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1.
Carbon-Fluorine Bondings of Fluorinated Fullerene and Graphite   总被引:1,自引:0,他引:1  
Carbon-fluorine bondings of fluorinated fullerenes and fluorine-graphite intercalation compound CxF were investigated in detail on the basis of XPS data and the potential model using the charge distribution calculated by semiempirical method. It has been confirmed by the present study that two peaks in the C1s spectra observed for fluorinated fullerenes are assigned to carbon atoms bonded to fluorine atoms and those unbound to fluorine atoms, and the small difference in charges and Madelung potentials of fluorine atoms in different circumstances well explains the single peak in F1s spectra of fluorinated fullerenes. In the calculated structures of 1,3-C60F2 and 1,2-C60Fx (x = 2?6) used as the models of CxF, three kinds of carbon-fluorine bondings were observed corresponding to nearly ionic, semicovalent and covalent C? F bondings. The calculated result supports that the bi-intercalation structure of stage 1 CxF consists of nearly ionic and semi-covalent fluorines.  相似文献   

2.
The partial fluorination of polycyclic aromatic hydrocarbons often produces a layered crystal packing, where fluorinated aromatic surfaces are stacked over nonfluorinated aromatic surfaces. Herein, we report the synthesis and crystal packing of partially fluorinated [4]helicenes with steric congestion resulting from H and F atoms in the fjord region. F6‐[4]Helicene forms head‐to‐tail columnar stacks consisting of an alternate arrangement of perfluorinated and nonfluorinated naphthalene moieties. With decreasing fluorine content, aromatic stacking switched from arene?fluoroarene (ArH?ArF) hetero‐stacking to ArH?ArH/ArF?ArF homo‐stacking with the help of intermolecular C?H???F contacts in the fjord region. As a result, head‐to‐head columnar stacks appear. Therefore, the conventional ArH?ArF stacking motif is not always applicable to Fn‐[4]helicenes with twisted π‐surfaces.  相似文献   

3.
4‐Fluorinated levoglucosans were synthesised to test if OH???F H‐bonds are feasible even when the O???F distance is increased. The fluorinated 1,6‐anhydro‐β‐D ‐glucopyranoses were synthesised from 1,6 : 3,4‐dianhydro‐β‐D ‐galactopyranose ( 8 ). Treatment of 8 with KHF2 and KF gave 43% of 4‐deoxy‐4‐fluorolevoglucosan ( 9 ), which was transformed into the 3‐O‐protected derivatives 13 by silylation and 15 by silylation, acetylation, and desilylation. 4‐Deoxy‐4‐methyllevoglucosan ( 19 ) and 4‐deoxylevoglucosan ( 21 ) were prepared as reference compounds that can only form a bivalent H‐bond from HO? C(2) to O? C(5). They were synthesised from the iPr3Si‐protected derivative of 8 . Intramolecular bifurcated H‐bonds from HO? C(2) to F? C(4) and O? C(5) of the 4‐fluorinated levoglucosans in CDCl3 solution are evidenced by the 1H‐NMR scalar couplings h1J(F,OH) and 3J(H,OH). The OH???F H‐bond over an O???F distance of ca. 3.0 Å is thus formed in apolar solvents, at least when favoured by the simultaneous formation of an OH???O H‐bond.  相似文献   

