New zinc(II) dyes with enhanced two-photon absorption cross sections based on the imidazolyl ligand (vol 6, pg 77849, 2016)

A series of new zinc(II) complexes (Dyes 1-3) were obtained by self-assembly of the donor-bridge-donor (D-pi-D) type ligand L with ZnX2 (X = Br, I, SCN). The single crystal of Dye 3 was obtained by slow evaporation of a mixture solution of methanol and dichloromethane. The molecular structure has been determined by X-ray crystallography. Hydrogen bonds (C-H center dot center dot center dot N, C-H center dot center dot center dot S) play significant roles in the final topological structures. Linear and nonlinear optical properties of the ligand and complexes were investigated in details. Experimental results revealed that effective two-photon absorption (TPA) cross sections of these complexes are larger than that of ligand L (18.7 GM) with the maximum values of 88.7 GM (Dye 1), 41.9 GM (Dye 2) and 46.5 GM (Dye 3) in DMF, respectively. The biological imaging result shows that L and Dyes 1-3 had excellent penetrability in living cells.