MARCUS INTERNATIONAL SYMPOSIUM (INTL. SYMP. ON SOLUTION CHEMISTRY SUSTAINABLE DEVELOPMENT)

Surface tensiometry is a non invasive analytic technique capable to determine the surface tension of liquids and the surface free energy of solid substrates [1]. The contact angle (CA: deg) method is commonly used for the determination of the wettability of solid substrates, and in particular for the evaluation of the hydration state of biomaterials such as skin [2] and plant leaves [3]. The hydration analysis of skin consent to determine functionality of the stratum corneum, while the moisturize content of leaves is a parameter capable to classify different plant species in relation to their habitats and evaluate the relationships between wettability and photosynthesis, canopy interception, pathogen infections, and environmental quality [3]. However, the surface tensiometry comparison between different kind biomaterials and their correlations was not deepened studied. On this base, the aim of our work was the determination of the hydration of different species of ex-vivo samples of plant leaves and the correlation with the moisturize level of in-vivo skin of a subject test in order to identify the human skin as a possible reference’s tissue for the evaluation of leaves hydration. The water CA analysis of skin and leaves were performed in the same environmental conditions and time using portable MobilDrop DSA2 tenskinmeter [4]. Our work demonstrated that the variations of water CAs measured on the under edge surface of leaves (CA: 97.7±19.8 deg, 97.15±23.2 deg) were higher than that measured on the upper edge surface (CA: 97.9±5.0 deg, 96.61±7.64 deg). The water CAs measured on skin surface (CA: 73.1±11.1 deg and 75.3±9.6 deg) demonstrated also the differences in the hydration level between the two biomaterials. The correlation analysis between the water CAs measured on skin surface and that performed on more (R2=0.87, R2=0.93) and less (R2=0.54, R2=0.015) hydrated surfaces of leaves opened at the hypothesis to consider the human epidermis as a possible reference biological substrate for the evaluation of different kind of plant species on the base of their moisturize contents. Our investigation could represent a important perspective in the study of the environmental pollution within the sustainable development in agriculture field. This because surface tensiometry is a non invasive, rapid and cheap analytic technique capable to reveal the changes in the wettability of vegetal surfaces in relation to phytosanitary treatments also.

In recent years, the number of indicator displacement assays (IDAs) [1] has increased as an eminent strategy for changing a synthetic receptor (host) into an optical sensor. In a conventional IDA, an indicator (dye) is first permitted to reversibly bind a host, before being dislodged from the host by a competitive analyte (drug) and thus the strategy regulates an optical signal despite the analyte and the host are both spectroscopically inactive. It is quite crucial that the indicator and analyte have similar affinity for the receptor.[2–6]
A new fluorescent dye (4PBZC) comprises of coumarin, piperazine and benzimidazole (BZ) was designed, prepared and complexed to cucurbit[7]uril (CB7) to detect carnosol (CAR) anticancer drug in sub-nanomolar concentrations utilizing the supramolecular indicator displacement assay (IDA) strategy, the CB7-assisted pKa shift and the CB7-retarded photoinduced electron transfer (PET) process. The 2:1 host−guest complexation was confirmed by UV−visible absorption, fluorescence and proton NMR spectroscopy, which confirm binding to 4PBZC via the BZ and coumarin moieties. Also, CB7 preferentially binds the indicator dye via the protonated BZ group compared to the neutral BZ group, demonstrated by a high 2:1 binding constant (e.g., K = 5.5 × 106 M−1) of the complex in its protonated form, which led to an increase in the pKa of the BZ moiety by ca. 3.0 units after the addition of CB7. In the aqueous solution under pH of 6, switching the emission signals between 4PBZH+C/CB7 (ON state) and CAR/CB7NPs (OFF state) was achieved by displacement of the protonated dye from the cavity of CB7 by the CAR analyte. An efficient sensor was fabricated for the highly sensitive detection of CAR in aqueous solution at pH 6 with a low-detection limit (LOD) of 0.06 ng/mL (0.2 nM).

The paper presents the supramolecular control of photoisomerization reactions of cinnamic acid (CA), belonging to the class of α,β-unsaturated carbonyl compounds, utilizing the rigid cavity of cucurbit[7]uril (CB7). Irradiation by UV light (300 and 254 nm) of an aqueous solution of the complex induces the E-to-Z-conformational change, as evidenced by UV-visible absorption spectroscopic and 1H-NMR techniques. CA and CB7 form a stable 1:1 host–guest complex with moderate binding constant (K = 3.3 x 103 M-1). The photo-switchable “on-off” host–guest system shows a higher reversibility and switching efficiency, when compared to the unbound molecules, which makes it potentially useful in designing photoresponsive gating systems. The results presented herein highlight the value of a supramolecular approach in achieving selectivity in photoreactions and opening reaction pathways that are latent in solution chemistry.

