Donor- and acceptor-functionalized dibenzo[a,e]pentalenes: modulation of the electronic band gap
Dibenzo[a,e]pentalene (DBP) is a low-bandgap organic semiconductor. A versatile synthetic route to DBPs substituted with aryl or alkyl groups in the 5,10-positions and electron-donating or -accepting functionalities in the 2,7-positions is described. Six donor- or acceptor-functionalized DBP derivatives were synthesized that show amphoteric redox behavior and band gaps around 2 eV. Through choice of the 2,7-substituents, the HOMO/LUMO energy levels and band gaps can be adjusted within a range of up to 0.6 eV. In the solid state, the DBP derivatives assume herringbone-type packing structures.