New trifluoromethylated derivatives of [60]fullerene, C60(CF3)n with n = 12 and 14

New isomers of C(60)(CF(3))(12) and C(60)(CF(3))(14) have been isolated from mixtures obtained via reaction of C(60) or S(6)-C(60)(CF(3))(12) with CF(3)I; they were characterized by single crystal XRD study and investigated theoretically by means of DFT calculations.     

Trifluoromethyl derivatives of insoluble small-HOMO-LUMO-gap hollow higher fullerenes. NMR and DFT structure elucidation of C2-(C74-D3h)(CF3)12, Cs-(C76-Td(2))(CF3)12, C2-(C78-D3h(5))(CF3)12, Cs-(C80-C2v(5))(CF3)12, and C2-(C82-C2(5))(CF3)12

Reaction of a mixture of insoluble higher fullerenes with CF3I at 500 degrees C produced a single abundant isomer of C74(CF3)12, C76(CF3)12, and C80(CF3)12, two abundant isomers of C78(CF3)12 and C82(CF3)12, and an indeterminant number of isomers of C84(CF3)12. Using a combination of 19F NMR spectroscopy, DFT calculations, and the structures and spectra of previously reported fullerene(CF3)n compounds, the most-probable structures of six of the seven isolated compounds were determined to be specific isomers of C2-(C74-D3h)(CF3)12, Cs-(C76-Td(2))(CF3)12), C2-(C78-D3h(5))(CF3)12), Cs-(C80-C2v(5))(CF3)12), C2-(C82-C2(5))(CF3)12), and C2-(C82-C2(3))(CF3)12) containing ribbons and/or loops of edge-sharing para-C6(CF3)2 hexagons. The seventh isolated compound is a C1 isomer of C78(CF3)12 containing two such ribbons. This set of compounds represents only the second reported isolable compound with the hollow C74-D3h cage and the first experimental evidence for the existence of the hollow fullerenes C76-Td(2), C78-D3h(5), C80-C2v(5), and C82-C2(5) in arc-discharge soots.     

Poly(trifluoromethyl)fullerene radical anions. An ESR/Vis-NIR Spectroelectrochemical Study of C60F2,4 and C60(CF3)2,10

Cyclic voltammograms are reported for C(60)(CF(3))(n) derivatives for the first time. The compounds studied were 1,9-C(60)(CF(3))(2) and 3 isomers of C(60)(CF(3))(10), including the structurally characterized derivative 1,3,7,10,14,17,23,28,31,40-C(60)(CF(3))(10) (C(60)(CF(3))(10)-3). The compound 1,9-C(60)(CF(3))(2) exhibited 3 reversible reductions; C(60)(CF(3))(10)-3 exhibited 2 reversible reductions; the other 2 isomers of C(60)(CF(3))(10) each exhibited 1 reversible reduction. ESR and near-IR spectroelectrochemical experiments were performed to characterize some of the C(60)(CF(3))(n)(-) and C(60)(CF(3))(n)(2-) species generated by cyclic voltammetry. The ESR spectrum of the C(60)(CF(3))(10)-3(-) radical anion consisted of an envelope of 25 lines centered at g = 2.0032 (the apparent a value is ca. 0.5 G), evidence of coupling between the unpaired electron and a significant number of the CF(3) fluorine atoms. The most significant finding is that this radical anion has a half-life in solution at 25 degrees C of about 7 min.     

Synthesis, structure and theoretical study of mixed fluoro-trifluoromethyl derivatives of C60. Molecular structures of C60F18(CF3)6 and C60F16(CF3)6

A series of novel mixed C60Fn(CF3)m compounds has been produced by trifluoromethylation of C60F18 with CF3I in ampoules at 380-420 degrees C. Two of these compounds, C60F18(CF3)6 and C60F16(CF3)6, have been characterized by X-ray crystallography, which has revealed addition of six CF3 groups to the C3v-C60F18 for the former and replacement/elimination of two outermost F atoms in the latter. Quantum chemical calculations have been employed to predict the most stable possible isomers of C60F16/18(CF3)6 in order to rationalize the experimental results.     

