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An efficient OFET-based memory is designed using spiropyran molecular switch operating via two complementary mechanisms: reversible photoisomerization and light-induced electron transfer involving [Cr(C2O4)3]3− counterion.

High-molecular-weight dinitrosyl iron complexes (DNICs) are formed in living systems and are a stable depot of nitrogen monoxide (NO). In this work, using experimental and theoretical methods, we investigated the interaction of their synthetic analog, a promising cardiotropic complex of the composition [Fe(SC(NH

Single-crystal XRD structure of binuclear tetranitrosyliron complex [Fe2(SR)2(NO)4] (1), R = 4-aminothiophenyl, has been described. The properties of 1 were studied by IR, Mössbauer, mass spectroscopy, and amperometry. Complex 1 was shown to form long-living nitrosyl intermediates in solution, which underlies its prolonged NO donor activity. In HeLa cells, 1 caused accumulation of NF-κB p50 but decreased the levels of NF-κB p65 in the nucleus, which led to inhibition of NF-κB dependent genes. The complex also induced increase of p53 protein levels and p21 gene activity, which led to the apoptotic cell death after G2/M cell cycle phase.

The structures of a number of the products for the reaction of the NO donor (cation of the dinitrosyl iron complex [Fe(SC(NH2)2)2(NO)2] • Cl•H2O) with poly-N-vinylpyrrolidone in water were studied using the density functional method and QTAIM analysis. The quantum chemical calculations of the basic geometric and energy parameters of the formed compounds were performed. The expected forms of existence of this system in aqueous solutions were described on the basis of the obtained results. The retention of the NO-donor activity in the formed polymeric structures is related to the preservation of the Fe(NO)2 fragment in them.

The kinetics of nitrogen oxide release by binuclear dinitrosyl iron complexes (B-DNICs) with thiolate ligands based on thiophenol and its several oxy, amino, and nitro derivatives was studied using a suspension of red blood cells simulating the internal medium of a blood vessel. The NO donating ability of the complexes was estimated by the kinetic parameters of first-order equation, which described the formation of intra-erythrocytic methemoglobin. Three typical kinetic profiles of NO donation were distinguished: pseudosaturation donation and donation with prolonged and explosive profiles. In the case of first-type NO donation typical of complexes with thiophenol and its nitro derivatives, the curves display a fast coming to saturation long before the complete release of all NO groups contained in the structure of the starting complex into a solution. Such a type of donation is likely due to the formation of long-lived nitrosyl intermediates in the system. The prolonged type of NO donation shown by the complex with hydroxyphenyl ligand is characterized by virtually constant rate of NO release into a solution without pronounced transition to saturation during experiment (10–12 min). In the case of explosive-type donation characteristic of the complex with aminophenyl ligands, a considerable portion of NO was fast released into a solution within 1–3 min. All complexes under study caused hemolysis of a 0.2% suspension of red blood cells. The complex with aminophenyl ligands exhibited the highest hemolytic activity.

The mechanism of the interaction of six sulfur-nitrosyl iron complexes capable of releasing nitric oxide as a result of the spontaneous hydrolytic decomposition with a erythrocyte suspension is studied. A kinetic model of the process, which includes reactions of the NO released from the complex into the solution, the NO interaction with oxyhemoglobin within the erythrocyte and dissolved oxygen, and the adsorption of complexes on the surface of erythrocytes, is proposed. The values of the kinetic parameters are determined. The developed model quantitatively describes the experimental data on the accumulation of methemoglobin (the product of the interaction of oxyhemoglobin with nitric oxide) obtained at different concentrations of the studied complexes and erythrocytes in the system.

The reaction of the tetranitrosyl iron complex containing the thiosulfate ligand (TNIC) (NO donor) with phosphoenolpyruvic acid (PEP), which is one of the main biological macroergic compounds, was studied by mass spectrometry. The use of mass spectrometry made it possible to perform studies in an aqueous medium, separate the substances, and quantitatively correlate the peak intensities with the concentrations of the substances. The products of the reaction of PEP with TNIC were identified by IR spectroscopy and mass spectrometry. The reaction product was found to have a Fe–O–C bond. Among the reaction products, the ions with m/z = 318 and 256 belong to the compounds [O3S2–Fe–PEP]–2, and [S-Fe–PEP]–2, respectively.

