Coordination Chemistry of Cobalt Biguanide Complex: Ligand Interaction and Metal Complex Stability

Abstract

Biguanides are versatile organic compounds known for their broad applications in medicinal chemistry, coordination chemistry, and catalysis. Biguanide, C?N?H? is a nitrogen donor bidentate ligand. Structurally, they contain two linked guanidine moieties, which enable strong chelation with metal ions, forming stable complexes. The ability of biguanides to interact with transition metals has led to the development of metal-biguanide complexes with remarkable biological and catalytic properties. These complexes exhibit diverse coordination modes influenced by steric and electronic factors, resulting in distinct physicochemical behaviours. Spectroscopic and crystallographic studies reveal their structural variations, while computational methods provide insights into their electronic configurations and reactivity. Biguanide-metal complexes have been investigated for their role in antimicrobial, anticancer, and catalytic applications, making them essential in modern chemistry. This abstract outline the synthesis, characterisation, and potential applications of biguanide-based metal complexes, emphasizing their importance in material science and medicinal research.

Introduction

Biguanides are open-chain compounds formed by condensing two guanidine molecules, notable for their basic nature and medicinal uses, especially as monoprotonated forms. First synthesized in 1879, biguanide derivatives like metformin are widely used as hypoglycemic agents, with others applied as antimalarials and disinfectants. Structurally, biguanides act as bidentate ligands coordinating metals such as cobalt (III).

The experimental work involved synthesizing biguanide sulfate from dicyandiamide and ammonium chloride by heating, followed by preparing a cobalt (III) complex with dibenzylamine. Characterization included elemental analysis, UV-Vis, and FT-IR spectroscopy.

Results showed the ligand as a white crystalline solid (melting point ~231-232°C), while the cobalt complex was brownish-orange and stable in air. FT-IR spectra confirmed characteristic NH and CN stretching bands for the ligand, and metal-ligand bonds were indicated by peaks around 517 cm?¹ in the complex. Electronic spectral analysis of the cobalt complex suggested an octahedral geometry around Co(III).

Conclusion

On the basis of stoichiometry, magnetic measurements, spectral studies (IR & electronic absorption) and physico-chemical properties, Octahedral structure have been proposed for these mixed ligand metal biguanide complexes. Following below is the proposed structure of Metal Complex

References

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Copyright

Copyright © 2025 Dipti ., Sudipti , Bina Rani, Madhu Kumari Gupta. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.