Syntheses,crystal structures,and electrochemistry of novel Fe2SN and FeSN carbonyl complexes with pendant bases

Reactions of Fe₂(CO)₉ with thioacylhydrazones ArCH=NNHCSPh in THF afford Fe₂(CO)₆(μ-κ²S:κ²N-PhC(S)=NNCHArCHArN(CHAr)N=CSPh) (1, Ar?=?C₆H₅; 3, Ar?=?4-CH₃C₆H₄) and Fe(CO)₃(κ²S:N-PhC(=S)NHNCHArCHArN(CHAr)N=CSPh) (2, Ar?=?C₆H₅; 4, Ar?=?4-CH₃C₆H₄). They have been characterized by elemental analyses, IR, ¹H NMR, and ¹³C NMR and structurally determined by X-ray crystallography. Electrochemical studies reveal that when using HOAc as a proton source, they exhibit high catalytic H₂-production.     

A Comparative PMR study of Exchange reactions in organo- Mercury, -TIN and -LEAD derivatives of some thiols

Metal—proton and metal—metal exchange reactions have been studied by PMR for thiophenol, 2-methylthiophenol, 2,6-dimethylthiophenol, benzyl mercaptan and their C₆H₅HG, (C₆H₅)₃Sn and (C₆H₅)₃Pb derivatives in chlorobenzene and pyridine solutions. In chlorobenzene the metal—metal exchange has been found to proceed in many cases at a greater rate than the metal—proton type, the exchange mobility of hydrogen and organometallic groups in chlorobenzene increasing in the order (C₆H₅)₃Sn<H<(C₆H₅)₃Pb<C₆H₅Hg. In the case of the (C₆H₅)₃Sn and (C₆H₅)₃Pb groups, pyridine accelerates the metal—proton exchange to a greater extent than the metal—metal exchange.The influence of various factors on the exchange reactions has been studied Analysis of the experimental findings and literature data has led to the conclusion that most probably the mechanism of the exchange reactions involves an associative pathway, the ease of exchange being mainly determined by the ability of the migrating group to form a cyclic transition state with delocalized bonds. The data on the exchange equilibria of the organometallic derivatives of 2-methylthiophenol and 2,6-dimethylthiophenol with thiophenol and its derivatives demonstrate that the C₆H₅HgS, (C₆H₅)₃SnS and (C₆H₅)₃PbS groups have equal steric requirements when involved in non-bonded interactions with o-methyl substituents.     

A sandwich-type POM containing mixed cations: synthesis,thermal performance and proton-conducting properties

A new sandwich-type polyoxometalate, Na₅H[N(CH₃)₄]₂[Co(C₃N₂H₄)₂(H₂O)₄][Co₄(H₂O)₂(PW₉O₃₄)₂]·21H₂O (1), has been synthesized. 1 is composed of a Weakley-type polyanion, [Co₄₍H₂O)₂(PW₉O₃₄)₂]^10?, four kinds of cations (five Na⁺, two [N(CH₃)₄]⁺, one [Co(C₃N₂H₄)₂(H₂O)₄]²⁺, and one H⁺), and 21 crystalline H₂O molecules. The surface oxygen of the polyanion in 1, the crystalline water, and coordinated water molecules make an extended 3-D hydrogen-bonding network. Alternating current (AC) impedance experiments of 1 reveal good proton conductivity for 1 of 5.03 × 10^??4 S cm^?1 at 25 °C under 98% relative humidity (RH). Activation energy of 1 calculated from Arrhenius plots is 0.358 eV, indicating Grotthuss mechanism is dominant in the proton transfer. Thermal decomposition behavior of 1 was examined by thermogravimetry/mass spectrometry (TG/MS) measurements.     

