New Low Bandgap Compounds Comprised of Pyromellitic Diimide and Imine Units

New bisimide derivatives, low molecular compounds with π-π* conjugated system consisting of a pyromellitic diimide core and imine linkages were synthesized by Schiff bases reactions, the studied compounds were prepared from N,N'-bis amino pyromellitic diimide which was condensed with different derivatives of aldehydes, the materials show a high melting point and some above 300 ◦C depended intramolecular attractive and the Vander Waals attraction between various substituent groups. The optical properties of the prepared compounds were investigated by UV–vis measurement. The prepared compounds showed the highest intensity with maximum absorbance at 243-908 nm. In all studied molecules, the electrochemically estimated theoretical HOMO level is in the range of -7.515 to -7320 eV, whereas the LUMO level is close to 7.219 eV and -5.889 eV. The estimated compounds exhibited low electrochemical band gap (