Thermally stable perfluoroalkylfullerenes with the skew-pentagonal-pyramid pattern: C60(C2F5)4O, C60(CF3)4O, and C60(CF3)6

Reaction of C(60) with CF(3)I at 550 degrees C, which is known to produce a single isomer of C(60)(CF(3))(2,4,6) and multiple isomers of C(60)(CF(3))(8,10), has now been found to produce an isomer of C(60)(CF(3))(6) with the C(s)-C(60)X(6) skew-pentagonal-pyramid (SPP) addition pattern and an epoxide with the C(s)-C(60)X(4)O variation of the SPP addition pattern, C(s)-C(60)(CF(3))(4)O. The structurally similar epoxide C(s)-C(60)(C(2)F(5))(4)O is one of the products of the reaction of C(60) with C(2)F(5)I at 430 degrees C. The three compounds have been characterized by mass spectrometry, DFT quantum chemical calculations, Raman, visible, and (19)F NMR spectroscopy, and, in the case of the two epoxides, single-crystal X-ray diffraction. The compound C(s)-C(60)(CF(3))(6) is the first [60]fullerene derivative with adjacent R(f) groups that are sufficiently sterically hindered to cause the (DFT-predicted) lengthening of the cage (CF(3))C-C(CF(3)) bond to 1.60 A as well as to give rise to a rare, non-fast-exchange-limit (19)F NMR spectrum at 20 degrees C. The compounds C(s)-C(60)(CF(3))(4)O and C(s)-C(60)(C(2)F(5))(4)O are the first poly(perfluoroalkyl)fullerene derivatives with a non-fluorine-containing exohedral substituent and the first fullerene epoxides known to be stable at elevated temperatures. All three compounds demonstrate that the SPP addition pattern is at least kinetically stable, if not thermodynamically stable, at temperatures exceeding 400 degrees C. The high-temperature synthesis of the two epoxides also indicates that perfluoroalkyl substituents can enhance the thermal stability of fullerene derivatives with other substituents.     

Synthesis and X-ray or NMR/DFT structure elucidation of twenty-one new trifluoromethyl derivatives of soluble cage isomers of C76, C78, C84, and C90

Adding 1% of the metallic elements cerium, lanthanum, and yttrium to graphite rod electrodes resulted in different amounts of the hollow higher fullerenes (HHFs) C76-D2(1), C78-C2v(2), and C78-C2v(3) in carbon-arc fullerene-containing soots. The reaction of trifluoroiodomethane with these and other soluble HHFs at 520-550 degrees C produced 21 new C76,78,84,90(CF3)n derivatives (n = 6, 8, 10, 12, 14). The reaction with C76-D2(1) produced an abundant isomer of C2-(C76-D2(1))(CF3)10 plus smaller amounts of an isomer of C1-(C76-D2(1))(CF3)6, two isomers of C1-(C76-D2(1))(CF3)8, four isomers of C1-(C76-D2(1))(CF3)10, and one isomer of C2-(C76-D2(1))(CF3)12. The reaction with a mixture of C78-D3(1), C78-C2v(2), and C78-C2v(3) produced the previously reported isomer C1-(C78-C2v(3))(CF3)12 (characterized by X-ray crystallography in this work) and the following new compounds: C2-(C78-C2v(3))(CF3)8; C2-(C78-D3(1))(CF3)10 and C(s)-(C78-C2v(2))(CF3)10 (both characterized by X-ray crystallography in this work); C2-(C78-C2v(2))(CF3)10; and C1-C78(CF3)14 (cage isomer unknown). The reaction of a mixture of soluble higher fullerenes including C84 and C90 produced the new compounds C1-C84(CF3)10 (cage isomer unknown), C1-(C84-C2(11))(CF3)12 (X-ray structure reported recently), D2-(C84-D2(22))(CF3)12, C2-(C84-D2(22))(CF3)12, C1-C84(CF3)14 (cage isomer unknown), C1-(C90-C1(32))(CF3)12, and another isomer of C1-C90(CF3)12 (cage isomer unknown). All compounds were studied by mass spectrometry, (19)F NMR spectroscopy, and DFT calculations. An analysis of the addition patterns of these compounds and three other HHF(X) n compounds with bulky X groups has led to the discovery of the following addition-pattern principle for HHFs: In general, the most pyramidal cage C(sp(2)) atoms in the parent HHF, which form the most electron-rich and therefore the most reactive cage C-C bonds as far as 1,2-additions are concerned, are not the cage C atoms to which bulky substituents are added. Instead, ribbons of edge-sharing p-C6(X)2 hexagons, with X groups on less pyramidal cage C atoms, are formed, and the otherwise "most reactive" fullerene double bonds remain intact.     

