From Packed "Sandwich" to "Russian Doll": Assembly by Charge-Transfer Interactions in Cucurbit[10]uril.
Chemistry
; 22(49): 17612-17618, 2016 Dec 05.
Article
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| MEDLINE
| ID: mdl-27862408
ABSTRACT
As the host possessing the largest cavity in the cucurbit[n]uril (CB[n]) family, CB[10] has previously displayed unusual recognition and assembly properties with guests but much remains to be explored. Herein, we present the recognition properties of CB[10] toward a series of bipyridinium guests including the tetracationic cyclophane known as blue box along with electron-rich guests and detail the influence of encapsulation on the charge-transfer interactions between guests. For the mono-bipyridinium guest (methylviologen, MV2+ ), CB[10] not only forms 11 and 12 inclusion complexes, but also enhances the charge-transfer interactions between methylviologen and dihydroxynaphthalene (HN) by mainly forming the 121 packed "sandwich" complex (CB[10]â
2 MV2+ â
HN). For guest 1 with two bipyridinium units, an interesting conformational switching from linear to "U" shape is observed by adding catechol to the solution of CB[10] and the guest. For the tetracationic cyclophane-blue box, CB[10] forms a stable 11 inclusion complex; the two bipyridinium units tilt inside the cavity of CB[10] according to the X-ray crystal structure. Finally, a supramolecular "Russian doll" was built up by threading a guest through the cavities of both blue box and CB[10].
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