulgare L. cultivar Karat

Nanoparticles (NPs) have a significant impact on the environment and living organisms. The influence of NPs on plants is intensively studied and most of the data indicate that NPs can penetrate into plants. The studies presented here were performed on the roots of Hordeum vulgare L. seedlings using neutral-charge gold nanoparticles (AuNPs) of different sizes. In contrast to the majority of the published data, the results presented here showed that during the culture period, AuNPs: 1/did not enter the root regardless of their size and concentration, 2/that are applied directly into the cells of a root do not move into neighbouring cells. The results that were obtained indicate that in order to extend our knowledge about the mechanisms of the interactions between NPs and plants, further studies including, among others, on different species and a variety of growth conditions are needed.

Influence of nickel on the electronic structure and magnetic properties in Gd7Pd3-xNix

Abstract With increasing amount of nickel in the Gd7Pd3-xNix series, the unit cell volume decreases due to difference between atomic radius of Pd and Ni but the type of crystal structure is preserved. The paper presents X-ray diffraction, Scanning Electron Microscopy with Energy Dispersive X-ray Spectrometer, Transmission Electron Microscopy, AC and DC magnetic susceptibility and magnetocaloric examinations of the series. The Ni substitution into Pd position causes the decrease in the Curie temperature. Moreover, the dispersion observed in the AC-susceptibility at different frequencies vanishes at the Curie point. Just below the ordering temperature, a Hopkinson peak is observed. Complex processes depending on frequency and magnetic field occur in the transition region. The magnetization phenomena are very sensitive to the applied DC magnetic field and even very weak fields producing thermomagnetic hysteresis. A reorientation process around 150 K exists in all compounds and it is connected with increasing interactions at low temperatures. After nickel substitution, the relative cooling power (RCP) is greater in comparison to the parent compound.