title: ExBox: a polycyclic aromatic hydrocarbon scavenger.
abstract: A template-directed protocol, which capitalizes on donor-acceptor interactions, is employed to synthesize a semi-rigid cyclophane (ExBox(4+)) that adopts a box-like geometry and is comprised of π-electron-poor 1,4-phenylene-bridged ("extended") bipyridinium units (ExBIPY(2+)). ExBox(4+) functions as a high-affinity scavenger of an array of different polycyclic aromatic hydrocarbons (PAHs), ranging from two to seven fused rings, as a result of its large, accommodating cavity (approximately 3.5 Å in width and 11.2 Å in length when considering the van der Waals radii) and its ability to form strong non-covalent bonding interactions with π-electron-rich PAHs in either organic or aqueous media. In all, 11 PAH guests were observed to form inclusion complexes with ExBox(4+), with coronene being the largest included guest. Single-crystal X-ray diffraction data for the 11 inclusion complexes ExBox(4+)⊂PAH as well as UV/vis spectroscopic data for 10 of the complexes provide evidence of the promiscuity of ExBox(4+) for the various PAHs. Nuclear magnetic resonance spectroscopy and isothermal titration calorimetric analyses of 10 of the inclusion complexes are employed to further characterize the host-guest interactions in solution and determine the degree with which ExBox(4+) binds each PAH compound. As a proof-of-concept, a batch of crude oil from Saudi Arabia was subjected to extraction with the water-soluble form of the PAH receptor, ExBox·4Cl, resulting in the isolation of different aromatic compounds after ExBox·4Cl was regenerated.
authors.affiliation: Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Barnes
authors.forename: Michal
authors.initials: M
authors.lastname: Juríček
authors.forename: Nathan L
authors.initials: NL
authors.lastname: Strutt
authors.forename: Marco
authors.initials: M
authors.lastname: Frasconi
authors.forename: Srinivasan
authors.initials: S
authors.lastname: Sampath
authors.forename: Marc A
authors.initials: MA
authors.lastname: Giesener
authors.forename: Psaras L
authors.initials: PL
authors.lastname: McGrier
authors.forename: Carson J
authors.initials: CJ
authors.lastname: Bruns
authors.forename: Charlotte L
authors.initials: CL
authors.lastname: Stern
authors.forename: Amy A
authors.initials: AA
authors.lastname: Sarjeant
authors.forename: J Fraser
authors.initials: JF
authors.lastname: Stoddart
mesh_terms: D018360:Crystallography, X-Ray; D008958:Models, Molecular; D015394:Molecular Structure; D011084:Polycyclic Aromatic Hydrocarbons / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D011084:Polycyclic Aromatic Hydrocarbons