Dinitrosyl iron complexes (DNICs) are a depot and potential source of free NO in organisms. Their synthetic analog, N-ethylthiourea DNIC [Fe(SC(NH

The metabolic syndrome, which covers a wide variety of pathological concerns, is rapidly becoming a global pandemic. This syndrome is difficult to treat pharmacologically. Physiotherapy techniques, which have both local and systemic effects, can be employed as a suitable substitute. The purpose of this study was to investigate the therapeutic effects of a program of simultaneous physiotherapy that included migrant transcranial magnetic stimulation (TMS) and the exposure to an alternating low-frequency electrostatic field (LFEF) in the treatment of metabolic syndrome patients. Ninety patients were randomly assigned to three study groups. While continuing the usual drug therapy the first group (30 patients) received LFEF intervention, the second group (30 patients) received TMS, and the third group (30 patients) underwent the simultaneous use of these non-invasive techniques (LFEF + TMS). All treatments involved 10 sessions with daily frequency. In all the patients before and after treatment body weight, blood pressure parameters, levels of insulin, cortisol, glucose, total cholesterol, high density lipoproteins, malondialdehyde, and Schiff bases, the activity of the antioxidant enzymes catalase and of the superoxide dismutase were studied. The changes in the outcomes assessed revealed a different reaction to therapy with LFEF or TMS, as well as a greater benefit when both treatments were used at the same time. A simultaneous LFEF and TMS intervention seems a promising resource for the treatment of the metabolic syndrome, particularly of the lipid and carbohydrate metabolism disorders. However, further studies are needed to confirm these findings and investigate the underlying mechanisms.

Arterial hypertension (AH) is a burning problem in the world. Antihypertensive pharmacological therapy combined by physical exercises is well-studied in patients with mild and moderate AH. However, studies that have investigated relaxation in patients with severe AH in addition to drug therapy are lacking. Optimization of a comprehensive treatment for patients with severe AH, by using a multicomponent rational antihypertensive pharmacotherapy (PT) with subsequent application of relaxation exercise therapy (RET). The study involved 32 male patients with severe AH. Initially, clinical-instrumental and laboratory examination, blood pressure registration and daily arterial blood pressure monitoring were carried out. Suitable PT was selected for all the patients. 3 months after starting PT the patients were divided in 2 groups. The patients of the 1st group were prescribed RET in addition to PT. The 2nd group of patients continued receiving PT alone. 3 months later, average daily blood pressure (ADBP)-syst and ADBP-diast were compared in both groups. Three months after PT both groups demonstrated a significant decrease in ADBP-syst and ADBP diast, but these indicators remained higher than normal and did not reach the target level. Three months after the inclusion of RET in the comprehensive treatment, the 1st group demonstrated a significant decrease in ADBP (systolic and diastolic), not only in comparison with the initial data, but also with the data observed three months after PT. After 6 months, ADBP-syst and ADBP-diast in the 1st group were significantly lower compared with those of patients in the 2nd group. The inclusion of RET in addition to a multicomponent antihypertensive PT is a promising treatment option for severe AH.

A new binuclear μ-NSC-type nitrosyl iron complex [Fe2(SR)2(NO)4] (R is 5-phenyl-1H-1,2,4-triazole-3-thiolyl) was synthesized. The composition and structure of the newly synthesized complex were determined by atomic absorption, IR, EPR, and Mossbauer spectroscopy and SQUID magnetometry. Amperometric analysis showed that the new complex is an effective nitric oxide (NO) donor in a 1% aqueous DMSO solution. The amounts of NO generated by the complex [Fe2(SR)2(NO)4] in aqueous solutions at physiological pH values were determined. The new complex was shown to have higher antibacterial activity against the gram-positive bacteria Micrococcus luteus compared to kanamycin and streptomycin. According to assays, sulfur-containing ligands of the 1,2,4-triazole-3-thiol series are promising for the design of new antibacterial agents containing the {Fe(NO)2} structural moiety.

