Cationic Adducts Research Articles

الدراسة التركيبية والطاقية لأيونات الليثيوم مع الأحماض الدهنية ميثيل استر [[FAME (9Z-18:1) + Li+ باستخدام الطريقة الكيميائية الكمومية (PM3)

Lithium (Li) ions are being used in a variety of fields ranging from energy storage to the treatment of mental illnesses including bipolar disorder and schizophrenia. Lithium caton (Li+) is able to form cationic adducts with various compounds and they can stabilize the biomacromolecules that interact with. Here, the interaction of lithium ions with fatty acid methyl ester [FAME (9Z-18:1)] has been theoretically investigated to gain insight into the structure and energetics of [FAME (9Z-18:1) + Li+]. All theoretical calculations were performed using Gaussian09 software via a graphic user interface. Geometry optimisations with harmonic vibrational analysis of conformations for chelated and extended forms of [FAME (9Z-18:1) + Li+] were carried out using semi-empirical method PM3. To obtain accurate energetic, zero-point energy (ZPE) corrections were included in all optimized energies and relative energies between conformers. The calculations indicated that the chelated form is relatively more stable than extended forms by 25 and 118 kJmol-1 when lithium is bound to the carbonyl oxygen (O-Li+) or olefin (C=C-Li+), respectively. The comparison between the relative stabilization energies of extended (O-Li+) versus extended (C=C-Li+) reveals that the lithium cation energetically prefers to bind to with carbonyl oxygen over the carbon-carbon double bond. Keywords: lithium ions, geometry optimization, sim-empirical method, Gaussian 09.

Cyclic (Alkyl)(Amino)Carbene-Iminoboryl Compounds with Three Formal Oxidation States.

BN/CC isosterism is an effective strategy to build hybrid functional molecules with unique properties. In contrast to the alkynyl iminium salts derived from cyclic (alkyl)(amino)carbenes (CAACs) that feature only one reversible reduction wave, the isoelectronic cationic CAAC-iminoboryl adducts could be singly and doubly reduced smoothly. Both the resultant neutral radical and anionic azaborataallenes bear NBC-mixed allenic structures. The former radical has a high spin-density of 0.55e at CCAAC carbon, yet exhibits formal boron-centered radical reactivity. The latter azaborataallenes feature the nucleophilic CCAAC center and polar N(δ-)═B(δ+)═C(δ-) unit, and readily undergo nucleophilic substitution, isocyanide insertion, dipolar addition and cycloaddition reactions etc. The N-substituents have been shown to have a significant influence on the solid-state structure, thermal stability, and reactivity of azaborataallenes. This work showcases the allenic BN-unsaturated species as versatile building blocks in organic synthesis.

Rhodium-Catalyzed Double Hydroboration of Quinolines

Selective double hydroelementation of N-heteroarenes can be one of the most straightforward and atom-economic routes toward dearomatized N-heterocycles bearing a (chiral) sp3 C–E bond (E = B, Si, etc.) at a specific site. Herein, we describe the development of a one-pot, site- and stereoselective borylative reduction of quinolines leading to a series of tetrahydroquinolines that possess an (enantioenriched) C(sp3)–B bond in the 4-position. A cationic Rh precatalyst [Rh(cod)2]OTf with a phosphine ligand DPEPhos enabled the borylative reduction of a range of quinolines with HBpin to provide the C4-borylated tetrahydroquinolines (THQ) in good to high yields under mild conditions. Mechanistic studies elucidated the Rh-mediated stepwise dearomative reduction cascade: (i) moderately regioselective hydroboration of quinoline resulting in a mixture of 1,2- and 1,4-dihydroquinolines (DHQ), (ii) regioselective hydroboration of the 1,2-DHQ intermediate to give the C4-borylated THQ, (iii) slow isomerization of the 1,4-DHQ to the 1,2-DHQ, and (iv) formation of the cationic Rh-quinoline adduct as a catalytic resting species. The C4-selective asymmetric borylative reduction within the cationic Rh/(S)-BINAP system was accomplished albeit with moderate enantioselectivity on average in moderate to good yields. The installed C(sp3)–Bpin unit in the 4-position was transformed to various functional groups through simple organic reactions.

