or -Isomers Arising from the Geometries of Ligands in the Mercury Complex of 2-(Anthracen-9-ylmethylene)--phenylhydrazine Carbothioamide.

An anionic mercury(II) complex of 2-(anthracen-9-ylmethylene)--phenylhydrazine carbothioamide () and two isomers of a neutral mercury(II) complex of the anion of the same ligand () were reported. The anionic complex had a monodentate ligand (a neutral form of the ligand) and chloride ligands. The two conformational isomers were of the neutral mercury(II) complex . The two isomers were from the or geometry of the ligands across the conjugated C=N-N=C-N scaffold of the coordinated ligand. The two isomers of the complex were independently prepared and characterized. The spectroscopic properties of the isomers in solution were studied by H NMR as well as fluorescence spectroscopy. Facile conversion of the -isomer to the -isomer in solution was observed. Density functional theory (DFT) calculations revealed that the Z-isomer of the complex was stable compared to the E-isomer by an energy of 14.35 kJ/mol; whereas, E isomer of the ligand was more stable than Z isomer by 8.37 KJ/mol. The activation barrier for the conversion of the -isomer to the -isomer of the ligand was 167.37 kJ/mol. The role of the mercury ion in the conversion of the -form to the -form was discussed. The mercury complex · had the -form of the ligand. Distinct photophysical features of these mercury complexes were presented.