Photophysical and Electrochemical Properties of Functionalized Benzo[ghi]perylene and Coronene Derivatives

Planar polycyclic aromatic hydrocarbons (PAHs) such as benzo[ghi]perylene (Bp) and coronene (Cor) are expected for electronic device applications and solar energy conversion because of their π-conjugated structures and ordered aggregate properties. In this work, a series of Bp and Cor derivatives substituted by methoxycarbonyl (COOMe: electron-withdrawing unit) and methoxy (MeO: electron-donating unit) groups were systematically synthesized considering the differences in types and numbers of substituent groups (Figure 1).

The electrochemical, spectroscopic and photophysical properties of these molecules were investigated in full detail by cyclic voltammetry, steady-state and time-resolved spectroscopy and quantum yield measurements of fluorescence and intersystem crossing. The synthetic introduction of proper substituents on the aromatic ring therefore enables us to successfully control the electrochemical behavior. For example, with increasing the number of COOMe groups, the reduction and oxidation potentials are significantly shifted to positive direction. On the other hand, the steady-state absorption and fluorescence spectra also become red-shifted and broadened as compared to those of unsubstituted Bp and Cor.

Additionally, a systematic comparison of quantum yields and rate constants of the excited-state dynamics also reveals that the fluorescence quantum yields dramatically increase with an increase of the number of COOMe groups in both Bp and Cor derivatives. The fabrication and measurement of filed effect transistors (FET) utilizing these derivatives are also discussed in this presentation.