Noble gas cations as Lewis acids: Adduct formation with Lewis bases with high ionization energies

Interactions of three simple Lewis bases (LB) of varying strength: H2O, NH3, and CH2O with Noble gas (Ng) cations He+, Ne+, Ar+, Kr+, Xe+ were studied using the MP2 and CCSD(T) methods. Ng+ and LBs react via two competing pathways, charge exchange reaction and cationic adduct formation. Two kinds of [Ng/LB]+ adducts were obtained after geometry optimization. In most cases, the hydrogen atoms of the LBs were the most favored sites for interactions with Ng+. Exceptions were observed for the [Xe/NH3]+, [Xe/H2O]+, and [Kr/H2O]+ systems in which interaction is via their N and O atoms. We showed that fluorination of the LBs increases their ionization energies, avoiding charge transfer, hence, F2O, NF3, and CF2O can act as LBs interacting with Ng+ via their O and N atoms. Using fluorination of the Lewis bases, the formation of [Kr/CF2O]+, [Kr/NF3]+, [Xe/CF2O]+, and [Xe/NF3]+ was more favorable than charge exchange reaction.

Reactions of a Lewis acidic methylene phosphonium cationic adduct with olefins.

Efforts to deprotonate the halophosphonium cations [Ph2P(X)Me]+ (X = F, Cl) generated species of the form [Ph2(X)PC(H)PPh2Me][X']. The derivative where X = O3SCF3 provides access to a methylene phosphonium cation. The coordinated triflate anion can be replaced by Et3PO and dimethylaminopyridine (DMAP). In addition, the cation reacts with the olefins R2CCH2 (R = Ph, Me) and PhMeCCH2. While Ph2CCH2 was shown to give the species [Ph2(Ph2CCH)PCH2PPh2Me][O3SCF3]2 with a pendant vinyl group, reactions with methyl substituted olefins undergo additional isomerization to form [Ph2(RCH2CCH2)PCH2PPh2Me][O3SCF3]2 (R = Ph, Me) featuring pendant allyl moieties.

Recent advances in sulfur tetrafluoride chemistry: syntheses, structures, and applications.

Sulfur and fluorine occupy crucial positions in main group chemistry because these two elements form a variety of compounds with versatile bond modalities and unique functionalities. Among sulfur-fluorine compounds, the importance of SF4 and its derivatives is recognized in the literature. The amphoteric nature of SF4 results in its rich Lewis acidic and basic reactivities; the reactions with F- acceptors and donors yield [SF3]+ and [SF5]- salts, respectively. Lewis basic molecules can also form adducts with SF4via various interaction motifs. The deoxofluorinating properties of SF4 have been used by organic chemists to selectively introduce fluorine atoms in specific substrates, extending also to industrial applications. Although the properties and reactivity of SF4 have been studied since its first synthesis, the recent progress in the SF4-related chemistry is striking, involving various fields of chemistry. In this Frontier article, recent advances, mainly the last ten years, in syntheses and structures of SF4-related compounds including its cationic and anionic derivatives and adducts with Lewis bases are concisely reviewed. Their uses in fundamental and applied inorganic chemistries are also described.

Pt(II) Derivatives with Rollover-Coordinated 6-substituted 2,2′-bipyridines: Ligands with Multiple Personalities

We report here the synthesis, characterization and behavior of a series of Pt(II) cyclometalated rollover complexes with two substituted bipyridines, 6-ethyl-2,2′-bipyridine (bpy6Et) and 6-methoxy-2,2′-bipyridine (bpy6OMe), in comparison with previously studied 2,2′-bipyridine complexes. The two ligands have similar steric hindrance but different electronic properties. As a result, the reactivity of the two series of complexes follows very different routes. In particular, the new complexes behave differently towards protonation reactions, differences given by substituents and ancillary ligands, added to the presence of several nucleophilic centers. Reaction of complex [Pt(bpy6OMe-H)(PPh3)Me)] with [H3O⋅18-crown-6][BF4] results in a retro-rollover reaction whose final product is the cationic adduct [Pt(bpy6OMe)(PPh3)Me)]+. Surprisingly, only the isomer with the cis-PPh3-OMe geometry is formed; in spite of an expected instability due to steric hindrance, Density-Functional theory (DFT) calculations showed that this isomer is the most stable. This result shows that the cone angle is far from being a real “solid cone” and should lead to a different interpretation of well-known concepts concerning steric bulk of ligands, such as cone angle. Proton affinity values of ligands, neutral complexes and their protonated counterparts were analyzed by means of DFT calculations, allowing a comparison of their properties.

