Fig. 5: Molecular structures and schematic energy levels for Fe-NTMPA2 complexes.
From: Phosphonate-based iron complex for a cost-effective and long cycling aqueous iron redox flow battery
a Two possible molecular structures of Fe-NTMPA2 after density function theory (DFT) geometry optimization. Structure-1 (S1) shows octahedral coordination of Fe ion with two NTMPA ligands, and two phosphonate groups of each NTMPA contribute the first coordination shell. Structure-2(S2) shows a similar octahedral coordination, except all phosphonate groups of each NTMPA involve to the bonds with Fe ion. b Schematic view of the redox reaction pathway and the free energy profiles for Fe(II)-NTMPA2 and Fe(III))-NTMPA2 complexes with different coordination structures.
