A comprehensive MD + QC methodology was developed and applied to evaluate various aspects of Arbidol interactions with functional amino acids of surface proteins of influenza virus and SARS-CoV-2. The spatial structure, solvation features, conformational behavior of Arb AA (AA–Trp, Tyr, Phe, and Val) complexes were established, and the statistics of intermolecular interactions in the complex were described. It was found that Arb can participate in strong and long-lived π-π stacking interactions with aromatic amino acids. The binding energy (BE) of Arbidol and amino acids in aqueous solution was estimated using an explicit solvation model, QTAIM analysis and correlation of BE vs. total electron density at the bond critical points of the complex. Theoretical calculations were validated by experimental studies of fluorescence (FL) quenching of aromatic AA by Arbidol. Spectral-fluorescent properties of Arbidol hydrochloride in aqueous solutions were studied, and the luminescence quantum yield for the electronically excited state of Arb was determined.

The spectral and luminescent properties of 21 thiazolylpyrazole derivatives exhibiting intense emission in the 350-480 nm region, with photoluminescence (PL) maxima at approximately 380 and 400 nm, were investigated. The excited-state lifetimes (1.4-3.5 ns) and photoluminescence quantum yields (PLQY) were measured and found to vary from 0.014 to 0.72 depending on the emitter structure. The relationship between the PL quantum yield of thiazolylpyrazoles and the structural features of the three molecular blocks (thiazolyl, pyrazolyl, and aromatic) within the test set of compounds was analyzed. Factors responsible for both coarse and fine tuning of the luminescent properties were identified. Using TD-DFT calculations and analysis of the electronic distribution in the ground and electronically excited states of thiazolylpyrazoles, threshold values of the parameters Delta epsilon = e(HOMO)-e(HOMO1), the Peach index Lambda, and the Delta r index were established, which determine the switching of radiative transition efficiency from a high level (local excitation) to a moderately low level (charge transfer).

The methodology of the complete set of isodesmic reactions, CS IDR, was developed and applied to a test set of 154 small organic compounds, including three- and four-atom linear and cyclic CNO-containing structures, to evaluate their standard enthalpies of formation, ΔfH°. The CS IDR approach was tested using ten quantum-chemical methods: seven DFT approximations, DLPNO-CCSD(T), and two composite methods, G4 and W1BD. It was found that DFT methods do not provide high accuracy in estimating ΔfH°. In terms of calculation quality, the ab initio methods are ranked as G4 > W1BD > DLPNO-CCSD(T), with the accuracy characterized by mean absolute deviations (MAD) of 1.29, 1.52, and 2.24 kJ mol-1, respectively. Analysis of the calculation results revealed that composite methods are characterized by a systematic error, the magnitude of which is proportional to the enthalpy of the reference reaction. Eliminating the systematic error of composite methods and improving the agreement between calculation and experiment is possible using averaged estimate according to the equation ΔfH° = 0.5×(ΔfH°(G4) + ΔfH°(W1BD)) - 0.78 kJ mol-1.

The kinetics of low-temperature luminescence (LTL) of poly(diphenylene phthalide) (PDPh) has been studied. LTL of PDPh-film refers to the radiative deactivation of the polymer chain's triplet excited diphenylene (DP) fragment in the visible spectral range (lambda max approximate to 550 nm). DP excitation occurs upon recombination of the spatially separated ion-radical states (SIRS) generated by UV-irradiation with an energy of up to 6 eV. It was established that an electron transfer (ET) from triaryl methyl (TAM) anion-radical formed due to lactone ring breaking in the phthalide fragment to DP cation-radical plays an important role in SIRS recombination. ET rate constant (kET) is determined by electron trap depth of TAM (ETD(TAM) = 2.66 eV, B97-2/6-311 + G(d,p)), the distance between recombining species (r), and an energy barrier (Ea) of mechanical relaxation process activated at 77 K. Ea was found through mathematical modelling to be equal to 14.7-15.0 kJ & sdot;mol- 1 correlating well enough with one of carboxylate-ion rotation estimated at DFT level (16.0-17.9 kJ & sdot;mol- 1). kET vs r exponential dependence and the bell-shaped distribution of initial content of SIRS from r lying in the range of 11-16 & Aring; determine the experimentally observed poly-exponential pattern of LTL kinetics of PDPh.

