title: From Packed "Sandwich" to "Russian Doll": Assembly by Charge-Transfer Interactions in Cucurbit[10]uril.
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 1:1 and 1:2 inclusion complexes, but also enhances the charge-transfer interactions between methylviologen and dihydroxynaphthalene (HN) by mainly forming the 1:2:1 packed "sandwich" complex (CB[10]⋅2 MV2+⋅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 1:1 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].
authors.affiliation: School of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, Wuhan, 430081, P.R. China.
authors.forename: Wanjun
authors.identifier: http://orcid.org/0000-0002-3099-032X
authors.initials: W
authors.lastname: Gong
authors.affiliation: School of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, Wuhan, 430081, P.R. China.
authors.forename: Xiran
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA.
authors.forename: Peter Y
authors.identifier: http://orcid.org/0000-0001-5762-3469
authors.initials: PY
authors.lastname: Zavalij
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA.
authors.forename: Lyle
authors.identifier: http://orcid.org/0000-0002-4079-332X
authors.initials: L
authors.lastname: Isaacs
authors.affiliation: School of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, Wuhan, 430081, P.R. China.
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: School of Chemistry and Chemical Engineering, Wuhan University of Science and Technology, Wuhan, 430081, P.R. China.|The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, 430081, P.R. China.
authors.forename: Simin
authors.identifier: http://orcid.org/0000-0002-8696-4833
authors.initials: S
authors.lastname: Liu
keywords: Russian dolls; charge-transfer interactions; cucurbituril; host-guest systems; supramolecular chemistry