Variable-temperature 19F NMR and theoretical study of 1,9- and 1,7-C60F(CF3) and C(s-) and C1-C60F17(CF3): hindered CF3 rotation and through-space J(FF) coupling

Milligram amounts of the new compounds 1,9- and 1,7-C60F(CF3) (ca. 85:15 mixture of isomers) and C60F3(CF3) were isolated from a high-temperature C60/K2PtF6 reaction mixture and purified to 98 mol % compositional purity by two-dimensional high-performance liquid chromatography using Buckyprep and Buckyclutcher columns. The previously observed compounds C60F5(CF3) and C60F7(CF3) were also purified to 90+ mol % for the first time. Variable-temperature 19F NMR spectra of the mixture of C60F(CF3) isomers and the previously reported mixture of C(s)- and C1-C60F17(CF3) isomers demonstrate for the first time that fullerene(F)n(CF3)m derivatives with adjacent F and CF3 substituents exhibit slow-exchange limit hindered CF3 rotation spectra at -40 +/- 10 degrees C. The experimental and density functional theory (DFT) predicted deltaH++ values for CF3 rotation in 1,9-C60F(CF3) are 46.8(7) and 46 kJ mol(-1), respectively. The DFT-predicted deltaH++ values for 1,7-C60F(CF3), C(s)-C60F17(CF3), and C1-C60F17(CF3) are 20, 44, and 54 kJ mol(-1), respectively. The (> or = 4)J(FF) values from the slow-exchange-limit 19F spectra, which vary from ca. 0 to 48(1) Hz, show that the dominant nuclear spin-spin coupling mechanism is through-space coupling (i.e., direct overlap of fluorine atom lone-pair orbitals) rather than coupling through the sigma-bond framework. The 2J(FF) values within the CF3 groups vary from 107(1) to 126(1) Hz. Collectively, the NMR data provide an unambiguous set of (> or = 4)J(FF) values for three different compounds that can be correlated with DFT-predicted or X-ray diffraction derived distances and angles and an unambiguous set of 2J(FF) values that can serve as an internal standard for all future J(FF) calculations.     

Electrochemical, spectroscopic, and DFT study of C60(CF3)n frontier orbitals (n = 2-18): the link between double bonds in pentagons and reduction potentials

The frontier orbitals of 22 isolated and characterized C(60)(CF(3))(n) derivatives, including seven reported here for the first time, have been investigated by electronic spectroscopy (n = 2 [1], 4 [1], 6 [2], 8 [5], 10 [6], 12 [3]; the number of isomers for each composition is shown in square brackets) fluorescence spectroscopy (n = 10 [4]), cyclic voltammetry under air-free conditions (all compounds with n 相似文献   

Synthesis, structure, and 19F NMR spectra of 1,3,7,10,14,17,23,28,31,40-C60(CF3)10

