Nitrosonium Research Articles

Investigating the Low Temperature Formation of CuII -(N,O) Species on Cu-CHA Zeolites for the Selective Catalytic Reduction of NOx.

In this work, we show the potentiality of operando FTIR spectroscopy to follow the formation of CuII -(N,O) species on Cu exchanged chabazite zeolites (Cu-CHA), active for the selective catalytic reduction of NOx with NH3 (NH3 -SCR). In particular, we investigated the reaction of NO and O2 at low temperature (200 and 50 °C) on a series of Cu-CHA zeolites with different composition (Si/Al and Cu/Al ratios), to investigate the nature of the formed copper nitrates, which have been proposed to be key intermediates in the oxidation part of the SCR cycle. Our results show that chelating bidentate nitrates are the main structures formed at 200 °C. At lower temperature a mixture of chelating and monodentate nitrates are formed, together with the nitrosonium ion NO+ , whose amount was found to be proportional to the zeolite Brønsted site concentration. Nitrates were found to mainly form with CuII ions stabilized by one negative framework charge (Z), Z-[Cu(OH]I or Z-[Cu(O2 ]I , without involvement of Z2 -CuII ones. This evidence, together with the absence of bridging nitrates in samples with high probability for Cu-Cu pairs, indicate that the nitrate ligands are not able to mobilize copper ions, at variance with what recently reported for NH3 . Finally, water was found to replace preformed chelating copper nitrates and deplete NO+ (though with different kinetics) at both temperatures, while favouring the presence of monodentate ones.

EPR Characterization of Dinitrosyl Iron Complexes with Thiol-Containing Ligands as an Approach to Their Identification in Biological Objects: An Overview.

The overview demonstrates how the use of only one physico-chemical approach, viz., the electron paramagnetic resonance method, allowed detection and identification of dinitrosyl iron complexes with thiol-containing ligands in various animal and bacterial cells. These complexes are formed in biological objects in the paramagnetic (electron paramagnetic resonance-active) mononuclear and diamagnetic (electron paramagnetic resonance-silent) binuclear forms and control the activity of nitrogen monoxide, one of the most universal regulators of metabolic processes in the organism. The analysis of electronic and spatial structures of dinitrosyl iron complex sheds additional light on the mechanism whereby dinitrosyl iron complex with thiol-containing ligands function in human and animal cells as donors of nitrogen monoxide and its ionized form, viz., nitrosonium ions (NO+).

Dinitrosyl iron complexes with thiol-containing ligands as a base for developing drugs with diverse therapeutic activities: Physicochemical and biological substantiation

Dinitrosyl iron complexes (DNICs) with thiol-containing ligands occur in animal tissues as paramagnetic (EPR-active) mononuclear and diamagnetic (EPR-silent) binuclear species with the presence of nitric oxide. They provide stabilization and storage (within protein-bound DNICs) of nitric oxide, as well as its transport (within low-molecular-weight DNICs) to biological targets to serve as donors of not only nitric oxide itself but also of the nitrosonium ion (NO+). The latter function determines the ability of DNICs to S-nitrosylate various thiol-containing proteins. In this way, the complexes participate in a wide range of physiological and biochemical processes. With respect to the high and diverse level of biological activity and dose dependence of DNICs, they mimic the endogenous nitric oxide system. Taken together with the broad occurrence of DNICs (predominantly in the diamagnetic form) in animal tissues, this fact points to their role as an “operating form” of nitric oxide. It is thought that drugs designed on the basis of DNICs can substantially improve the efficiency of modern medical practice.

Nitrosonium-Mediated Phenol–Arene Cross-Coupling Involving Direct C–H Activation

The nitrosonium ion (NO+) is a highly versatile nitration and nitrosation reagent, as well as a strong one-electron oxidant. Herein, we describe an environmentally benign and mild method for the in situ formation of NO+ from readily available inorganic nitrate salts, i.e. lithium nitrate, through a finely tuned interplay between formic acid and MeOH, which are used as the solvent system. This methodology was applied to the NO+-induced oxidative C–H activation of methoxy-substituted phenols, which are versatile lignin-derived aromatic feedstocks, to achieve C–C cross-coupling reactions with arenes. The regeneration of NO+ by atmospheric molecular oxygen enables substoichiometric use of the nitrate.

