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1.
The X‐ray crystal structures of the polyfluorinated complexes [5,5′‐bis(HCF 2CF 2CF 2CF 2CH 2OCH 2)‐2,2′‐bpy]MI 2 ( 55‐8F‐PtI 2 and 55‐8F‐PdI 2 where M = Pt and Pd, respectively) were obtained. These two structures are found to show not only two different types of intramolecular, six‐membered cyclic C–H···F–C interactions (F 2C–H···F–C and HC–H···F–C) as important structural features but also alternating fluorinated and non‐fluorinated layers. The F 2C–H···F–C interactions, which are close to the metal core, are much better structurally characterized in this type of complexes with fluorous ponytails at the 5,5′ positions than those previously reported at the 4,4′ positions. The molecular planes of (bpy)MI 2 are extended by self‐matching, using two C–H···I hydrogen bonds and one C–H···F–C blue‐shifting hydrogen bond. The F 2C–H···F–C hydrogen bonds interact at the supramolecular level such that one polyfluorinated ponytail of the title compounds is transoid without an intramolecular C–H···F–C interaction, while the other polyfluorinated ponytail is cisoid with an intramolecular C–H···F–C interaction. Why one ponytail is cisoidal while the other is transoidal will be explained. Furthermore, the second type of C–H···F–C interactions involving the methylene H atom has been identified for the first time. In addition, these two metal structures are studied by density functional theory (DFT). 相似文献
2.
In this study, four ferrocenyl indenyl derivatives, C 9H 7–C≡C–Fc ( 1), C 9H 7–C≡C–Ph–Fc ( 2), C 9H 7–C≡C–Ph–C≡C–Fc ( 3), and C 9H 7–Ph–C≡C–Fc ( 4) (where C 9H 7=indenyl; Fc=C 5H 5FeC 5H 4; Ph=C 6H 5), have been synthesized by Sonogashira and Suzuki cross-coupling reactions and characterized by elemental analysis, and FT-IR, 1H, 13C-NMR, and MS spectroscopic methods, respectively. The molecular structures of 1, 2, and 4 were determined by X-ray single crystal diffraction. Two molecules appeared in the crystal structure of 4, and they interact through an intermolecular hydrogen bond. The electrochemical redox potential differences in 1–4 were investigated using cyclic voltammetry and calculations. 相似文献
3.
The reaction dynamics for C–Br dissociation within BrH 2C–C≡CH (ads) adsorbed on an Ag(111) surface has been investigated by combining density functional theory-based molecular dynamics simulations with short-time Fourier transform (STFT) analysis of the dipole moment autocorrelation function. Two possible reaction pathways for C–Br scission within BrH 2C–C≡CH (ads) have been proposed on the basis of different initial structural models. Firstly, the initial perpendicular orientation of adsorbed BrH 2C–C≡CH (ads) with a stronger C–Br bond will undergo dynamic rotation leading to the final parallel orientation of BrH 2C–C≡CH (ads) to cause the C–Br scission, namely, an indirect dissociation pathway. Secondly, the initial parallel orientation of adsorbed BrH 2C–C≡C (ads) with a weaker C–Br bond will directly cause the C–Br scission within BrH 2C–C≡CH (ads), namely, a direct dissociation pathway. To further investigate the evolution of different vibrational modes of BrH 2C–C≡CH (ads) along these two reaction pathways, the STFT analysis is performed to illustrate that the infrared (IR) active peaks of BrH 2C–C≡CH (ads) such as vCH 2 [2956 cm ?1(s) and 3020 cm ?1(as)], v≡CH (3320 cm ?1) and vC≡C (2150 cm ?1) gradually vanish as the rupture of C–Br bond occurs and then the resulting IR active peaks such as C=C=C (1812 cm ?1), ω-CH 2 (780 cm ?1) and δ-CH (894 cm ?1) appear due to the formation of H 2C=C=CH (ads) which are in a good agreement with experimental reflection adsorption infrared spectrum (RAIRS) at temperatures of 110 and 200 K, respectively. Finally, the total energy profiles indicate that the reaction barriers for the scission of C–Br within BrH 2C–C≡CH (ads) along both direct and indirect dissociation pathways are very close due to a similar rupture of C–Br bond leading to a similar transition state. 相似文献
4.