A significant improvement in the selectivity of fullerene trifluoromethylation reactions was achieved. Reaction of trifluoroiodomethane with [60]fullerene at 460 degrees C and [70]fullerene at 470 degrees C in a flow reactor led to isolation of cold-zone-condensed mixtures of C60(CF3)n and C70(CF3)n compounds with narrow composition ranges: 6 < or = n < or = 12 for C(60)(CF3)n and 8 < or = n < or = 14 for C70(CF3)n. The predominant products in the C(60) reaction, an estimated 40+ mol % of the cold-zone condensate, were three isomers of C60(CF3)10. Two of these were purified by two-stage HPLC to 80+% isomeric purity. The third isomer was purified by three-stage HPLC to 95% isomeric purity. Thirteen milligrams of this orange-brown compound was isolated (5% overall yield based on C60, and its C1-symmetric structure was determined to be 1,3,7,10,14,17,23,28,31,40-C60(CF3)10 by X-ray crystallography. The CF3 groups are either meta or para to one another on a p-m-p-p-p-m-p-m-p ribbon of edge-sharing C6(CF3)2 hexagons (each pair of adjacent hexagons shares a common CF3 group). The selectivity of the C70 reaction was even higher. The predominant product was a single C70(CF3)10 isomer representing >40 mol % of the cold-zone condensate. Single-stage HPLC led to the isolation of 12 mg of this brown compound in 95% isomeric purity (27% overall yield based on converted C70. The new compounds were characterized by EI or S(8)-MALDI mass spectrometry and 2D-COSY 19F NMR spectroscopy. The NMR data demonstrate that through-space coupling via direct overlap of fluorine orbitals is the predominant contribution to J(FF) values in these and most other fullerene(CF3)n compounds.     

Synthesis and characterization of difluoromethylene-homo[60]fullerene, C60(CF2)

Refluxing of the o-DCB solution of C60 with CF2ClCOONa and 18-crown-6 leads to formation of C60(CF2)n (n = 1-3); the monoadduct C60(CF2) has been found to consist of the main [6,6]- and minor [5,6]-isomers, both having an open structure.     

Preparation, crystallographic characterization and theoretical study of two isomers of C70(CF3)12

Two isomers of C70(CF3)12 have been isolated from a mixture obtained by trifluoromethylation of C70 with CF3I; their molecular structures determined by X-ray crystallography are in good agreement with the results of theoretical DFT calculations for the most stable C70(CF3)12 isomers.     

Simple organofluorine compounds giving field-dependent 13C and 19F NMR spectra with complex patterns: higher order effects and cross-correlated relaxation

The CF(3) signals in the (13)C{(1)H} spectrum of 1,1,1,3,3,3-hexafluoroisopropyl alcohol and the (CF(3))(2) CH signals in the corresponding triflate exhibit much greater complexity than might first be expected. The same holds for the (13)C satellites in the (19)F spectra. Complex patterns appear because of higher order effects resulting from the combination of a relatively large four-bond (19)F-(19)F J coupling in the ((13)CF(3))(12)CH((12)CF(3))-containing isotopomer and a typical large one-bond (13)C/(12)C isotope effect on the (19)F chemical shift. This complexity cannot be eliminated at very high magnetic field strengths. The triflate (CF(3))(2)CH-O-SO(2)CF(3) presents still additional complexity because of the presence of two different types of CF(3) groups exhibiting (6)J(FF) in any of the isotopomers and the chemical shift differences in hertz between the various (19)F signals in the two different (13)CF(3)-containing isotopomers. In addition, the presence of a small (5)J(CF) in the ((13)CF(3))((12)CF(3))(12)CH-O-SO(2) (12)CF(3) isotopomer is revealed only through simulations. The hexafluoroisopropyl CF(3) groups in the alcohol and triflate and the SO(2)CF(3) group in the triflate apparently provide the first examples of cross-correlated relaxation in (13)CF(3) groups. An analysis of the spectra in the context of previously reported work highlights the novel aspects of our findings. In particular, for each part of the complex hexafluoroisopropyl CF(3) quartet, peak height and linewidth variations resulting from cross-correlated relaxation are observed. These variations within a group of (13)C signals reflect different spin-lattice and spin-spin relaxation rates for the transitions within that group arising from higher order coupling effects.     

Preparation and structures of [6,6]-open difluoromethylene[60]fullerenes: C60(CF2) and C60(CF2)2

Difluoromethylenation of C60 with thermally decomposed CF2ClCO2Na provides novel C60(CF2) and C60(CF2)2 compounds with unique [6,6]-open structures. A theoretical survey of CF2 derivatives of C60 demonstrates that carbon cage opening can be controlled via charging of the molecule and that the thermodynamically preferable structures combine the trend to form open isomers with the compactness of the addition motifs, which results in the formation of windows in the fullerene cage.     