In this work, transformation of DNIC with thiourea ligands, [Fe(SС(NH2)2)2(NO)2]Сl∙H2O (I), in an aqueous buffer solution at neutral pH and in the presence of reduced glutathione (GSH) has been studied. Decomposition of the complex was shown to occur in the buffer solution, with removal of the first thiourea ligand having a higher rate (k=(3.8 ± 1.3)∙10-4 s-1) than the NO group release (k=(0.7 ± 0.2)∙10-4 s-1). This corroborates a quantum-chemical model of I decomposition suggested earlier. Using UV–Vis spectrophotometry and EPR spectrometry, the interaction of I with GSH in solution was shown to yield a new binuclear tetranitrosyl iron complex (TNIC) with two GS−- ligands (II). Using quantum-chemical modeling, the reaction scheme was suggested, which involves replacement of one thiourea ligand by GS−, and then dimerization of the forming complexes accompanied by removal of the second thiourea ligand. Theoretical UV–Vis spectra were calculated and interpreted for the initial I and for the product of the substitution reaction, II.

The biological activity of a series of sulfur-nitrosyl iron complexes (NICs) depends on the structure of the ligands and the position of the functional groups in the aromatic ring of the ligand. Differences in susceptibility of the gram-positive and gram-negative bacteria to the NICs was found. The series of the studied NICs suppresses the formation of biofilms of Micrococcus luteus bacteria. The obtained results demonstrate that the studied complexes can serve as the basis for the preparation of antibacterial agents.

New method for the synthesis of the mononuclear anionic iron dinitrosyl complexes (DNICs) as prospective agents for nitric oxide (NO) chemotherapy of oncological diseases has been developed. Mononuclear anionic DNIC of the composition (N2H5)+[Fe(SR)2(NO)2]- with R = 5-nitropyridinyl (I) has been synthesized by the reaction of aqueous solutions of Na2[Fе(S2O3)2(NO)2] and N2H5[SС5H3N2O2] salts. The latter one was synthesized by the reduction of bis-(5-nitro-pyridin-2-yl) disulfide with hydrazine hydrate in ethanol at T = 25 °C. Physical-chemical properties of the synthesized complex were studied by X-ray, SEM, IR-, EPR, Mossbauer spectroscopy and SQUID magnetometry in combination with DFT quantum-chemical calculation of molecular structure and spectroscopic properties. Complex I was found to generate NO in proton media without additional activation. The cytotoxicity of I to human tumor cells of various geneses, viz. ovarian cancer SKOV3, colon cancer LS174T and non-small cell lung cancer A549 was discovered for the first time.

Nitric oxide (NO) mediates diverse physiological processes in living organisms. Small molecular NO donors usually lack stability and have a short half‐life in human tissues, limiting the therapeutic application. The anionic tetranitrosyl iron complex with thiosulfate ligands (TNIC) is one of the most promising NO donors. This study shows that bovine serum albumin (BSA) can effectively stabilize the TNIC complex under aerobic (physiological) conditions, which contributes to its prolonged action as NO donor. Our results demonstrated that TNIC-BSA inhibits formation of TBARS – standard biomarker for the lipid peroxidation induced oxidative stress. Also, it was found that TNIC-BSA inhibits the catalytic activity of mitochondrial membrane-bound enzymes: cytochrome c oxidase and monoamine oxidase A. Together, these results demonstrate that, stabilization of TNIC with BSA opens up the possibility of its practical application in chemotherapy of socially significant diseases.

By means of quantum-chemical calculations using Density Functional Theory, Quantum Theory of Atoms in Molecules, and Natural Bond Orbitals, theoretical modeling of intermolecular interactions has been performed for eight nitrosyl iron complexes with aliphatic thiourea ligands, which was aimed at discovering the presence of the NO…NO intermolecular interactions and at studying the possibility of the NO…NO supramolecular synthon formation in their crystalline structure for explaining their unusual magnetic properties. Such interactions were shown to be either stacking or T-like interactions, depending on the relative position of nitrosyl ligands and energetically corresponding to Van der Waals bonds. Mainly LP(O), π (NO), and π*(NO) orbitals in various combinations participate in their formation, with π (FeN), π(FeО), and LP(N) orbitals hardly being participants. The involvement of the NO bond orbitals results in quenching the orbital moment of the NO groups. If NO groups are isolated from intermolecular interactions, they can preserve the unquenched orbital moment.