Nanoclusters of Pt, Pt–Rh, Pt–SnO 2 and Pt–Rh–SnO 2 were successfully synthesized by polyol method and deposited on high-area carbon. HRTEM and XRD analysis revealed two phases in the ternary Pt–Rh–SnO 2/C catalyst: solid solution of Rh in Pt and SnO 2. The activity of Pt–Rh–SnO 2/C for ethanol oxidation was found to be much higher than Pt/C and Pt–Rh/C and also superior to Pt–SnO 2/C. Quasi steady-state measurements at various temperatures (30–60 °C), ethanol concentrations (0.01–1 M) and H 2SO 4 concentrations (0.02–0.5 M) showed that Pt–Rh–SnO 2/C is about 20 times more active than Pt/C in the potential range of interest for the fuel cell application. 相似文献
5.
Experimental studies on diesel soot oxidation under a wide range of conditions relevant for modern diesel engine exhaust and continuously regenerating particle trap were performed. Hence, reactivity tests were carried out in a fixed bed reactor for various temperatures and different concentrations of oxygen, NO 2 and water (300–600 °C, 0–10% O 2, 0–600 ppm NO 2, 0–10% H 2O). The soot oxidation rate was determined by measuring the concentration of CO and CO 2 product gases. The parametric study shows that the overall oxidation process can be described by three parallel reactions: a direct C–NO 2 reaction, a direct C–O 2 reaction and a cooperative C–NO 2–O 2 reaction. C–NO 2 and C–NO 2–O 2 are the main reactions for soot oxidation between 300 and 450 °C. Water vapour acts as a catalyst on the direct C–NO 2 reaction. This catalytic effect decreases with the increase of temperature until 450 °C. Above 450 °C, the direct C–O 2 reaction contributes to the global soot oxidation rate. Water vapour has also a catalytic effect on the direct C–O 2 reaction between 450 °C and 600 °C. Above 600 °C, the direct C–O 2 reaction is the only main reaction for soot oxidation. Taking into account the established reaction mechanism, a one-dimensional model of soot oxidation was proposed. The roles of NO 2, O 2 and H 2O were considered and the kinetic constants were obtained. The suggested kinetic model may be useful for simulating the behaviour of a diesel particulate filter system during the regeneration process. 相似文献
6.
Ab initio calculations were used to analyze the interaction of C 4B 2H 6 with HF and LiH molecules at the mp2/6-311++g(2d,2p) computational level. Interaction of C 4B 2H 6 with HF results to H–F···H–C and C–B···H–F, C–C···H–F hydrogen bond as well as B–H···H–F dihydrogen bond complexes. Also interaction of C 4B 2H 6 with LiH results to B–C···LiH, C–C···LiH and B–H···LiH lithium bond as well as C–H···H–Li dihydrogen complexes. In the both cases, complexes involving interaction of HF or LiH with peripheral B–C and C–C bonds of the C 4B 2H 6 backbone have greater stabilities. The structures of complexes have been analyzed using AIM and NBO methodologies. 相似文献
7.
Palladium–catalyzed polycondensation between 2,5–diiodo–3–hexylthiophene I–Th(Hex)–I with mixtures of p–diethynylbenzene HCC—Ph—CCH and α,ω–diethynylalkane HCC(CH 2) lCCH (l = 3 or 8) gives poly(aryleneethynylene) PAE–type copolymers [CC(CH 2) lCC—Th(Hex)] m[CC—Ph—CC—Th(Hex)] n containing the methylene unit. The copolymers have a molecular weight ( Mn) of about 1.2 × 10 4 as determined by GPC (polystyrene standard) and are considered to possess essentially a random sequences in view of the —CC(CH 2) lCC— and —CC—Ph—CC— units as judged from their UV–visible spectra. By the incorporation of the (CH 2) l unit, the λ max position of the corresponding PAE homopolymer [CC—Ph—CC—Th(Hex)] n is shifted to a shorter wavelength. However, the copolymers give rise to a photoluminescence PL peak essentially agreeing with a PL peak of the homopolymer, suggesting occurrence of energy transfer in the copolymer. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2201–2207, 1998 相似文献
8.
