Synthesis and enhanced two-photon absorption properties of tetradonor-containing anthracene-centered 2-D cross-conjugated polymers

Abstract

In this paper, we demonstrate the synthesis and enhanced two-photon absorption (TPA) properties of two novel tetradonor-containing anthracene-centered cross-conjugated polymers with a 2,6-diarylenevinylene/9,10-diaryleneethynylene motif, poly[9,10-bis(p-didecylaminophenylethynyl)-2,6-anthracenevinylene-alt-N-octyl-3,6-/2,7-carbazolevinylene] (P1/P2). P1 and P2 are synthesized by means of a Sonogashira coupling of 9,10-dibromo-2,6-bis(diethylphosphorylmethyl)anthracene with arylethynylene followed by a Wittig–Horner reaction with arylene-dicarbaldehyde. They have number average molecular weights of 1.82 × 10⁴ and 2.15 × 10⁴ g mol^-1, respectively, and are readily soluble in common organic solvents and emit strong orange one- and two-photon excitation fluorescence with peaks around 555 nm. The maximal TPA cross sections (δ) of P1 and P2 in toluene, measured by the two-photon-induced fluorescence method, are 2360 and 1520 Gm per repeating unit, respectively. These δ values are significantly larger than the sum of that of the two corresponding linear analogues, indicating that the cooperatively enhanced δ has been achieved in the anthracene-centered cross-conjugated polymers, which are different from the reported characteristics of benzene- and pyrazine-centered cross-conjugated chromophores that show no enhancement of δ. These results underline that an anthracene ring is a promising cross π-center and can be used to construct novel cross-conjugated polymers exhibiting distinctive optoelectronic properties.