Interaction and transformation of the mononuclear cationic dinitrosyl iron complex [Fe(SC(NH2)2)2(NO)2]+ (complex 1) upon binding with bovine serum albumin (BSA) have been explored using kinetic measurements, UV-Vis and fluorescence spectroscopy, and computational molecular modeling. BSA was found to bind up to five molecules of complex 1 per one protein molecule; as a result, the rate of NO release by complex 1 into solution decreases by a factor of 10. The binding constant of complex 1 with BSA measured by the quenching of intrinsic fluorescence of BSA is 5 × 105 М-1. Molecular docking calculations at pH = 7 have determined five-six low-energy binding sites for complex 1 at subunits I and II of BSA. The most stable protein-ligand complexes are located at the protein pockets near Cys34. The spectroscopic measurements and docking calculations have shown that the decomposition product of complex 1, the Fe(NO)2+ fragment, can form an adduct Fe(Cys34)(His39)(NO)2 (complex 2) with the coordination bonds of Fe with atoms S of Cys34 and ND of His39. The structure of complex 2 was supported by the density functional calculations of the absorption spectrum. Decomposition of complex 2 leads to nitrosylation of BSA at atom S of Cys34. Complexes 1 (bound with BSA), 2 and the nitrosylated BSA can serve as NO depot in plasma.

The reactions of adenosine triphosphoric acid (ATP) with water-soluble binuclear tetranitrosyl iron complexes of the μ-S structural type with functional sulfur-containing ligands (thiosulfate (1) cysteamine (2), and penicillamine (3)) afford products of close structures. The hydrolysis products of the complexes (1–3) in aqueous aerobic solutions are studied by amperometry and mass electrospectrometry. The kinetic regularities of the reactions of the complexes (1–3) with ATP are studied by the spectrofluorimetric method. A generalized kinetic model describing the experimental data of three reactions is proposed for the process. From the qualitative point of view, the reactions of ATP with the studied complexes occur similarly in spite of the difference in the ligands. The rates of particular steps of the process depend on the nature of the ligands. The values determined for the kinetic parameters quantitatively characterize the influence of the ligand nature in complexes 1–3 on the reactivity toward ATP and increase in the order: cysteamine

Homogeneous composites based on poly(methyl methacrylate) and its copolymers with methacrylic acid and on the nitrosyl iron complexes with 2-mercaptobenzimidazole and 2-mercaptobenzthiazole were synthesized. An analysis of the experimental data obtained by the methods of small-angle X-ray diffraction and SQUID magnetometry in combination with the results of quantum chemical calculations showed that the nitrosyl complexes did not retain their initial binuclear structure under the matrix isolation conditions: some complexes decompose to mononuclear ones. The percentage ratio of the dimers and monomers depends on the fraction of the methacrylic acid copolymer in the polymeric matrix and is almost independent of the type of thiol ligand in the iron complex.

The effect of iron nitrosyl complexes, NO donors, of a general formula [Fe2(L)2(NO)4] with functional sulfur-containing ligands (L-3-nitro-phenol-2-yl, 4-nitro-phenol-2-yl, or 1-methyl-tetrazol-5-yl) on the activity of sarcoplasmic reticulum Ca2+-ATPase and cyclic guanosine monophosphate phosphodiesterase (cGMP PDE) was studied. The test complexes uncoupled the hydrolytic and transport functions of Ca2+- ATPase, thus disturbing the balance of Ca2+ ions in cells, which may affect the formation of thrombi and adhesion of metastatic cells to the endothelium of capillaries. They also inhibited the activity of cGMP PDE, thereby contributing to the accumulation of the second messenger cGMP. The studied iron nitrosyl complexes can be considered as potential drugs.

A new inhibitor of phosphodiesterase (PDE), i.e., nitric oxide (NO) donor, a water soluble DNIC Na[Fe(C7H5N4S)2(NO)2]⋅2·.5H2O (1), has been synthesized. The structure of the new complex, its physical–chemical properties in the solid state and in solutions have been studied experimentally (X-ray analysis, IR, UV–Vis, Mossbauer spectroscopy, mass-spectrometry, and amperometry) and theoretically (quantum-chemical modeling by DFT method).