The systems LaP/P and CeP/P were investigated. Polyphosphide phases with the compositions LaP 1.6–2.5 (A), LaP 3.5–5.3(B), LaP 5.8–9.0(C) and LaP 6.5–8.9(D), respectively, as well as CeP 1.7–2.4 (A′), CeP 3.5–6.5(B) CeP 6.5–9.0(C) and were found. The phases B and C of lanthanum and cerium are isotypic, but not the phases A and A′. The phases C and D of lanthanum are different modifications with approximately equal homogenity ranges. 相似文献
9.
The electrochemical reduction of oxygen on binary Pt–Ru alloy deposited onto microporous–mesoporous carbon support was studied in 0.5 M H 2SO 4 solution using cyclic voltammetry, rotating disk electrode (RDE), and impedance method. The microporous–mesoporous carbon support C(Mo 2C) with specific surface area of 1,990 m 2?g ?1 was prepared from Mo 2C at 600 °C using the chlorination method. Analysis of X-ray diffraction, photoelectron spectroscopy, and high-resolution transmission electron microscopy data confirms that the Pt–Ru alloy has been formed and the atomic fraction of Ru in the alloy was ~0.5. High cathodic oxygen reduction current densities (?160 A?m ?2 at 3,000 rev?min ?1) have been measured by the RDE method. The O 2 diffusion constant (1.9?±?0.3?×?10 ?5?cm 2?s ?1) and the number of electrons transferred per electroreduction of one O 2 molecule (~4), calculated from the Levich and Koutecky–Levich plots, are in agreement with literature data. Similarly to the Ru/RuO 2 system in H 2SO 4 aqueous solution, nearly capacitive behavior was observed from impedance data at very low ac frequencies, explained by slow electrical double-layer formation limited by the adsorption of reaction intermediates and products into microporous–mesoporous Pt–Ru–C(Mo 2C) catalyst. All results obtained for C(Mo 2C) and Pt–Ru–C(Mo 2C) electrodes have been compared with corresponding data for commercial carbon VULCAN® XC72 (C(Vulcan)) and Pt–Ru–C(Vulcan) electrodes processed and measured in the same experimental conditions. Higher activity for C(Mo 2C) and Pt–Ru–C(Mo 2C) has been demonstrated. 相似文献
10.
[{(CH 3) 3Si} 3C–Li–C{Si(CH 3) 3} 3][Li · 3(OC 4H 8)] and {(CH 3) 3Si} 3C–Li · O=C(Si(CH 3) 3) 2, two New Adducts of Lithium Trisylmethanide Sublimation of (Tsi–Li) · 2 THF (Tsi = –C(Si(CH 3) 3) 3) at 180 °C and 10 –4 hPa gives (Tsi–Li) · 1.5 THF in very low yield. The X‐ray structure determination shows an almost linear [Tsi–Li–Tsi] – anion connected by short agostic Li…C contacts with the threefold THF‐coordinated Li‐cation. Base‐free Tsi–Li, solved in toluene is decomposed by oxygen, forming the strawberry‐colored ketone O=C(SiMe 3) 2, which forms an 1 : 1 adduct with undecomposed Tsi–Li. The X‐ray structure elucidation of this compound is also discussed. 相似文献
11.
