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

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 x 10(4) and 2.15 x 10(4) 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 (delta) of P1 and P2 in toluene, measured by the two-photon-induced fluorescence method, are 2360 and 1520 Gm per repeating unit, respectively. These delta values are significantly larger than the sum of that of the two corresponding linear analogues, indicating that the cooperatively enhanced delta 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 delta. These results underline that an anthracene ring is a promising cross pi-center and can be used to construct novel cross-conjugated polymers exhibiting distinctive optoelectronic properties.