Synthesis of Dinuclear Mo-Fe Hydride Complexes and Catalytic Silylation of N2.

Two transition-metal atoms bridged by hydrides may represent a useful structural motif for N2 activation by molecular complexes and the enzyme active site. In this study, dinuclear MoIV -FeII complexes with bridging hydrides, CpR Mo(PMe3 )(H)(μ-H)3 FeCp* (2 a; CpR =Cp*=C5 Me5 , 2 b; CpR =C5 Me4 H), were synthesized via deprotonation of CpR Mo(PMe3 )H5 (1 a; CpR =Cp*, 1 b; CpR =C5 Me4 H) by Cp*FeN(SiMe3 )2 , and they were characterized by spectroscopy and crystallography. These Mo-Fe complexes reveal the shortest Mo-Fe distances ever reported (2.4005(3) Å for 2 a and 2.3952(3) Å for 2 b), and the Mo-Fe interactions were analyzed by computational studies. Removal of the terminal Mo-H hydride in 2 a-2 b by [Ph3 C]+ in THF led to the formation of cationic THF adducts [CpR Mo(PMe3 )(THF)(μ-H)3 FeCp*]+ (3 a; CpR =Cp*, 3 b; CpR =C5 Me4 H). Further reaction of 3 a with LiPPh2 gave rise to a phosphido-bridged complex Cp*Mo(PMe3 )(μ-H)(μ-PPh2 )FeCp* (4). A series of Mo-Fe complexes were subjected to catalytic silylation of N2 in the presence of Na and Me3 SiCl, furnishing up to 129±20 equiv of N(SiMe3 )3 per molecule of 2 b. Mechanism of the catalytic cycle was analyzed by DFT calculations.

A trigold carbide cation stabilized as a labile pyridine adduct

Auration of trimethylsilyldiazomethane by an (N-heterocyclic carbene)gold alkoxide affords a stable (silyldiazoalkyl)gold complex. The reaction of this species with a gold(I) fluoride, more efficient in the presence of an added gold cation equivalent, results in auration, desilylation, and N2 loss. The putative trigold carbide cation was isolated as its pyridine adduct, a stable N-(triauromethyl)pyridinium ion. Reaction of the cationic pyridine adduct with carbon monoxide breaks the CN bond, forming the stable trigold ketenylidene cation. DFT studies suggest substantial negative charge at the bridging carbon in the methylpyridinium analogue and in two possible intermediates, the trigold carbide cation and the pyridine adduct of a neutral digold carbide.

Occurrence and Degradation Potential of Fluoroalkylsilane Substances as Precursors of Perfluoroalkyl Carboxylic Acids.

Polyfluoroalkylsilanes (PFASis) are a class of artificial chemicals with wide applications in surface coating, which arouse attention due to their hydrophobic/oleophobic properties and potential biological effects. In this study, a robust high-resolution mass spectrometry method through direct injection into a Fourier transform ion cyclotron resonance instrument was established, with the aid of CF2-scaled Kendrick mass defect analysis and isotope fine structure elucidation. The occurrence of 8:2 polyfluoroalkyl trimethoxysilane (8:2 PTrMeOSi) and 8:2 polyfluoroalkyl triethoxysilane (8:2 PTrEtOSi), as well as their cationic adducts, solvent substitutions, and other compound analogues, were identified in commercial antifingerprint liquid products. In the hydroxyl radical-based total oxidizable precursor assay, differential molar yields of products were observed with regard to varied PFASi carbon-chain lengths and terminal groups. The yields of perfluoroalkyl carboxylic acids (PFCAs) from 8:2 PTrMeOSi conversion were the highest (92 ± 9%, n = 3), with the C ( n - 1) perfluoroheptanoic acid (PFHpA, 49 ± 11%, n = 3) as the dominating product. Distinct conversion of 8:2 PTrMeOSi in the simulated solar exposure experiments found that C ( n) perfluorooctanoic acid (PFOA, 0.6 ± 0.04 ‰, n = 3) was predominant, and 8:2 fluorotelomer carboxylic acid (8:2 FTCA, 0.59 ± 0.08‰, n = 3), 8:2 fluorotelomer unsaturated carboxylic acid (8:2 FTUCA, 0.09 ± 0.00‰, n = 3) intermediates were also observed. To our knowledge, this is the first report regarding the occurrence and degradation potential of several fluoroalkylsilane substances as PFCA precursors.

