91401-08-0Relevant academic research and scientific papers
Self-complementary [2]catenanes and their related [3]catenanes
Cabezon, Beatriz,Cao, Jianguo,Raymo, Francisco M.,Stoddart, J. Fraser,White, Andrew J. P.,Williams, David J.
, p. 2262 - 2273 (2007/10/03)
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 ×11 A) lined by π-electron-rich recognition sites and hydro-gen-bond acceptor groups. In spite of their apparently ideal recognition features, none of these [3]catenanes bind guests incorporating a π-electron-deficient bipyridinium unit. However, the template-directed syntheses of the [3]catenanes also produce, in yields of 2-23%, [2]catenanes incorporating a l,5-dioxynaphtho[38]crown-10 inter-locked with a bipyridinium-based tetracationic cyclophane. The X-ray structural analyses of two of these [2]catenanes revealed that a combination of [π...π] and [C-H...π] interactions is responsible for the formation of supramolecular homodimers in the solid state. 1H NMR spectroscopic investigations of the four [2]catenanes demonstrated that supramolecular homodimers are also formed (Ka= 17-31M-1, T= 185 K) in (CD3)2CO solutions. Dynamic 1H 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 (ΔGC? = 9-14 kcal mol-1) through each other's cavity in (CD3)2CO. Similarly, the 1,5-dioxynaphthalene and the bipyridinium ring systems rotate (ΔGc? =10-14 kcalmol-1) about their [O...O] and [N ... N] axes, respectively, in solution.
