Two new isomerically pure 1,7-substituted perylene-bisimide derivatives namely; 1,7-Di(4-tert-butylphenoxy)N,N'-bis[2-(diethylamino)ethyl]-3,4,9,10-perylene-tetracarboxylic diimide (6) and 1,7-Di(pyrrolidinyl)-N,N'-bis [2-(diethylamino)ethyl]-3,4,9,10-perylene- tetracarboxylic diimide (7), have been synthesized and their electronic absorption, steady-state fluorescence, and thermal properties were studied. Both compounds show good solubility in a range of organic solvents. Attachment of two electron donating tert-butyl-phenoxy groups at the 1,7-positions in (6) resulted in a red shifted absorption band with absorption maximum at 543 nm. UV-visible absorption spectrum of (7) shows a broad absorption band within the red region. Absorption maximum of lowest energy transition now shifts to 704 nm. Both compounds (6) and (7) exhibit low fluorescence quantum yields of 0.133 and 0.007, respectively. Density functional theory (DFT) calculations revealed that the attachment of electron donating groups at 1,7-positions of PDIs, results in an increase in frontier orbitals energy levels. Observed energy increase in HOMO is larger in each case, compared to the energy increase in LUMO levels. Calculated band gaps for (6) and (7) are 2.462 and 2.128 eV respectively.