Electrochemical and solution structural characterisation of Fe(III) azotochelin complexes: Examining the coordination behaviour of a tetradentate siderophore

TY - JOUR

T1 - Electrochemical and solution structural characterisation of Fe(III) azotochelin complexes

T2 - Examining the coordination behaviour of a tetradentate siderophore

AU - Baranska, Natalia

AU - Parkin, Alison

AU - Duhme-Klair, Anne-Kathrin

N1 - © 2022 The Authors

PY - 2022/12/5

Y1 - 2022/12/5

N2 - We report an electrochemical setup comprising a boron-doped diamond (BDD) working electrode for the electrochemical study of iron(III) catecholate siderophores. We demonstrate its successful application in the voltammetric investigation of iron(III) azotochelin, an iron complex of a bis(catecholate) siderophore. Cyclic voltammetry results, when complemented by UV-vis and native ESI-MS characterisation reveal the formation of a coordinatively-unsaturated tetracoordinate 1:1 complex of Fe:azotochelin (M1:L1) at neutral pH, contrary to iron(III) tetradentate siderophore complexes of other classes which favour the hexacoordinate environment of a M2:L3 species. A notable effect of pH and buffer composition on the reduction potential of iron(III) azotochelin is demonstrated. Lower pH values and buffers encompassing primary or secondary amines facilitate a positive potential shift of up to +290 mV and +250 mV vs Ag/AgCl 3M NaCl, respectively. The study was extended to the investigation of the iron(III) complexes of hexadentate siderophores. For tris(catecholate) siderophores, enterobactin and protochelin, the reduction potentials were found to lie beyond the potential window accessible to the BDD electrode, however, we were successful in observing the electrochemical behaviour of a tris(hydroxamate) siderophore, ferricrocin.

AB - We report an electrochemical setup comprising a boron-doped diamond (BDD) working electrode for the electrochemical study of iron(III) catecholate siderophores. We demonstrate its successful application in the voltammetric investigation of iron(III) azotochelin, an iron complex of a bis(catecholate) siderophore. Cyclic voltammetry results, when complemented by UV-vis and native ESI-MS characterisation reveal the formation of a coordinatively-unsaturated tetracoordinate 1:1 complex of Fe:azotochelin (M1:L1) at neutral pH, contrary to iron(III) tetradentate siderophore complexes of other classes which favour the hexacoordinate environment of a M2:L3 species. A notable effect of pH and buffer composition on the reduction potential of iron(III) azotochelin is demonstrated. Lower pH values and buffers encompassing primary or secondary amines facilitate a positive potential shift of up to +290 mV and +250 mV vs Ag/AgCl 3M NaCl, respectively. The study was extended to the investigation of the iron(III) complexes of hexadentate siderophores. For tris(catecholate) siderophores, enterobactin and protochelin, the reduction potentials were found to lie beyond the potential window accessible to the BDD electrode, however, we were successful in observing the electrochemical behaviour of a tris(hydroxamate) siderophore, ferricrocin.

KW - iron; siderophores; ligands; redox reactions; cyclic voltammetry

U2 - 10.1021/acs.inorgchem.2c02777

DO - 10.1021/acs.inorgchem.2c02777

M3 - Article

SN - 0020-1669

JO - Inorganic Chemistry

JF - Inorganic Chemistry

ER -