Photorefractive effects and structure/property correlation of oligothiophenes functionalized with nonlinear optical chromophores

A homologous series of fully functionalized regioregular oligo(3-alkylthiophenes) 10-12 bearing a nonlinear optical (NLO) chromophore was synthesized. An alternating sequence of bromination and Stille cross-coupling reactions was developed for the synthesis of these oligomers and regiochemically pure, trimethylsilyl-substituted bithiophene organostannane 2c was utilized as the building block. The resulting materials were shown to form stable amorphous films exhibiting a large photorefractive (PR) effect. Two-beam coupling and degenerate four-wave mixing experiments demonstrate large optical net gain and high diffraction efficiency. It was also found that the PR performance of these oligomers depends on the pi -conjugation chain length with an optimized conjugation length.