Graphene Derivative As a Highly Efficient Nitrosonium Source: A Reusable Catalyst for Diazotization and Coupling Reaction

AbstractAn efficient and a simple approach for the synthesis of azo dyes have been developed by the diazo coupling reactions of active aromatic compounds in the presence of in‐situ nitrite functionalized graphene oxide polyvinyl alcohol GO‐PVA composite as a highly efficient nitrosonium ion source. This methodology was objected to defeat the limitations of the earlier reported method such as use of acids, alkalis and toxic solvents, to reduce the stability of diazonium salts at room temperature, modest yields and long reaction time. Additionally, the attractive advantages of the process are that it incorporated mild conditions with excellent yield, simple product isolation process, fastest reaction time and recyclability of catalyst. The isolated products were characterized by FT‐IR spectrum, UV‐spectroscopy and 1H‐NMR. The as‐prepared composites were confirmed by UV‐Visible, XRD, XPS, FT‐IR spectrum, SEM and TGA analysis.

Quantum Chemical Investigation of the Transition States and Intermediates for the Reaction of the Nitrosonium Ion with the Pentaammineazidocobalt(III) Ion.

The water exchange reaction on Co(NH3)5OH23+ was investigated with various density functionals and basis sets. A Gibbs activation energy (ΔG⧧) agreeing with experiment was obtained with the long-range-corrected functionals ωB97X-D3 and LC-BOP-LRD, SMD hydration, and modified Karlsruhe def2-TZVP basis sets. This computational technique was then applied to the reaction of NO+ with Co(NH3)5N32+. All of the possible pathways were investigated, NO+ attack at the terminal N of Co(NH3)5N32+ via the E and the Z isomers of the transition states, and NO+ attack at the bound N of azide, also via both isomers. The most favorable pathway proceeds via the attack at the bound N via the Z isomer. This leads to the intermediate with an oxatetrazole ligand bound to Co(III) at the N in the 3-position, Co(NH3)5(cycl-N4O)3+, which undergoes N2 elimination to yield the Co(NH3)5N2O3+ intermediate. The subsequent substitution of N2O by water follows the Id mechanism with retention of the configuration. No evidence for the existence of the square-pyramidal pentacoordinated intermediate Co(NH3)53+ was found. All of the investigated intermediates, Co(NH3)5N23+, Co(NH3)5[E-N(N2)(NO)]3+, Co(NH3)5(E-ON4)3+, Co(NH3)5ON23+, Co(NH3)5(cycl-N4O)3+, and Co(NH3)5N2O3+, exhibit short lifetimes of less than ∼60 μs and react via the Id mechanism.

Nitrosation of 2-aryl-1-bromo-1-fluorocyclopropanes with nitrosonium tetrafluoroborate as an approach to the synthesis of 5-aryl-4-bromo-4-fluoroisoxazolines

Nitrosation of 2-aryl-1-bromo-1-fluorocyclopropanes with nitrosonium tetrafluoroborate as an approach to the synthesis of 5-aryl-4-bromo-4-fluoroisoxazolines

Resolving the HONO formation mechanism in the ionosphere via ab initio molecular dynamic simulations

