The reaction of diacetyl-2-(4-methyl-3-thiosemicarbazone) with 2-hydrazinopyridine leads to the formation of two products, LH2 and [LH3]Cl depending on the amount of HCl present in the reaction mixture. The reactivity of these molecules towards zinc(II), cadmium(II) and mercury(II) nitrates has been investigated under different reaction conditions. The new complexes have been fully characterized by 113Cd and 199Hg NMR, as well as 13C and 113Cd CP/MAS NMR and by X-ray diffraction. All the complexes have the same 1:1 ligand to metal ratio, but the protonation state of the ligand depends on the reaction conditions, from neutral to double deprotonated. The coordination numbers in the complexes depend on the metal preferences leading to the formation of complexes with different structural characteristics.