In this work, transformations of two cationic dinitrosyl iron complexes (DNICs), namely, mononuclear with N-ethylthiourea ligands [Fe(SC(NH2)(NHC2H5))2(NO)2]+Cl−∙[Fe(SC(NH2)(NHC2H5))Cl(NO)2]0 (complex 1) and binuclear with penicillamine ligands [Fe2(S(C(CH3)2CH(NH3)COOH))2(NO)4]SO4·5H2O (complex 2) have been investigated in an aqueous solution in the presence of bovine serum albumin (BSA) under anaerobic and aerobic conditions. The spectroscopic measurements have shown that the complexes bind to the protein, which leads to their stabilization. The resulting products are much more stable in the absence of oxygen. The fluorescence measurements indicated that complexes 1 and 2 interact with BSA with equilibrium constants K = 4.9∙105 M−1 and 5.3∙105 M−1, respectively. Complex 1 can bind to the surface due to weak intermolecular interactions, resulting in prolonged generation of NO. Also, the decay product of complex 1, both under anaerobic conditions and in the presence of oxygen, is coordinated with Cys34 and His39 in the hydrophobic pocket of albumin, as evidenced by the appearance of a shoulder at 370–410 nm. As a result of these interactions, a high molecular weight albumin-bound complex is formed, which then slowly decomposes in more than 40 h. Complex 2 and its products are adsorbed on the surface of the protein. However, in the presence of oxygen, protein does not significantly affect the NO release rate.

Possible reactions of the mononuclear iron nitrosyl complex [Fe(SC(NH2)2)2(NO)2]Сl•H2O in an aqueous solution were studied using quantum chemical modeling. The electronic structures of the possible intermediates were examined by the NBO and AIM methods. The substitution of the thio ligand in the iron—sulfur nitrosyl complex by a water molecule and the formation of dimeric intermediate complexes were found to facilitate the NO-donation process.

The decomposition of two neutral binuclear nitrosyl iron complexes (NICs) of the µ-S structural type and general composition [Fe2(SR)2(NO)4]0 was studied in comparison. The exchange reaction of the thiophenol or 2-aminothiophenol thiolate ligand by glutathione (GSH) in neutral NICs was studied. The reaction system was analyzed by spectrophotometry to prove the presence of a new NICs with the GS– ligand in it. It was found that, unlike the earlier studied binuclear cationic NICs of the µ-S type and general composition [Fe2(µ-SR)2(NO)4]2+SO4•nH2O with cysteamine and penicillamine ligands in which both thiolate ligands exchange by GS–, in these neutral complexes both thiolate ligands are de-tached by only one GSH ligand is attached. A water molecule is inserted into the second free site. It is assumed that the antitumor activity of the neutral NICs can be determined not only by their NO-donor activity but also by their ability to exchange the thiolate ligand by GS–, i.e., "to remove" GSH from the medium as in the case of cationic NICs. The discovered reaction can prevent, most likely, the S-glutathionylation of important metabolites in the presence of GSH and is very significant for metabolism of NICs.

Two decomposition mechanisms of nitrosyl iron complexes (NICs) [Fe2(μ-SR)(NO)4] in aqueous medium are known. One mechanism (for instance, in the case of complex [Fe2(μ-SC4H3N2)2(NO)4]) involves irreversible and rapid hydrolysis of NIC with the NO release accompanied with the formation of the products of further NO transformations. In the other mechanism (for instance, in the case of complexes [Fe2(μ-S(CH2)2NH3)2(NO)4]SO4• •2.5H2O and [Fe2(μ-SC5H11NO2)2(NO)4]SO4•5H2O), no hydrolysis occurs but NICs reversibly dissociate to release both NO and thiolate ligand into the medium. In the present work, the difference in the mechanisms of the NIC decomposition is explained by the difference in the NIC redox potentials. The experimental evidences of this fact are given.

Decomposition of binuclear neutral iron nitrosyl complex [Fe2(S2C7H4N)2(NO)4]0 (I) of μ-N–C–S structural type in aqueous solution has been studied. Effect of glutathione GSH on the decomposition of complex I has been studied.