A theoretical study of protonation of triatomic silicon–carbon compounds

Ab initio molecular orbital methods are employed to study the low-lying states of C₃H⁺, SiC₂H⁺, Si₂CH⁺, and Si₃H⁺. Special attention is paid to a comparative study between C₃H⁺ and Si₃H⁺. In both cases a ³B₂ state is found to lie the lowest at the HF level, although inclusion of correlation effects favor a linear structure (¹Σ⁺ state) for C₃H⁺, which lies 25 kcal/mol below the ³B₂ state at the MP 4 level, and a bent structure (¹A′ state) for Si₃H⁺, which lies just 2 kcal/mol below the ³B₂ state. The proton affinities of C₃, SiC₂, Si₂C, and Si₃ are estimated at different levels of theory. Both protonation at carbon and silicon atoms are considered for SiC₂ and Si₂C. It is found that C₃ comparatively has a low proton affinity. On the other hand, Si₃ has a relatively high proton affinity compared with the protonation at silicon atom for both SiC₂ and Si₂C. These results are discussed on the basis of electronic structure arguments.     

Characterization of 8-Deuterium Substituted Proton Pump Inhibitors by Nuclear Magnetic Resonance and Electrospray Ionization Mass Spectrometry

Nuclear magnetic resonance (NMR) was employed to characterize the hydrogen-deuterium exchange for the proton pump inhibitors pantoprazole sodium, esomeprazole sodium, rabeprazole sodium, lansoprazole, and ilaprazole in methanol-d₄. The results showed that the ¹H and ¹³C signals of 8-CH₂ (labeled as H_8a, H_8b, and C₈) next to the sulfinyl (S?O) group of the proton pump inhibitors decreased significantly. Electrospray ionization mass spectrometry showed the presence of deuterated products. Basing on the NMR data, H_8a and H_8b of proton pump inhibitors were more active for the hydrogen-deuterium exchange. The most significant parameter governing the exchange was the salt-formation of the benzimidazole group. Therefore, the influence of salt-formation on hydrogen-deuterium exchange was characterized for ilaprazole; replacement of NH by N–Na on the benzimidazole group accelerated the exchange process. Tandem mass spectrometry showed that CH?S–OH was formed by tautomerism involving sulfinyl and CH₂ groups in methanol-d_4.     

Does ionized diacetylene have a positive proton affinity?

Singly and doubly charged C₄H₃^+/2+ ions generated upon electron ionization (EI) of the neutral precursors 1,3-butadiene, benzene, and exo-methylene cyclopropane, respectively, are examined by sector-field mass-spectrometry. Charge stripping of the mass-selected monocations affords the corresponding dications and charge exchange of the C₄H₃²⁺ dications allows for the reverse redox process. Refined analysis and additional MS/MS studies suggest that the monocations are mixtures of isomeric ions formed upon ionization, whereas only a single type of dication seems to be formed. As an average of energy-resolved measurements, a vertical ionization energy of IE_v(C₄H₃⁺)=16.5±0.4 eV is derived. In addition to the experimental work, density functional theory is used for a computational exploration of the mono- and dicationic species. The best theoretical estimates are IE_a(C₄H₃⁺)=16.33 eV and IE_v(C₄H₃⁺)=16.49 eV for the most stable isomer H₂C=C---CCH⁺. Combination of the experimental and theoretical findings leads to the conclusion that the diacetylene cation C₄H₂⁺ has indeed a positive proton affinity of PA(C₄H₂⁺)=1.50±0.42 eV.     

Structure and fragmentation of [C6H13O]+ ions formed by chemical ionization

The structure and fragmentation of eight [C₆H₁₃O] ⁺ ions formed by protonation of C₆H₁₂O carbonyl compounds in the gas phase have been investigated using isotopic labeling and metastable ion studies to investigate the fragmentation reactions and collisional dissociation studies to probe ion structures. Protonated 3-methyl-2-pentanone and protonated 2-methyl-3-pentanone readily-interconvert by pinacolic-retro-pinacolic rearrangements; the remaining six ions represent stable ion structures, although in many cases fragmentation is preceded by pinacolic-type rearrangements. Unimolecular (metastable ion) fragmentation of the [C₆H₁₃O] ⁺ species occurs by elimination of H₂O, C₃H₆, C₄H₈ and C₂H₄O. The last three elimination reactions appear to occur through the intermediacy of a proton-bound complex of a carbonyl compound and an olefin, with the proton residing with the species of higher proton affinity on decomposition of the complex.     

