title: Complexation of polyoxometalates with cyclodextrins.
abstract: Although complexation of hydrophilic guests inside the cavities of hydrophobic hosts is considered to be unlikely, we demonstrate herein the complexation between γ- and β-cyclodextrins (γ- and β-CDs) with an archetypal polyoxometalate (POM)--namely, the [PMo12O40](3-) trianion--which has led to the formation of two organic-inorganic hybrid 2:1 complexes, namely [La(H2O)9]{[PMo12O40]⊂[γ-CD]2} (CD-POM-1) and [La(H2O)9] {[PMo12O40]⊂[β-CD]2} (CD-POM-2), in the solid state. The extent to which these complexes assemble in solution has been investigated by (i) (1)H, (13)C, and (31)P NMR spectroscopies and (ii) small- and wide-angle X-ray scattering, as well as (iii) mass spectrometry. Single-crystal X-ray diffraction reveals that both complexes have a sandwich-like structure, wherein one [PMo12O40](3-) trianion is encapsulated by the primary faces of two CD tori through intermolecular [C-H···O═Mo] interactions. X-ray crystal superstructures of CD-POM-1 and CD-POM-2 show also that both of these 2:1 complexes are lined up longitudinally in a one-dimensional columnar fashion by means of [O-H···O] interactions. A beneficial nanoconfinement-induced stabilizing effect is supported by the observation of slow color changes for these supermolecules in aqueous solution phase. Electrochemical studies show that the redox properties of [PMo12O40](3-) trianions encapsulated by CDs in the complexes are largely preserved in solution. The supramolecular complementarity between the CDs and the [PMo12O40](3-) trianion provides yet another opportunity for the functionalization of POMs under mild conditions by using host-guest chemistry.
authors.affiliation: †Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors.forename: Yilei
authors.initials: Y
authors.lastname: Wu
authors.affiliation: †Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.|∥Department of Chemistry, Loras College, 1450 Alta Vista Street, Dubuque, Iowa 52001, United States.
authors.forename: Rufei
authors.initials: R
authors.lastname: Shi
authors.affiliation: †Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors.forename: Yi-Lin
authors.initials: YL
authors.lastname: Wu
authors.affiliation: †Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors.forename: James M
authors.initials: JM
authors.lastname: Holcroft
authors.affiliation: †Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors.forename: Zhichang
authors.initials: Z
authors.lastname: Liu
authors.affiliation: †Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors.forename: Marco
authors.initials: M
authors.lastname: Frasconi
authors.affiliation: †Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Wasielewski
authors.affiliation: †Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.|‡Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry, Beijing Institute of Technology, Beijing 100081, P. R. China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: †Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States.
authors.forename: J Fraser
authors.initials: JF
authors.lastname: Stoddart
mesh_terms: D000838:Anions / Q000737:chemistry; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D017973:Tungsten Compounds / Q000737:chemistry*; D014961:X-Ray Diffraction; D047392:beta-Cyclodextrins / Q000737:chemistry*; D047408:gamma-Cyclodextrins / Q000737:chemistry*; D000099294:Polyoxometalates
chemical_list: D000838:Anions; D009942:Organometallic Compounds; D017973:Tungsten Compounds; D047392:beta-Cyclodextrins; D047408:gamma-Cyclodextrins; C102296:polyoxometalate I; D000099294:Polyoxometalates