Functional models of [Fe—S] nitrosyl proteins

The review surveys methods for the synthesis, as well as structures and properties of sulfur-containing iron nitrosyl complexes serving as models of active sites of [Fe—S] nitrosyl proteins, which are potential donors of nitrogen monoxide.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2326–2345, November, 2004.     

Carbonyldinitrosyltris(fluorosulfato)tungstate(II) and ‐Molybdate(II) Anions: Synthesis,Spectroscopy, and Density Functional Theory Calculations

Carbonyldinitrosyltris(fluorosulfato)tungstate(II) and ‐molybdate‐(II) anions, [fac‐M(CO)(NO)₂(SO₃F)₃]^? (M=W, Mo), which are novel weakly coordinating anions that contain a metal carbonyl/nitrosyl moiety, have been generated in fluorosulfonic acid and completely characterized by multinuclear NMR, IR, and Raman spectroscopy as well as ESI mass spectrometry. ESI MS measurements performed for the first time on a superacidic solution system unambiguously reveal the formation of the monoanionic, mononuclear W and Mo complexes formulated as [M(CO)(NO)₂(SO₃F)₃]^? (M=W, Mo). Multinuclear NMR spectroscopic studies at natural abundance and ¹³C and ¹⁵N enrichment clearly indicate the presence of one CO ligand, two equivalent NO ligands, and two types of nonequivalent SO₃F^? groups in a 2:1 ratio. The IR and Raman spectra reveal that the two equivalent NO ligands have a cis conformation, thus indicating a fac structure. Density functional calculations at the B3LYP level of theory predict that these anions have a singlet ground state (¹A′) with a C_s symmetry along with C–O and N–O vibrational frequencies that are in agreement with the experimental observations. Mulliken population analysis shows that the monovalent negative charge is dispersed on the bulky sphere, the surface of which is covered by all the negatively charged O and F atoms with charge densities much lower than SO₃F^?, suggesting that [fac‐M(CO)(NO)₂(SO₃F)₃]^? (M=W, Mo) are weakly nucleophilic and poorly coordinating anions.     

Metallorganische Lewis-Säuren. XLII. Carbonyl- und Nitrosyl-Komplexe von Mangan und Rhenium mit schwach koordinierten Anionen (Ph3P)2(ON)2MnX, (Ph3P)n(OC)5–nMX (M = Mn,Re; n = 1, 2; X = FBF3, OSO2CF3, OSO2F,OCORf)

Organometallic Lewis Acids. XLII. Carbonyl- and Nitrosyl Complexes of Manganese and Rhenium of Weakly Coordinated Anions (Ph₃P)₂(ON)₂MnX, (Ph₃P)_n(OC)_5–nMX (M = Mn, Re; n = 1, 2; X = FBF₃, OSO₂CF₃, OSO₂F, OCOR_f) The complexes (Ph₃P)₂(ON)₂MnX (X = FBF₃, OSO₂CF₃, OSO₂F, OCOCF₃, OCOC₃F₇) and (Ph₃P)_n(OC)_5–nMX (M = Mn, Re; n = 1, 2; X = FBF₃, OSO₂CF₃) have been obtained by reaction of (Ph₃P)₂(ON)₂MnH and (Ph₃P)_n(OC)_5–nMeMe with the corresponding acids HX or from (Ph₃P)_n(OC)_5–nReBr (n = 1, 2) with silver salts AgX, respectively. The compounds have been characterized by their IR and partially by ¹⁹F-NMR data. An efficient method for the preparation of the hydride (Ph₃P)₂(ON)₂MnH is reported.     

X‐Ray Emission Spectroscopy: A Spectroscopic Measure for the Determination of NO Oxidation States in Fe–NO Complexes

Extensive study of the electronic structure of Fe‐NO complexes using a variety of spectroscopic methods was attempted to understand how iron controls the binding and release of nitric oxide. The comparable energy levels of NO π* orbitals and Fe 3d orbitals complicate the bonding interaction within Fe? NO complexes and puzzle the quantitative assignment of NO oxidation state. Enemark–Feltham notation, {Fe(NO)_x}ⁿ, was devised to circumvent this puzzle. This 40‐year puzzle is revisited using valence‐to‐core X‐ray emission spectroscopy (V2C XES) in combination with computational study. DFT calculation establishes a linear relationship between ΔE_σ2s*‐σ2p of NO and its oxidation state. V2C Fe XES study of Fe? NO complexes reveals the ΔE_σ2s*‐σ2p of NO derived from NO σ_2s*/σ_2p→Fe_1s transitions and determines NO oxidation state in Fe? NO complexes. Quantitative assignment of NO oxidation state will correlate the feasible redox process of nitric oxide and Fe‐nitrosylation biology.     