4.
Partially fluorinated poly(vinyl ether)s with C4F9 and C6F12H groups in the side chain were synthesized via living cationic polymerization in the presence of an added base in a fluorine‐containing solvent, dichloropentafluoropropanes. For comparison, the polymerization of vinyl ether monomers with C2F5 and C6F13 groups and nonfluorinated monomers were also carried out. The characterization of the product polymers using size exclusion chromatography with a fluorinated solvent as an eluent indicated that all polymers had narrow molecular weight distributions (Mw/Mn ~ 1.1). Interestingly, the moderately fluorinated polymers with C4F9 exhibited upper critical solution temperature‐type phase separation in various organic solvents with wide‐ranging polarities, whereas highly fluorinated polymers with C6F13 are insoluble in nonfluorinated solvents. Polymers with C4F9 groups exhibited temperature dependent solubility transitions not only in common organic solvents (e.g., toluene, chloroform, tetrahydrofuran, and acetone) but also in perfluoro solvents [e.g., perfluoro(methylcyclohexane) and perfluorodecalin]. On the other hand, the solubility of polymers with C6F12H showed completely different from that of polymers with C6F13, despite their similar fluorine content. In addition, various types of fluorinated block copolymers were prepared in a living manner. The block copolymers with a thermosensitive fluorinated segment underwent temperature‐induced micellization and sol–gel transition in various organic solvents. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011  相似文献   

5.
We investigate the transition‐state (TS) region of the potential energy surface (PES) of the reaction tBu3P+H2+B(C6F5)3tBu3P‐H(+)+(?)H?B(C6F5)3 and the dynamics of the TS passage at room temperature. Owing to the conformational inertia of the phosphane???borane pocket involving heavy tBu3P and B(C6F5)3 species and features of the PES E(P???H, B???H | B???P) as a function of P???H, B???H, and B???P distances, a typical reactive scenario for this reaction is a trajectory that is trapped in the TS region for a period of time (about 350 fs on average across all calculated trajectories) in a quasi‐bound state (scattering resonance). The relationship between the timescale of the TS passage and the effective conformational inertia of the phosphane???borane pocket leads to a prediction that isotopically heavier Lewis base/Lewis acid pairs and normal counterparts could give measurably different reaction rates. Herein, the predicted quasi‐bound state could be verified in molecular collision experiments involving femtosecond spectroscopy.  相似文献   

6.
Novel fluorinated main‐chain liquid‐crystalline/crystalline polymers were prepared through thin film polymerization to investigate the effect of –(C6F4)– on the surface free energy. The fluorine in the phenyl rings does not lower the total surface free energy of the thin copolymer films, compared to those without fluorine. Interestingly, the Lewis acid components (γ+) of the surface free energy of the fluorine‐containing polymers increase with an increase in the –(C6F4)– content, indicating the increasing electron accepting character of the surface.  相似文献   

7.
The geometries and interaction energies of complexes of pyridine with C6F5X, C6H5X (X=I, Br, Cl, F and H) and RFI (RF=CF3, C2F5 and C3F7) have been studied by ab initio molecular orbital calculations. The CCSD(T) interaction energies (Eint) for the C6F5X–pyridine (X=I, Br, Cl, F and H) complexes at the basis set limit were estimated to be ?5.59, ?4.06, ?2.78, ?0.19 and ?4.37 kcal mol?1, respectively, whereas the Eint values for the C6H5X–pyridine (X=I, Br, Cl and H) complexes were estimated to be ?3.27, ?2.17, ?1.23 and ?1.78 kcal mol?1, respectively. Electrostatic interactions are the cause of the halogen dependence of the interaction energies and the enhancement of the attraction by the fluorine atoms in C6F5X. The values of Eint estimated for the RFI–pyridine (RF=CF3, C2F5 and C3F7) complexes (?5.14, ?5.38 and ?5.44 kcal mol?1, respectively) are close to that for the C6F5I–pyridine complex. Electrostatic interactions are the major source of the attraction in the strong halogen bond although induction and dispersion interactions also contribute to the attraction. Short‐range (charge‐transfer) interactions do not contribute significantly to the attraction. The magnitude of the directionality of the halogen bond correlates with the magnitude of the attraction. Electrostatic interactions are mainly responsible for the directionality of the halogen bond. The directionality of halogen bonds involving iodine and bromine is high, whereas that of chlorine is low and that of fluorine is negligible. The directionality of the halogen bonds in the C6F5I– and C2F5I–pyridine complexes is higher than that in the hydrogen bonds in the water dimer and water–formaldehyde complex. The calculations suggest that the C? I and C? Br halogen bonds play an important role in controlling the structures of molecular assemblies, that the C? Cl bonds play a less important role and that C? F bonds have a negligible impact.  相似文献   

