Phenanthridine-containing complexes of mercury(II) and cadmium(II): synthesis, characterization, crystal structure determination, and luminescence properties

Two new Hg(II), {[Hg(phend)2Cl2].(0.5 phend) (1) and [Hg(phend)2Br2].(0.5 phend) (2)} and a new Cd(II) {[CdI2(phend)2] (3)} complexes, containing phenanthridine (phend) ligand, have been synthesized from the reaction of HgCl2 (1), HgBr2(2), and CdI2 (3) with phend, respectively. The complexes were thoroughly characterized by elemental analysis, FT-IR, UV, NMR, and emission spectroscopies. Moreover, single-crystal X-ray diffraction studies were undertaken to examine the coordination geometry of complexes 1-3 in the solid-state. According to X-ray analysis, the complexes 1 (τ4 = 0.77) and 2 (τ4 = 0.74) exhibit distorted tetrahedral geometries and 3 (τ4 = 0.90) shows slightly distorted tetrahedral geometry. So, complexes 1 and 2 have similar structures. However, the emission maximum of complex 1 is stronger than 2, which indicates that the different coordinated counter anions play a significant role in determining the photoluminescence properties of the complexes. Meanwhile, all complexes 1-3 have stronger emissions than free phend ligand in the DMSO solution.