Rational Design of Microporous MOFs with Anionic Boron Cluster Functionality and Cooperative Dihydrogen Binding Sites for Highly Selective Capture of Acetylene

Separation of acetylene (C₂H₂) from carbon dioxide (CO₂) or ethylene (C₂H₄) is important in industry but limited by the low capacity and selectivity owing to their similar molecular sizes and physical properties. Herein, we report two novel dodecaborate‐hybrid metal–organic frameworks, MB₁₂H₁₂(dpb)₂ (termed as BSF‐3 and BSF‐3‐Co for M=Cu and Co), for highly selective capture of C₂H₂. The high C₂H₂ capacity and remarkable C₂H₂/CO₂ selectivity resulted from the unique anionic boron cluster functionality as well as the suitable pore size with cooperative proton‐hydride dihydrogen bonding sites (B?H^δ????H^δ+?C≡C?H^δ+???H^δ??B). This new type of C₂H₂‐specific functional sites represents a fresh paradigm distinct from those in previous leading materials based on open metal sites, strong electrostatics, or hydrogen bonding.     

New homo- and heteroleptic derivatives of trivalent ytterbium containing radical anion 1,4-diazadiene ligands. Synthesis, properties, and crystal structures of the complexes (C9H7)2Yb[2-MeC6H4NC(Me)C(Me)NC6H4Me-2] and [PhNC(Ph)C(Ph)NPh]3Yb

The interaction of the ytterbium bis(indenyl) complex (C₉H₇)₂Yb^II(THF)₂ (1) with the 1,4-diazabutadiene 2-MeC₆H₄N=C(Me)-C(Me)=NC₆H₄Me-2 (^MeDAD) is accompanied by the oxidation of the metal atom to the trivalent state and results in a paramagnetic compound of the metallocene type (C₉H₇)₂Yb^III(^MeDAD^−·) (3) containing the radical anion of 1,4-diazabutadiene. The structure of the complex 3 was determined by X-ray diffraction analysis. The reactions of the bis(indenyl) (1) and bis(fluorenyl) (C₁₃H₉)₂Yb^II(THF)₂ (2) derivatives of divalent ytterbium with the 1,4-diazabutadiene PhN=C(Ph)-C(Ph)=NPh (^PhDAD) (with the molar ratio of the reactants 1:2) proceed with a complete cleavage of the bonds Yb-C and the oxidation of the ytterbium atom to the trivalent state and result in a homoligand complex (^PhDAD^−·)₃Yb (6) containing three radical anion 1,4-diazadiene ligands. Complex 6 was also obtained by an exchange reaction of YbCl₃ with ^PhDAD^−·K⁺ (1: 3) in THF. Complex 6 was characterized by X-ray diffraction analysis.     

Fluorescent aluminum chelate complexes as modified precursors for nano-structured alumina

A series of new mononuclear heteroleptic derivatives of aluminum(III), {[(CH₃COCHCOCH₃)AlL] (1 and 4)}, {[(C₆H₅COCHCOC₆H₅)AlL] (2, 5, and 7)}, and {[(C₉H₆NO)AlL] (3 and 6)}, have been synthesized by reacting Al(OPrⁱ)₃ with tridentate Schiff base H₂L^x (H₂L¹ = C₁₃H₁₀BrNO₂; H₂L² = C₁₄H₁₃NO₃; H₂L³ = C₁₇H₁₃NO₂) and β-diketone/8-hydroxyquinoline (β-diketone = acetylacetone/dibenzoylmethane) in 1?:?1?:?1 stoichiometry using anhydrous benzene and ethanol. All the complexes were characterized by elemental analysis, FTIR, and NMR (¹H and ¹³C) spectral studies. Molecular structures obtained from single-crystal XRD of aqua 1 (1a) and DMSO coordinated 2 (2a) authenticate their existence. Further, nanostructured α-alumina was synthesized from 1 by well-established sol–gel method and was characterized by powder XRD, TEM, and EDX analyses.     