In the radical-chain oxidation of cumene by molecular oxygen in the presence of Zn, Cd, and Hg 2-ethylhexanoates (hereinafter Me(EH)2), Cd 2-ethylhexanoate exhibits the highest catalytic activity. The structure and catalytic activity of Cd 2-ethylhexanoate adducts with cumene hydroperoxide (ROOH) were investigated by using density functional theory (IEF-PCM + B3PW91-GD3/x2c-TZVPall). Thermodynamic parameters indicated the formation of intermediate 1:1 and 1:2 adducts of Cd 2-ethylhexanoate with ROOH and dimethylphenylcarbinol (ROH), including a mixed ROH···ROOH·Cd(EH)2 adduct. The formation of 1:2 adducts is thermodynamically more favorable due to a more stable octahedral environment around the Cd atom. Modeling of ROOH radical decomposition in these adducts showed that ROOH in the associated ROH···α-ROOH·Cd(EH)2 adduct decomposes faster into free radicals compared with the free ROOH molecule. This ensures effective ROOH decomposition at the degenerate chain branching stage, leading to a general acceleration of cumene oxidation. Based on these quantum chemical modeling results, a mechanism for the catalytic effect of Cd 2-ethylhexanoate in the radical-chain oxidation of cumene by molecular oxygen has been proposed. The results of this study will allow for the construction of a complete and reliable kinetic scheme for the process, aiming at its optimization.

Direct interactions of 1-arylpent-1-en-4-yn-3-ones with 2-hydrazinylbenzo[d]thiazoles lead to the formation of the mixtures of 3-styryl- and 5-styryl-1-(benzo[d]thiazol-2-yl)pyrazoles. Under the same conditions, 1,5-diarylpent-1-en-4-yn-3-ones give 5-aryl-3-arylethynyl-1-(benzo[d]thiazol-2-yl)-4,5-dihydro-1H-pyrazoles. We have described and estimated the highly regioselective one-pot synthetic route to luminescent 5-styrylsubstituted pyrazoles containing thiazole and benzo[d]thiazole fragments on the basis of pent-1-en-4-yn-3-ones (cross-conjugated enynones) and 2-hydrazinylbenzo[d]thiazoles. The synthetic protocol involves a preliminary addition of piperidine via the triple bond of pointed cross-conjugated enynones resulting in 1-(piperidin-1-yl)penta-1,4-dien-3-ones that in turn readily form 5-styryl-1-(benzo[d]thiazol-2-yl)pyrazoles with high regioselectivity in excellent yields. The proposed methodology is applicable to a wide range of 1-mono- and 1,5-disubstituted cross-conjugated enynones and monosubstituted hydrazines containing aryl and benzothiazole substituents. The obtained substances exhibit strong luminescence activity (absolute quantum yield reaches 0.7). Structural and regiochemical aspects of the newly synthesized pyrazoles were confirmed by spectral and analytical data.

Gas phase bond dissociation energies (BDE) O-H/N-H in hydroquinone (H2Q), 4-aminophenol (AP), 1,4-phenylenediamine (PDA), 4-hydroxydiphenylamine (HDPA), N,N'-diphenyl-1,4-phenylenediamine (DPPDA) as well as in their phenoxyl/aminyl radicals have been determined using a combined technique of quantum chemical calculation. The technique included a series of DFT (PBE1PBE, TPSSTPSS, M06-2X), ab initio (DLPNO-CCSD(T)) methods with valence 3ξ-basis sets, composite methods of Gaussian family (G4) and Weizmann theory with ab initio Brueckner Doubles (W1BD), as well as reference reactions of different levels of structural similarity. W1BD method was used in combination with isodesmic reactions for BDE estimation (kJ∙mol-1) of compounds with the only aromatic fragment: BDEO-H = 352.3 (H2Q), 340.0 (AP), BDEN-H = 371.2 (AP), 364.1 (PDA) - in molecules; and BDEO-H = 230.4 (H2Q), 228.8 (AP), BDEN-H = 260.0 (AP), 257.1 (PDA) - in corresponding radicals. These values were further applied to estimate the BDEs in HDPA and DPPDA within the homodesmotic reference process and less resource-intensive ab initio methods: BDEO-H = 341.4 (HDPA), BDEN-H = 352.9 (HDPA), 351.3 (DPPDA) for molecules; BDEO-H = 237.4 (HDPA), BDEN-H = 247.4 (HDPA), 252.6 (DPPDA) for radicals. DFT methods give similar results but a slightly larger standard error of calculation. The found values of BDE(O-H/N-H) are compared with literature data; the effect of solvation on BDEs is discussed.