Fused five-membered rings determine the stability of C60F60

The structure and stability of a set of (CF)60 isomers have been computed at the B3LYP/6-31G(d) density functional theory level. The most stable isomer (6, F4@C60F56) has tube-like structure with four endo C-F bonds and fused five-membered rings at the end of the tube, while the reported most stable cage structure (2, F8@C60F52) with eight endo C-F bonds is higher in energy by 22.6 kcal/mol. This is in contrast to the isolated pentagon rule for the stability of fullerenes. The mean bond dissociation energy of 6 is larger than those of the experimental known C60F36, C60F48, and graphite fluoride. The relative energy per CF unit of 6 to graphite fluoride (CF)n is 3.7 kcal/mol, which is smaller than that of C60 fullerene per carbon to graphite (about 9-10 kcal/mol).     

Examination of intermolecular electronic interactions in the crystal structure of C60(CF3)12 by experimental electron density determination

From a high resolution X-ray data set measured at 20 K the experimental electron density of the fullerene C(60)(CF(3))(12) was derived and topologically analyzed to yield, in addition to bond topological and atomic properties, information about the density distribution in the region where hexagons of adjacent molecules approach closely at only 3.3 A.     

Experimental and theoretical studies of the C2F4 + O reaction: nonadiabatic reaction mechanism

In this work, the C(2)F(4)(X(1)A(g)) + O((3)P) reaction was investigated experimentally using molecular beam-threshold ionization mass spectrometry (MB-TIMS). The major primary products were observed to be CF(2)O (+ CF(2)) and CF(3) (+ CFO), with measured approximate yields of % versus %, respectively, neglecting minor products. Furthermore, the lowest-lying triplet and singlet potential energy surfaces for this reaction were constructed theoretically using B3LYP, G2M(UCC, MP2), CBS-QB3, and G3 methods in combination with various basis sets such as 6-31G(d), 6-311+G(3df), and cc-pVDZ. The primary product distribution for the multiwell multichannel reaction was then determined by RRKM statistical rate theory and weak-collision master equation analysis. It was found that the observed production of CF(3) (+ CFO) can only occur on the singlet surface, in parallel with formation of ca. 5 times more CF(2)O(X) + CF(2)(X(1)A(1)). This requires fast intersystem crossing (ISC) from the triplet to the singlet surface at a rate of ca. 4 x 10(12) s(-1). The theoretical calculations combined with the experimental results thus indicate that the yield of triplet CF(2)(?(3)B(1)) + CF(2)O formed on the triplet surface prior to ISC is < or =35%, whereas singlet CF(2)(X(1)A(1)) + CF(2)O is produced with yield > or =60%, after ISC. In addition, the thermal rate coefficients k(O + C(2)F(4)) in the T = 150-1500 K range were computed using multistate transition state theory and can be expressed as k(T) = 1.67 x 10(-16) x T(1.48) cm(3) molecule(-1) s(-1); they are in agreement with the available experimental results in the T = 298-500 K range.     

Preparation, crystallographic characterization and theoretical study of C70(CF3)16 and C70(CF3)18

C70(CF3)16 and C70(CF3)18, the first trifluoromethylated fullerene derivatives to comprise a pair of adjacent CF3 groups, have been isolated from a mixture obtained via reaction of C70 with CF3I, characterized in a single crystal XRD study and theoretically investigated at the DFT level of theory.     

