New template reactions of salicylaldehyde S-methyl-isothiosemicarbazone with 2-formylpyridine promoted by Ni(II) or Cu(II) metal ions

► New Ni(II) complex of salicylaldehyde S-CH3-isothiosemicarbazone derivative. ► New Cu(II) complex of salicylaldehyde S-CH3-isothiosemicarbazone derivative. ► Template reactions of salicylaldehyde S-CH3-isothiosemicarbazone and 2-formylpyridine. ► New tetradentate ligands derivated from S-alkylated-isothiosemicarbazide.