Synthesis of a ruthenium(II) bipyridyl complex coordinated by a functionalized Schiff base ligand: Characterization, spectroscopic and isothermal titration calorimetry measurements of M2+ binding and sensing (M2+ = Ca2+, Mg2+)

Bis-[methylsalicylidine-4′benzoic acid]-ethylene (LH2) complexed with cis-Ru(bpy)2Cl2·2H2O provides a complex of composition [Ru(bpy)2L]·2NH4PF6 (1), which has been characterized spectroscopically. Its binding behaviour towards Mg2+ and Ca2+ ions is monitored using 1H NMR titration, isothermal titration calorimetry (ITC) and luminescence microscopy. The luminescent ruthenium complex binds Ca2+ in a more selective manner as compared to Mg2+.