A series of monomers bearing fluorene and silafluorene with different bridging atoms and 3,4-ethylenedioxythiophene (EDOT) and 3,4-propylenedioxythiophene (ProDOT) as the donor units were synthesized via Stille coupling. To investigate the effect of different donor units and different bridging atoms, the optical and electrochemical behaviors of the monomers and their corresponding polymers were investigated by some electroanalytical and spectroscopic techniques. Electropolymerization of monomers was carried out potentiodynamically via repetitive cycling. Electrochemical investigations revealed that silafluorene bearing monomers and their corresponding polymers were found to exhibit slightly lower oxidation potentials and lower band gap (Eg) values as compared to their fluorene-containing analogs. Moreover, a comparison between two different donor groups revealed that the Eg of polymers bearing EDOT units was found to be lower (about 0.30 eV) as compared to ProDOT bearing ones due to the twist structure of ProDOT that reduces the overlap between the oxygen lone pairs and the aromatic thiophene ring. The results were further confirmed by DFT calculations.