Three new five-coordinated mercury (II) dyes: Structure and enhanced two-photon absorption

A new donor–bridge–acceptor (D–π–A) type ligand (L: 4′-(4-[4-(imidazole)styryl]phenyl)-2,2′:6′,2″-terpyridine) with two-photon absorption and coordination ability was designed and synthesized. Self-assembly of the ligand with HgX2 (X = Cl, Br, I) yielded a series of new coordination complexes (Dyes 1–3) with five-coordinated mercury (ΙΙ), which were characterized by single crystal X-ray diffraction determination. Solvent molecules and various weak interactions, including hydrogen bonds (C–H···N, C–H···X) and π–π interactions played significant roles in the final topological structures. Linear and nonlinear optical properties of the ligand and three dyes were described. Experimental results revealed that two-photon absorption cross sections of three dyes are extraordinary stronger than that of ligand.

► We designed and synthesized a new donor-bridge-acceptor type ligand.
► Self-assembly of the ligand with HgX2 (X = Cl, Br, I) yielded a series of new coordination complexes with five-coordinated.
► These were characterized by single crystal X-ray diffraction determination.
► Linear and nonlinear optical properties of the ligand and three dyes were described.
► Experimental results revealed that two-photon absorption cross-sections of three dyes are extraordinary stronger than that of ligand.