Pentacoordinated, square pyramidal cationic PCP Ni(II) pincer complexes: ELF and QTAIM topological analyses of nickel–triflate interactions

A previous report introduced a new series of cationic nickel(II) complexes ligated by PCP-type pincer ligands featuring a charge-bearing imidazoliophosphine binding moiety and described their catalytic reactivities in hydroamination of nitriles into amidines. Solid-state characterization of the cationic acetonitrile adducts [(R-PIMIOCOP+)Ni(NCMe)(triflate)]+ (R-PIMIOCOP+ = κP,κC,κP-{2-(R2PO),6-(R2PC4H5N2)C6H3}; R = i-Pr, [1]+; Ph, [2]+) carried out in this follow-up study showed a distorted square pyramidal geometry and a Ni–triflate distance that was shorter than the sum of the Ni and O van der Waals radii, features suggestive of an unusual pentacoordination at the Ni(II) center. In contrast, the related aquo adduct [(i-Pr-PIMIOCOP+)Ni(OH2)(triflate)]+, [3]+, displayed a more conventional square planar geometry. Detailed structural comparisons and theoretical analyses conducted on these and related compounds have allowed a thorough examination of the Ni–triflate interactions in this family of complexes. Thus, topological analysis of the electron localization function (ELF) and quantum theory of atoms in molecules (QTAIM) showed that the Ni–triflate interaction is mostly ionic in nature, but has a weak covalence degree. The monosynaptic V(Ni) subvalence basin of nickel is indeed the ELF signature of the covalence degree of the ionic Ni–O bond, which can be quantified by the negative QTAIM energy density at the Ni–O bond critical point and by the absolute value of the ELF covariance 〈σ2(V(O), C(Ni))〉. The ionic character of the Ni–O bond is also reflected in an energy decomposition analysis, showing that this interaction is mostly electrostatic in nature. The computational analyses carried out on this family of complexes provide valuable insight into the character and relative strengths of various Ni–ligand interactions, and allow a number of useful conclusions, including the following: (1) significant Ni–anion interactions at the apical site are observed only with pincer-type ligands featuring at least one cationic imidazoliophosphine binding moiety; (2) these primarily electrostatic Ni–O interactions gain increasing covalence degree when different pincer backbone, co-ligand L, or counter-anions are introduced to enhance the electron deficiency of the Ni(II) center.

Rapid Analysis of Anabolic Steroid Metabolites in Urine by Combining Field Asymmetric Waveform Ion Mobility Spectrometry with Liquid Chromatography and Mass Spectrometry.

The combination of field asymmetric waveform ion mobility spectrometry with liquid chromatography-mass spectrometry (LC-FAIMS-MS) has been developed for the analysis of glucuronide and sulfate metabolites of seven anabolic-androgenic steroids in urine. Separation by FAIMS-MS was investigated in positive ion mode for selected cationic adducts (H+, NH4+, Na+, K+, and Cs+). LC-FAIMS-MS analysis of the doubly sodiated adducts ([M + 2Na - H]+) of isobaric and coeluting steroid metabolites allowed their rapid (8 min) qualitative and quantitative determination in spiked urine using hydrophilic interaction liquid chromatography prior to FAIMS-MS separation, with discrimination >95% achieved between the steroids investigated. A quantitative evaluation of the LC-FAIMS-MS method was performed giving limits of detection in the range 1-6 ng mL-1, limits of quantification in the range 3-20 ng mL-1, with reproducibility (%RSD < 10%; n = 6) and linearity (R2 > 0.99). The LC-FAIMS-MS method demonstrates increases in signal-to-noise ratios for the doubly sodiated steroid metabolites in unspiked urine (>250%) by the reduction of isobaric interferences from the matrix. An alternative or additional tool for identification of the steroid metabolites is based on the observations of different patterns of sodium acetate clusters that are characteristic for each metabolite.

