作者:Beatriz Cabezon、Jianguo Cao、Françisco M. Raymo、J. Fraser Stoddart、Andrew J. P. White、David J. Williams
DOI:10.1002/1521-3765(20000616)6:12<2262::aid-chem2262>3.0.co;2-g
日期:2000.6.16
Three [3]catenanes with cavities large enough to accommodate aromatic guests have been designed and synthesized (yields = 5-20 %) by means of kinetically controlled self-assembly processes The X-ray structural analysis of one of three [3]catenanes confirmed the presence of a rectangular cavity (dimensions = 7 x 11 Angstrom) lined by pi-electron-rich recognition sites and hydrogen-bond acceptor groups. Ln spite of their apparently ideal recognition features, none of these [3]catenanes bind guests incorporating a pi-electron-deficient bipyridinium unit. However, the template-directed syntheses of the [3]catenanes also produce, in yields of 2-23%, [2]catenanes incorporating a 1,5-dioxynaphtho[38]crown-10 interlocked with a bipyridinium-based tetracationic cyclophane. The X-ray structural analyses of two of these [2]catenanes revealed that a combination of [pi ... pi] and [C-H ... pi] interactions is responsible for the formation of supramolecular homodimers in the solid state. H-1 NMR spectroscopic investigations of the four [2]catenanes demonstrated that supramolecular homodimers are also formed (K-a-17-31 M-1, T = 185 K) in (CD3)(2)CO solutions. Dynamic H-1 NMR spectroscopy revealed that the 1,5-dioxynaphtho[38]crown-10 and tetracationic cyclophane components in the four [2]catenanes and in the three [3]catenanes circumrotate: (Delta G(c)* = 9-14 kcal mol(-1)) through each other's cavity in (CD3)(2)CO. Similarly, the 1,5-dioxynaphthalene and the bipyridinium ring systems rotate (Delta G(c)* = 10-14 kcal mol(-1)) about their [O ... O] and [N ... N] axes, respectively, in solution.