The antioxidant and antiradical properties of the tetra nitrosyl iron complex with thiosulfate ligands (TNIC) were studied in vitro in mouse brain homogenates. It was found for the first time that TNIC is an effective antioxidant. The effect of TNIC on the catalytic activity of mitochondrial enzymes cytochrome c oxidase and monoamine oxidase A was studied. It was shown for the first time that TNIC is an inhibitor of the catalytic activity of cytochrome c oxidase and monoamine oxidase A in animal brain mitochondria in vitro.

Density functional quantum chemical calculations of Roussin’s red esters with phenyl [Fe2(SPh)2(NO)4] and ortho-aminophenyl [Fe2(SC6H4NH2)2(NO)4] ligands, as well as products of partial and complete replacement of functional ligands by glutathione were carried out. Main characteristics of the Fe—S bonds in these compounds were estimated within the framework of the NBO approach and the AIM theory. The possibility for ligand substitution reactions to occur was demonstrated. A possible mechanism of these processes is proposed.

The kinetic regularities of nitric oxide donation in the presence of erythrocytes by representatives of a new class of synthetic nitric oxide donors, binuclear tetranitrosyl iron complexes (B-TNIC) [Fe2(SR)2(NO)4] with thiol-containing ligands, where R is pyrimidin-2-yl, 1-methylimidazol-2-yl, benzothiazol-2-yl, and penicillamine residue, were established. The NO-donating ability of B-TNIC was estimated from the apparent rate constants of the first order for the formation of intraerythrocyte methemoglobin with the variation of the initial concentration of the complex. During the standard experimental time (15—17 min), three of the four complexes released in the solution no more than a quarter of available NO groups. Their NO-donating ability turned out to be variable increasing with an increase in the initial concentration of the complex. At the same time, the complex bearing penicillamine residues as ligands donated almost all NO groups within approximately 1 min. Features of NO donation by the B-TNIC in the presence of erythrocytes are related to the formation in the system of an additional equilibrium pool of the membrane-associated complex, which is characterized by a reduced rate of hydrolytic dissociation with NO releasing to the solution. The NO-donating ability of the B-TNIC in the presence of erythrocytes is determined by the ratio of volumes of the free and membrane-associated pools of the complex.

We studied the effects of water-soluble cationic dinitrosyl iron complexes with thiocarbamide and its aliphatic derivatives, new synthetic analogs of natural NO donors, active centers of nitrosyl [1Fe-2S]proteins, on activities of Ca2+-ATPase of sarcoplasmic reticulum and cGMP phosphodiesterase. Nitrosyl iron complexes [Fe(C3N2H8S)Cl(NO)2]0[Fe(NO)2(C3N2H8S)2]+Cl— (I), [Fe(SC(N(CH3)2)2(NO)2]Cl (II), [Fe(SC(NH2)2)2(NO)2Cl×H2O (III), and [Fe(SC(NH2)2)2(NO)2]2SO4×H2O (IV) in a concentration of 10—4 M completely inhibited the transporting and hydrolytic functions of Ca2+-ATPase. In a concentration of 10—5 M, they inhibited active Ca2+ transport by 57±6, 75±8, 80±8, and 85±9% and ATP hydrolysis by 0, 40±4, 48±5, and 38±4%, respectively. Complex II reversibly and noncompetitively inhibited the hydrolytic function of Ca2+-ATPase (Ki=1.7×10—6 M). All the studied iron—sulphur complexes in a concentration of 10—4 M inhibited cGMP phosphodiesterase function. These data suggest that the studied complexes can exhibit antimetastatic, antiaggregation, vasodilatatory, and antihypertensive activities.

The reaction of the tetranitrosyl iron complex (nitric oxide donor) bearing the cysteamine ligand (CAC) with adenosine triphosphoric acid (ATP) was studied. The product of the reaction of CAC with ATP was isolated in the solid state and characterized by UV and IR spectroscopy. The interaction of CAC with the adenine moiety of the ATP molecule was shown using spectrofluorimetry, and the stability constant (complexation constant) of the reaction product was determined: K = (2.1 ± 0.2)∙104 mol−1 L. Ions with the mass numbers 569 and 491 m/z corresponding to [Fe–S–P3N5C10H6O12]+ and [Fe–S–P2N5C10H7O9]+ were identified in the mass spectrum of the product.

