Aryl pyrazaboles: a new class of tunable and highly fluorescent materials

Abstract

Novel aryl substituted pyrazaboles 2–9 with direct and acetylenic linkages were synthesized by Pd-catalyzed Suzuki or Sonogashira cross-coupling reactions. Their structural, thermal, and photonic properties were investigated. The results show that the aryl pyrazaboles 2–9 exhibit good thermal stability, high fluorescence quantum yield, and tunable photophysical properties. The aryl substituted acetylenic pyrazaboles 6–9 exhibit red shifted absorption, small Stokes shifts, and high quantum yields as compared to directly linked aryl pyrazaboles 2–5. The X-ray structures of the pyrazaboles 2, 5, and 7 are discussed. The computational studies were used to calculate the relative energy levels, and band gap in the pyrazaboles. The computational results show good agreement with the experimental results.