Synthesis and antifungal activity of slow-release pyridinylcarbonyl chitooligosaccharide copper complexes

Copper fungicides are fungicides have a wide application, but their toxicity to plant growth and the damage they cause to the environment cannot be ignored. As such, the novel, low toxicity biogenic copper fungicide has strong industrial application prospects. Herein, pyridinylcarbonyl chitooligosaccharide ligands (pCOSx) and their copper complexes (pCOSx-Cu) were synthesized. The results showed that a p-π-π conjugated system was formed in pCOSx, resulting in the formation of a slowly dissociated coordination bond between the nitrogen atom of pyridyl and Cu²⁺ in pCOSx-Cu. The cumulative release rate of Cu²⁺ is positively correlated with the electron donating ability of pyridyl. Compared with the commercial copper fungicide thiodiazole‑copper, pCOSx-Cu exhibited better antifungal activity, lower phytotoxicity and better biocompatibility. This work demonstrated that it was feasible to construct a conjugated system in a chitooligosaccharide copper complex to improve slow-release performance, which laid a foundation for the in-depth study of green copper fungicides. CHEMICAL COMPOUNDS: Chitooligosaccharide (PubChem CID: 3086191); Nicotinoyl chloride hydrochloride (PubChem CID: 88438); Isonicotinoyl chloride hydrochloride (PubChem CID: 12262826); 2-chloronicotinoyl chloride (PubChem CID: 2774541); Trimethylchlorosilane (PubChem CID: 6397); Tetrabutylammonium fluoride (PubChem CID: 2724141); Copper (II) acetate monohydrate (PubChem CID: 165397).