Arene-perfluoroarene interactions in crystal engineering: structural preferences in polyfluorinated tolans
作者:Caroline E. Smith、Philip S. Smith、Rhodri Ll. Thomas、Edward G. Robins、Jonathan C. Collings、Chaoyang Dai、Andrew J. Scott、Simon Borwick、Andrei S. Batsanov、Stephen W. Watt、Stewart J. Clark、Christopher Viney、Judith A. K. Howard、William Clegg、Todd B. Marder
DOI:10.1039/b314094f
日期:——
The compounds 4-ROC6F4C=CPh ( 4) where R = Me ( a), Et ( b), Pr-n ( c), Pr-i ( d), Bu-n ( e), n-C5H11 (f), PhCH2 (g), PhCH2CH2 (h), 4-MeC6H4 (i), 4-EtC6H4 (j) and menthyl (k), have been prepared by reaction of C6F5C=CPh (3) with ROH in the presence of KOH, and characterised by NMR (H-1, C-13, F-19) and mass spectroscopy. The single-crystal structures of PhC=CPh.C(6)F5C=CC6F5 (1: 2), 3 and 4a, c, d, f, g, i have been determined by X-ray diffraction at 120 - 160 K, and that of 3 also calculated by an ab initio pseudo-potential DFT method. The tolan moiety is nearly planar in each molecule except 4a, which has a Ph/C6F5 dihedral angle of 25.8degrees. The R group adopts an out-of-plane orientation except in 4f, where the n-pentyl chain is nearly coplanar with the C6F5 group at the cost of severe distortion of the C(ar) - C(ar)-O angles ( which differ by 13.5degrees). The structures of 1: 2, 3 (pseudo-isomorphous with 1: 2), 4a, 4g ( disordered) and 4i contain stacks of alternating arene and perfluoroarene moieties; 4c and 4d form discrete centrosymmetric dimers with arene/ perfluoroarene overlap, while 4f forms infinite stacks without such overlap. Differential thermal analysis and transmitted polarised light microscopy revealed no liquid-crystalline behaviour of 3 and 4.