Combined Intrinsic and Extrinsic Proton Conduction in Robust Covalent Organic Frameworks for Hydrogen Fuel Cell Applications

Developing new materials for the fabrication of proton exchange membranes (PEMs) for fuel cells is of great significance. Herein, a series of highly crystalline, porous, and stable new covalent organic frameworks (COFs) have been developed by a stepwise synthesis strategy. The synthesized COFs exhibit high hydrophilicity and excellent stability in strong acid or base (e.g., 12 m NaOH or HCl) and boiling water. These features make them ideal platforms for proton conduction applications. Upon loading with H₃PO₄, the COFs (H₃PO₄@COFs) realize an ultrahigh proton conductivity of 1.13×10^?1 S cm^?1, the highest among all COF materials, and maintain high proton conductivity across a wide relative humidity (40–100 %) and temperature range (20–80 °C). Furthermore, membrane electrode assemblies were fabricated using H₃PO₄@COFs as the solid electrolyte membrane for proton exchange resulting in a maximum power density of 81 mW cm^?2 and a maximum current density of 456 mA cm^?2, which exceeds all previously reported COF materials.     

Synthesis and structures of fulvene-bridged diruthenium complexes

Three diruthenium carbonyl complexes, namely (η ³:η ⁵-C₅H₄C(CH₂)₂)Ru₂(CO)₅ (1), (η ³:η ⁵-C₅H₄C(CHCH₂)(C₂H₅))Ru₂(CO)₅ (2), and (η ¹:η ⁵-C₅H₄C₅H₈)Ru₂(CO)₆ (3), were obtained from the reactions of C₅H₄C(Me)₂, C₅H₄C(Et)₂, and C₅H₄C(CH₂)₄, respectively, with Ru₃(CO)₁₂ in refluxing xylene. The complexes were characterized by elemental analysis, IR and ¹H NMR spectra. Single-crystal X-ray diffraction analysis for complexes 1 and 2 revealed that the fulvene ligands bridge two ruthenium atoms in η ³:η ⁵ fashion.     

New pharmaceutical salts containing pyridoxine

Two mixed crystals were obtained by crystallizing the active pharmaceutical ingredient pyridoxine [systematic name: 4,5‐bis(hydroxymethyl)‐2‐methylpyridin‐3‐ol, PN] with (E )‐3‐(4‐hydroxy‐3‐methoxyphenyl)prop‐2‐enoic acid (ferulic acid) and 4‐hydroxy‐3,5‐dimethoxybenzoic acid (syringic acid). PN and the coformers crystallize in the form of pharmaceutical salts in a 1:1 stoichiometric ratio, namely 3‐hydroxy‐4,5‐bis(hydroxymethyl)‐2‐methylpyridin‐1‐ium (E )‐3‐(4‐hydroxy‐3‐methoxyphenyl)prop‐2‐enoate, C₈H₁₂NO₃⁺·C₉H₉O₅⁻, and 3‐hydroxy‐4,5‐bis(hydroxymethyl)‐2‐methylpyridin‐1‐ium 4‐hydroxy‐3,5‐dimethoxybenzoate monohydrate, C₈H₁₂NO₃⁺·C₁₀H₁₁O₅⁻·H₂O, the proton exchange between PN and the acidic partner being supported by the differences of the pK _a values of the two components and by the C—O bond lengths of the carboxylate groups. Besides complex hydrogen‐bonding networks, π–π interactions between aromatic moieties have been found to be important for the packing architecture in both crystals. Hirshfeld surface analysis was used to explore the intermolecular interactions in detail and compare them with the interactions found in similar pyridoxine/carboxylic acid salts.     