Neutral and Cationic Bis-Chelate Monoorganosilicon(IV) Complexes of 1-Hydroxy-2-pyridinone

A series of spirocyclic monoorganosilicon compounds of the form RSi(OPO)2Cl (R = phenyl (1), p-tolyl (2), benzyl (3), Me (4), tBu (5), thexyl (6); OPO = 1-oxo-2-pyridinone) was synthesized and characterized by 1H, 13C, and 29Si NMR spectroscopy, X-ray crystallography, and elemental analysis. In the solid state, complexes 1–3 are neutral and possess cis-OPO ligands in an octahedral arrangement and complexes 4–6 are cationic and possess effectively trans-OPO ligands in nearly ideal square-pyramidal geometries along the Berry pseudorotation coordinate. In 4–6, chloride dissociation is attributed to the additive effect of multiple intermolecular C–H···Cl interactions in their crystals. In DMSO-d6 solution, compounds 1–6 form cationic hexacoordinate DMSO adducts with trans-OPO ligands, all of which undergo dynamic isomerization with energy barriers of ∼18–19 kcal/mol. Compounds with better leaving groups, (p-tolyl)Si(OPO)2X (X = I (7), X = triflate (8)), exhibit solution NMR spectra identical with those of 2, ...

The Development of Novel Nanodiamond Based MALDI Matrices for the Analysis of Small Organic Pharmaceuticals.

The utility of novel functionalized nanodiamonds (NDs) as matrices for matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) is described herein. MALDI-MS analysis of small organic compounds (<1000 Da) is typically complex because of interferences from numerous cluster ions formed when using conventional matrices. To expand the use of MALDI for the analysis of small molecules, novel matrices were designed by covalently linking conventional matrices (or a lysine moiety) to detonated NDs. Four new functionalized NDs were evaluated for their ionization capabilities using five pharmaceuticals with varying molecular structures. Two ND matrices were able to ionize all tested pharmaceuticals in the negative ion mode, producing the deprotonated ions [M - H](-). Ion intensity for target analytes was generally strong with enhanced signal-to-noise ratios compared with conventional matrices. The negative ion mode is of great importance for biological samples as interference from endogenous compounds is inherently minimized in the negative ion mode. Since the molecular structures of the tested pharmaceuticals did not suggest that negative ion mode would be preferable, this result magnifies the importance of these findings. On the other hand, conventional matrices primarily facilitated the ionization as expected in the positive ion mode, producing either the protonated molecules [M + H](+) or cationic adducts (typically producing complex spectra with numerous adduct peaks). The data presented in this study suggests that these matrices may offer advantages for the analysis of low molecular weight pharmaceuticals/metabolites. Graphical Abstract ᅟ.

Proton Affinities of Cationic Carbone Adducts [AC(PPh3 )2 ](+) (A=Halogen, Hydrogen, Methyl) and Unusual Electronic Structures of the Cations and Dications [AC(H)(PPh3 )2 ](2.).

This work reports the syntheses and the first crystal structures of the cationic carbone adducts [FC(PPh3 )2 ](+) and [BrC(PPh3 )2 ](+) and the protonated dication [FC(H)(PPh3 )2 ](2+) , which are derived from the carbone C(PPh3 )2 . Quantum chemical calculations and bonding analyses were carried out for the series of cations [AC(PPh3 )2 ](+) and dications [AC(H)(PPh3 )2 ](2+) , where A=H, Me, F, Cl, Br, I. The bonding analysis suggests that the cations are best described as phosphane complexes L→(CA)(+) ←L (L=PPh3 ), which are related to the neutral borylene adducts L→(BA)←L (L=cyclic carbene; A=H, aryl) that were recently isolated. The carbone adducts [AC(PPh3 )2 ](+) possess a π electron lone pair at carbon and they can easily be protonated to the dications [AC(H)(PPh3 )2 ](2+) . The calculations of the dications indicate that the molecules are best represented as complexes L→(CHA)(2+) ←L (L=PPh3 ) where a carbene dication is stabilized by the ligands. The central carbon atom in the cations and even in the dications carries a negative partial charge, which is larger than the negative charge at fluorine. There is also the peculiar situation in which the carbon-fluorine bonds in [FC(PPh3 )2 ](+) and [FC(H)(PPh3 )2 ](2+) exhibit the expected polarity with the negative end at fluorine, but the carbon atom has a larger negative charge than fluorine. Given the similarity of carbodiphosphorane C(PPh3 )2 and carbodicarbene C(NHC)2 , we expect that analogous compounds [AC(NHC)2 ](+) and [AC(H)(NHC)2 ](2+) with similar features as [AC(PPh3 )2 ](+) and [AC(H)(PPh3 )2 ](2+) can be isolated.

