Kharkiv University Bulletin. Chemical Series

To the 80th anniversary of the birthday of professor Valeriy Dmytrovych Orlov (14.08.1941–14.12.2017)

Andrey Doroshenko — 2021-09-03

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Low molecular weight gelators based on steroid derivatives and pentacyclic triterpenoids

Victoria Lipson — 2021-09-21

The article is an overview of the latest achievements in the study of low molecular weight gelling agents based on steroids - cholesterol, estradiol, dehydroepi-androsterone and pentacyclic triterpenoids - arjunolic, glycyrrhetinic acids. These compounds are used as components of smart gels and are of interest for supramolecular chemistry. A gelling agent is a substance that is able to bind various solvents at low concentrations, and the resulting gel has a solid structure which rheological properties are similar to those of solids. Non-covalent interactions: dipole-dipole, van der Waals, electrostatic, hydrogen bonds and π-stacking, are considered as the driving forces for the formation a fibrous network by low molecular weight gelator. In contrast to decades of research into the gelation of polymers, proteins and inorganic substances, low molecular weight organic gelling agents have only recently begun to be actively studied. Their chemical structure is derived from urea, amino acids, carbohydrates, cholesterol and bile acids. Unlike steroid-based gels, information on the use of pentacyclic triterpenoids for the development of low molecular weight gelling agents is extremely limited. The interest in such systems is due to the fact that, like steroids, they have a developed, rigidly organized nanosized molecular platform, making them capable of self-association in polar and nonpolar organic solvents. In addition, the presence of molecules of these compounds in several functional groups that are easily chemically modified, low toxicity and biocompatibility allows them to be considered as promising starting materials for the pharmaceutical industry, in particular for the development of mild dosage forms.

Magnetic properties of generalized polyallyl spin chain

Maksym Pokhmura — 2021-10-07

The work is devoted to the theoretical simulation of low-temperature magnetic properties of generalized polyallyl spin chain with the antiferromagnetic coupling of the neighboring spins (GPSC) - spin model of a family of quasi-one dimensional molecular ferrimagnets. First, the exact energy spectra of Heisenberg spin Hamiltonians of the finite lattice clusters of GPSC with the spins of the main chain s=1/2 and pendant spins š=1 have been studied by means of the exact diagonalization method. The calculations were performed for different positive values of the coupling parameters for neighboring spins of the main chain of GPSC clusters. On the base of the above exact energy spectra and the Boltzmann distribution law the field dependencies of magnetization of finite lattice clusters are calculated numerically at different temperatures. In the result, for low temperatures the presence of intermediate plateau in field dependencies of the cluster magnetization has been shown. These calculations demonstrated the stabilization of the intermediate magnetization plateau with the growth of the spin coupling along the main chain of GPSC clusters. In addition, the numerical study of temperature dependence of zero field magnetic susceptibility of 12- spin clusters of GPSC gives the results which are similar to the 1D model of molecular ferrimagnets like necklace spin ladder.

Similar calculations of the magnetization profile were performed for infinite Heisenberg –Ising GPSC model with Ising type of the antiferromagnetic interactions between the neighboring spins of the main chain. The classical transfer- matrix method was used for this purpose. In the result, it was shown the presence of an intermediate plateau in the low-temperature magnetization profile of infinite chain model and the increase of the plateau size with increasing of the Ising coupling between the spins of the main chain.

Problems of training scientific and pedagogical staff in chemistry in pre-revolutionary universities of Ukraine (19th – early 20th centuries)

Sergii Kulish — 2021-11-03

The article identifies a number of problems that arose in the process of training students in chemistry at Ukrainian universities in the 19^th – early 20^th centuries. There were not enough chemistry teachers during this period, but they did a lot of work to find ways to stimulate students’ research, although chemical laboratories were insufficiently equipped and staffed. The role of university professors in public life and everyday problems of the population of Ukraine is shown. They participated in the preparation of literature for the population of Kharkiv and Odessa, provided assistance in studying the physical and chemical properties of products and non-product substances.

During this period, new areas of focus emerged in the study of chemistry (agrochemistry, thermochemistry, electrochemistry, etc.). The problems of various scientific schools in chemistry, which led to conflicts among lecturers, university administrations and the Ministry of Public Education, are considered. During this period, the authorities tightened control over the national factor of university teachers. At the end of the 19^th century the Ministry of Public Education demanded to strengthen the Russian element in the teaching staff, refrained from hiring teachers of the Jewish and Catholic religion. The article also considers the problems of scientific trips of teachers abroad and the use in teaching students of foreign experience in teaching chemistry.