Exciplex-like emission from a closely-spaced, orthogonally-sited anthracenyl-boron dipyrromethene (Bodipy) molecular dyad

Abstract

A molecular dyad, ANTBD, has been prepared that incorporates a boron dipyrromethene (Bodipy) group functionalized at the meso position with an anthracenyl unit. Emission from the dyad contains contributions from both localized fluorescence from the Bodipy unit and exciplex-like emission associated with an intramolecular charge-transfer state. The peak position, intensity and lifetime of this exciplex emission are solvent dependent and the shift in the emission maximum shows a linear relationship to the solvent polarity function (Δf). The calculated dipole moment for the exciplex is 22.5 ± 2.2 D. The radiative rate constant (k_RAD) for exciplex emission decreases progressively with increasing solvent polarity. In this latter case, k_RAD shows an obvious dependence on the energy gap between the exciplex state and the first-excited singlet state resident on the Bodipy unit. The emission characteristics for ANTBD dissolved in perfluorooctane are used to characterize the refractive index and dielectric constant of the solvent.