New diorganotin(IV) complexes R2Sn(Ln) 1-5 (where R = Et, t-Bu, Ph) with O,N,S-donor tridentate Schiff bases containing chlorine or trifluoromethyl groups were synthesized in 49-67% yields. Compounds 1-5 were characterized by 1H, 13C NMR, IR spectroscopy, and elemental analysis. The molecular structures of 2, 3, and 5in the crystalline state were determined by single-crystal X-ray diffraction. The organotin complexes are mononuclear and five-coordinate, with ligands adopting a dianionic form. Electrochemical studies revealed that the electrooxidation process is irreversible while the electrochemical reduction generates relatively stable monoanionic complexes. Complex 3, along with previously reported related phenyl-or ethyl-substituted tin compounds, exhibits luminescence in chloroform. The radical scavenging activity of the complexes was evaluated in reactions with ABTS radical cation or superoxide radical anion in NBT assay. The highest neutralizing properties were observed for complexes with ethyl substituents at tin atom; their IC50 values ranged from 6 to 35 mu M. In the oxidative DNA damage assays, most compounds exhibited a promoting effect suggesting their potential role in DNA cleavage under oxidative stress. However, in the lipid peroxidation model reaction in vitro, an antioxidant effect was observed for most compounds, particularly for hydrophobic tert-butyl-containing complexes 2 and 4.

New unsymmetrical sulfoxides containing a redox-active sterically hindered catechol fragment and a nonpolar hydrocarbon substituent at the sulfoxide group were synthesized via the oxidation of the corresponding catechol thioethers with hydrogen peroxide. The yield of the reaction products ranges from 42 to 89%. The crystal structures of catechol sulfoxides with isopropyl, cyclopentyl, adamantyl, benzyl and 1-naphthyl moieties were established by single-crystal X-ray analysis. The possibility of forming intra- and intermolecular hydrogen bonds has been shown for these compounds. The electrochemical behavior of sulfoxides was studied in comparison with that of the parent catechol thioethers. The redox transition corresponding to catechol fragment oxidation is shifted to the anodic region relative to the initial thioethers, which is attributed to the more electron-withdrawing nature of the S=O group. The second redox stage characterizes the transformation of the sulfoxide fragment and is observed in most cases at 1.82–1.91 V. The radical-scavenging activity and antioxidant properties of the unsymmetrical sulfoxides and their precursor thioethers were evaluated using the reaction with the 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH) and the 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS+•). In both assays, the lowest IC50 values among the studied catechol sulfoxides were found for compounds bearing isopropyl and tert-butyl substituents on the sulfoxide group.

A series of novel diorganogermanium(IV) complexes of the type [R2Ge(Ln)] (where R is Et, Ph) with O,N,O'tridentate redox-active Schiff bases has been synthesized. Compounds 1 - 7 were characterized by 1 H, 13 C{ 1 H} NMR, IR spectroscopy, and elemental analysis. The molecular structures of complexes 1 , 3 , and 7 in crystal state have been established using single-crystal X-ray analysis. The complexes are pentacoordinate mononuclear compounds of germanium(IV). The bond lengths in tridentate ligands correspond to their diamagnetic dianionic forms. The electrochemical properties of complexes 1 - 7 were studied by cyclic voltammetry. A feature of the electrochemical behavior of target complexes is the ability to form relatively stable reduced/oxidized species as a result of the one-electron transfer. The stability of electrogenerated forms is influenced by both the organic groups at the germanium(IV) atom and the substituents in the Schiff bases. The energy gap (Delta Eel) between the boundary redox orbitals obtained from electrochemical data for the complexes varies from 2.43 to 2.60 eV, while the optical Delta E was observed in the narrow range (2.46 - 2.50 eV). Luminescent activity was detected for some complexes in the solution. The maximal values of the relative quantum yield were determined for complexes containing an electron-withdrawing nitro group in the redox-active ligand. In the reaction with ABTS radical cation, compound 1 only possessed the radical scavenging activity while the other compounds are characterized by weak neutralizing properties. The dual anti/prooxidant action was observed for compounds 1 - 7 in the process of rat liver (Wistar) homogenate lipid peroxidation.