Spectral-luminescent research indicates the formation of inclusion complexes during the interaction of uranys nitrate and a cyclodextrin (a-CD) in aqueous solutions. The chiral o-CD matrix imparts optical activity to the electronically excited uranyl ion "UO in the clathrate, which manifests itself in the chiral discrimination of the quanching of "UO by tryptophan enantiomers. It was found that the Stern-Volmer constant for D-Tep is 1.8 0.2 times higher than that for L-Trp. A mechanistic explanation for the observed effect is proposed by DFT calculations

Dissociation energies (DC—H) of labile C—H bonds in radical adducts formed by coordination of thiyl radicals across the cyclohexadiene rings of 1,4-benzoquinone, N-phenyl-1,4-benzoquinone monoimine, and N,N′-diphenyl-1,4-benzoquinone diimine have been determined using composite methods of the Gaussian family and data on the enthalpies of formal homodesmotic reactions involving the adducts and simpler reference compounds. The DC—H values were found to be in the range of 140–170 kJ mol−1. These values are typical of the strength of bonds between atomic hydrogen and olefins. The weakness of the C—H bonds in both types of compounds is due to the compensation of bond breaking by the stabilization of the reaction products, viz., an olefin molecule or the cyclohexadiene ring of a quinoid. The proximity of the DC—H values in these adducts and the significant difference (∼50 kJ mol−1) between these values and the strength of the C—H bond in the adduct of atomic hydrogen with a benzene molecule confirms the fact that quinones and quinone imines are not aromatic compounds. The obtained DC—H values are required for the quantitative interpretation of the kinetic regularities found for the chain reactions of thiols with quinoids, as well as the catalysis of these reactions at the stage of chain propagation under the action of compounds with X—H groups (X = O, S, etc.).

The photooxidation of aromatic azides with the general formula 4-R-C6H4N3 (R = -Ph, -CH2Ph, -OPh) leads to the sequential generation of two reactive intermediates: first, the corresponding aromatic nitroso oxide 4-RC6H4NOO is formed. Its chemical potential is sufficient to destroy the aromatic ring as a result of an intramolecular ortho-cyclization. This reaction gives 4 -aryl -substituted 6-oxohexa-2,4-diene nitrile oxide, which retains a significant part of the chemical potential of its precursor and reacts further via various directions depending on the nature of the substituent R. It was found that in the case of R = -Ph, yet another aromatic system was destroyed as a result of the intramolecular (3 + 2)-cycloaddition of nitrile oxide at the ortho-meta- carbon atoms of the phenyl substituent, which led to the formation of 2Z/E-(5H-naphtho[1,8-cd]isoxazol-5- ylidene)acetaldehyde as a mixture of isomers. In the case of R = -OPh, nitrile oxide was involved in the intermolecular (3 + 2)-cyclization with the C---N triple bond of acetonitrile used in our experiments as solvent. In the case of R = -CH2Ph, both possibilities of (3 + 2)-cyclization were competitively realized, namely, (a) the formation of an isomeric mixture of (2E/Z,4E)-3-benzyl-5-(5-methyl-1,2,4-oxadiazol-3-yl)penta-2,4-dienal, which is the product of the reaction of nitrile oxide with acetonitrile, and (b) accumulation of 2-(E/Z)-4aH-dibenzo[c,d] isoxazol-9(10H)-ylidene)acetaldehyde formed as a result of the intramolecular cyclization of nitrile oxide at the aromatic ring of the substituent R. The presence of the methylene spacer shifts the aromatic C-C bond reacting with the nitrile oxide group: the ipso-ortho-cycloaddition leads to a tricyclic structure with a spiro-carbon atom. The proposed reaction mechanism and the most probable composition of the products were confirmed by DFT calculations in M06L/6-311+G(d,p) + IEFPCM(SD) approximation.

