Novel Panchromatic Absorption Material, Isoindigo-based A-[pi]-A-[pi]-A Small Molecule

One A-[pi]-A-[pi]-A small molecule [I(TPTA)2], containing two planar acceptor units, isoindigo, and 2,4,6-triphenyl-1,3,5-triazine (TPTA) with thiophene as bridge, was synthesized by the Suzuki coupling reaction. The obtained molecule exhibits panchromatic absorption between 300 and 720 nm with a large half band width up to 350 nm in thin solid film. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of [I(TPTA)2] are -5.50 and -3.82 eV. Density functional theory (DFT) calculations indicated that the structure of [I(TPTA)2] is quite planar and that the electron density is mainly delocalized over the central isoindigo and thiophene units.