In this work, transformations of the anionic binuclear tetranitrosyl iron complex with thiosulfato ligands (Na2[Fe2(S2O3)2(NO)4]·4H2O) (1) have been studied in aqueous anaerobic and aerobic solutions. Under anaerobic conditions, complex 1 was shown to undergo intramolecular isomerization, in addition to NO generation, due to embedding of the oxygen atom of the thiosulfato ligand in the Fe-S bonds. The complex becomes more stable, so its further transformation, including NO release, is unlikely. The model for the complex decomposition has been suggested, and reaction rate constants have been calculated using the kinetic modeling method. As follows from the experimental data, under aerobic conditions, complex 1 is oxidized and becomes a more effective NO donor. Due to the incorporation of the oxygen atom into the Fe-S bonds, mononuclear nitrosyl intermediates are formed, which have a typical EPR signal (g = 2.03).

The results of the study of the effect of a mononuclear dinitrosyl iron complex (DNIC7) with functional sulfur-containing ligands (NO donors) on the viability of multiple myeloma cells are presented. It was shown that DNIC7 decreased cell viability and inhibited the proliferation of multiple myeloma cells, i.e., exhibits cytotoxic properties. Fluorescent analysis showed that the DNIC7 compound decreases the level of intracellular glutathione and increases the level of reactive oxygen species in multiple myeloma cells. It is assumed that DNIC7 has a therapeutic potential for the treatment of cancer.

The electrochemical method and quantum chemical modeling were used to study the NO-donor activity of the mononuclear nitrosyl complex with the thiourea ligand and the influence of the pH of the medium on the reaction. It is shown experimentally that this complex evolves nitrogen monoxide and the character of this process depends on the pH of the medium. For a neutral medium, the curve of nitrogen monoxide evolution reaches a plateau, whereas the curve increases linearly with time for an alkaline medium. The quantum chemical modeling (using DFT methods with the B3LYP and BP86 functionals) of possible processes in an aqueous solution of the complex in neutral and alkaline media allowed us to propose the schemes of the NO-donation reaction, which explain the experimental data on the pH effect.

In this paper, the kinetics of the interaction of the nitrosyl iron complex with the ligands penicillamine [Fe2(SC5H11NО2)2(NO)4]SO4·5H2O (I) with deoxyhemoglobin (Hb) was studied. The kinetic modeling method defined the number of binding (I) molecules and equilibrium constant of the coupling reaction of (Biomedicine, Iron-Sulfur Cluster, Ligand Binding, Heme, Nitric Oxide ) with Hb (Ks). At equimolar concentrations of (I) and Hb (2 × 10−5 M), the Hb molecule binds only one (I) with Ks equal to 4.3 × 107 M−1. When increasing the (Biomedicine, Iron-Sulfur Cluster, Ligand Binding, Heme, Nitric Oxide ) concentration, the number of binding sites of Hb increases and Ks decreases. These results are analyzed in accordance with the data on the existence of cations binding sites in Hb.

The kinetics of nitric oxide release by representatives of a new class of synthetic nitric oxide donors, binuclear tetranitrosyl iron complexes (B-TNIC) with a structure of [Fe2(SR)2(NO)4], where R is pyrimidin-2-yl, 1-methylimidazol-2-yl, benzothiazol-2-yl, cysteamine, and penicillamine, was studied under the conditions simulating the blood vessel internal environment, when an erythrocyte suspension was used as a natural trap of nitric oxide. The apparent firstorder rate constants for intraerythrocyte methemoglobin formation were determined on the basis of the kinetic data. The NO-donating ability of B-TNIC was estimated from the values of these rate constants. It is assumed that the rate for the hydrolytic decomposition of B-TNIC decreases in the presence of erythrocytes due to binding of the complexes with the cell surface, leading to the restriction of their contact with an aqueous medium. Nitric oxide donating by the complex bearing penicillamine as a ligand is stoichiometric and independent of the presence of erythrocytes. This can be due to high hydrophilicity of this complex determined from the criterion of partition coefficient in an octanol-water system. This evidently provides a high level of solvation of the complex in an aqueous medium that prevents its binding with the erythrocyte surface.

