Unraveling the N-Co coordination mechanism in chitosan‑cobalt complexes: Structural elucidation and in vivo cobalt supplementation effect.

Polysaccharide-metal complexes possess superior properties and exhibit broad applications with significant developmental potential. In this study, we systematically elucidated the coordination model and mechanisms between chitosan and cobalt(II). First, combining DFT calculations and experimental results, a coordination chemical mechanism of CS-Co(II) was revealed that Co(II) ions preferentially accept electrons from the N atoms of -NH2 to coordinate with CS, forming a twisted octahedron configuration via sp3d2 hybridization. N-Co coordination bonds were dominated by ionic bonding, with a small amount of covalency present. In chain features, Co(II) introduction caused slight chitosan chain degradation and compact conformation. Furthermore, lambs supplemented with CS-Co(II) exhibited higher serum Co content and kidney VB12 levels, and no abnormalities in blood biochemical indexes were observed, indicating CS-Co(II) provide potential applications in animal production. This investigation provided a novel insight for developing polysaccharide-metal complexes as functional nutritional supplements through elucidation of coordination mechanisms.