Krzysztof Wozniak

PEGylated Nanoceria as Radical Scavenger with Tunable Redox Chemistry

We report the direct synthesis of cerium oxide nanoparticles (CNPs) in polyethylene glycol (PEG) based solutions with efficient radical scavenging properties. Synthesis of CNPs in PEG demonstrated a concentration dependent (of PEG) redox activity characterized by UV-visible spectroscopy. PEGylated CNPs acted as efficient radical scavengers, and superoxide dismutase (SOD) activity of CNPs synthesized in various concentration of PEG did not reduce compared to bare nanoceria. In addition to superoxide, PEGylated nanoceria demonstrated quenching of peroxide radicals as well. It was observed that the reaction with hydrogen peroxide leads to the formation of a charge transfer complex governed by the concentration of PEG. The stability of the charge transfer complex provides the tunable oxidation state of CNPs. The stability of this complex influences the regenerative capacity of the active 3+ oxidation state of CNPs. The cell viability as well as SOD activity of PEGylated CNPs is compared to those of bare CNPs, and the differences are outlined.

Intramolecular hydrogen bonding in N-salicylideneanilines. X-ray diffraction and solid-state NMR studies

The crystal structures of four Schiff bases: N-(3,5-dichlorosalicylidene)-4-dimethylaminoaniline, N-(3,5-dichlorosalicylidene)-4-diethylaminoaniline, N-(3-nitrosalicylidene)-4-diethylaminoaniline and N-(2- hydroxynaphthylidene)-4-dimethylaminoaniline have been determined by single-crystal X-ray diffraction and solid-state NMR. We discuss the relationship between the variation of the hydrogen bonding on the one hand, and the geometry and electron density distribution in the N-salicylideneaniline fragment on the other. Mesomerism involving ionic structures is the dominant effect in changing the geometric parameters of the fragment. The concentration of ionic structures correlates very well with the C—O bond length and other structural parameters.

ESCA studies of the coordination state of aluminium in oxide environments

X-Ray photoelectron spectroscopy (known as XPS or ESCA) can differentiate between tetrahedral and octahedral Al atoms in inorganic solids. Although primarily used for the study of aluminosilicates, this semi-quantitative technique is applicable to other materials, irrespective of whether they contain aluminium in one or more coordinations with respect to oxygen. If less sensitive to the coordination of Al, the range of ESCA, a surface-oriented technique, is thus not very different from that of the bulk-oriented solid-state NMR. The procedures described here are successful with any high-resolution ESCA system, but are greatly facilitated by flood gun technology which removes insulator-induced charging shifts. Areas of potential difficulty are also discussed.

Neutron diffraction of a complex of 1,8-bis(dimethylamino)naphthalene with 1,2-dichloromaleic acid

A neutron study of the crystalline complex of 1,8-bis(dimethylamino)naphthalene (DMAN) with 1,2-dichloromaleic acid (ClMH2) has been carried out at 100 K using the Laue time-of-flight technique. The moieties are planar. The neutron data indicate that both [N—H⋯N]+ and [O—H⋯O]− hydrogen bonds in the complex are asymmetric. There are significant differences between the neutron and X-ray temperature factors, C—H, N—H and O—H bond lengths. There is a strong correlation between the neutron and X-ray temperature factors for non-H atoms and no correlation for H-atom temperature factors. According to the neutron data the involvement of a given H atom in a weak C—H⋯O hydrogen bond can be correlated with the ratio of equivalent temperature factors of the H and non-H atoms to which they are attached.

Multiplicity dependence of strangeness production in S + Pb collisions at 200 GeV/c per nucleon

Abstract Production of Λ, Λ , and K s 0 has been measured for a wide range of event multiplicity in S+Pb reactions at 200 GeV/c per nucleon. The production of Λ is shown to increase with multiplicity faster than expected from a superposition of p+p collisions. The effect is seen for low multiplicity (below 100 negative particles).