Metastable ions in chemical ionization

The ion [C₃H₅]⁺ generated in a chemical ionization source by a variety of methods, including protonation and charge exchange, exhibits a metastable peak for H₂ loss which is two orders of magnitude weaker than that formed in an electron impact source. The stable [C₃H₅]⁺ ions generated by electron impact and chemical ionization undergo collision-induced dissociation to a comparable extent, both losing H₂ by only one of the two competitive mechanisms observed for metastable ions. In contrast to the behavior of [C₃H₅]⁺, the molecular ions of p-substituted nitrobenzene, generated by charge exchange at high source pressure, yield composite metastable peaks for NO loss which are very similar in shape and intensity to those generated by electron impact. The contrasting behavior of the metastable ions extracted from high pressure ion sources in the two systems may be due to differences in the efficiencies of quenching of the ionic states responsible for fragmentation as metastable ions. It is noteworthy that the NO loss reactions require considerably lower activation energies than does the H₂ loss reaction.     

Synthesis,structural characterization,and in vitro antimicrobial properties of salicylate and pyrazoline complexes of bismuth(III)

Displacement reactions of dichlorobismuth(III)pyrazolinates with oxygen donors such as sodium salicylate and acetate in 1?:?1 and 1?:?2 molar ratio in refluxing anhydrous benzene yields (C₁₂H₁₅N₂OX)Bi(C₆H₄O₃), (CH₃COO)BiCl(C₁₅H₁₂N₂OX), and (CH₃COO)₂Bi(C₁₅H₁₂N₂OX) [C₁₂H₁₅N₂OX?=?3(2′-hydroxyphenyl)-5-(4-X-substituted phenyl) pyrazoline X?=?H in 1,5,9, CH₃ in 2,6,10, OCH₃ in 3,7,11, and Cl in 4,8,12, respectively, (C₆H₄O₃)?=?salicylate and (CH₃COO)?=?acetate]. Newly synthesized derivatives are brown solids, soluble in organic solvents like benzene, chloroform, and acetone. The compounds have been characterized by elemental analyses (C, H, N, Cl, and Bi), molecular weight measurements, and spectral (IR, ¹H NMR, ¹³C NMR) studies. The (C₁₂H₁₅N₂OX) and (C₆H₄O₃) are bidentate while (CH₃COO) is monodentate to bismuth(III), leading to a distorted trigonal bipyramidal structure. The complexes were screened against different bacteria and fungi showing potential antibacterial and antifungal activities.     

Syntheses,crystal structures,and magnetic properties of a series of Fe2Ln complexes

A family of phenoxo-bridged heterometallic Schiff base trinuclear complexes, [Fe₂LnL₂(C₃H₇COO)(H₂O)]·CH₃OH·CH₃CN·H₂O (Ln = Sm, 1; Gd, 2; Tb, 3; Dy, 4) is reported. Those complexes were afforded by “one-pot” reaction of a polydentate Schiff base ligand 2-hydroxy-3-methoxy-phenylsalicylaldimine (H₂L) with Fe(NO₃)₃·9H₂O, Ln(NO₃)₃·6H₂O and sodium butyrate (C₃H₇COONa) in a mixture of methanol and acetonitrile in the presence of triethylamine as a base. Single-crystal X-ray diffraction analysis reveals that the structures of the four complexes are isomorphic. In each complex, two anionic [FeL₂]^? units coordinate to the central lanthanide ion as a tetradentate ligand using its four phenoxo oxygens, forming a two-blade propeller-like molecular shape. Magnetic properties of 1–4 were investigated using variable temperature magnetic susceptibility, and weak ferromagnetic exchange between the Fe^III and Ln^III ions has been established for the Gd derivative. The Tb and Dy complexes show no evidence of slow relaxation behavior above 2.0 K.     

