Threading a Linear Molecule Through a Macrocycle Thanks to Boron: Optical Properties of the Threaded Species and Synthesis of a Rotaxane

Two BODIPYs and two boron beta-diketonates were threaded through a macrocycle bearing a 2,2'-biphenol unit, showing thus the ability of boron to act as a gathering atom. The new threaded species were characterized by 1D and 2D NMR spectroscopy as well as by X-ray crystallography for one of them and their properties rationalized with quantum chemistry to unravel the vibronic contributions. The BODIPYs exhibited interesting fluorescence features with quantum yields up to 91 % and enhanced photostability compared to their non-threaded homologues. A rotaxane was synthesized using this threading strategy after stoppering and removing the boron with potassium hydroxide. Boron-containing species were threaded through macrocycles bearing a 2,2'-biphenol unit. The new threaded species exhibited interesting fluorescence features with quantum yields up to 91 % and an enhanced photostability. Their properties were rationalized with quantum chemistry to unravel the vibronic contributions. This methodology was used to synthesize a rotaxane. image