Unusual addition patterns in trifluoromethylation of [60]fullerene

From pyrolytic trifluoromethylation of [60]fullerene with CF3CO2Ag at 300 degrees C we have isolated ca. sixty C60(CF3)n isomers (numbers in parentheses) as follows: n = 2(1), 4(8), 6(13), 8(21), 10(11), 12(5), 14(4), twenty-one of which have been characterised by 19F NMR. Compounds with addition levels up to n = 20 have also been identified. With increasing value of n, yields decrease and the separation of compounds of similar HPLC retention time but different addend levels becomes more difficult. Many of the 19F NMR spectra show combinations of quartets and septets (the latter tending to be more downfield) due to 'linear' addend arrays. The spectra are consistent with addition across both 6:6- and 5:6-ring junctions [double (1.2) and single (1.6) bonds, respectively], giving corresponding coupling constants for adjacent addends of ca. 14.5 and 12.0 Hz respectively, the differences being attributable to the different 1.2- and 1.6-bond lengths. The 13C NMR spectrum of C60(CF3)2 shows the CF3 groups are in either a 1.4- or 1.6-relationship; the UV-vis band appears at 442 nm. Other unsymmetrical tetra-adducts are comprised of isolated pairs of CF3 groups. The exceptionally large number of derivatives and isomers, (much greater than in any other fullerene reaction), no dominant product, and unusual addition pattern indicates that thermodynamic stability is not of primary importance in governing product formation. EI mass spectrometry of trifluoromethylfullerenes is characterised by loss of CF3 groups, the more highly addended compounds also showing fragmentation by CF2 loss, attributable to steric compression. The CF3 group shows strong IR bands at ca. 1260 and 1190 cm-1. The compounds are stable to aq. acetone, which contrasts to the behaviour of fluorofullerenes. Trifluoromethylation by the Scherer radical (C9F19.) gave addition of up to eight CF3 groups, together with hydrogen in some products. During EI mass spectrometry of some of these, loss of HF attributable to CF3 and H adjacency can occur, giving CF2-containing derivatives.     

Structural, thermodynamic, and mesomorphic consequences of replacing nitrates with trifluoroacetate counteranions in ternary lanthanide complexes with hexacatenar tridentate ligands

The promesogenic hexacatenar tridentate ligands L3(Cn) (I shape) and L4(Cn) (V shape) react with trivalent lanthanide trifluoroacetates, Ln((CF3CO2)3, to give either monometallic [Ln(Li(Cn))(CF3CO2)3] or trifluoroacetato-bridged bimetallic [Ln(Li(Cn))(CF3CO2)3]2 complexes in the solid state, as exemplified by the crystal structures of [Lu(L4(CO))(CF3CO2)3(H2O)], [Lu(L4(CO))(CF3CO2)3]2, and [La(L3(C4))(CF3CO2)3]2. Although the dimerization process is influenced by the competiting complexation of anions or solvent molecules, the coordination of CF3CO2- instead of NO3- to Ln(III) produces a significant lengthening of the Ln-N(ligand) bond distances. This translates into a considerable decrease of the affinity of the Li(C12) (i = 3, 4) ligands for Ln(CF3CO2)3 in solution, thus leading to significant dissociation of the [Ln(Li(C12))(CF3CO2)3] complexes at millimolar concentrations. The thermal properties of these complexes also suffer from their limited thermodynamic stability, and the thermotropic liquid crystalline phases produced at high temperatures reflect mixtures of different species. However, a hexagonal columnar organization characterizes the main component in the mesophases obtained with [Ln(L3(C12))(CF3CO2)3] at high temperature. A tentative interpretation of the small-angle X-ray scattering (SAXS) profiles suggests that disklike dimers of [Ln(L3(C12))(CF3CO2)3]2 are packed along the columnar axes. For [Ln(L4(C12))(CF3CO2)3], SAXS profiles are compatible with a lamellar organization in the mesophases originating from the existence of rodlike dimers of [Ln(L4(C12))(CF3CO2)3]2 as the major component in the liquid-crystal state.     

Trifluoroselenoacetic acid, CF(3)C(O)SeH: preparation and properties

The hitherto unknown trifluoroselenoacetic acid was prepared through the reaction of trifluoroacetic acid with Woollins' reagent. The compound was fully characterized by mass spectrometry, (1)H, (19)F, (77)Se, and (13)C NMR, UV-visible, IR and Raman spectroscopy, and the boiling point at 46 °C was estimated from the vapor pressure curve. An IR matrix isolation study revealed the presence of two different syn-anti and anti-syn conformers. The IR spectra of the two stereoisomers have been assigned, aided by DFT, and ab initio calculations. The UV photolysis of Ar matrix isolated CF(3)C(O)SeH yielded CO, OCSe, CF(3)SeH, and CHF(3). Apart from CF(3)SeH, these products were also obtained by vacuum flash-pyrolysis (310 °C) of gaseous CF(3)C(O)SeH. Instead of CF(3)SeH, CF(2)Se, and HF were detected among the pyrolysis products. The different decomposition pathways of CF(3)C(O)SeH are discussed.