Iron: fullerides were prepared by chemical methodes in the solution using nitric acid as activation agent. Experimental results
of thermal analyses, X-ray diffraction and Mössbauer spectroscopy of the products are presented. To interpret these results,
standard quantum chemistry calculations were used to determine the geometry and charge distribution in Fe:C60 complexes, which might be formed in the reaction.
Authors:P. Byszewski, E. Kowalska, and R. Diduszko
Iron in the fullerite lattice binds fullerences in a sandwich type C60FeC60 complexes. At the concentration C60Fe2 it crystallizes in the monoclinic lattice. The structure is thermally unstable, with the energy release of 606 kJ·mol−1 it returns to fee lattice. Two possible sites in the reconstructed fee lattice are discussed, Fe bond to C60 and Fe inside the C60 cage.
Authors:P. Byszewski, E. Kowalska, and R. Diduszko
Fullerences C60 with adamantane (C10H16), hexamethylotetramine (HMT, C6H12N4) or 1,4-diazabicyclooctane (DABCO, C6H12N2) crystallize, at the relative concentration C60/guest=2/1, in the pseudotetragonal lattice in which C60 retains almost the same positions as in pure fullerides. The ‘guest’ molecules occupy the octahedral interstitial sites.
The mixed crystals which exhibit interesting physical properties are thermally unstable. The decomposition starts at 40–50°C.
Authors:E. Kowalska, P. Byszewski, Z. Klusek, M. Popławska, and J. Radomska
Molecules that may adopt various stable conformations might be applied to store information. The conformational changes could
be induced by suitable polarized tip of STM. For the STM experiments two types of fullerene:ferrocene cycloadducts (C60:Fn) were selected where ferrocene fragment is bound to C60 at the 6-6 bond by different heterocyclic pentagon rings. According to semiempirical quantum chemistry calculation one of
them may be used to STM observation without any modification, while the second cycloadduct must be exposed to thermal treatment
in order to obtain bistable molecule.
Authors:M. Sajewicz, E. John, D. Kronenbach, M. Gontarska, and T. Kowalska
Enantiomer separation by TLC is still much less frequent than with other, mostly instrumental, chromatographic techniques. From a literature survey it is apparent that separation of the enantiomers of d,l-lactic acid is primarily of interest to the diary industry and that this particular separation is less frequently performed by chromatographic than by membrane techniques. As far as we are aware, before our studies only one report of TLC separation of the enantiomers of d,l-lactic acid was available in the literature; this is dated 1991 and describes the use of non-instrumental TLC only. In this study, we started by reproducing the TLC procedure originating from 1991, for this purpose using TLC with automatic sample application and densitometric detection. We managed to repeat the earlier procedure and to achieve full, i.e. baseline, separation of the enantiomers, with a remarkable distance between the two antimers. However, we revealed a significant drawback of this separation procedure — d-(−)-lactic acid was transported almost with the mobile-phase front and its densitometric quantification was barely possible because of the relatively high UV absorption of the mobile-phase front line. The reference method for separation of the enantiomers of d,l-lactic acid consisted in preliminary impregnation of commercial silica gel TLC plates with copper(II) acetate. In-situ formation of bidentate complexes of the d,l-lactic acid antimers with the Cu2+ cation resulted in different mobilities of these complex cations in the planar chromatographic system. The objectives of this study were twofold — to investigate separation of the enantiomers of d,l-lactic acid with other transition metal cations (i.e., Co2+, Ni2+, and Mn2+) used to impregnate the silica gel (to achieve resolution that might enable quantification of the two lactic acid antimers and not only the l-(+) enantiomer) and to gain deeper insight into the mechanism of separation with these metal cations. For purposes of comparison, we chromatographed d,l-lactic acid on non-impregnated silica gel layers. As a result, we managed to establish efficient separation conditions with the Ni2+ and Co2+ cations that outperformed the earlier established procedure involving the Cu2+ cation, and — partially at least — to elucidate the mechanism of separation of the enantiomers of d,l-lactic acid by these TLC systems. The Mn2+ cation proved unsuitable for the purpose. Finally, we managed to separate the enantiomers of d, l-lactic acid on non-impregnated silica gel layer also, which seems yet more proof of the microcrystalline chirality of silica gel used as stationary phase and of its substantial contribution to the enantiomer separation investigated.
