AbstractThe coordination reaction characteristics and mechanisms of the title new ligands (1(H2plpa), 2(H2plal), and 3(H3plas) stated in the order) to iron(III) have been investigated in an aqueous 0.10mol dm−3sodium perchlorate solution at 25°C by means of electronic absorption spectral and stopped‐flow spectrophotometric methods. They equally form the corresponding bis(ligand)iron(III) complexes with slower coordination of the first one through the same two parallel pathways of Fe3++H3+L+ (or 0)and FeOH2++H4L2+(or +)and also another pathway of FeOH2++H3L+(or0)(L is fully deprotonated species of 1, 2, and 3); the mechanistic rate‐determining step is the coordination of phenolato oxygen of the first ligand. The thermodynamic stability constant (logβ12/mol−2dm6. 0.10mol dm−3(NaClO4), 25°C) of iron(III)‐3 complex (48.33±0.21) is very large in comparison with the constants of the iron(III) complexes of 1(39.06 ±0.26) and 2(39.81 ± 0.20). A possibility is concluded for the formation of more stable iron(III) complexes without changing the complex formation reaction mechanism by designing the ligand structure of the amino acid moiety of pyridoxal‐L‐amino acid derivat