Synthesis, characterization, and theoretical study of stable isomers of C70(CF3)n (n=2, 4, 6, 8, 10)статья

Статья опубликована в высокорейтинговом журнале

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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.

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[1] Synthesis, characterization, and theoretical study of stable isomers of c70(cf3)n (n=2, 4, 6, 8, 10) / E. I. Dorozhkin, D. V. Ignat'eva, N. B. Tamm et al. // Chemistry - A European Journal. — 2006. — Vol. 12, no. 14. — P. 3876–3889. Reaction of C-70 with ten equivalents of silver(i) trifluoroacetate at 320-340 degrees C followed by fractional sublimation at 420-540 degrees C and HPLC processing led to the isolation of a single abundant isomer of C-70(CF3)(n) for n = 2, 4, 6, and 10, and two abundant isomers of C-70(CF3)(8). These six compounds were characterized by using matrix-assisted laser desorption ionization (MALDI) mass spectrometry, 2D-COSY and/or 1D F-19 NMR spectroscopy, and quantum-chemical calculations at the density functional theory (DFT) level. Some were also characterized by Raman spectroscopy. The addition patterns for the isolated compounds were unambiguously found to be C-1-7,24-C-70(CF3)(2), C-1-7,24,44,47-C-70(CF3)(4), C-2-1,4,11,19,31,41-C-70(CF3)(6), C-5-1,4,11,19,31,41,51,64-C-70(CF3)(8), C-2- 1,4,11,19,31,41,51,60-C-70(CF3)(8), and C-1-1,4,10,19,25,41,49,60,66,69-C-70(CF3)(10) (lUPAC numbering). Except for the last compound, which is identical to the recently reported, crystallographically characterized C-70(CF3)(10) derivative prepared by a different synthetic route, these compounds have not previously been shown to have the indicated addition patterns. The largest relative yield under an optimized set of reaction conditions was for the (, isomer of C-70(CF3)(8) (ca. 30 mol % of the sublimed mixture of products based on HPLC integration). The results demonstrate that thermally stable C-70(CF3)(n) isomers tend to have their CF3 groups arranged on isolated para-C-6(CF3)(2) hexagons and/or on a ribbon of edge-sharing meta- and/or para-C-6(CF3)(2) hexagons. For C-5- and C-2-C-70(CF3)(8) and for C-2-C-70(CF3)(6), the ribbons straddle the C-70 equatorial belt; for C-1-C-70(CF3)(4), the para-meta-para ribbon includes three polar hexagons; for C-1-C-70(CF3)(4), the para-meta-para ribbon includes three polar hexagons; for C-1-7,24-C-70(CF3)(2), the para-C-6(CF3)(2) hexagon includes one of the carbon atoms on a C-70 polar pentagon. The 10.3-16.2 Hz (7)J(F,F) NMR coupling constants for the end-of-ribbon CF3 groups, which are always para to their nearest-neighbor CF3 group, are consistent with through-space Fermi-contact interactions between the fluorine atoms of proximate, rapidly rotating CF3 groups. [ DOI ]

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