Hydrogallation of Me 3Si–C≡C–NR' 2 with R 2Ga–H (R = tBu, CH 2tBu, iBu) yielded Ga/N‐based active Lewis pairs, R 2Ga–C(SiMe 3)=C(H)–NR' 2 ( 7 ). The Ga and N atoms adopt cis‐positions at the C=C bonds and show weak Ga–N interactions. tBu 2GaH and Me 3Si–C≡C–N(C 2H 4) 2NMe afforded under exposure of daylight the trifunctional digallium(II) compound [MeN(C 2H 4) 2N](H)C=C(SiMe 3)Ga( tBu)–Ga( tBu)C(SiMe 3)=C(H)[N(C 2H 4) 2NMe] ( 8 ), which results from elimination of isobutene and H 2 and Ga–Ga bond formation. 8 was selectively obtained from the ynamine and [ tBu(H)Ga–Ga(H) tBu] 2[HGa tBu 2] 2. 7a (R = tBu; NR' 2 = 2,6‐Me 2NC 5H 8) and H 8C 4N–C≡N afforded the adduct tBu 2Ga‐C(SiMe 3)=C(H)(2,6‐Me 2NC 5H 8) · N≡C–NC 4H 8 ( 11 ) with the nitrile bound to gallium. The analogous ALP with harder Al atoms yielded an adduct of the nitrile dimer or oligomers of the nitrile at room temperature. The reaction of 7a with Ph–N=C=O led to the insertion of two NCO groups into the Ga–C vinyl bond to yield a GaOCNCN heterocycle with Ga bound to O and N atoms ( 12 ). 相似文献
12.
The relative chemical shifts (Δ δ) were put forward to investigate the microscopic structure of 1-ethyl-3-methyl-imidazolium tetrafluoroborate (EmimBF 4) during the dilution process with water. The concentration-dependent Δ δ (C2)H–(C4)H, Δ δ (C2)H–(C5)H and Δ δ (C4)H–(C5)H were analyzed. The results reveal that the variations of the microscopic structures of three aromatic protons are inconsistent. The strength of the H-bond between water and three aromatic protons follows the order: (C2)H…O > (C4)H…O > (C5)H…O. The concentration-dependent Δ δ (C6)H–(C7)H and Δ δ (C6)H–(C8)H indicate the formation of the H-bonds of (C alkyl)H…O is impossible, and more water is located around (C6)H than around (C7)H or (C8)H. The concentration-dependent Δ δ (C2)H–(C4)H and Δ δ (C2)H–(C5)H both increase rapidly when x water > 0.9 or so, suggesting the ionic pairs of EmimBF 4 are dissociated rapidly. The turning points of concentration-dependent Δ δ (C2)H–(C4)H and Δ δ (C2)H–(C5)H indicate that some physical properties of the EmimBF 4/water mixtures also change at the corresponding concentration point. The microscopic structures of EmimBF 4 in water could be clearly detected by the relative chemical shifts. 相似文献
13.
The potential energy surfaces for the reaction of bare niobium cation with ethane, as a prototype of the C–H and C–C bonds activation in alkanes by transition metal cations, have been investigated employing the Density Functional Theory in its B3LYP formulation. All the minima and key transition states have been examined along both high- and low-spin surfaces. For both the C–H and C–C activation pathways the rate determining step is that corresponding to the insertion of the Nb cation into C–H and C–C bond, respectively. However, along the C–H activation reaction coordinate the barrier that is necessary to overcome is 0.13 eV below the energy of the ground state reactants asymptote, while in the C–C activation branch the corresponding barrier is about 0.58 eV above the energy of reactants in their ground state. The overall calculated reaction exothermicities are comparable. Since the spin of the ground state reactants is different from that of both H–Nb +–C 2H 5 and CH 3–Nb +–CH 3 insertion intermediates and products, spin multiplicity has to change along the reaction paths. All the obtained results, including Nb +–R binding energies for R fragments relevant to the examined PESs, have been compared with existing experimental and theoretical data. 相似文献
14.