Authors:M. Sajewicz, M. Gontarska, D. Kronenbach, E. Berry, and T. Kowalska
In our earlier studies, we were the first to discover a spontaneous chiral conversion of the low-molecular-weight carboxylic acids dissolved in aqueous media, running in vitro. The investigated chiral carboxylic acids belong to the classes of profen drugs, amino acids, and hydroxy acids. Then, the spontaneous chiral conversion running in vitro and accompanied by the spontaneous condensation of the discussed compounds was discovered. From the literature, we learnt that spontaneous condensation of certain chiral compounds sometimes can be oscillatory in nature. Thus, we considered it noteworthy to check if spontaneous condensation of the chiral low-molecular-weight carboxylic acids follows a linear or a nonlinear dynamic pattern. In this paper, we present the results of our studies on the dynamics of condensation of S-, R-, and rac-mandelic acid, carried out with the aid of the high-performance liquid chromatography with the diode-array detection (HPLC-DAD), and with the aid of mass spectrometry (MS). The obtained data furnish reliable evidence that condensation of mandelic acid is oscillatory in nature. Finally, a theoretical model is recalled, which jointly describes the oscillatory chiral conversion and the oscillatory condensation with S-, R-, and rac-mandelic acid.
Authors:E. Kowalska, P. Byszewski, R. Diduszko, A. Huczko, and J. Mieczkowski
The crystalline solvates containing fullerenes and (di)methylnaphthalenes were investigated by thermal analyses and X-ray
diffraction methods. It was found that C60 with (di)methylnaphthalenes forms two types of stable solvates: either at the molar ratio 1:2 decomposing at temperatures
close to 100C or at 1:1 molar ratio decomposing in the temperature range 120–214C. Crystalline lattice and thermal stability
of the solvates depends on the structure of the solvent molecules. The strong solute-solvent interaction is also manifested
by the modification of the C60 absorption spectra in solution. The results are discussed using semiempirical quantum chemistry methods.
Authors:D. Sternik, M. Błachnio, P. Staszczuk, G. Chądzyński, and E. Kowalska
properties (adsorption capacity, desorption energy distribution and pore-size
distribution functions) of nanomaterial surfaces from selected materials,
based on sorptometric and liquid thermodesorption measurements under quasi-equilibrium
conditions, are presented. The fractal dimensions of nanotubes using sorptometric
and AFM data have been evaluated.
Comparison of thermogravimetric
and other data provide new information about the adsorption and pore structure
of the studied materials. The fractal dimensions of nanomaterial surfaces
using sorptometry are in good agreement with those from AFM.
Authors:P. Staszczuk, M. Błachnio, E. Kowalska, and D. Sternik
Calculations based on the fractal geometry in the estimation of surface
heterogeneity are superior compared with conventional calculation methods
(e.g. from the data of gas adsorption or X-ray radiation scattering) as they
can be applied without limitation as far as the range of surface sizes of
the studied structures is concerned. This paper presents structural characteristics
of carbon and carbon- free nanomaterials based on the determined surface and
volumetric fractal coefficients. Fractal coefficients were determined from
the data obtained by means of two independent methods: sorptometry and atomic
force microscopy (AFM). Correlation between porosity parameters and fractal
coefficients is presented.
Authors:B. Bartoś, E. Kowalska, A. Bilewicz, and G. Skarnemark
103mRh is a very promising radionuclide for Auger electron therapy due to its very low photon/electron ratio. The goal of the
present work was the elaboration a method for production of large quantities of 103mRh for generator system. It was found that the combination of solvent extraction with evaporation of 103RuO4 followed by decomposition of H5IO6 makes it possible to produce 103mRh of high radionuclidic and chemical purity.