New conjugated polymerizable pyrrole and 2,5-dithienylpyrrole azobenzene dyes: synthesis and spectroelectrochemical properties

We describe the first easy syntheses of new fully conjugated monomers and their derived polymers containing a photoisomerizable azobenzene group, along with their electrochemical properties. Two classes of compounds have been studied differing in the nature of the polymerizable unit: pyrrole or 2, 5-dithienylpyrrole. A rather effective electronic interaction between the pyrrole and azo moieties has been demonstrated, while the conjugation is much less pronounced in the case of the terheterocycle. This behavior has been ascribed to a twisted conformation of the 2,5-dithienylpyrrole compounds in the neutral form, as demonstrated by theoretical modeling. All these molecules are electropolymerizable monomers, although the 2,5-dithienylpyrrole compounds lead only to thin films of conducting polymers when compared to their pyrrole analogs.