A reagent- and waste-free method for the transformation of hydrogen sulfide and thiols with С3-С8 hydrocarbons groups into value-added di- and trisulfides is proposed under the microwave irradiation. The hydrogen sulfide solution in N-methylpyrrolidone was used as the reaction medium to occur the interaction with different thiols. The influence of the microwave irradiation power, duration, the temperature and thiol structure on the yield and ratio of target products has been investigated. It is found that the effective microwave power for activation of H2S and RSH should be at least 200 W, while increasing the reaction temperature reduces the contact time. The maximum values for the yield of di- and trisulfides were obtained at 280 W and 100 °C. High selectivity of trisulfide formation was observed in the case of alkanethiols C3-C5, especially for compounds with isomeric hydrocarbons groups. Differences in the mechanisms of H2S interaction with linear and branched thiols based on the formation of alkylhydropolysulfide intermediates have been identified. The proposed scheme of utilization of H2S and low-molecular-weight thiols into organic polysulfides under microwave irradiation was suggested.

The studies of the antioxidant and cryoprotective activities of bicyclic pyrrolidine derivatives containing a 2,6-di-tert-butylphenol fragment in the in vitro experiments showed the greater activity of these compounds compared to ionol. The analysis of the kinetic profile of the reactions of these compounds with 2,2-diphenyl-1-picrylhydrazyl radical (DPPH test) and radical cation of 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) showed that the first step consisted in the rapid single electron transfer (SET), which was followed by the hydrogen atom transfer (HAT). The high activity in the reaction of Fe3+ reduction (FRAP test) was characteristic of methyl (1S*,3R*,3aS*,6aR*)-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-1-methyl-5-(2-nitrophenyl)-4,6-dioxooctahydropyrrolo[3,4-c]-pyrrole-1-carboxylate. The compounds under study were found to be able to terminate chain reactions due to the chelation of metals involved in the Fenton reaction. The compounds also exhibited prolonged antioxidant activity under autoxidation conditions and conditions of oxidative stress promoted by FeCl2. An increase in the viability of reproductive cells of sturgeon breeds in the presence of the pyrrolidine derivatives indicated the possibility of their use as promising antioxidant protectors during hypothermic storage and under conditions of deep freezing of germ cells of economically valuable fish species.

New tin(IV) complexes (Ln)SnR2 (R = n-Bu (I, II), t-Bu (III–V), and Ph (VI)) with O,N,O'-donor Schiff bases are synthesized. The molecular structures of compounds I and IV in the crystalline state are determined by XRD (CIF files CCDC nos. 2309864 (I) and 2309422 (IV)). The photophysical properties of the complexes are studied in comparison with the previously synthesized compounds containing phenyl or ethyl hydrocarbon groups at the tin atom. All compounds luminesce in chloroform: the emission bands are observed in the range from 580 to 638 nm. Both the groups at the tin atom and nature of the substituents in Schiff bases significantly affect the relative quantum yield. The anti/prooxidant activity of (Ln)SnR2 in the reactions with the ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) radical cation and superoxide radical anion, in the oxidative DNA damage, and during lipid peroxidation in vitro is studied. A weak antibacterial activity against the bacterial strains Staphylococcus aureus ANCC 6538 and E. faecium ATCC 3576 are observed for some compounds. The in vitro antiproliferative properties for a number of the complexes are studied for the HTC-116 and А-549 cancer cell lines. The coordination of the organometallic fragment with the O,N,O'-tridentate ligands is found to induce a pronounced decrease in the cytotoxicity of the complexes.

New sulfur-containing mono- and bis-1,4-naphthoquinone thioethers, which are thiolated analogs of vitamin K, were synthesized. The molecular structure in the crystal-line state of the thioether with a pyrazinylethyl substituent at the sulfur atom was determined by X-ray diffraction analysis. The electrochemical transformations and spectral properties in the UV-vis range of the spectrum were studied for the obtained compounds. Most bis-1,4-naphthoquinone thioethers are characterized by two reversible two-electron reduction processes. The compound with a diphenyl sulfide bridging linker was found to have four cathodic stages corresponding to the sequential reduction of naphthoquinone fragments. Sulfides containing two naphthoquinone fragments showed the highest radical scavenging activity. The studied compounds exerted an anti/prooxidant effect in the process of lipid peroxidation of rat liver homogenate in vitro depending on the time of incubation. The thioethers exhibited antibacterial activity (9.76–78.13 µg mL−1) against Gram-positive bacteria (S. aureus ATCC 6538 and ATCC 43300, E. faecium ATCC 3576 and ATCC 28212).

