Synthesis, Optical and Electrochemical Properties of Benzofuro[2,3-c]carbazoloquinol Fluorescent Dyes

Abstract

Benzofuro[2,3-c]carbazoloquinol derivatives, a new type of fluorescent dyes, were derived from the corresponding quinone, and their optical and electrochemical properties were investigated by photoabsorption and fluorescence spectroscopy, cyclic voltammetry (CV) and density functional theory (DFT) calculation. The quinol derivatives in 1,4-dioxane showed the photoabsorption band at around 435 nm (molar extinction coefficient (ε_max) = ca. 6000–8000 M⁻¹ cm⁻¹) and the fluorescence band at around 520 nm (fluorescence quantum yield (Φ_fl) = 0.24–0.28). The CV demonstrated that the quinol derivatives exhibit an irreversible oxidation wave at around −0.28 V versus Fc/Fc⁺. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of the quinol derivatives which were calculated using DFT at the B3LYP/6-31G(d,p) level are in good agreement with the experimental results.