New five-coordinated mercury (II) dyes based on a novel 2,2′:6′,2″-terpyridine ligand: Structures, photophysical properties and DFT calculations to evaluate the halogen effect on the two-photon absorption

Article abstract of DOI:10.1016/j.dyepig.2012.07.005

A simple D-π-A type ligand (L: 4′-(4-[4-(1H-[1,2,4]-triazolyl) styryl]phenyl)-2,2′:6′,2″-terpyridine) was designed and synthesized, which reacted with HgX₂ (X = Cl, Br, I, SCN) yielding a series of uncommon five-coordinated mercury (II) complexes (Dyes 1-4). The ligand and Dye 4 were characterized by single crystal X-ray diffraction determination. Linear and nonlinear optical properties of the ligand and dyes were exhibited. Experimental results revealed that the two-photon absorption (TPA) cross-sections of the four dyes are considerably larger than that of the ligand. Density function theory (DFT) calculations performed on Dyes 1-4 showed that the halogens affect the accepting capability of the complexed metal due to different electron inductive effects, which finally influence the TPA cross-section values.