Zinc(II)-Mediated Carbene Insertion into C-H Bonds in Alkanes.

The cationic zinc adduct {[HB(3,5-(CF3)2Pz)3]Zn(NCMe)2}ClO4 catalyzes the functionalization of tertiary, secondary, and primary C-H bonds of alkanes via carbene insertion. Ethyl diazoacetate serves as the :CHCO2Et carbene precursor. The counteranion, supporting ligand, and coordinating solvents affect the catalytic activity. An in situ generated {[HB(3,5-(CF3)2Pz)3]Zn}(+) species containing a bulkier {B[3,5-(CF3)2C6H3]4}(-) anion gives the best results among the zinc catalysts used.

Charge Effects in PCP Pincer Complexes of Ni(II) bearing Phosphinite and Imidazol(i)ophosphine Coordinating Jaws: From Synthesis to Catalysis through Bonding Analysis.

This contribution reports on a new family of Ni(II) pincer complexes featuring phosphinite and functional imidazolyl arms. The proligands (R) PIMC(H) OP(R') react at room temperature with Ni(II) precursors to give the corresponding complexes [((R) PIMCOP(R') )NiBr], where (R) PIMCOP(R) =κ(P) ,κ(C) ,κ(P) -{2-(R'2 PO),6-(R2 PC3 H2 N2 )C6 H3 }, R=iPr, R'=iPr (3 b, 84 %) or Ph (3 c, 45 %). Selective N-methylation of the imidazole imine moiety in 3 b by MeOTf (OTf=OSO2 CF3 ) gave the corresponding imidazoliophosphine [((iPr) PIMIOCOP(iPr) )NiBr][OTf], 4 b, in 89 % yield ((iPr) PIMIOCOP(iPr) =κ(P) ,κ(C) ,κ(P) -{2-(iPr2 PO),6-(iPr2 PC4 H5 N2 )C6 H3 }). Treating 4 b with NaOEt led to the NHC derivative [(NHCCOP(iPr) )NiBr], 5 b, in 47 % yield (NHCCOP(iPr) =κ(P) ,κ(C) ,κ(C) -{2-(iPr2 PO),6-(C4 H5 N2 )C6 H3 )}). The bromo derivatives 3-5 were then treated with AgOTf in acetonitrile to give the corresponding cationic species [((R) PIMCOP(R) )Ni(MeCN)][OTf] [R=Ph, 6 a (89 %) or iPr, 6 b (90 %)], [((R) PIMIOCOP(R) )Ni(MeCN)][OTf]2 [R=Ph, 7 a (79 %) or iPr, 7 b (88 %)], and [(NHCCOP(R) )Ni(MeCN)][OTf] [R=Ph, 8 a (85 %) or iPr, 8 b (84 %)]. All new complexes have been characterized by NMR and IR spectroscopy, whereas 3 b, 3 c, 5 b, 6 b, and 8 a were also subjected to X-ray diffraction studies. The acetonitrile adducts 6-8 were further studied by using various theoretical analysis tools. In the presence of excess nitrile and amine, the cationic acetonitrile adducts 6-8 catalyze hydroamination of nitriles to give unsymmetrical amidines with catalytic turnover numbers of up to 95.

Characterization of nitrogen mustard formamidopyrimidine adduct formation of bis(2-chloroethyl)ethylamine with calf thymus DNA and a human mammary cancer cell line.