8.
The notion of weak attractive ligand–polymer interactions is introduced, and its potential application, importance, and conceptual links with “cooperative” ligand–substrate interactions are discussed. Synthetic models of weak attractive ligand–polymer interactions are described, in which intramolecular weak C? H???F? C interactions (the existence of which remains contentious) have been detected by NMR spectroscopy and neutron and X‐ray diffraction experiments. These C? H???F? C interactions carry important implications for the design of catalysts for olefin polymerization, because they provide support for the practical feasibility of ortho‐F???Hβ ligand–polymer contacts proposed for living Group 4 fluorinated phenoxyimine catalysts. The notion of weak attractive noncovalent interactions between an “active” ligand and the growing polymer chain is a novel concept in polyolefin catalysis.  相似文献   

9.
The cocrystallization of a weakly luminescent platinum complex [Pt(btpy)(PPh3)Cl] ( 1 ) (Hbtpy=2‐(2benzothienyl)pyridine; emission quantum yield Φem=0.03) with fluorinated bromo‐ and iodoarenes C6F6‐nXn (X=Br, I; n=1, 2) results in the formation of efficient halogen‐bonding (XB) interactions Pt? Cl???X? R. An up to 22‐fold enhancement (Φem=0.65) in the luminescence intensity of the cocrystallized compound is detected, without a substantial change of the emission energy. Based on crystallographic, photophysical, and theoretical investigations, the contribution of the XB donors C6F6‐nXn to the amplification of luminescence intensity is attributed to the enhancement of spin–orbit coupling through the heavy‐atom effect, and simultaneously to the suppression of the nonradiative relaxation pathways by increasing the rigidity of the chromophore center.  相似文献   

10.
Hydrosilylation of fluorinated olefins with polyhydromethylsiloxane (PHMS) in the presence of a platinum catalyst was investigated to synthesize fluorosilicone having highly fluorinated alkyl side chains (Rf; CnF2n+1? ). The hydrosilylation of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10‐heptadecafluoro‐1‐decene (C8F17CH?CH2) ( 1 ) with poly(dimethylsiloxane‐co‐hydromethylsiloxane) {(CH3)3SiO[? (H)CH3SiO? ]8[? (CH3)2 SiO? ]18Si(CH3)3} ( 4 ) converted the hydrogen bonded to silicons into the 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10‐heptadecafluorodecyl group or fluorine bonded to silicons in the ratio of about 52:48, and the formation of the byproduct C7F15CF?CHCH3 ( 8 ) was observed. The hydrosilylation of 7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,14‐heptadecafluoro‐4‐oxa‐1‐tetradecene (C8F17CH2CH2OCH2CH?CH2) ( 2 ) with 4 converted the hydrogen bonded to silicons into the 7,7,8,8,9,9,10,10,11,11,12,12,13,13,14,14,14‐heptadecafluoro‐4‐oxa‐tetradocyl group bonded to silicons, but an excess amount of 2 was required to complete the reaction because the isomerization of 2 occurred in part to form C8F17CH2CH2OCH?CHCH3 ( 9 ). The hydrosilylation of 4,4,5,5,6,6,7,7,8,8,9,9, 10,10,11,11,11‐heptadecafluoro‐1‐undecene (C8F17CH2CH?CH2) ( 3 ) with 4 converted the hydrogen bonded to silicons into the 4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11‐heptadecafluoroundecyl group bonded to silicons. This type of fluorinated olefin was successfully applied to the hydrosilylation with other PHMS's that involved a homopolymer of PHMS and a cyclic PHMS. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3120–3128, 2002  相似文献   

