Metal-Free, Regioselective Diyne Polycyclotrimerization:  Synthesis, Photoluminescence, Solvatochromism, and Two-Photon Absorption of a Triphenylamine-Containing Hyperbranched Poly(aroylarylene)

A hyperbranched poly(aroylarylene) containing triphenylamine (TPA) moiety (hb-P1) is synthesized by metal-free polycyclotrimerization of N,N-bis(4-ethynylcarbonylphenyl)aniline (1) in a high yield (86%) with a perfect 1,3,5-regioregularity. The polymer is soluble in common organic solvents such as THF and chloroform and is thermally stable, losing 5% of its weight when heated to a temperature as high as ∼450 °C. The polymer is fluorescent and solvatochromic, whose emission color changes from ∼455 nm (blue) in toluene to 549 nm (yellow) in DMF. The polymer exhibits a large two-photon absorption cross-section due to the intramolecular charge transfer between its electron-donating TPA and electron-withdrawing 1,3,5-tricarbonylbenzene groups.