The cleavage behavior of covalent bonds in Xilinguole (XLGL) lignite and changes in chemical structure of lignite and its chars during low-temperature pyrolysis were investigated by thermogravimetric (TG) analysis and Fourier-transform infrared (FTIR) spectroscopy. Based on the TG and differential thermogravimetric (DTG) analysis results, the cleavage of different types of chemical bonds in lignite occurred mainly at four certain temperatures, 170 °C, 376 °C, 432 °C, and 521 °C. The latter three were selected as the final pyrolysis temperatures of chars evaluated in this study. The FTIR analysis results indicate that thermal treatment increased the relative content of two and three adjacent H deformation structures but decreased that of four adjacent H deformation structure. This was caused by the cleavage of Cal–Cal and Car–Cal bonds. The oxygen-containing functional groups in lignite are dominated by C–O and C–OH groups with a lower chemical reactivity than C=O–C and conjugated C=O groups. Moreover, XLGL lignite has the highest ratio of CH2/CH3 which declines with increasing temperature, indicating the decrease in the length of aliphatic chains and increase in the degree of branching of aliphatic side chains. This change mainly resulted from the cleavage of Cal–O, Cal–Cal, and Car–Cal bonds. Furthermore, XLGL lignite and its chars contain five specific hydrogen bonds: OH–N, cyclic OH, OH–ether O, OH–OH, and OH–π hydrogen bonds. The relative content of OH–OH hydrogen bond was the highest, indicating that OH–OH hydrogen bond has the highest thermal stability. 相似文献
15.
Fe xC–C hybrid material as a support for Pt anode catalyst in direct formic acid fuel cell was investigated for the first time. The resultant Pt/Fe xC–C catalysts were prepared by using a simple reduction reaction to load Pt on Fe xC–C hybrid material, which was synthesized through the carbonization of sucrose and Fe(NO 3) 3. It was found that the Pt/Fe xC–C catalysts exhibited excellent catalytic activity for formic acid electrooxidation. The great improvement in the catalytic performance is attributed to the fact that Fe xC–C hybrid material ameliorated the tolerance to CO adsorption of Pt and facilitated the uniform dispersion of Pt. 相似文献
16.
The geometric parameters of the molecular structures and thermodynamic parameters of macrotricyclic M(II) (M = Mn, Fe, Co, Ni, Cu, Zn) complexes with an MN 2S 2 chelate core formed by the template reactions of the M(II) with N-methylthiocarbohydrazide H 3C–HN–HN–C(=S)–NH–NH 2 and hexanedione- 2,5 H 3C–C(=O)–CH 2–CH 2–C(=O)–CH 3 have been calculated by the DFT method with the Gaussian09 program package. The bond lengths, bond angles, and some nonbonded angles in these complexes have been determined. In all the complexes, the M(II) central ion is pseudotetrahedrally coordinated by the donor atoms of an inner-sphere tetradentate ligand; the (N 2S 2) group of the donor atoms is not planar. The additional seven-membered chelate rings show significant deviations from coplanarity (>60°). The noncoplanatiry of the five-membered rings is less pronounced. 相似文献
17.
Conformational analysis of 5,6,7,8-tetrahydropteroic acid and 5,6,7,8-tetrahydro-L -folic acid In the 360-MHz- 1H-NMR.-spectrum of (6 R, S)-9,9-dideuterio-5, 6, 7, 8-tetrahydropteroic acid (racemic) (XIII) ( AMX-System, Fig. 4) and (6 R, S)-9,9-dideuterio-5, 6, 7, 8-tetrahydro-L -folic acid (diastereomeric) (XVI) the H a–C(6) and H a–C(7) show a vicinal coupling constant of 6,7 Hz and the H a–C(6) and H e–C(7) one of 3,2 Hz. The first coupling constant provides evidence for an approximate trans-diaxal arrangement of H a–C(6) and H a–C(7), and the second for a gauche conformation of H a–C(6) and H e–C(7). The tetrahydropyrazine ring in the racemic 5, 6, 7, 8-tetrahydropteroic acid (III) and in the diastereomeric 5, 6, 7, 8-tetrahydro-L -folic acid (XVII) exists therefore in a half-chair conformation with a pseudoequatorial position of the side chain at C(6) (Fig.5). 相似文献
18.