Three new representatives of thiacalix[4]arene-containing tetranuclear 3d-4f metal complexes with the M2Ln2 fragment (M = MnII, CoII; Ln = EuIII, PrIII) were synthesized. Their molecular and crystal structures were studied by X-ray diffraction analysis. According to the magnetochemical measurements, the complexes exhibit the paramagnetic properties with weak antiferromagnetic interactions at low temperatures (T < 30–50 K). The influence of the environment of the rare-earth elements on the spin-orbital coupling and magnetic properties of the complexes was found.

The quantum chemical study of the redox potentials of ten iron nitrosyl complexes with functional bridging μ-SCN-type ligands was performed by the DFT method combined with the polarizable continuum model (PCM) in order to clarify the influence of the ligand on the redox properties of the complex. The geometry optimization in terms of the PCM approach gave redox potentials, which are in the best agreement with the experimental values. The redox potential depends on the nature of the heteroatom in the five-membered azole ring, the number of N atoms in the ring, and the presence of the fused benzene ring in the aromatic system of the ligand.

The substitution of the glutathione ligand for penicillamine and cysteamine ligands in the cationic nitrosyl iron complexes with the penicillamine thiyl ligand, [Fe2(SC5H11NO2)2(NO)4]SO4·2H2O, and the cysteamine thiyl ligand, [Fe2(S(CH)2NH3)2(NO)4]SO4·2H2O, was studied by quantum chemical methods. Quantum chemical calculations were performed with the full geometry optimization of the starting and final complexes by the DFT method using the local BP86 and OPBE functionals. The structures of the intermediate and final complexes were predicted. The S-C bond in the complexes with the penicillamine ligand is longer than in other complexes of this type. The calculated energy of the detachment of the ligand from the complex with penicillamine is lower than that for the complex with the cysteamine ligand. The ligand substitution in the complex with the penicillamine ligand does not require considerable energy and can easily proceed in aqueous solution, whereas this reaction in the complex with the cysteamine ligand is thermodynamically unfavorable.

Reduction of neutral binuclear nitrosyl iron complexes of “μ-S” structural type [Fe2(SR)2(NO)4] with R = 3-nitro-phenol-2-yl, 4-nitro-phenol-2-yl, 5-nitropyridine-2-yl and pyridine-2-yl in aprotic solution has been studied by a cyclic voltammetry (CVA) method at a wide range of potential scan rates. A complex with R = 3-nitro-phenol-2-yl was synthesized for the first time; therefore it was studied by X-ray and Mossbauer spectroscopy. The parameters of the Mossbauer spectrum are: isomer shift δFe = 0.115(1) mm s−1, quadrupole splitting ΔEQ = 1.171(1) mm s−1, and line width = 0.241(1) mm s−1 at 85 K. From the current–voltage curve, the transfer of the first electron was found to be reversible, and the redox-potentials of these reactions were determined. The further reduction of the complexes was determined to be irreversible because the product of the second electron addition is instable and decomposes partially during the potential scan. Calculations of geometric and electronic structures of monoanions and dianions of the complexes under study and their theoretical redox-potentials were performed by DFT methods. Introduction of the electron-acceptor NO2 group into the phenyl and pyridine rings of sulfur-containing ligands of the nitrosyl iron complexes was found to affect the geometry of the anions and the distribution of the additional negative charge, as well as to increase the redox-potential and to facilitate reduction of these complexes.

A new tetranitrosyl binuclear iron complex, [Fe2(SC6H6N)2(NO)4] (1), has been synthesized by two methods. Molecular and crystalline structure of 1 were determined by X-ray analysis; the complex is binuclear of “μ-S” type with ~2.7052(4) A between the irons. The compound crystallizes in monoclinic, space group P21/n, Z = 2; parameters of the unit cell: a = 6.6257(2) A, b = 7.9337(2) A, c = 16.7858(4) A, β = 96.742(2)°, V = 876.26(4) A3. Parameters of Mossbauer spectrum for 1 are: isomer shift δFe = 0.096(1) mm/s, quadrupole splitting ΔEQ = 1.122(1) mm/s, line width 0.264(1) mm/s at 293 K. As follows from the electrochemical analysis of aqueous solutions of 1, it generates NO in protonic media without additional activation. NO amount and the rate of its activation are much higher in acidic solutions than in neutral and alkali ones. The constants of hydrolytic decomposition of 1 were calculated. The geometry and electronic structure of isolated 1 were studied using the density functional theory. Differential...