Fluorescent macromolecular perylene diimides containing pyrene or indole units in bay positions

Novel, symmetric and unsymmetric perylene diimide dyes with pyrene or indole units in the bay positions of the perylene ring were synthesized and characterized using FT-IR, 1H and 13C NMR, MS, UV-Vis spectra and cyclic voltammetry. The λ max in different solvents were in the range 526–585 nm and emission wavelengths of the dyes exhibited positive solvatochromism with increasing solvent polarity. Long wavelength emissions >750 nm of dyes with pyrene units displayed charge-separated state of perylene–pyrene system. Dyes with pyrene or indole units showed greater photostability in toluene than dyes which did not contain these bulky substituents. Incorporating electron-donating indole substituents lowered the band gap energies and, therefore, the HOMO energy levels were increased. The energy density and shape of the molecular orbitals were calculated theoretically.