The sodium cation is ubiquitous in aqueous chemistry and biological systems. Yet, in spite of numerous studies, the (average) distance between the sodium cation and its water ligands, and the corresponding ionic radii, are still controversial. Recent experimental values in solution are notably smaller than those from previous X-ray studies and ab initio molecular dynamics. Here we adopt a “bottom-up” approach of obtaining these distances from quantum chemistry calculations [full MP2 with the 6-31++G(d,p) and cc-pVTZ basis-sets] of gas-phase Na⁺(H₂O)_n clusters, as a function of the sodium coordination number (CN = 2–6). The bulk limit is obtained by the polarizable continuum model, which acts to increase the interatomic distances at small CN, but has a diminishing effect as the CN increases. This extends the CN dependence of the sodium-water distances from crystal structures (CN = 4–12) to lower CN values, revealing a switch between two power laws, having a small exponent at small CNs and a larger one at large CNs. We utilize Bader’s theory of atoms in molecules to bisect the Na⁺–O distances into Na⁺ and water radii. Contrary to common wisdom, the water radius is not constant, decreasing even more than that of Na⁺ as the CN decreases. We also find that the electron density at the bond critical point increases exponentially as the sodium radius decreases.

The invasion of nuclear magnetic isotopes of magnesium, calcium, and zinc in enzymatic catalysis discovered new facets of gene chemistry related to magnetism [1-3]. Numerous experimental observations convincingly demonstrate that the genes are sensitive to the magnetic fields, both permanent and oscillating [4]. The focus of this paper is placed on the molecular mechanism of the magnetic effects as a means for elucidating magneto-chemistry of genes, for understanding and using magnetic effects in medicine. The loading of polymerases with 25Mg2+, 43Ca2+, and 67Zn2+ ions carrying magnetic nuclei instead of 24Mg2+, 40Ca2+, and 64Zn2+ ions with nonmagnetic nuclei disclosed a huge isotope effect: the former ions suppress DNA synthesis by 3-5 times with respect to the latter ions. The effect certifies new, enzymatic radical pair mechanism (ERPM), which includes electron transfer from the growing DNA chain to the catalyzing ion. This mechanism is induced by compression of the catalytic site in the DNA polymerases; the compression removes water molecules from the site and partly dehydrates catalyzing ions, switching on electron transfer and ERPM. The key processes of gene functioning (DNA synthesis, DNA damage, and DNA repair) are shown to be magnetically controlled and mechanism of the control is physically substantiated [5]. A new anti-cancer strategy is suggested based on the using of the nuclear magnetic ions of magnesium, calcium, and zinc as a powerful and universal means to selectively kill only cancer cells; they are supposed to be highly promising for medical applications.
Both magnetic isotope and magnetic field effects convincingly demonstrate that the three processes – the DNA synthesis, which elongates DNA chains and creates genes; the cleavage, the scission of DNA chains which produces DNA damage and destroys genes; and the DNA repair – are magnetically vulnerable and result to the total magnetic control of genes.

A novel class of molten salts referred to as ionic liquids possess the unique combination of particular properties, unlike molecular liquids, namely negligible vapour pressure (~ 10^-11 to 10^-10 bar at room temperature), wide thermal window (~ -50 °C to +250 °C), wide electrochemical window (~ ±3 Volt vs. NHE), non-flammability, high ionic conductivity and a highly solvating capacity for organic, inorganic and organometallic compounds. This unique combination of particular properties leads them to be exploited as “alternatives to organic solvents” and giving them increasing attention in academic and industrial research. The research areas on ionic liquids are growing very rapidly and the potential applications are numerous, mainly due to the fact that simple changes in the cation and anion combinations or the nature of the moieties attached to each ion allow the physical properties of ionic liquids such as hydrophobicity, viscosity, density, coordinating ability, ion selectivity, and chemical and electrochemical stability to be tailored for specific applications. The proposed talk will include the brief introduction of ionic liquids and understanding unique thermophysical properties of novel ionic liquids for metal ion extraction, CO₂ capture, desulphurization of fuels and aqueous biphasic systems for the extraction of value-added products. Further, the effects of thermophysical properties of ionic liquids on these applications and current research trends on ionic liquids as solvents for the chemical industry will be discussed.

