Authors:O. Pietraszkiewicz, E. Utzig, W. Zielenkiewicz, and M. Pietraszkiewicz
Lipophilic calixresorcinarene derived from lauryl aldehyde forms stable crystalline solvates with a range of organic solvents:
acetone, 1,4-dioxane, methylethylvketone, dimethylformamide, dimethylacetamide, N-methylpyrrolidinone, butyronitrile, methanol,
1,2-dimethoxybenzene and acetonitrile. The composition and thermal stability of these solvates was followed by thermogravimetric
method, indicating a stoichiometry ranging from 1 to 3 (calixresorcinarene/solvent). The activation energy was evaluated for
the selected solvates. Molecular modelling, using Hyperchem 5.0 software, was applied to the selected solvates.
Authors:T. Ageeva, E. Utzig, O. Golubchikov, and W. Zielenkiewicz
Porphyrins are known as unique ligands forming some of the most stable complexes with various metal ions. In this work the
thermokinetic investigations of complex formation of tetraphenylporphyrins with copper(II) acetate were carried out in two
anhydrous organic solvents: acetic acid and DMF at 25C. Measurements were performed in a heat conduction microcalorimeter
 adapted for non-aqueous solvents. Total heat effects and thermokinetics were determined. The results were discussed together
with spectrophotometric data.
Taking into account the high stability of metalloporphyrin complexes, the heat of their formation is rather small (in the
case of acetic acid ΔQ=32.71.2 kJ mol−1, for DMF ΔQ=26.21.3 kJ mol−1). Such result can suggest that: 1) the stability of complexes is influenced strongly by an entropy factor, 2) the complexation
involves breaking of the NH-bond in the porphyrin coordination centre, accompanied by high consumption of energy.
Authors:W. Zielenkiewicz, I. Terekhova, M. Wszelaka-Rylik, and R. Kumeev
Calorimetry, densimetry, 1H NMR and UV–vis spectroscopy were used to characterize inclusion complex formation of hydroxypropylated α- and β-cyclodextrins
with meta- and para-aminobenzoic acids in aqueous solutions at 298.15 K. Formation of more stable inclusion complexes between para-aminobenzoic acid and cyclodextrins was observed. The binding of aminobenzoic acids with hydroxypropyl-α-cyclodextrin was
found to be enthalpy-governed owing to the prevalence of van der Waals interactions and possible H-binding. Complex formation
of hydroxypropyl-β-cyclodextrin with both acids is mainly entropy driven. The increased entropy contribution observed in this
case is determined by dehydration of solutes occurring during the revealed deeper insertion of aminobenzoic acids into the
cavity of hydroxypropyl-β-cyclodextrin. By comparing complex formation of aminobenzoic acids with native and substituted cyclodextrins
it was found that the availability of hydroxypropyl groups slightly influenced the thermodynamic parameters and did not change
the binding mode or driving forces of interaction.
Authors:W. Zielenkiewicz, I. Terekhova, M. Koźbiał, and R. Kumeev
The inclusion complex formation of riboflavin (RF) with hydroxypropyl-β-cyclodextrin (HP-β-CD) in water was investigated by
1H NMR, UV-vis spectroscopy, and solubility methods. A 1:1 stoichiometry and thermodynamic parameters of complex formation
(K, ΔcG0, ΔcH0, and ΔcS0) were determined. Complexation was characterized by negative enthalpy and entropy changes due to prevalence of van der Waals
interactions and hydrogen bonding between polar groups of the solutes. A partial insertion of RF into macrocyclic cavity was
revealed on the basis of 1H NMR data and molecular mechanics calculation. Location of benzene ring of RF molecule inside the hydrophobic cavity of HP-β-CD
results in an increase of aqueous solubility of the former.
Authors:W. Zielenkiewicz, N. Lebedeva, M. Kamiński, E. Antina, and A. Vyugin
Titration calorimetry was used in a thermodynamic study on the interactions of pyridine with natural zinc(II) porphyrin derivatives in benzene and chloroform at 298.15 K. The ability of zinc porphyrins to coordinate to pyridine is higher in benzene than in chloroform and also depends on the molecular structure of the metalloporphyrin.
Authors:W. Zielenkiewicz, I. Terekhova, A. Marcinowicz, M. Koźbial, and J. Poznanski
Interactions of native and modified α- and β-cyclodextrins with nicotinic acid, pyridoxine and pyridoxal were studied by isothermal
titration calorimetry, solution calorimetry, and 1H NMR spectroscopy at 298.15 K and pH 6.8. Weak 1:1 complex formation was found only between α-cyclodextrin and nicotinic
acid. The stability constant and corresponding thermodynamic parameters of complex formation (ΔcG, ΔcH and ΔcS) were calculated using the calorimetric data. The 1H NMR data indicate the shallow insertion of the carboxylic group of the nicotinic acid molecule into α-CD cavity. For all
other compounds the weak interactions, not accompanied by complex formation, were characterized by the enthalpic virial coefficients
calculated on the basis of McMillan-Mayer approach. The obtained thermodynamic parameters were analyzed in the terms of influence
of the solutes’ structure on the selectivity of intermolecular host-guest interactions.
Authors:W Zielenkiewicz, R Swierzewski, F Attanasio, and G Rialdi
of lysozyme–polyethylene glycol system were made by differential scanning
calorimetry, fluorescence and density techniques. The values of unfolding
enthalpies, ΔHNU, unfolding temperatures, Tm,
excess molar heat capacities, ΔCp,
and apparent molar volumes, VΦ
, were determined as functions of PEG concentration. The three PEGs of average
molecular mass (MW) 6000, 10000, 20000
were used as macromolecular crowding agents. The concentration of polymers
was changed in the range 0–30% mass per volume (w/v). The values of ΔHNU remained
constant with no dependence on PEG concentration, while PEG addition to buffered
lysozyme solutions caused linear decrease of Tm.
The values of ΔCp
and VΦ of lysozyme
dramatically changed in the range of 8–10% of PEG concentration. The
fluorescence spectroscopy was used in order to investigate the polymer influence
on possible solvent–lysozyme interactions. The electrical properties
of polymer–water and polymer–buffer systems, the dielectric constants
of solutions were determined with use of impedance spectroscopy.
Authors:F. Attanasio, G. Rialdi, R. Swierzewski, and W. Zielenkiewicz
The physico-chemical properties
of poly(ethylene) glycol solutions in water have been studied with use of
pressure perturbation calorimetry. The three PEGs of average molecular mass
(Mr) 6000, 10000,
20000 were used. The concentration of polymers was changed in the range 0–30%
mass per volume (w/v%).
On the basic of VP-DSC measurements with use of PPC technique the dependencies
of thermal expansion coefficient (α) and excess specific heat capacity
(Cp,exc) on temperature
were determinated for PEG–water solutions.
Authors:N. Lebedeva, W. Zielenkiewicz, E. Utzig, Y. Gubarev, V. Andreev, and Ya. Nizhnik
Thermogravimetry, differential thermal analysis and differential scanning calorimetry were applied for investigation of molecular
complexes of heterocyclic N-oxide with zinc(II)tetraphenylporphyrin. The kinetic characteristics of the process of the thermal
oxidative destruction for individual compounds and their molecular complexes have been calculated. The obtained results indicate
that the complex formation of ZnTPhP with heteroaromatic N-oxides leads to an increase of the thermal stability both the metalloporphyrin
and the ligands. It has been shown that the stability of the molecular complexes of ZnTPhP with heteroaromatic N-oxides depends
on basicity of the coordinated ligand.