A robust, quantitative ultraperformance liquid chromatography ion trap multistage scanning mass spectrometric (UPLC/MS(3)) method was established to characterize and measure five guanine adducts formed by reaction of the chemotherapeutic nitrogen mustard (NM) bis(2-chloroethyl)ethylamine with calf thymus (CT) DNA. In addition to the known N7-guanine (NM-G) adduct and its cross-link (G-NM-G), the ring-opened formamidopyrimidine (FapyG) monoadduct (NM-FapyG) and cross-links in which one (FapyG-NM-G) or both (FapyG-NM-FapyG) guanines underwent ring-opening to FapyG units were identified. Authentic standards of all adducts were synthesized and characterized by NMR and mass spectrometry. These adducts were quantified in CT DNA treated with NM (1 μM) as their deglycosylated bases. A two-stage neutral thermal hydrolysis was developed to mitigate the artifactual formation of ring-opened FapyG adducts involving hydrolysis of the cationic adduct at 37 °C, followed by hydrolysis of the FapyG adducts at 95 °C. The limit of quantification values ranged between 0.3 and 1.6 adducts per 10(7) DNA bases when the equivalent of 5 μg of DNA hydrolysate was assayed on column. The principal adduct formed was the G-NM-G cross-link, followed by the NM-G monoadduct; the FapyG-NM-G cross-link adduct; and the FapyG-NM-FapyG was below the limit of detection. The NM-FapyG adducts were formed in CT DNA at a level ∼20% that of the NM-G adduct. NM-FapyG has not been previously quanitified, and the FapyG-NM-G and FapyG-NM-FapyG adducts have not been previously characterized. Our validated analytical method was then applied to measure DNA adduct formation in the MDA-MB-231 mammary tumor cell line exposed to NM (100 μM) for 24 h. The major adduct formed was NM-G (970 adducts per 10(7) bases), followed by G-NM-G (240 adducts per 10(7) bases), NM-FapyG (180 adducts per 10(7) bases), and, last, the FapyG-NM-G cross-link adduct (6.0 adducts per 10(7) bases). These lesions are expected to contribute to NM-mediated toxicity and genotoxicity in vivo.

POCOP-Type Pincer Complexes of Nickel: Synthesis, Characterization, and Ligand Exchange Reactivities of New Cationic Acetonitrile Adducts

This report describes the synthesis, characterization, and ligand exchange studies of a family of cationic acetonitrile adducts of nickel featuring resorcinol-based, pincer-type POCOP ligands. The compounds [(R-POCOPR′)Ni(NCMe)][OSO2CF3] (R-POCOPR′ = 2,6-(R′2PO)2(RnC6H3–n); R′ = i-Pr: R = H (1), p-Me (2), p-OMe (3), p-CO2Me (4), p-Br (5), m,m-t-Bu2 (6), m-OMe (7), m-CO2Me (8); R′ = t-Bu: R = H (9), p-CO2Me (10)) were prepared in 80–93% yields by reacting the corresponding charge-neutral bromo derivatives with Ag(OSO2CF3) in acetonitrile. The impact of the R- and R′-substituents on electronics and structures of 1–10 have been probed by NMR, UV–vis, and IR spectra, X-ray crystallography, and cyclic voltammetry measurements. The observed ν(C≡N) values were found to increase with the increasing electron-withdrawing nature of R, i.e., in the order 7 < 3 ∼ 2 ∼ 6 < 1 < 5 ∼ 8 < 4 and 9 < 10. This trend is consistent with the anticipation that enhanced electrophilicity of the nickel center should result in an incr...

Statistical modeling of the reactions Fe(+) + N2O → FeO(+) + N2 and FeO(+) + CO → Fe(+) + CO2.

The rates of the reactions Fe(+) + N2O → FeO(+) + N2 and FeO(+) + CO → Fe(+) + CO2 are modeled by statistical rate theory accounting for energy- and angular momentum-specific rate constants for formation of the primary and secondary cationic adducts and their backward and forward reactions. The reactions are both suggested to proceed on sextet and quartet potential energy surfaces with efficient, but probably not complete, equilibration by spin-inversion of the populations of the sextet and quartet adducts. The influence of spin-inversion on the overall reaction rate is investigated. The differences of the two reaction rates mostly are due to different numbers of entrance states (atom + linear rotor or linear rotor + linear rotor, respectively). The reaction Fe(+) + N2O was studied either with (6)Fe(+) or with (4)Fe(+) reactants. Differences in the rate constants of (6)Fe(+) and (4)Fe(+) reacting with N2O are attributed to different contributions from electronically excited potential energy surfaces, such as they originate from the open-electronic shell reactants.