Selective fluorescence sensing of Ni2+ by tetradentate ligands: Synthesis of nickel complexes and crystal structures

Nickel complexes [(Ni(Gimpy)(μ–Cl))2](ClO4)2 (Gimpy, ((1Z,2Z)-1,2-bis(2-phenyl-2-(pyridine-2-yl)hydrazono)ethane)) (1) and [(Ni(Timpy)(μ–Cl))2](ClO4)2·2(CH3)2CO (Timpy, (1,2-bis((E)-(2-phenyl-2-(pyridine-2-yl)hydrazono)methyl)benzene)) (2·2(CH3)2CO) were synthesized and characterized by spectroscopic studies. The molecular structures of ligand Gimpy and [(Ni(Timpy)(μ–Cl))2](ClO4)2·2(CH3)2CO were established by X-ray crystallography. Redox and magnetic properties are also described. Both Gimpy and Timpy exhibited fluorescence characteristics which were significantly enhanced in the presence of Ni2+ in methanol indicating that these molecules may be exploited as molecular sensors for Ni2+ ion.