We present a statistical-thermodynamic description of the diversified influence of pairwise interactions on the position of chemical equilibrium in reactions of various types, such as the dimerization, the formation of heteronuclear molecules, and the complex formation in molten salts with di- and three-valent metals. Models of pair interactions from the simplest potential of hard spheres, through the potential with square well, to the potential of charged hard spheres with different ionic diameters were considered. The dumbbell shape for binary molecules is additionally taken into account and a significant diversity of deviations from ideality were described.
The effects of the excluded volume on the shift of chemical equilibrium in binary systems containing the inert solvent have been analyzed [1]. With an increase in the size of the solvent particles, the character of the concentration dependence for the enthalpy of mixing changes from purely endothermic to sign alternative, which has a pronounced exothermic effect at low and medium concentrations.
The association in binary hard-sphere liquids was considered taking into account the dumbbell-like shape of heteronuclear molecules [2]. The excess entropy for such a reacting mixture describes the most pronounced ordering with a larger difference in the diameters of monomers, but with a lower their fusion.
The influence of attraction between particles on the position of dimerization equilibrium was estimated within the model of square well [3]. An amplification in the attraction between monomers leads to a shift in equilibrium towards the dissociation, while an amplification in the attraction between dimers contributes a shift in equilibrium towards the formation of dimerization products. The inclusion of interparticle attraction, especially between dimeric molecules, leads to an increase in the packing fraction.
The evaluation of concentrations of the complex anionic (MX4)2‒ and (MX6)3‒ groups in molten salts have been performed [4, 5]. The calculation according to the ideal mass action law provides a significant overestimation of the concentration of complexes, at that the fraction of complexes is practically equal to the maximum possible (1/2) in the considered temperature range. We will demonstrate that in Coulombic systems there is a temperature threshold above which the complete dissociation of anionic complexes contained in pure and binary molten halides of two- and three- valent metals occurs.
Thus, the deviations from ideality in various liquids play an important role can be described by using only a set of parameters characterizing the ratio of particle sizes in a mixture. The report will summarize all the results obtained by us up to date.
The reported study was funded by RFBR, project number 18-03-00606.

We present a statistical-thermodynamic description of the diversified influence of pairwise interactions on the position of chemical equilibrium in reactions of various types, such as the dimerization, the formation of heteronuclear molecules, and the complex formation in molten salts with di- and three-valent metals. Models of pair interactions from the simplest potential of hard spheres, through the potential with square well, to the potential of charged hard spheres with different ionic diameters were considered. The dumbbell shape for binary molecules is additionally taken into account and a significant diversity of deviations from ideality were described.
The effects of the excluded volume on the shift of chemical equilibrium in binary systems containing the inert solvent have been analyzed [1]. With an increase in the size of the solvent particles, the character of the concentration dependence for the enthalpy of mixing changes from purely endothermic to sign alternative, which has a pronounced exothermic effect at low and medium concentrations.
The association in binary hard-sphere liquids was considered taking into account the dumbbell-like shape of heteronuclear molecules [2]. The excess entropy for such a reacting mixture describes the most pronounced ordering with a larger difference in the diameters of monomers, but with a lower their fusion.
The influence of attraction between particles on the position of dimerization equilibrium was estimated within the model of square well [3]. An amplification in the attraction between monomers leads to a shift in equilibrium towards the dissociation, while an amplification in the attraction between dimers contributes a shift in equilibrium towards the formation of dimerization products. The inclusion of interparticle attraction, especially between dimeric molecules, leads to an increase in the packing fraction.
The evaluation of concentrations of the complex anionic (MX4)2‒ and (MX6)3‒ groups in molten salts have been performed [4, 5]. The calculation according to the ideal mass action law provides a significant overestimation of the concentration of complexes, at that the fraction of complexes is practically equal to the maximum possible (1/2) in the considered temperature range. We will demonstrate that in Coulombic systems there is a temperature threshold above which the complete dissociation of anionic complexes contained in pure and binary molten halides of two- and three- valent metals occurs.
Thus, the deviations from ideality in various liquids play an important role can be described by using only a set of parameters characterizing the ratio of particle sizes in a mixture. The report will summarize all the results obtained by us up to date.

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