Ildikó Mohammed-Ziegler

Surface free energy of natural and surface-modified tropical and European wood species

To describe the wetting properties of various wood types from a practical point of view, the surface free energy of six tropical (guava, almond, teak, cloves, mango and neem) and six European wood species (English oak, Norway maple, hazel, ash, alder and Scots pine) were calculated using contact angles by the sessile-drop method. In order to provide water-repellent characteristics to the samples, they were silanized by a less used silylating reagent (using chloroform solution of trimethylsilyl N, N-dimethylcarbamate) and the results were compared with the effect of two commonly used reagents (chloroform solutions of chlorotrimethylsilane and octadecyltrichlorosilane). Since the Lifshitz–van der Waals/acid–base model is widely used in studies of biological surfaces, the energetics of the resultant wood surfaces were quantitatively described in terms of this model. For the mainly hydrophobic wood samples, anomalous surface behaviour (i.e. extremely high water contact angles (130–145°) and in certain cases unreasonably low surface free energy values) was found. Since the Lifshitz–van der Waals/acid–base model did not yield numerical results in some cases and the calculated surface free energies depended on the test liquid triplet used, the limitations in the applicability of this model are also discussed. For comparison, we analyzed our data also in terms of the Chang model.

Selective complex formation of some chromogenic calix[4]arene derivatives detected by Fourier transform infrared spectroscopy 2. Solid experiments

Two chromogenic calix[4]arene derivatives having identical coordination sphere (consisting of ester groups) but different chromogenic units (pyridinium type and dinitro-phenyl type) were the subject of structural studies with sodium(I) and thallium(I) ions in solid state, both as bulk and surface complexes. Their diffuse reflectance infrared Fourier transform (DRIFTS) spectra were recorded and the characteristic changes of the vibrational spectra due to complex formation were analysed based on curve fitting.

Transportation behavior of alkali ions through a cell membrane ion channel. A Quantum chemical description of a simplified isolated model

AbstractQuantum chemical model calculations were carried out for modeling the ion transport through an isolated ion channel of a cell membrane. An isolated part of a natural ion channel was modeled. The model channel was a calixarene derivative, hydrated sodium and potassium ions were the models of the transported ion. The electrostatic potential of the channel and the energy of the channel-ion system were calculated as a function of the alkali ion position. Both attractive and repulsive ion-channel interactions were found. The calculations – namely the dependence of the system energy and the atomic charges of the water molecules with respect to the position of the alkali ion in the channel – revealed the molecular-structural background of the potassium selectivity of this artificial ion channel. It was concluded that the studied ion channel mimics real biological ion channel quite well. FigureTransportation behavior of alkali ions through a cell membrane ion channel

Vibrational Spectroscopy of Phenols and Phenolic Polymers. Theory, Experiment, and Applications

Abstract In the first part of this review, the authors give a survey on the literature of vibrational spectroscopy of phenol, phenol derivatives, and other phenolic componds from the last decade of the last century through today. The classical and modern methods of vibrational spectroscopy are also introduced and a glossary is included to aid comprehension. The second part deals with the literature regarding the importance of vibrational spectroscopy in the investigation and identification of phenolic compounds in natural substances, the application of vibrational spectroscopy in composite and synthetic polymer chemistry, and following of chemical processes and investigating their resulting products. Vibrational spectroscopy is a very good tool for determination of molecular structures and is important in chemical analysis and in the chemical industry.

Methanol in its own gravy. A PCM study for simulation of vibrational spectra

For studying both hydrogen bond and dipole-dipole interactions between methanol molecules (self-association) the geometry of clusters of increasing numbers of methanol molecules (n = 1,2,3) were optimized and also their vibrational frequencies were calculated with quantum chemical methods. Beside these B3LYP/6-311G** calculations, PCM calculations were also done for all systems with PCM at the same quantum chemical method and basis set, for considering the effect of the liquid continuum on the cluster properties. Comparing the results, the measured and calculated infrared spectra are in good accordance.

Formyl- and acetylindols: Vibrational spectroscopy of an expectably pharmacologically active compound family

In the present paper, indole and its seven derivatives were compared, namely 3-formylindole, 1-methyl-3-formylindole, 1-ethyl-3-formylindole, 3-acetylindole, 1-methyl-3-acetylindole, 1-ethyl-3-acetylindole and 1,3-diacetylindole. The substitution of indole in position 3 with aldehydes and with alkyl groups cause only minor changes in the molecular geometry, however, substantially larger alterations are found in the charge distribution and in the vibrational force constants. The appearance of the aldehyde groups increased the degree of association as it was observable on the shape of infrared NH stretching band and its shifts. The alkyl substitution shifts the aldehyde carbonyl stretch band frequencies to somewhat higher values. The effect of the second acetyl group in position 1 is not comparable with those of the 1-alkyl groups. The latter effect is observable in the molecular geometry, however, it is more pronounced in the changes of the net charge distribution, the vibrational force constants and the infrared spectra.

Complex Formation of Some Tetraamido-type Calix[4]arene Derivatives Detected by Vibrational Spectroscopy

Complex formation of five teraamido-type calix [4] arene derivatives—containing a heteroaromatic ring on the carboxamide moieties forming the coordination sphere—with alkali/alkali earth ions were the subject of FT–IR studies. The selectivity of these ligands toward different cations were found in acetonitrile solution, with the best detection in the case of the thiophene derivative, ligand 3, that exhibited selectivity to thallium(I) and thallium(III) ions over alkali/alkaline earth ions. Calixarenes 2 and 4 exhibit selectivity to potassium and ligand 5 to lithium ions among alkali/alkaline earth ions, however, thallium(I) ions show interference with these measurements. Moreover, selectivity was observed in solid state when surface complexes were prepared on sodium chloride, potassium chloride, bromide and iodide, calcium chloride and fluoride. The solid samples were examined by FT–Raman and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) method. Calixarenes 2 and 4 are of potential analytical application for the recognition of cations among alkali/alkaline earth metal ions in solid state by FT–IR spectroscopic detection. The number of methylene units in the substituents of calixarenes influences the efficiency of the complexation process significantly, as it can be seen from the comparison of ligands 1 and 2 both in solution and in the solid state. FT–Raman measurements on calcium chloride show that the attachment of the ligand molecules to the salt surface is accompanied by the squeezing of water molecules from some special positions of the hydrated salt lattice.

1H and 7Li NMR Study on the Complex Formation of Lithium Cations with Pyridinium Derivatives of Calix[4]arenes

Complexation of lithium ions by three chromoionophoric calix[4]arenes has been studied by 1H and 7Li NMR spectroscopy. The signalling unit of the chromoionophores is the N-methylpyridinium(methyleneimino) group in conjugation with a phenolic group of the calixarene ring while the coordination spheres contain esteric (ethoxycarbonylmethoxy) or etheric (ethoxy, propoxy) units. 1H NMR and NOESY measurements suggest the dominance of cone conformations of the calixarene rings with slight, solvent-dependent distortions. Complexation occurs only in the presence of a weak base. The interaction with lithium ions causes a broadening of both the 1H and 7Li NMR signals. Analysis of the chemical shifts in the three complexes indicates a different coordination environment for the lithium with the calixarene containing esteric groups from those having etheric groups. This explains the differences in the stabilities of the lithium complexes of the two types of calixarenes.