A series of new RS−, RS−CH2− and R2N−CH2-functionalized сatechols with heterocyclic fragments such as 1,3,4-oxadiazole, 1,2,4-triazole, thiazole, or pyridine were synthesized by the reaction of 3,5-di-tert-butyl-o-benzoquinone or 3,5-di-tert-butyl-6-methoxymethylcatechol with different heterocyclic thiols. The S-functionalized catechols were prepared by the Michael reaction from 3,5-di-tert-butyl-o-benzoquinone and the corresponding thiols. The starting reagents such as substituted 1,3,4-oxadiazole-2-thiols and 4H-triazole-3-thiols are characterized by thiol–thione tautomerism, therefore their reactions with 3,5-di-tert-butyl-6-methoxymethylcatechol can proceed at the sulfur or nitrogen atom. In the case of mercapto-derivatives of thiazole or pyridine, this process leads to the formation of the corresponding thioethers with a methylene linker. At the same time, thiolated 1,3,4-oxadiazole or 1,2,4-triazole undergo alkylation at the nitrogen atom in the reaction with 3,5-di-tert-butyl-6-methoxymethylcatechol to form the corresponding thiones. The yield of reaction products ranges from 42 to 80%. The crystal structures of catechols with 3-nitropyridine or 1,3,4-oxadiazole-2(3H)-thione moieties were established by single-crystal X-ray analysis. The possibility of forming intra- and intermolecular hydrogen bonds has been established for these compounds. The electrochemical behavior of the studied compounds is influenced by several factors: the nature of the heterocycle and its substituents, the presence of a sulfur atom in the catechol ring, or a thione group in the heterocyclic core. The radical scavenging activity and antioxidant properties were determined using the reaction with synthetic radicals, the cupric reducing antioxidant capacity assay, the inhibition process of superoxide radical anion formation by xanthine oxidase, and the process of lipid peroxidation of rat liver (Wistar) homogenates in vitro.

A series of novel organogermanium(IV) catecholates 1–9 of the general formula R’2Ge(Cat), where R’ = Ph, Et, have been synthesized. Compounds were characterized by 1H, 13C NMR, IR spectroscopy, and elemental analysis. The molecular structures of 1–3, 6, and 8 in crystal state were established using single-crystal X-ray analysis. The complexes are tetracoordinate germanium(IV) compounds containing a dioxolene ligand in a dianion (catecholato) form. Electrochemical transformations of target germanium(IV) complexes have been studied by cyclic voltammetry. The electro-oxidation mechanism of complexes 1–5, 7, and 10 (the related complex Ph2Ge(3,5-Cat) where 3,5-Cat is 3,5-di-tert-butylcatecholate) involves the consecutive formation of mono- and dicationic derivatives containing the oxidized forms of redox-active ligands. The stability of the generated monocations depends both on the hydrocarbon groups at the germanium atom and on the substituents in the catecholate ring. Compounds 6, 8, and 9 are oxidized irreversibly under the electrochemical conditions with the formation of unstable complexes. The radical scavenging activity and antioxidant properties of new complexes were estimated in the reaction with DPPH radical, ABTS radical cation, and CUPRACTEAC assay. It has been found that compounds 8 and 9 with benzothiazole or phenol fragments are more active in DPPH test. The presence of electron-rich moieties in the catecholate ligand makes complexes 5 and 7–9 more reactive to ABTS radical cation. The value of CUPRACTEAC for organogermanium(IV) catecholates varies from 0.23 to 1.45. The effect of compounds 1–9 in the process of lipid peroxidation of rat liver (Wistar) homogenate was determined in vitro. It was found that most compounds are characterized by pronounced antioxidant activity. A feature of complexes 1, 3, and 5–9 is the intensification of the antioxidant action with the incubation time. In the presence of additives of complexes 3, 5, 6, and 8, an induction period was observed during the process of lipid peroxidation.