Thermoplastic-aluminum systems are used in the manufacture of corrosion-resistant lightweight constructions in aerospace and automotive industries. The adhesion strength of such systems is determined by the mechanism of adhesion interaction. In this article, adhesion interactions between the surfaces of polyethylene terephthalate, poly(propylene carbonate), poly(methyl methacrylate), polystyrene, polypropylene and aluminum were studied to identify a correlation between the acid-base properties of the studied surfaces, the mechanism of adhesion interaction and energy characteristics in thermoplastic-aluminum systems using experimental and theoretical approaches. The experimental approach consisted of finding the values of the free surface energy components, the acidity parameters of thermoplastics and aluminum by the E.J. Berger and van Oss-Chaudhuery-Good methods. The theoretical approach consisted of the study of adhesion interactions in thermoplastic-aluminum systems using the quantum chemistry method B3LYP-GD3/6-31G(d,p). It was theoretically established the functional groups to be the active sites on the thermoplastics surface. At the same time, the strongest adhesion interaction is manifested in systems formed by a carbonyl oxygen atom.The experimental values of the components of the free surface energy of thermoplastics and aluminum are in good agreement with the theoretical values of the energy and force of the adhesion interaction of the systems under consideration.

The interaction of tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedionato)europium(III), (Eu(FOD)3), with xenon difluoride in acetonitrile solution was found to be accompanied by chemiluminescence (CL). The kinetic curve of CL at a ratio of reagents Eu3+/XeF2 of 1:2 has a complex form; an initial rapid decrease is replaced by an increase in CL intensity, the maximum of which is reached approximately 10 min after the start of the reaction. Next, an exponential decay of the CL intensity is observed over several tens of minutes. The CL spectrum is located in the wavelength range 400–750 nm and corresponds to the emission of an electronically excited europium (III) ion coordinated with FOD and fluoride ion. Spectral methods were used to identify the reaction products – europium (III) fluoride in the sediment and oxygen difluoride in the gas phase. A mechanism for chemiexcitation of europium(III) has been proposed, including: 1) acceptance of fluorine anion from the XeF2 molecule by europium ion with the formation of active intermediate XeF+; 2) oxidative fluorination of the ligand, which is initiated by the interaction of oxygen atom of the FOD ligand with XeF+ cation and ends with the formation of oxygen difluoride and the electronically excited product P*, presumably a fluorinated ketone; 3) non-radiative transfer of excitation energy from P* to the europium ion within its coordination sphere, followed by its radiative deactivation.

The recombination of separated ion-radical states (SIRS) in poly(arylenephthalide) (PAPh) films accompanied by emission of light with a maximum of similar to 500 nm has been analyzed. The density functional theory methods [PBE1PBE/6-311+G(d,p)] and mathematical modeling were used for description of thermally stimulated luminescence (TSL) kinetics of PAPh. The versatility of the earlier proposed three-step kinetic model of metastable (X) and labile (Y) SIRS recombination was demonstrated on the example of various cardo polymers. The contribution of X-SIRS recombination to total luminescence was found to be characterized by the vanishingly small intensity in a vacuum and moderate and maximum one in inert gases and an oxygen-containing medium, respectively. It was found out that the recombination of labile SIRS does not depend on the nature of the atmosphere. It was theoretically substantiated that SIRS recombination can proceed via the transfer of both positive and negative charges. It was shown that the key factor determining the efficiency of thermal activation of recombination processes is the ratio of radiant and conductive channels of energy transfer from the heating element to the polymer sample.

The kinetics of the decay of phenoxy radicals In• 2,6-diisobornyl-4-methylphenol (DBP) and 2,6‑ditretbutyl-4-methylphenol (ionol) in toluene at 295 K is studied by ESR. The first-order effective rate constants of the decay of In• are determined: kef = 0.30 s–1 (I) and 8.4 × 10–3 s–1 for DBP and ionol, respectively. Using the density functional theory, the mechanism of the decay of In• is analyzed. It is found that the phenoxy radicals of DBP are dimerized with the formation of the p-C,O-dimer, while In• ionol predominantly forms the p,p-C,C-dimer. The dimers are in reversible equilibrium with phenoxy radicals, while the irreversible consumption of In• occurs in the reaction of their disproportionation. Based on the density functional theory (DFT) research and published data, it was found that the value kef = k/2K of DBP is higher due to the much higher disproportionation rate constant of In•, although the equilibrium constant K of the reversible dimerization of the phenoxy radicals of DBP is also higher than the equilibrium constant for In• ionol.

