Synthesis, Crystal Structure, Electrochemical and Fluorescence Studies of a Novel Zn(II)-Fluorophore, 1,10-Phenanthroline-5,6-dione (Phen-dione)

The crystal structure of 1,10-phenanthroline-5,6-dione ligand with Zn(II), tris(1,10-phenanthroline-5,6-dione)zinc(II) hexafluorophosphate, [Zn(phen-dione)3](PF6)2, is reported. The complex was characterized by elemental analysis, IR, 1H NMR,electronic absorption spectroscopies, cyclic voltammetry and X-ray crystallography. Yellow crystals of [Zn(phen-dione)3](PF6)2 were formed by ether diffusion into an acetonitrile solution of the complex. The title complex crystallized in monoclinic crystal system (Z = 2) with space groups of P21, a = 12.0299(15) Å, b = 14.5306(19) Å, c = 13.1879(17) Å, = 94.058(2)° and V = 2299.5(5) Å3. The structure was refined by using 10048 independent reflections, with I > 2s(I) to an R factor of 0.0490. Singlecristal structure showed that the coordination geometry around the Zn(II) was a distorted octahedron. The complex showed an intense fluorescence band at visible region (690 nm) in CH3CN with an excitation wavelength of 310 nm at 25.0 ± 0.1 ºC. Cyclic voltammogram of the title complex showed two quasi-reversible reduction couples at negative potential, which were assigned to the consecutive reduction of phen-dione ligand to phen-semiquinonate and phen-diolate respectively by analogy to other phen-dione complexes at scan rate 200 mV s-1.