A number of novel triphenylantimony(V) complexes with O,N,O'-or O,N,S redox-active Schiff bases (Ph3Sb(Ln) were synthesized. Compounds 1-5 were characterized by 1H, 13C NMR, IR spectroscopy, and elemental analysis. The molecular structures of complexes 1 and 2 in crystal state were established by means of single-crystal X-ray analysis. Both complexes are mononuclear hexacoordinated triphenylantimony(V) compounds containing dia-nionic forms of O,N,O'-coordinated ligands. The electrochemical properties of complexes 1-5 were studied. In the cathode region, stable monoanionic forms were formed for all compounds, while the electrooxidation process is irreversible for most complexes. A quasi-reversible one-electron anode stage was observed only for complex 2 with donor tert-butyl groups. Based on electrochemical data, the energy gap Delta Eel between the boundary redox orbitals of complexes varies from 2.64 to 2.95 eV, while the optical Delta E has lower values (2.75 - 2.80 eV). Triphenylantimony(V) complexes possess luminescence in solutions. The maximum luminescence intensity and quantum yields change depending on the nature of the substituents in the coordinated Schiff bases. The radical scavenging activity of new complexes was estimated in the ABTS assay. It has been found that compounds 2 and 3 with tert-butyl or chlorine substituents in ligand have IC50 values compared with Trolox. The anti/prooxidant effects of compounds 1-5 on the process of rat liver (Wistar) homogenate lipid peroxidation and the promoted oxidative damage of the DNA were determined.

The modern trends in the development of synthetic approaches to the preparation of organic symmetrical and unsymmetrical disulfides are reviewed. The main trend in the synthesis of disulfides is the transition from the reactions involving metal-containing catalysts to the use of physical methods for the activation of sulfur substrates. The main attention is given to the works published since 2013 to the present time and devoted to the synthesis of disulfides in the presence of transition and nontransition metal complexes and organic and inorganic oxidants, as well as under the electric current action and photo- or microwave irradiation.

The antiradical activity of polycyclic compounds with indole and isoindole moieties was evaluated in vitro using a number of assays. All tested compounds, except for 3,5-di( tert -butyl)-4-hydroxybenzenecarbaldehyde N -(2-oxo-1,2-dihydro-3 H -indole-3-ylidene)hydrazone, demonstrated much lower activity towards DPPH, ABTS •+ , and NO • radicals than the well-known antioxidant ionol. All compounds showed a high radical-scavenging capacity relative to the superoxide radical anion generated in the enzymatic (NBT assay) and non-enzymatic (epinephrine autoxidation) systems. The high antiradical activity of 3,5-di( tert -butyl)-4-hydroxybenzenecarbaldehyde N -(2-oxo-1,2-dihydro-3 H -indol-3-ylidene) hydrazone is attributable to the presence of 2,6-di- tert -butylphenol, indoline, and azine moieties, which promote the formation of a stable intermediate.

In recent years, the possibility of increasing the low cryoresistance of sturgeon sperm by using antioxidants in basic cryoprotective media has been studied. The goal of this work was to review the current literature on impact of the cryoprotectors, well-known antioxidants and new multifunctional compounds on the activity indicators and fertilizing capability of sperm, as well as on biomarkers of cryostress. A special attention is given to the radical scavenging activity of studied compounds in relation to the highly reactive oxygen species, to prevent and negate oxidative stress damage of sturgeon sperm. Also, new trends for future research through the application of novel polyfunctional antioxidants to sturgeon sperm cryopreservation were indicated.

The mechanism of biological activity of various sulfur-containing compounds and sulfur fragments of both natural and synthetic origins is presented. Unique characteristics of organosulfur compounds that are present in natural plant products are considered to reveal the most efficient sulfur components of the natural origin. An insufficient efficiency of the pharmacological action of plant raw materials and undesirable effects indisputably confirm the topical character of research on the preparation of modified analogs of natural biologically active sulfur-containing compounds. The modern data on the development of new polytopic organosulfur compounds combining different redox-active functional groups in the structure, which should favor their efficiency and a decrease in side manifestations, are reviewed. Sulfur-containing metal complexes with antimicrobial, antiviral, and anticancer properties are among the most promising pharmacologically active compounds. In spite of the success achieved in this field of chemistry, the preparation of new target-oriented biodrugs based on bioessential metals (Cu, Zn, Se) and biomimetic organosulfur fragments remains to be an urgent problem. The developments in this direction should favor to understand mechanisms of the therapeutic action of new drugs and to prepare drugs of the new generation followed by their implementation in clinical practice.