Synthesis, reactivity, crystal and molecular structure of [5,14-dihydro-7,16-bis(2-oxo-3H-furan-5-yl)-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecinato(2-)-κ4N]nickel(II)

Abstract The reaction of the Ni(II) complex of 5,14-dihydro-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine with succinyl dichloride leads to di- and monosubstituted derivatives bearing β,γ-unsaturated-γ-lactonic rings at the meso positions of the macrocycle. An aminolytic cleavage of these lactonic substituents gives rise to open-chain pendant groups containing the corresponding amide functions. A range of new complexes have been synthesized in this way with use of primary and secondary aliphatic and heterocyclic amines. The new products have been characterized by elemental analyses, 1H, 13C NMR, IR and ESI-MS spectral data. Single crystal X-ray studies revealed that the saddle-shaped molecules of [5,14-dihydro-7,16-bis(2-oxo-3H-furan-5-yl)-6,8,15,17-tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecinato(2-)-κ4N]nickel(II) act as receptors with molecules of toluene forming 1:1 supramolecular complexes.

Ab initio calculation of 1H and 13C NMR shielding constants in solid acetylene.

The gauge-independent atomic orbital (GIAO) method has been used within the coupled Hartree-Fock (CHF) approximation to compute 1H and 13C NMR shielding constants for solid acetylene. As the amount of surrounding crystal lattice is increased, the shielding anisotropy of the carbon nuclei decreases and that of the protons increases. The influence of intermolecular interactions on the 13C shielding constant is non-additive. The GIAO approach at the HF level is sufficiently sensitive to differentiate between the two polymorphic forms of acetylene.

X-ray studies of the intra- and intermolecular H-bonding in two phenolic Mannich bases

Abstract The crystal structures of two phenolic Mannich bases, 1-[(2,3,4,5-tetrachloro-6-hydroxy)phenyl]-N,N-dimethylmethanamine (1) and 1-[(3-nitro-6-hydroxy)phenyl]-N,N-diisobutylmethanamine (2), were determined by using the single crystal X-ray diffraction method. The results and conditions for molecule 1, C9H9NOCl4 are: Mr = 288.99, monoclinic, C2/c, a = 21.88(2)A, b = 8.419(7)A, c = 14.63(1)A, β = 119.62(4)°, V = 2344(3)A3, Z = 8, Dcacl = 1.638 g cm−3, λ(MoKα) = 0.71069 A,μ = 9.87 cm−1, F(000) = 1168, T = 296 K, R = 0.043 for 1559 observed reflections. For molecule 2, C15H24N2O3, results and conditions are: Mr = 280.37, orthorhombic, P212121, a = 8.850(7)A, b = 29.399(6)A, c = 6.22(1)A, V = 1620(4)A3, Dcalc = 1.150 g cm−3, λ(Mokα) = 0.71069 A, μ = 0.75 cm−1, F(000) = 608, T = 296 K, R = 0.062 for 755 observed reflections. Compounds 1 was determined to have intermolecular hydrogen bonding involving the zwitterionic form N+H⋯O−1. For compound 2 intramolecular H-bonding was observed with the N⋯HO form retained. Complementary IR measurements in the solid state were in good agreement with the X-ray results. The geometry of the hydrogen bond present depends on the substituents at the amine nitrogen atom.

X-ray diffraction and 13C solid-state NMR studies of the solvate of tetra(C-undecyl)calix[4]resorcinarene with dimethylacetamide

Single crystal X-ray diffraction (XRD) analysis of the complex of calix[4]resorcinarene (CAV11) with dimethylacetamide (DMA) shows that the CAV11 molecules form centrosymmetric dimers, held by van der Waals interactions of the C-undecyl aliphatic chains. The dimers are associated in layers with hydroxyl groups at the surfaces. The DMA molecules are found between the CAV11 layers, above the cavities formed by the resorcine units and distant from them. They join the layers of CAV11 by molecular forces, in particular by various hydrogen bonds, and are relatively immobile. The 13C CP/MAS spectra are in reasonable agreement with the XRD results.

Complexation behaviour of p-tert-butylcalix[4]arene and p-tert-butylcalix[6]arene towards acetone

Novel 1:1 complexes of acetone with p-tert-butylcalix[4]arene and p-tert-butylcalix[6]arene were prepared and characterized by TGA, DSC, PXRD and 13C and 2H solid-state NMR. The behaviour of both molecules towards acetone is very similar, with the same orientation of the guest, and the same activation energy for the rotation of the C–D bond of acetone about its threefold axis. This is interpreted in terms of the pinched-cone conformation of p-tert-bultylcalix[6]arene in the complex, which can be viewed as two edge-sharing p-tert-bultylcalix[4]arene molecules in the cone conformation.