Solar emission produces copious nitrosonium ions (NO(+)) in the D layer of the ionosphere, 60 to 90 km above the Earth's surface. NO(+) is believed to transfer its charge to water clusters in that region, leading to the formation of gaseous nitrous acid (HONO) and protonated water cluster. The dynamics of this reaction at the ionospheric temperature (200-220 K) and the associated mechanistic details are largely unknown. Using ab initio molecular dynamics (AIMD) simulations and transition-state search, key structures of the water hydrates-tetrahydrate NO(+)(H2O)4 and pentahydrate NO(+)(H2O)5-are identified and shown to be responsible for HONO formation in the ionosphere. The critical tetrahydrate NO(+)(H2O)4 exhibits a chain-like structure through which all of the lowest-energy isomers must go. However, most lowest-energy isomers of pentahydrate NO(+)(H2O)5 can be converted to the HONO-containing product, encountering very low barriers, via a chain-like or a three-armed, star-like structure. Although these structures are not the global minima, at 220 K, most lowest-energy NO(+)(H2O)4 and NO(+)(H2O)5 isomers tend to channel through these highly populated isomers toward HONO formation.

Quantum chemical study of nitrosonium complexes of the 9-methyladenine-1-methylthymine complementary pair. Structure and dynamics

Nitrosonium complexes of 1-methylthymine and 9-methyladenine, as well as of their complementary pair, have been studied at the RI-MP2/L1 level of theory. The addition of nitrosonium ion to molecules of these compounds or their H-bonded pair gives a set of nitrosonium complexes of different types (1η–3η). The complex with the NO+ ion coordinated to N3 of the adenine moiety corresponds to the global minimum on the potential energy surface. The gain in energy in the interaction of nitrosonium complexes of 1-methylthymine and 9-methyladenine with 9-methyladenine and 1-methylthymine, respectively, is larger than in the formation of a neutral 9-methyladenine–1-methylthymine couple. Specific structural features and dynamics of the nitrosonium complexes are discussed.

Carboxyl and nitrite functionalized graphene quantum dots as a highly active reagent and catalyst for rapid diazotization reaction and synthesis of azo-dyes under solvent-free conditions

Carboxyl and nitrite functionalized graphene quantum dots was prepared from carboxyl and hydroxyl functionalized graphene quantum dots using NaNO2 in the absence of mineral acids. This functional group conversion was confirmed by FT-IR spectroscopy, photoluminescence and X-ray diffraction. The carboxyl and nitrite functionalized graphene quantum dots was used as an effective nitrosonium ion source and reusable catalyst for the efficient diazotization of a variety of arylamines without using any additional acid. Subsequent azo-coupling of these freshly prepared diazonium salts with a range of active aromatic compounds led to the requisite azo-dyes in excellent yields in very short reaction times with a simple experimental procedure.

Graphene Defects as Active Catalytic Sites that are Superior to Platinum Catalysts in Electrochemical Nitrate Reduction

AbstractWe report that graphene defects serve as active catalytic sites for the electrochemical nitrate reduction reaction (NRR). A defective graphene (without foreign elements) electrode exhibits an onset potential of 0.95 V versus Ag/AgCl for the electrochemical NRR in 5 MHNO3, which is 200 mV more positive than that exhibited by a platinum electrode. In addition, although the cathodic current of the platinum electrode during nitrate reduction decreases by 70 % upon the addition of 100 mMmethanol, the graphene electrode does not show any poisoning effects. The NRR on the graphene electrode shows autocatalytic behavior, including an induction period prior to the onset of the cathodic current. Moreover, the reduction reaction is accelerated by the addition of nitrite ions, and this indicates that nitrite is a key intermediate species in the autocatalytic mechanism. Density functional theory calculations reveal that a nitrosonium ion, which is an essential electrochemically active intermediate for the NRR, can strongly adsorb on the defect sites of a graphene sheet with electronic interaction, which indicates that the defect site can act as the active center for the NRR.