Unsymmetrical 4,4 '-biphenyl derivative with tris(trifluoromethyl)germylethynyl -C =C-Ge(CF3)3 and ferrocenylethynyl Fc-C =C- substitutes have been prepared ( 21 ), its properties have been studied and compared with those full non-fluorinated analogue of trimethylgermylethynyl -C =C-Ge(CH3)3 compound ( 20 ). UV-visible, absorption, steady state, and time-resolved fluorescence spectra in solution for these germanium and a number of similar compounds ( 15 -17, 22 ) have been investigated. The process of photoinduced electron transfer from the n-conjugated system to the germanium center is confirmed for 21 , as well as for the first time discovered earlier [19] in the 4-biphenyl -C =C-Ge(CF3)3 molecule ( 9 ). It was found that the lifetime of the radical-ion pair 21 in the excited state (kCR2 = 1.2 x 10 5 s-1 ) is approximately an order of magnitude longer than for 9 , which can be explained by the stabilizing effect of the electron donor Fc-C =C- group. Density-functional theory (DFT) computations was used to calculate the optimized geometry of 21 in excited state, and two main bands in the emission spectrum at laser excitation (340 and 386 nm) an excellent fit to the experimental data. An additional data on the nature of the (CF3)3Ge group, including geometry, electronegativity, and contributions 4d AOs of germanium into lowest unoccupied molecular orbital (LUMO) in a wide range of fluorinated and non -fluorinated compounds were also calculated. The molecular structure of compound 21 was determined by X-ray structural analysis. In the crystal lattice of 21 , numerous intermolecular F middotmiddotmiddotF interactions shortened in comparison with the van der Waals radii were detected, which leads to the formation of quasi-two-dimensional fluorinated layers in crystals.(c) 2022 Elsevier B.V. All rights reserved.

A number of novel di- and triorganotin(IV) complexes 1–5 (Ph2SnL1, Ph2SnL2, Et2SnL2, Ph3SnL3, Ph3SnL4) with mono- or dianionic forms of thio-Schiff bases containing antioxidant sterically hindered phenol or catechol fragments were synthesized. Compounds 1–5 were characterized by 1H, 13C NMR, IR spectroscopy, and elemental analysis. The molecular structures of complexes 1 and 2 in the crystal state were established by single-crystal X-ray analysis. The antioxidant activity of new complexes as radical scavengers was estimated in DPPH and ABTS assays. It was found that compounds 4 and 5 with free phenol or catechol fragments are more active in these tests than complexes 1–3 with tridentate O,N,S-coordinated ligands. The effect of compounds 1–5 on the promoted oxidative damage of the DNA by 2,2’-azobis(2-amidinopropane) dihydrochloride and in the process of rat liver (Wistar) homogenate lipid peroxidation in vitro was determined. Complexes 4 and 5 were characterized by more pronounced antioxidant activity in the reaction of lipid peroxidation in vitro than compounds 1–3. The antiproliferative activity of compounds 1–5 was investigated against MCF-7, HTC-116, and A-549 cell lines by an MTT test. The values of IC50 are significantly affected by the presence of free antioxidant fragments and the coordination site for binding.

A possibility of using metal complexes with redox-active ligands in organic electrosynthesis is demonstrated on the basis of literature data analysis. Unlike homogeneous catalysis, many examples are known for the application of complexes of this type in electrocatalytic processes characterized by a higher selectivity and milder conditions. Interest in metal complexes with redox-active ligands is due to their use in the heterogeneous electrocatalysis as well. The main attention is given to advantages of the indirect electrosynthesis of organic compounds, in particular, sulfur derivatives, in the presence of mediators or electrocatalysts based on metal complexes with redox-active ligands. Active forms of metal complexes are generated at the electrodes and can initiate the further transformations of inert substrates. A significant decrease in power expenses compared to the direct redox activation of reagents is the main advantage of indirect electrosynthesis. The cyclic processes favoring a permanent regeneration of metal complexes lead to an increase in the yield of target compounds.