Several hypotheses have been proposed to explain the origin of the conformational stabilities of 1,2-difluoroalkanes, for which bond orbital interactions are an important factor. However, there is a limit to the effectiveness of the traditional approach focusing on only the antiperiplanar interactions between bonding and antibonding orbitals such as σ C–H/σ C–F*, σ C–C/σ C–F*, and σ C–F/σ C–F*, which cannot actually explain the conformational stabilities of 2,3-difuluorobutanes. In this study, to elucidate the effect of bond orbital interactions on the conformational stabilities of 1,2-difluoroethane, erythro-2,3-difluorobutane, and threo-2,3-difluorobutane, we extended the range of interactions considered to beyond these conventional interactions. The results showed that for 1,2-difluoroethane, the conformational stability can be understood by considering all antiperiplanar bond orbital interactions around the C1–C2 bond, and for 2,3-difluorobutanes, by considering all antiperiplanar bond orbital interactions around the C2–C3 bond in addition to bond orbital interactions between the methyl groups. 相似文献
19.
The complexation reaction between UO 2 2+ cation with macrocyclic ligand, 18-crown-6 (18C6), was studied in acetonitrile–methanol (AN–MeOH), nitromethane–methanol (NM–MeOH) and propylencarbonate–ethanol (PC–EtOH) binary mixed systems at 25 °C. In addition, the complexation process between UO 2 2+ cation with diaza-18-crown-6 (DA18C6) was studied in acetonitrile–methanol (AN–MeOH), acetonitrile–ethanol (AN–EtOH), acetonitrile–ethylacetate (AN–EtOAc), methanol–water (MeOH–H 2O), ethanol–water (EtOH–H 2O), acetonitrile–water (AN–H 2O), dimethylformamide–methanol (DMF–MeOH), dimethylformamide–ethanol (DMF–EtOH), and dimethylformamide–ethylacetate (DMF–EtOAc) binary solutions at 25 °C using the conductometric method. The conductance data show that the stoichiometry of the complexes formed between (18C6) and (DA18C6) with UO 2 2+ cation in most cases is 1:1 [M:L], but in some solvent 1:2 [M:L 2] complex is formed in solutions. The values of stability constants (log K f) of (18C6 · UO 2 2+) and (DA18C6 · UO 2 2+) complexes which were obtained from conductometric data, show that the nature and also the composition of the solvent systems are important factors that are effective on the stability and even the stoichiometry of the complexes formed in solutions. In all cases, a non-linear relationship is observed for the changes of stability constants (log K f) of the (18C6 · UO 2 2+) and (DA18C6 · UO 2 2+) complexes versus the composition of the binary mixed solvents. The stability order of (18C6 · UO 2 2+) complex in pure studied solvents was found to be: EtOH > AN ≈ NM > PC ≈ MeOH, but in the case of (DA18C6 · UO 2 2+) complex it was : H 2O > MeOH > EtOH. 相似文献
20.
Three diorganocobalt chlorides [CoClMe(PMe 3) 2–{(C 5H 6)–CH=O}] ( 4 ), [CoClMe(PMe 3) 2–{(C 6H 8)–CH=O}] ( 5 ), and [CoClMe(PMe 3) 2–{(C 6H 7Me meta)–CH=O}] ( 6 ) were synthesized through cyclometalation reactions with aldehyde as an anchoring group involving aliphatic vinylic C–Cl bond activation. Complexes 4 – 6 were characterized by IR and NMR spectroscopy. The crystal and molecular structures of complexes 4 and 5 were determined by single‐crystal X‐ray diffraction. Complexes 4 – 6 are stable in solution at room temperature, but they decompose at above 30 °C affording C,C‐couplings products with the formation of [Co(PMe 3) 3Cl]. The results of this work will be important for people to deepen the understanding of the C–Cl bond activation mechanism. 相似文献
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