Transnitrosation of alicyclic N-nitrosamines containing a sulfur atom

Aromatic and aliphatic nitrosamines are known to transfer a nitrosonium ion to another amine. The transnitrosation of alicyclic N-nitroso compounds generates S-nitrosothiols, which are potential nitric oxide donors in vivo. In this study, certain alicyclic N-nitroso compounds based on non-mutagenic N-nitrosoproline or N-nitrosothioproline were synthesised, and the formation of S-nitrosoglutathione (GSNO) was quantified under acidic conditions. We then investigated the effect of a sulfur atom as the substituent and as a ring component on the GSNO formation. In the presence of thiourea under acidic conditions, GSNO was formed from N-nitrosoproline and glutathione, and an N-nitroso compound containing a sulfur atom and glutathione produced GSNO without thiourea. The quantity of GSNO derived from the reaction of the N-nitrosamines containing a sulfur atom and glutathione was higher than that from the N-nitrosoproline and glutathione plus thiourea. Among the analogues that contained a sulfur atom either in the ring or as a substituent, the thiazolidines produced a slightly higher quantity of GSNO than the analogue with a thioamide group. A compound containing sulfur atoms both in the ring and as a substituent exhibited the highest activity for GSNO formation among the alicyclic N-nitrosamines tested. The results indicate that the intramolecular sulfur atom plays an important role in the transnitrosation via alicyclic N-nitroso compounds to form GSNO.

Quantum-chemical study on cytosine nitrosonium complexes

Cytosine complexes with nitrosonium ion were studied by the RI-MP2/L1 method. Addition of nitrosonium ion to cytosine tautomers leads to formation of a set of nitrosonium complexes with different structures (1η–3η). n-Complexes formed via NO+ coordination to the nitrogen and oxygen atoms are energetically more favorable than π-complexes. The complex of cytosine as 4-aminopyrimidin-2(1H)-one tautomer with nitrosonium ion coordinated to the carbonyl oxygen atom occupies the global minimum on the potential energy surface. Structural features of the complexes are discussed.

Dinitrosyl iron complexes with glutathione largely relieve rats of experimental endometriosis

A study was made of the effect of binuclear dinitrosyl iron complexes (DNIC) with glutathione in rats with experimental endometriosis. The latter was induced in an autotransplantation model, where two fragments of endometrium with myometrium (2 × 2 mm) from the left uterine horn were grafted to the inner surface of the anterior abdominal wall. After 4 weeks, the test animals received i.p. injections of 0.5 mL DNIC-glutathione at a dose of 12.5 μmol/kg daily for 12 days. This treatment more than halved the total volume of endometrioid tumors. Remarkably, tumor growths from grafts in control rats were often attended by tumors spontaneously arising nearby or in other locations; no such secondary tumors were observed in DNIC-treated animals. The EPR signal with gav = 2.03 characteristic of protein-bound DNIC with thiol ligands was recorded in liver and endometrioid implants of control as well as treated animals. Activation of ribonucleotide reductase, detected by a doublet EPR signal at g = 2.0 with 2.3-mT hyperfine splitting, was found in small tumors. The beneficial effect of DNIC-glutathione was suggested to be due to DNIC breakdown near the tumors, with release of a large amount of molecular nitric oxide and nitrosonium ions that resulted in selective local cytotoxicity.

Physicochemical features of dinitrosyl iron complexes with natural thiol-containing ligands underlying the biological activities of these complexes

Current notions and new experimental data of the authors on physico-chemical features of dinitrosyl iron complexes with natural thiol-containing ligands (glutathione or cysteine), underlying the ability of the complexes to act as NO molecule and nitrosonium ion donors, are considered. This ability determines various biological activities of dinitrosyl iron complexes--inducing long-lasting vasodilation and thereby long-lasting hypotension in human and animals, inhibiting pellet aggregation, increasing red blood cell elasticity, thereby stimulating microcirculation, and reducing necrotic zone in animals with myocardial infarction. Moreover, dinitrosyl iron complexes are capable of accelerating skin wound healing, improving the function of penile cavernous tissue, blocking apoptosis development in cell cultures. When decomposed dinitrosyl iron complexes can exert cytotoxic effect that can be used for curing infectious and carcinogenic pathologies.

