C3 symmetric hydrazine scaffold: new coordinating hydrazones for metal cations

Two C3-symmetric hydrazine scaffolds, 1,2,3-triaminoguanidine (TAG) and 2,4,6-trihydrazino-1,3,5-triazine (THT), were first synthesized by the reactions of guanidine and 1,2,3-trichlorotriazine, respectively, with hydrazine hydrate. Hydrazone derivatives of TAG and THT were subsequently prepared by condensation with 2-, 3-, and 4-pyridinecarboxaldehydes as well as salicylaldehyde. The synthesized compounds were characterized by spectroscopic methods.

Owing to the presence of both pyridine and hydrazone donor groups, these compounds are expected to exhibit good coordination ability towards metal ions.¹ Since transition-metal and heavy-metal ions are important environmental contaminants,² the coordination properties of the synthesized hydrazones were investigated in aqueous media. Ethanolic solutions of hydrazones were added to aqueous solutions containing Fe³⁺, Co²⁺, Ni²⁺, Sb³⁺, Pb²⁺, Sn²⁺, and Hg²⁺ ions. Formation of precipitates and/or colored complexes was observed for several metal ions, indicating efficient coordination.

These results suggest that the synthesized hydrazones could be promising ligands for metal-ion coordination and could be useful as analytical reagents for the detection of metal ions in water by visible spectroscopy or gravimetric methods.

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2- S. Kaya, C. W. B. Bezerra, R. Fernandes de Farias, A. Çetindağ Çiltaş, M. Elik, Metal cations toxicity: An inorganic interpretation, J. Indian Chem. Soc., 2023, 100, (1) 1, 2023, 100840; doi: 10.1016/j.jics.2022.100840