11.
Understanding the details of the electronic structure in face‐to‐face arranged tetrathiafulvalenes (TTFs) is very important for the design of supramolecular functional materials and superior conductive organic materials. This article is a comprehensive study of the interactions among columnar stacked TTFs using trimeric (trimer) and tetrameric (tetramer) TTFs linked by alkylenedithio groups (‐S(CH2)nS‐, n=1–4) as models of triple‐ and quadruple‐decker TTF arrays. Single‐crystal X‐ray analyses of neutral trimeric TTFs revealed that the three TTF moieties are oriented in a zigzag arrangement. Cyclic voltammetry measurements (CV) reveal that the trimer and tetramer exhibited diverse reversible redox processes with multi‐electron transfers, depending on the length of the ‐S(CH2)nS‐ units and substituents. The electronic spectra of the radical cations, prepared by electrochemical oxidation, showed charge resonance (CR) bands in the NIR/IR region (1630–1850 nm), attributed to a mixed valence (MV) state of the triple‐ and quadruple‐decker TTF arrays. In the trimeric systems, the dicationic state (+2; 0.66 cation per TTF unit) was found to be a stable state, whereas the monocationic state (+1) was not observed in the electronic spectra. In the tetrameric system, substituent‐dependent redox processes were observed. Moreover, π‐trimers and π‐tetramers, which show a significant Davydov blueshift in the spectra, are formed in the tricationic (trimer) and tetracationic (tetramer) state. In addition, these attractive interactions are strongly dependent on the length of the linkage unit.  相似文献   

12.
The current work describes the synthesis and full characterization of zerovalent nickel complexes of the type [(dippe)Ni(η2C,C‐Fn‐alkyne)] (dippe=1,2‐bis(di‐isopropylphosphino‐ethane), Fn‐alkyne=fluorinated aromatic alkyne, n=1, 3, 5; 3a , 3b , 3c ) and [{(dippe)Ni}22C,C‐Fn‐alkyne)] ( 4 ). Reactions with complexes 3a , 3b , 3c , and water as the hydrogen source, yield selective semihydrogenation of the bound alkyne to the corresponding alkene, accompanied by partial hydrodefluorination of the aromatic ring. Different alkynes were tested; on using the alkyne with five fluorine atoms over the aromatic ring, partial defluorination was achieved under the mildest reaction conditions, followed in reactivity by the alkyne with three fluorine atoms. The alkyne with only one fluorine atom was barely defluorinated. The use of triethylsilane as a sacrificial hydride source resulted in an overall increase in reactivity towards defluorination.  相似文献   

13.
We have fluorinated few‐layer graphene (FLG) by using a low‐temperature fluorination route with gaseous ClF3. The treatment process resulted in a new graphene derivative with a finite approximate composition of C2F. TEM studies showed that the product consisted of thin transparent sheets with no more than 10 fluorographene layers stacked together. Spectroscopic methods revealed a predominantly covalent nature of the C? F bonds in the as‐synthesized product and we found no evidence for the existence of so‐called “semi‐ionic” C? F bonds, as observed in bulk CxF. In contrast to the case of graphite and typical (thick) expanded graphites, fluorination of FLG did not lead to the intercalation of ClF3 molecules, owing to the lack of a 3D layered structure. The approximate “critical” number of graphene layers that were necessary to form a phase of intercalated compound was estimated to be more than 12, thus providing a “chemical proof” of the difference between the properties of few‐layered graphenes and bulk graphites. Fluorographene C2F was successfully delaminated into thinner layers in organic solvents, which is an important property for its integration into electronic devices, nanohybrids, etc.  相似文献   

