A Sulfur-Terminal Zn(II) Complex and Its Two-Photon Microscopy Biological Imaging Application

A novel sulfur-terminal Zn(II) complex Zn(S)2L (L = N-hexyl-3-{2-[4-(2,2′:6′,2′′-terpyridin-4′-yl)phenyl] ethenyl}carbazole) was obtained by a facile solvothermal process. The unique feature in this new reaction design is the use of ZnS nanocrystals as a precursor and bulky chromophoric L as an ancillary ligand. The versatility of the two terminal sulfur atoms is relevant to biological system. The resulting Zn(S)2L complex shows two-photon excited fluorescence (TPEF), which has been proven to be potentially useful for two-photon microscopy imaging in living cells. In addition, cytotoxicity tests showed that the low-micromolar concentrations of Zn(S)2L did not cause significant reduction in cell viability over a period of at least 24 h and should be safe for further biological studies.