Dinitrosyl iron complexes with glutathione as NO and NO+ donors

It has been found that heating of solutions of the binuclear form of dinitrosyl iron complexes (B-DNIC) with glutathione in a degassed Thunberg apparatus (рН 1.0, 70°С, 6h) results in their decomposition with a concomitant release of four gaseous NO molecules per one B-DNIC. Further injection of air into the Thunberg apparatus initiates fast oxidation of NO to NO2 and formation of two GS-NO molecules per one B-DNIC. Under similar conditions, the decomposition of B-DNIC solutions in the Thunberg apparatus in the presence of air is complete within 30–40min and is accompanied by formation of four GS-NO molecules per one B-DNIC. It is suggested that the latter events are determined by oxidation of B-DNIC iron and concominant release of four nitrosonium ions (NO+) from each complex. Binding of NO+ to thiol groups of glutathione provokes GS-NO synthesis. At neutral рН, decomposition of B-DNIC is initiated by strong iron chelators, viz., о-phenanthroline and N-methyl-d-glucamine dithiocarbamate (MGD). In the former case, the reaction occurs under anaerobic conditions (degassed Thunberg apparatus) and is accompanied by a release of four NO molecules from B-DNIC. Under identical conditions, MGD-induced decomposition of B-DNIC gives two EPR-active mononuclear mononitrosyl iron complexes with MGD (MNIC–MGD) able to incorporate two iron molecules and two NO molecules from each B-DNIC. The other two NO molecules released from B-DNIC (most probably, in the form of nitrosonium ions) bind to thiol groups of MGD to give corresponding S-nitrosothiols. Acidification of test solutions to рН 1.0 initiates hydrolysis of MGD and, as a consequence, decomposition of MNIC–MGD and the S-nitrosated form of MGD; the gaseous phase contains four NO molecules (as calculated per each B-DNIC). The data obtained testify to the ability of B-DNIC with glutathione (and, probably, of B-DNIC with other thiol-containing ligands) to release both NO molecules and nitrosonium ions upon their decomposition. As far as nitrosyl iron complexes with non-thiol-containing ligands predominantly represented by the mononuclear mononitrosyl iron form (MNIC) are concerned, their decomposition yields exclusively NO molecules.

Reactions of Organozinc Thiolates with Nitrosonium Ion: C-Nitroso Formation by Possible Transnitrosation

The organometallic complexes [ZnPAThEt] and [ZnPAThMes], where PATh is 2-methyl-1-[methyl-(2-pyridin-2-yl-ethyl)amino]propane-2-thiolate, were prepared and their reactions with NOBF4 investigated. Formation of C-nitrosoethane and C-nitrosomesitylene, respectively, was established, and structural characterization of the latter by X-ray crystallography conclusively proved the dimeric nature of [MesNO]2 in the solid state. A transnitrosation pathway for C-nitroso formation is proposed based on theoretical calculations.

ChemInform Abstract: Electronic and Spatial Structures of Water‐Soluble Dinitrosyl Iron Complexes with Thiol‐Containing Ligands Underlying Their Ability to Act as Nitric Oxide and Nitrosonium Ion Donors

AbstractReview: 90 refs.

Quantum-chemical study on adenine nitrosonium complexes

Adenine complexes with nitrosonium ion have been studied by the RI-MP2/L1 quantum-chemical method. Addition of nitrosonium ion to adenine tautomers produces a set of nitrosonium complexes of different types (1η–3η). n-Complexes involving NO+ coordination to nitrogen atoms are more energetically favorable than π-complexes. The global minimum on the potential energy surface is occupied by the complex of 7H-adenine tautomer with nitrosonium ion coordinated at the N3 atom.

Quantum-chemical study on uracil and thymine nitrosonium complexes

Quantum-chemical calculations at the RI-MP2/L1 level of theory showed that the most energetically favorable complexes of uracil and thymine with nitrosonium cation are those of n-type with NO+ coordination at the nitrogen or oxygen atom. A correlation was found between the experimental and calculated affinities of the dioxo tautomer of thymine for nitrosonium ion (\( A_{NO^ + } \)). A linear relation was revealed between \( A_{NO^ + } \) values for structurally similar tautomers of uracil and thymine.