亚硝酰硫酸的离子色谱分析方法研究

建立了离子色谱法(IC)测定亚硝酰硫酸含量的分析方法。考察了亚硝酰硫酸选择性水解生成硝酸和硫酸的条件。亚硝酰硫酸的最佳色谱分析条件为:电导检测器,pH3.5的磷酸二氢钾缓冲溶液作流动相,流速1 mL.min-1,柱温45℃。在优化实验条件下,NO2-、NO3-和SO42-的线性范围分别为2.375~9.515、0.375~1.548、2.051~8.263 mmol.L-1,相关系数均大于0.999 9。样品中NO2-、NO3-和SO24-的加标回收率为99%~101%,其相对标准偏差(RSD)均小于1.0%。通过对各离子含量的测定,用氮平衡法计算出亚硝酰硫酸的含量,相对标准偏差均在0.1%以内。建立的方法与传统的氧化还原滴定法分析亚硝酰硫酸相比,具有分析结果准确、简便快速、成本低的特点,已用于工厂中该产品的质量控制。     

飞秒强激光场下亚硝酰氯分子的电离和解离

Ionization and dissociation of nitrosyl chloride ClNO were studied using femtosecond laser mass spectra tech-nique.Strong fragmental ions NO~ and Cl~ were observed with the laser intensity varied from 3.2×10~(14) to 2.5×10~(15) W/cm~2.These fragmental ions were attributed to the direct dissociation of the parent ions.Electronic structurecalculations were also carried out with Hartree-Fock,density functional and correlated levels of theory to under-stand the possible fragmentation pathways.The very low N-Cl bond energy in the parent ion of nitrosyl chloride isa clear reason for the absence of ClNO~ and ClN~ ion peaks from the femtosecond laser mass spectrum.     

Rhodium nitrosyl catalysts for CO2 hydrogenation to formic acid under mild conditions

A new synthetic protocol for catalysing CO₂ hydrogenation to formic acid under mild conditions is reported, and the CO₂ hydrogenation is efficiently achieved by dcpe‐rhodium‐nitrosyl catalyst precursors, Rh(NO)(dcpe) (1) (dcpe = 1,2‐dicyclohexylphosphinoethane) and Rh(III)(NO)(dcpe)Cl₂ (2). The catalytic activity of 1 is noteworthy for being able to proceed in the absence of protic conditions. Compound 2 is characterized by NMR, IR and X‐ray crystallography. In particular, 2 is observed to bear a bent NO ligand with a Rh–N–O angle of 115.7(3)°, representing one of the smallest M–N–O angles known. Copyright © 2012 John Wiley & Sons, Ltd.     

APCI as an innovative ionization mode compared with EI and CI for the analysis of a large range of organophosphate esters using GC‐MS/MS

Organophosphate esters (OPEs) are chemical compounds incorporated into materials as flame‐proof and/or plasticizing agents. In this work, 13 non‐halogenated and 5 halogenated OPEs were studied. Their mass spectra were interpreted and compared in terms of fragmentation patterns and dominant ions via various ionization techniques [electron ionization (EI) and chemical ionization (CI) under vacuum and corona discharge atmospheric pressure chemical ionization (APCI)] on gas chromatography coupled to mass spectrometry (GC‐MS). The novelty of this paper relies on the investigation of APCI technique for the analysis of OPEs via favored protonation mechanism, where the mass spectra were mostly dominated by the quasi‐molecular ion [M + H]⁺. The EI mass spectra were dominated by ions such as [H₄PO₄]⁺, [M–R]⁺, [M–Cl]⁺, and [M–Br]⁺, and for some non‐halogenated aryl OPEs, [M]^+● was also observed. The CI mass spectra in positive mode were dominated by [M + H]⁺ and sometimes by [M–R]⁺, while in negative mode, [M–R]⁻ and more particularly [X]^‐ and [X₂]^‐● were mainly observed for the halogenated OPEs. Both EI and APCI techniques showed promising results for further development of instrumental method operating in selective reaction monitoring mode. Instrumental detection limits by using APCI mode were 2.5 to 25 times lower than using EI mode for the non‐brominated OPEs, while they were determined at 50‐100 times lower by the APCI mode than by the EI mode, for the two brominated OPEs. The method was applied to fish samples, and monitored transitions by using APCI mode showed higher specificity but lower stability compared with EI mode. The sensitivity in terms of signal‐to‐noise ratio varying from one compound to another. Copyright © 2016 John Wiley & Sons, Ltd.     

Electronic Structure Modulation in an Exceptionally Stable Non‐Heme Nitrosyl Iron(II) Spin‐Crossover Complex

The highly stable nitrosyl iron(II) mononuclear complex [Fe(bztpen)(NO)](PF₆)₂ (bztpen=N‐benzyl‐N,N′,N′‐tris(2‐pyridylmethyl)ethylenediamine) displays an S=1/2?S=3/2 spin crossover (SCO) behavior (T_1/2=370 K, ΔH=12.48 kJ mol^?1, ΔS=33 J K^?1 mol^?1) stemming from strong magnetic coupling between the NO radical (S=1/2) and thermally interconverted (S=0?S=2) ferrous spin states. The crystal structure of this robust complex has been investigated in the temperature range 120–420 K affording a detailed picture of how the electronic distribution of the t_2g–e_g orbitals modulates the structure of the {FeNO}⁷ bond, providing valuable magneto–structural and spectroscopic correlations and DFT analysis.