14.
《中国化学》2018,36(9):845-850
The arylthio‐substituted tetrathiafulvalenes (Ar‐S‐TTFs) are electron donors having three reversible states, neutral, cation radical, and dication. The charge‐transfer (CT) between Ar‐S‐TTFs ( TTF1 — TTF3 ) and iodine (I2) is reported herein. TTF1 — TTF3 show the CT with I2 in the CH2Cl2 solution, but they are not completely converted into cation radical state. In CT complexes of TTF1 — TTF3 with I2, the charged states of Ar‐S‐TTFs are distinct from those in solution. TTF1 is at cation radical state, and TTF2 — TTF3 are oxidized to dication. The iodine components in complexes show various structures including 1‐D chain of V‐shaped (I5), and 2‐D and 3‐D iodine networks composed of I2 and (I3).  相似文献   

15.
α‐Halogenoacetanilides (X=F, Cl, Br) were examined as H‐bonding organocatalysts designed for the double activation of C?O bonds through NH and CH donor groups. Depending on the halide substituents, the double H‐bond involved a nonconventional C?H???O interaction with either a H?CXn (n=1–2, X=Cl, Br) or a H?CAr bond (X=F), as shown in the solid‐state crystal structures and by molecular modeling. In addition, the catalytic properties of α‐halogenoacetanilides were evaluated in the ring‐opening polymerization of lactide, in the presence of a tertiary amine as cocatalyst. The α‐dichloro‐ and α‐dibromoacetanilides containing electron‐deficient aromatic groups afforded the most attractive double H‐bonding properties towards C?O bonds, with a N?H???O???H?CX2 interaction.  相似文献   

16.
Ab initio molecular‐orbital (MO) calculations were carried out, at the MP2/6‐311++G(d,p)//MP2/6‐31G(d) level, to investigate the conformational Gibbs energy of alkyl 1‐cyclohexylethyl ketones, cyclo‐C6H11CHCH3? CO? R (R=Me, Et, iPr, and tBu). In each case, one of the equatorial conformations was shown to be the most stable. Conformers with the axial CHCH3COR group were also shown to be present in an appreciable concentration. Short C? H???C?O and C? H???O?C distances were found in each stable conformation. The result was interpreted on the grounds of C? H???π(C?O) and C? H???O hydrogen bonds, which stabilize the geometry of the molecule. The ratio of the diastereomeric secondary alcohols produced in the nucleophilic addition to cyclo‐C6H11CHCH3? CO? R was estimated on the basis of the conformer distribution. The calculated result was consistent with the experimental data previously reported: the gradual increase in the product ratio (major/minor) along the series was followed by a drop at R=tBu. The energy of the diastereomeric transition states in the addition of LiH to cyclo‐C6H11CHCH3? CO? R was also calculated for R=Me and tBu. The product ratio did not differ significantly in going from R=Me to tBu in the case of the aliphatic ketones. This is compatible with the above result calculated on the basis of the conformer distribution. Thus, the mechanism of the π‐facial selection can be explained in terms of the simple premise that the geometry of the transition state resembles the ground‐state conformation of the substrates and that the nucleophilic reagent approaches from the less‐hindered side of the carbonyl π face.  相似文献   

17.
The Perlin effect and its analog for fluorinated compounds (the fluorine Perlin-like effect) manifest on one-bond C─H (C─F for the fluorine Perlin-like effect) spin–spin coupling constants (SSCCs) in six-membered rings. These effects can be useful to probe the stereochemistry (axial or equatorial) of the C─H and C─F bonds, respectively. The origin of these effects has been debatable in the literature as being due to hyperconjugative interactions, dipolar effects, and induced current density. Accordingly, a variety of model compounds has been used to probe such effects since the cyclohexanone carbonyl group and the endocyclic heteroatom lone pairs play different roles on the above-mentioned effects. Thus, the 1JC─F SSCC in fluorinated lactams and lactones were theoretically studied to gain further insight on the nature of the fluorine Perlin-like effect. In addition, because the intramolecular α-effect has recently gained attention for its importance in the reactivity and stereoelectronic interactions in peroxide compounds, some fluorinated 1,2-dioxanes and 1,2-dithianes were studied to evaluate the role of the α-effect on the behavior of 1JC─F SSCCs. Differently from fluorinated ketones and ethers, the fluorine Perlin-like effect in the amides and esters cannot be explained by hyperconjugative or dipolar interactions alone, because the resonance in these groups affect the 1JC─F values. The O─O and S─S-containing systems exhibit a strong fluorine Perlin-like effect, but unlike the α-effect, this behavior cannot be explained neither by hyperconjugation nor by dipolar interactions alone; the spatial proximity of the C─F and O─O/S─S bonds is proposed to affect the magnitude of the 1JC─F SSCC.  相似文献   

