Excited State Interactions in Calix[4]arene−Perylene Bisimide Dye Conjugates:  Global and Target Analysis of Supramolecular Building Blocks

Abstract

The photophysical properties of two supramolecular building blocks oc and oc2 consisting of a perylene bisimide chromophore substituted with either one or two calix[4]arene units in the N -imide position as well as those of the reference compound oref without calix[4]arene substituents were investigated. A complete picture of the processes taking place after photoexcitation in toluene, CH 2 Cl 2, and benzonitrile was obtained by means of UV/vis absorption, steady state and time-resolved emission, and femtosecond transient absorption spectroscopy. It has been found that the fluorescence emission of compounds oc ( Φ fl = 0.03 in CH 2 Cl 2 ) and oc2 ( Φ fl < 0.01 in CH 2 Cl 2 ) is almost completely quenched compared with the highly emissive reference compound oref ( Φ fl = 0.99 in CH 2 Cl 2 ) because of fast electron-transfer processes from the calix[4]arene moieties to the perylene bisimide chromophore. This predominantly takes place with rate constants of k CS = 3 × 10 10 s -1 ( τ CS = 32 ps) for compound oc and k CS = 9 × 10 10 s -1 ( τ CS = 11 ps) for compound oc2 (in CH 2 Cl 2 ) leading to a short-lived charge-separated state consisting of the reduced perylene bisimide unit and the oxidized calix[4]arene moiety.