Sequential FRET Processes in Calix[4]arene-Linked Orange-Red-Green Perylene Bisimide Dye Arrays

  • Catharina Hippius, Institute of Materials Research and Engineering (IMRE), Singapore
  • Dr Ivo van Stokkum, Vrije Universiteit van Amsterdam, The Netherlands
  • Marcel Gsaenger, University of Wuerzburg, Germany
  • Michiel Groeneveld, Universiteit van Amsterdam, The Netherlands
  • Dr R Williams, Universiteit van Amsterdam, The Netherlands
  • Prof F Wuerthner, University of Wuerzburg, Germany
  • A comprehensive series of perylene bisimide (PBI) – calix[4]arene arrays composed of up to three different types of PBI chromophores (orange, red and green) has been synthesized. Within these arrays calix[4]arene scaffolds are applied to organize the PBI chromophores in a zigzag-type arrangement providing defined distances and angles between the individual dye units (see Figure). The characteristic feature of the as such constructed arrays is that the individual chromophoric building blocks can be easily replaced by each other as well as their optical properties can be fine-tuned without influencing the overall geometric arrangement of the supramolecular system. Owing to the excellent spectral overlap of the individual dye units, these arrays display very efficient sequential energy transfer processes. A quantitative analysis of the photophysical processes after photoexcitation as well as their rates have been obtained by using UV/vis absorption, steady state and time-resolved emission, femtosecond transient absorption spectroscopy and spectrotemporal analysis of the femtosecond transient absorption data. According to these studies, rate constants for the energy transfer from the orange perylene bisimide chromophoric unit to the red chromophoric unit (k = 6.4 x E11s-1 for compound or), from the red PBI moiety to the green dye unit (k = 4.0 x E11s-1 for compound rg), and slightly less efficient from the orange to the green PBI chromophore (k = 1.5 x E11s-1 for compound og) have been determined within these systems. The experimentally obtained rate constants are in very good agreement with those calculated according to the Förster theory.