18.
In Inclusion compounds of fluorinated graphite with chlorine trifluoride C2. xClF3 and hexafluoro-benzene C2F. xC6F6 , the guest molecules are characterized by rotational mobility and weak bonds with the host matrix. 19F NMR chemical shift tensors are determined for the fluorine nuclei of the matrix and the guest molecules, including the structurally nonequivalent fluorine atoms ofClFj molecules [δ (Fl) = −700, δ(F1) = −280; δ|| (F2) = −440, δ±(F2) = −220ppm relative to F2]. It is shown that C-F bonds in the host matrix are close to those in aromatic fluorocarbons. Translated from Zhumal Stmktumoi Khimii, Vol. 41, No. 1, pp. 80-85, January–February, 2000.  相似文献   

19.
The fluorinations of hexachlorobenzene and pentachloropyridine were carried out in sealed tubes with KF in presence of inert gas; the fluorinated derivatives C6FxCly x + y = 6 0?x?6 and C5FxClyN x + y = 5 0?x?5 are obtained. The influence of contact time, temperature and the concentration of the ion F? are investigated and compared; the molar yield varied from 45% to 90%. It is possible to get directly and selectively some fluorinated derivatives as C5Cl2F3N. The fluorinations in liquid KFKCl and solid KF are compared.  相似文献   

20.
A series of fluorinated graphites, Fluorographites, of varying fluorine content has been examined by ESCA, and the chemical shifts and relative intensities of the core electron lines yield a consistent picture of the compositions and structures in the surface regions of the materials. Fluorographites of composition (C1F0.81)n to (C1F1.00)n are fully fluorinated in the outermost ~40 Å and consist of a bulk structure composed of tertiary →CF groups with ? CF2? groups at the prismatic edges of the fluorinated graphite layers. This is also the case for (C1F1.05)n, but, in addition, some of the C? C bonds involving edge →CF carbons are broken and replaced by C? F bonds, giving a higher concentration of ? CF2? groups at the outermost surfaces of the particles of this material. The ESCA data for (C1F0.25)n are consistent with a structure comprising six-membered aromatic rings in which each ring carbon is attached to a →CF group acting as a bridge among three similar rings, with the C? F bonds alternately pointing up and down with respect to the plane defined by the carbon atoms. At the immediate surface the valence requirements of the carbon atoms at the prismatic edges of the graphite-like layers are satisfied by bonding with oxygen. This is also the apparent structure of (C1F0.37)n, but in addition there exist discrete regions of composition (C1F1)n distributed uniformly throughout this material. The Fluorographites (C1F0.34)n, and (C1F0.40)n, and (C1F0.63)n consist of blocks of C1F1 stoichiometry and blocks of unreacted graphite. The presence of ? CF2? groups and the complete absence of oxygen in the surface regions of these Fluorographites suggests that the prismatic edge sites are fully fluorinated. The inhomogeneous block-like structures of (C1F0.37)n, (C1F0.37)n, and (C1F0.34)n, (C1F0.40)n, and (C1F0.63)n, give rise to differential sample charging, resulting in apparent shifts in the binding energy scales between the spectral components originating from different regions of the samples. Such differential sample charging is also described for a number of mixtures of the Fluorographites and of graphite with the Fluorographites. It is pointed out that in view of these results it is necessary to exercise considerable caution in using the ESCA lines of an added compound as a reference in measuring core electron-binding energies.  相似文献   

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