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, CH2Cl2, 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 (Φfl = 0.03 in CH2Cl2) and oc2 (Φfl < 0.01 in CH2Cl2) is almost completely quenched compared with the highly emissive reference compound oref (Φfl = 0.99 in CH2Cl2) 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 kCS = 3 × 1010 s-1 (τCS = 32 ps) for compound oc and kCS = 9 × 1010 s-1 (τCS = 11 ps) for compound oc2 (in CH2Cl2) leading to a short-lived charge-separated state consisting of the reduced perylene bisimide unit and the oxidized calix[4]arene moiety.
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