Foldamer with a spiral perylene bisimide staircase aggregate structure

Although the precise control of dye-dye interactions is known to be of fundamental importance to achieve desired functional properties in pi-conjugated materials, there are only sporadic examples where precise structural control of dye-dye interactions could be achieved by the attachment of the chromophores to an oligomeric or polymeric backbone. In this edge article, we introduce an oligophenylene ethynylene/perylene bisimide (PBI) dye system which is conceived by the foldamer concept. The molecular design enables folding of the pi-conjugated oligomer to give a geometrically well-defined pi-stack of intrastrand PBI molecules. The synthesis of the foldamer and its characterization by MALDI-TOF mass spectrometry are described, and the average size is estimated by gel permeation chromatography (GPC) and diffusion ordered NMR spectroscopy (DOSY). The folding dynamics are demonstrated by ultraviolet/visible absorption and fluorescence emission spectroscopic studies as the folded and unfolded states possess distinct optical properties. Quantum dynamic considerations revealed a good agreement of the calculated aggregate absorption spectrum with those obtained experimentally.