An exclusively stereoselective reaction of AcOH elimination in the title acetate of cloprostenol was described, which led with high yield under Pd(PPh3)4-NaH-THF catalysis to the corresponding 13E,15Z-derivative. In contrast, under the same conditions, the use of methyl ester of 15-acetate 11-deoxyprostaglandin E1 results in regioisomeric reductive elimination products.

The results of the oxidative polymerization of methylene-separated bis-thieno[3,2- b ]pyrroles and thieno[3,2- b ]pyrrolopyrroles in the reaction with NBS and Br 2 with the formation of insoluble polymeric materials are discussed, and the electrochemical properties of the polymers are studied.

Gas-phase standard enthalpies of formation (Δ f H °) of cis - and trans -isomers of fourteen para -substituted aromatic nitroso oxides ArNOO were estimated using the G4 composite method and a comparative analysis of thermochemical characteristics of reference compounds. It was found that the differences between the enthalpies of ArNOO and isomeric nitro compounds ArNO 2 obtained from the G4 calculations are in the range of 270–280 kJ mol −1 and depend only slightly on the electronic properties of the para -substituent. The Δ f H ° values for aromatic nitroso oxides can be estimated more reliably using the homodesmotic reference reaction p -RC 6 H 4 NOO + C 6 H 6 → C 6 H 5 R + C 6 H 5 NOO. A correlation equation Δ f H °( p -RC 6 H 4 NOO) = Δ f H °(C 6 H 5 R) + (250.8±4.3) + + (20.5±1.1) σ p kJ mol −1 ( R = 0.98, σ p is the Hammett constant of the para-substituent R) obtained for the cis -isomers of nitroso oxides ArNOO can be recommended for rapid estimation of the enthalpy of formation of para-substituted aromatic nitroso oxides.

The complete sets of homodesmotic reactions (HDR) for 107 acyclic alkyl free radicals С4-С9 of normal and branched structure were constructed using the graph-theoretic representation and analysis of a tested compound. The absolute enthalpies of the studied compounds and HDR reference structures were calculated using the M062X/cc-pVTZ level of theory. Based on these data, the thermal effects of HDRs were calculated and then applied to determine the standard enthalpies of formation of the studied radicals using the known enthalpies of formation of reference structures. The dissociation energies of BDE C–H and C–CH3 bonds were also calculated. The effect of radical structure on the BDE value is discussed, and a new effect of stabilization of the radical center in the skewed conformation of free radical is established; this effect has not been previously described in the scientific literature.

Using reaction model systems (nitroso oxide ArNOO, Ar = Me2NC6H4 or O2NC6H4; exhaustive set of methyl- and cyano-substituted ethylenes), a detailed study of the reaction mechanism of ArNOO with unsaturated compounds was carried out using the density functional theory (M06L/6311 + G(d,p)). The reaction is preceded by the formation of a reagent complex of stacking type, which is favorable for further transformation. Depending on the structure of alkene, the reaction may proceed via two extreme mechanisms: synchronous (3 + 2)-cycloaddition (the most typical case) or one-center nucleophilic attack of the terminal oxygen atom of ArNOO on the less substituted carbon atom of the double bond. The last direction becomes dominant only under special reaction conditions: ArNOO with a strong electron-donating substituent in the aromatic ring, an unsaturated compound with a significantly depleted electron density on C═C bonds, and a polar solvent. In other cases, a different degree of asynchrony in the (3 + 2)-cycloaddition is possible; however, the main intermediate preceding stable reaction products is 4,5-substituted 3-aryl-1,2,3 dioxazolidine in any event. Both thermodynamic and kinetic arguments suggest the most probable decomposition of dioxazolidine into a nitrone and a carbonyl compound. It has been shown for the first time that the polarization of the C═C bond is a powerful factor regulating the reactivity in the reaction under study. The results of the theoretical study show excellent agreement with known experimental data for a wide variety of reacting systems.