A Raman and computational study of two dithienyl naphthodithiophenes:: Synthesis and characterization of new polymers showing low band gap optical and electroactive features

Two isomeric dithienyl naphthodithiophenes and their corresponding polymers have been thoroughly studied by using a combination of spectroscopic, electrochemical, and quantum chemistry techniques. The change between the syn and anti configuration of the sulfur atoms of the core translates into important differences in their optical and electrochemical properties. This study reveals the existence in the syn isomer of a bonding interaction, while in the anti isomer there exists a more delocalized pi-electron distribution. The full assignment of the Raman spectra of the monomers has allowed to interpret, assign, and correlate the spectra of the polymers. Upon polymerization the Raman data indicate an increment of the bond length relaxation pattern for the electronic structure of the polymer regarding the monomers. The two polymers are surprisingly strong amphoters, showing very stable oxidation and reduction waves at relatively low potentials at the same time that they behave as low band gap polymers. From a material point of view, these polymers are very interesting substrates for electrically active layers with relevant photophysical properties.