Synthesis, Characterization, Theoretical Modeling, and Polymerization of New Fluorophore-Containing Derivatives of Thiophene and Pyrrole

Two new derivatives of thiophene and pyrrole containing an anthracene model fluorophoric core were synthesized and characterized by NMR and IR spectroscopies, elemental analyses, voltammetry, and spectrofluorometry. Molecular orbital calculations were used to assess the conformational preferences and spin populations of these compounds. The cyclic voltammograms of these compounds contained signatures assignable to both the anthracene and the parent heterocyclic moieties. In this regard, these compounds represent good models for the concept of an electrophoric group discussed in our previous work. In the case of the thiophene derivative, the electrochemistry of the anthracene moiety preceded that of the thiophene ring. Open-shell calculations of the spin density within the unrestricted Hartree-Fock approximation revealed the electron density to be mostly delocalized onto the anthracene moiety. This coupled with unfavorable energetics inhibited polymerization of the thiophene derivative. On the other hand, polymerization of the pyrrole derivative was facile and readily probed by voltammetry. The electroactivity of the polymeric films was investigated with a ferrocene redox probe. In both cases, the fluorescence of the anthracene core was strongly quenched by the polymer backbone.