title: Perylene Bisimide Cyclophanes with High Binding Affinity for Large Planar Polycyclic Aromatic Hydrocarbons: Host-Guest Complexation versus Self-Encapsulation of Side Arms.
abstract: Binding of guest molecules with high affinity and selectivity requires well-designed hosts to provide optimized interactions in the host-guest complexes. Herein we report the design and synthesis of new cyclophanes 2PBI(2,6-iPr)2and 2PBI(2,6-Ph)2based on core-disubstituted perylene bisimide (PBI) chromophores bearing two phenoxy bay-substituents that evoke almost planar PBI scaffolds. This strategy afforded the new cyclophanes with conformationally rigid cavities to ensure strong binding to stiff planar polycyclic aromatic hydrocarbons (PAHs). Our detailed host-guest binding studies with different PAHs by UV/Vis and fluorescence titration experiments revealed record binding strengths for PAHs with binding constants of up to 1.6×106m-1in chloroform at room temperature. One- and two-dimensional NMR experiments and solvent-dependent titration studies revealed self-encapsulation of the side arms of PBI bay-substituents into the cavities that attained high fluorescence quantum yields of these cyclophanes close to unity by preventing the interaction of PBI subunits in the excited states. The binding constants and Gibbs free energies of host-guest complexations disclosed significant effects of PBI bay-substituents and core twist on the binding affinity of the cyclophanes.
authors.affiliation: Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Spenst
authors.affiliation: Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Sieblist
authors.affiliation: Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074, Würzburg, Germany.|Center for Nanosystems Chemistry & Bavarian Polymer Institute (BPI), Universität Würzburg, Theodor-Boveri-Weg, 97074, Würzburg, Germany.
authors.forename: Frank
authors.identifier: http://orcid.org/0000-0001-7245-0471
authors.initials: F
authors.lastname: Würthner
keywords: cyclophanes; dyes/pigments; host-guest chemistry; perylene bisimides; self-encapsulation