Design and Synthesis of Two New Two-Photon Absorbing Pyridine Salts as Ligands and Their Rare Earth Complexes

Two new donor−bridge−acceptor (D−π−A) type ligands (<b>L</b><sup><b>1</b></sup>: <i>trans</i>-4-[(<i>p</i>-<i>N</i>,<i>N</i>-dimethylamino)styryl]-<i>N</i>-acetic-acid pyridinium and <b>L</b><sup><b>2</b></sup>: <i>trans</i>-4-[(<i>p</i>-<i>N</i>-2-hydroxyethyl-<i>N</i>-methylamino)styryl]-<i>N</i>-acetic-acid pyridinium) were designed and synthesized, which have double functions, two-photon absorption and coordination ability. Fourteen novel rare earth complexes have been prepared by the reaction of rare earth salts with the two ligands in ethanol solution, respectively. The two novel ligands and their complexes were characterized by single crystal X-ray diffraction determination. Linear and nonlinear optical properties of the ligands and three representative complexes are described. All these compounds exhibit relatively large two-photon absorption (TPA) cross sections. When pumped by a 1064 nm laser beam, two-photon-pump cavity lasing was observed in these compounds. Analysis of the lasing efficiencies and TPA cross sections show that rare earth ions have a significant influence on two-photon absorption properties of the complexes by adjusting the density of the chromophores.