Electrogenerated Chemiluminescence of a BODIPY Derivative with Extended Conjugation

The electrochemical properties and electrogenerated chemiluminescence (ECL) of a borondipyrromethane (BODIPY) derivative, 2,8-bis(4-isopropylphenyl)-difuro[2, 3-b][3, 2-g]-5,5-difluoro-5-bora-3a,4a-diaza-s-indacene (Derivative 1, Figure) are described. Derivative 1 emitted ECL in the range of 650∼800 nm by using tripropylamine (TPA) as a coreactant. In the cyclic voltammogram, Derivative 1 showed a reversible oxidation wave, whereas the reduction wave was irreversible. Energetically, it is likely that triplet-triplet annihilation is the main pathway to emit ECL through the ion annihilation of the radical anions and cations of Derivative 1 whereas the lowest excited singlet state of Derivative 1 is directly produced with TPA. The maximum ECL wavelengths (670 nm at 0.01 mM) were red-shifted with increasing the concentration of Derivative 1 because of the self-absorption resulted from a small Stokes shift (∼10 nm). Relative ECL efficiency of Derivative 1 was 0.13 compared to that of a Ru(bpy)²⁺/TPA system.