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Encapsulation‐Induced Remarkable Stability of a Hydrogen‐Bonded Heterocapsule |
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| Authors: | Keisuke Ichihara Prof Hidetoshi Kawai Yuka Togari Emi Kikuta Hitomi Kitagawa Prof Seiji Tsuzuki Dr Kenji Yoza Prof Masamichi Yamanaka Prof Kenji Kobayashi |
| Institution: | 1. Department of Chemistry, Faculty of Science, Shizuoka University, 836 Ohya, Suruga‐ku, Shizuoka 422‐8529 (Japan), Fax: (+81)?54‐238‐4933;2. Department of Chemistry, Faculty of Science, Tokyo University of Science, Kagurazaka 1‐3, Shinjuku‐ku, Tokyo 162‐8601 (Japan);3. Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305‐8568 (Japan), Fax: (+81)?29‐851‐5426;4. Bruker axs, 3‐9‐B Moriya, Kanagawa‐ku, Yokohama 221‐0022 (Japan) |
| Abstract: | Remarkably enhanced stability of the self‐assembled hydrogen‐bonded heterocapsule 1?2 by the encapsulation of 1,4‐bis(1‐propynyl)benzene 3 a was found with Ka=1.14×109 M ?1 in CDCl3 and Ka2=1.59×108 M ?2 in CD3OD/CDCl3 (10 % v/v) at 298 K. The formation of 3 a @( 1?2 ) was enthalpically driven (ΔH°<0 and ΔS°<0) and there was a unique inflection point in the correlation between ΔH° versus ΔS° as a function of polar solvent content. The ab initio calculations revealed that favorable guest–capsule dispersion and electrostatic interactions between the acetylenic parts (triple bonds) of 3 a and the aromatic inner space of 1?2 , as well as less structural deformation of 1?2 upon encapsulation of 3 a , play important roles in the remarkable stability of 3 a @( 1?2 ). |
| Keywords: | capsules cavitands host– guest systems hydrogen bonds supramolecular chemistry |