Beyond traditional chelates: optimizing Fe-EDDHA and pioneering bio-inspired iron chelates for sustainable agriculture

Iron chlorosis is a critical agricultural challenge that severely limits global crop yields, particularly in highly calcareous soils. To address the economic and environmental limitations of traditional synthetic iron chelates, this thesis presents a tripartite investigation into the development, optimisation, and formulation of advanced iron chelating agents. First, the industrial synthesis of the golden standard chelate, FeEDDHA, was optimised. By systematically tuning kinetic parameters and introducing multiple Lewis acid catalysts to induce a stereochemical template effect, the yield of the agronomically active o,o-isomer was successfully maximised. Greener solvents and alternative extraction methods were also explored to reduce the process's toxicological footprint. Second, the formulation of bio-based liquid iron fertilisers using natural amino acids and amines was evaluated. Small, polar amino acids formed highly stable, soluble bidentate chelates, whereas bulkier or redox-active amino acids failed to maintain coordination. Additionally, utilising ethylamine as an asymmetric organic counter-ion for the anionic Fe(III)-EDTA complex drastically increased formulation solubility by favourably disrupting the solid crystal lattice. Finally, a novel library of structurally simplified, cost-effective analogues of the natural phytosiderophore 2’-deoxymugineic acid was developed. In vivo evaluations confirmed that some derivatives successfully solubilised native iron and reversed severe induced chlorosis in plant models, matching the performance of native molecule. Ultimately, this research provides actionable advancements toward sustainable, highly efficient global iron chlorosis management.