title: Extended and contorted conformations of alkanediammonium ions in symmetrical α,α',δ,δ'-tetramethylcucurbit[6]uril cavity.
abstract: Binding interactions between symmetrical α,α',δ,δ'-tetramethylcucurbit[6]uril (TMeQ[6]) and a series of alkyldiammonium ions in aqueous solution and in the solid state were investigated by (1)H NMR spectroscopy, MALDI-TOF mass spectrometry, X-ray crystallography, and isothermal titration calorimetry (ITC). Their (1)H NMR spectra reveal that the actual binding behaviors vary depending upon the alkyl chain length. Their single-crystal X-ray diffraction analyses indicate the guest 1,2-ethanediammonium is located outside of the TMeQ[6] portal, while the other four alkyldiammonium guests can be accommodated in the TMeQ[6] cavity, forming 1:1 inclusion complexes. Most importantly, the long-chain alkyldiammoniums (1,8-octanediammonium and 1,10-decanediammonium) take a contorted conformation when bound within the TMeQ[6] cavity. Additionally, ITC experiments show that the complexation of the alkyldiammonium guests with TMeQ[6] is mainly enthalpy driven, which benefits from ion-dipole interactions.
authors.affiliation: Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province, Guizhou University , Guiyang 550025, P. R. China.
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.forename: Li-Mei
authors.initials: LM
authors.lastname: Zheng
authors.forename: Zhong-Zheng
authors.initials: ZZ
authors.lastname: Gao
authors.forename: Xin
authors.initials: X
authors.lastname: Xiao
authors.forename: Qian-Jiang
authors.initials: QJ
authors.lastname: Zhu
authors.forename: Sai-Feng
authors.initials: SF
authors.lastname: Xue
authors.forename: Zhu
authors.initials: Z
authors.lastname: Tao
authors.forename: Jing-Xin
authors.initials: JX
authors.lastname: Liu
authors.forename: Gang
authors.initials: G
authors.lastname: Wei