Interfacial Properties of Aqueous Nonionic Fluorocarbon Surfactant Solutions

The equilibrium, dynamic surface tensions, and surface dilatational elasticity of aqueous solutions of nonionic fluorocarbon surfactant are reported. The critical micellar concentration, CMC (0.023 mM) and equilibrium surface tension (24.6 m N . m^?1) at CMC were measured by Wilhelmy plate method for aqueous solution of C₈F₁₇SO₂N(C₃H₇)(C₂H₄O)_nH (n=20), abbreviated as EF122A. The surface tension decay is slower for C₈F₁₇SO₂N(C₃H₇)(C₂H₄O)_nH (n=10) system, abbreviated as EF122B compared to the EF122A system over short time region, which indicates the slow transport of the surfactant molecules to the surface. The relaxation time for surface tension decay is estimated by fitting a series of exponentials to the dynamic surface tension data and it decreases with temperature for EF122A. Slow exchange of monomers between bulk and interface is reflected in the high elasticity value of the air‐liquid interface for EF122B compared with EF122A within measured frequency window (0.125–1.25 Hz).     

超临界条件下离子液体催化苯与丙烯烷基化的反应机理研究

用FT-IR和¹H NMR分析KOH无水乙醇溶液滴定前后的盐酸三乙胺无水乙醇溶液, 发现(C₂H₅)₃NHCl中的H具有显著的质子酸性, 且在滴定过程中有KCl生成, 滴定后的¹H NMR谱中δ 7.3处的谱峰完全消失. 将合成的(C₂H₅)₃NHCl/AlCl₃离子液体脱水, 在超临界条件下催化全氘代苯与丙烯的烷基化. 用同位素取代法, 研究了反应机理. 结果表明, 脱水后的离子液体仍然可以催化烷基化反应, 液体产物的GC-MS分析结果支持正碳离子机理. 对比反应前后离子液体的¹H NMR谱图发现, 反应后离子液体中盐酸三乙胺中与N相连H的谱峰强度较反应前降低了80.12%, 可能是引发反应消耗了这部分H.     

Coordination diversity in palladium(II)-picolinamide ligand complexes: structural and quantum chemical studies

The separation of different metal ions can be successfully accomplished by using picolinamide-based ligands. We herein report the first X-ray structure of picolinamide-based ligands of the type C₅H₄NCONR₂ (where R=ⁱC₃H₇ (L1) and ⁱC₄H₉ (L2)) and C₅H₄NCONHR (R=^tC₄H₉ (L3)) with palladium(II) ion. We have synthesized and characterized the structures of two palladium complexes, [PdCl₂(L1)₂] (1) and [PdCl₂L3] (3). In 1, ligand L1 forms a 2?:?1 complex with palladium(II) chloride, whereas in 3, the ligand L3 forms a 1?:?1 complex. Further, in 1, the ligand L1 acts as a monodentate ligand and is bound only through pyridyl-N atom, whereas in 3, the ligand L3 acts as a bidentate chelating ligand and is bound through both the pyridyl-N and amido-O atoms to the Pd(II) center. Electronic structure calculations are carried out to understand the experimental coordination diversity in the Pd complexes. Our calculations clearly suggest that a combination of steric hindrance of the ligand and the electronic effect of metal ions may modulate the coordination preferences.     

Disruptive influence of the host cage C60 on the guest He–H+ bond and bonding in H3+

Although a helium atom prefers to stay at the centre of a fullerene (C₆₀) cage and a proton binds with one of the carbon atoms from inside, DFT(MN15)/cc-pVTZ and DLPNO-MP2/def2-TZVP calculations show that the helium atom and the proton in HeH⁺ prefer to stay away from the centre of the cage, weakening the He–H⁺ covalent bond considerably. Both the helium atom and the proton exhibit noncovalent interactions with the carbon atoms of two pentagons at the opposite ends of the fullerene cage. Our calculations also show that a linear arrangement of H₃⁺ (inside C₆₀), pointing towards the centres of two pentagons opposite to each other, with the proton breaking away from H_2, is energetically more favored over the equilateral triangle geometry of free H₃⁺.