New gold(I) phosphine thiolate complexes [(Ph 3 P)Au(SL n )] I – V with Schiff bases L n SH containing redox-active catechol, phenol, or quinone methide moieties were synthesized and characterized. The molecular structure of compound I in the crystalline state was established by X-ray diffraction (CCDC no. 2237815). The electrochemical behavior of compounds I – V was studieв by cyclic voltammetry. The proposed electrooxidation mechanism of the complexes involves the Au–S bond cleavage, the disulfide formation, as well as the oxidation of the redox active group of the ligand. In the cathode region, complexes I – III tend to form relatively stable monoanionic species. The radical scavenging activity of complexes decreases in comparison to free ligands in the reactions with synthetic radicals and the CUPRAC test. Compounds I , II , IV , and V have no clear-cut effect on the promoted DNA damage; however, they show antioxidant action in the non-enzymatic lipid peroxidation of rat liver homogenate. Compounds I – V demonstrate a weak antibacterial activity against Staphylococcus aureus strains . The gold(I) complexes cytotoxicity was studied against A-549, MCF-7, and HTC-116 cancer cell lines using MTT assay. The test compounds are characterized by higher selectivity to certain types of cells than the sulfur-containing Schiff bases. The presence of quinone methide moiety in the ligand in case of V significantly increases the cytotoxicity against all of the cell lines.

A search for new approaches to sulfurous waste utilization is one of the urgent tasks of chemical technology. Thiol-disulfide exchange reaction (TDE) is one of the possible ways to involve technogenic wastes in organic synthesis. Electricity can promote such type of interactions. In this paper, we have studied TDE reactions involving low molecular weight thiols or their dimers under electrochemical conditions. The exchange processes were examined using the model reaction between 1-propanethiol and phenyl disulfide. Electrolysis was performed in the presence of redox mediators such as arylphosphines, substituted amines, o-, p-aminophenols or catechol. These compounds can initiate a TDE process with a formation of unsymmetrical disulfides. 4-Amino-2,6-diphenylphenol was chosen as the most effective redox mediator, which reduces the anodic overvoltage of a thiol oxidation by 1.20 V. The advantage of electrolysis in an undivided cell is the increased yield of target unsymmetrical disulfides due to the possibility of reduction ofhomodimers at the cathode. The involvement of refining waste, such as C3–C4 disulfide oil, in the reaction with substituted thiophenols made it possible to obtain a number of unsymmetrical arylalkyl disulfides with biologically active fragments in a high yield (up to 97%) under indirect electrolysis conditions.

The paper presents the results of a theoretical and experimental study of the effectiveness of adsorption desulfurization of hydrocarbon motor fuels using silica gel modified with zinc(II) pivalate. The expediency of using powdered silica gel in the process of removing toxic and highly corrosive hydrogen sulfide and thiols are shown. Based on the effective parameters of adsorptive desulphurization established in laboratory conditions, a schematic process flow diagram for the process of removing acidic sulfur compounds from the gasoline fraction at a temperature of 25 degrees C and a pressure close to atmospheric are proposed. The possibility of solvent regeneration of the saturated adsorbent of the desulfurization process at a temperature of 25 degrees Cand a pressure close to atmospheric are shown. The most effective solvent for the regeneration process is isopropyl alcohol. To maintain the activity and stability of the adsorbent during the desulphurization process, the technological scheme provides for ultrasonic feeding of the regenerated adsorbent with a saturated solution of the modifier, followed by drying with fuel gas. The recovery of isopropyl alcohol after washing the saturated adsorbent is carried out by distillation at a temperature of 90 degrees C and a pres-sure close to atmospheric. Technology based on adsorption by a scavenger consisting of a carrier and a polynuclear carboxylate complex of transition metal allows the removal of sulfur -contain-ing compounds directly in the feed stream. A reactor with a suspension adsorbent bed is proposed as the main apparatus for the process of adsorption desulphurization. The process of washing and separating the suspension of adsorbent and fuel takes place in drum vacuum filters. The concentrate of sulfur compounds obtained during the purification process can be used as a feed-stock in chemical and petrochemical processes in order to obtain practically important sulfur -containing compounds.