Electrode reactions of tris(1,10-phenanthroline) iron complexes, [Fe(phen)(3)](3+/2+), were investigated in some amide-type ionic liquids. The diffusion coefficients of [Fe(phen)(3)](2+) and [Fe(phen)(3)](3+) were smaller than those of tris(2,2'-bipyridine) iron complexes, [Fe(bpy)(3)](2+) and [Fe(bpy)(3)](3+), in each ionic liquid, reflecting the phen complexes are larger than the bpy complexes. The ratio of diffusion coefficient of the trivalent species to that of the divalent one for [Fe(phen)(3)](3+/2+) was smaller than that for [Fe(bpy)(3)](3+/2+), indicating the coulombic interaction between the charged species and the ions composing the ionic liquid is dependent on the charge densities of complexes. The rate constants for [Fe(phen)(3)](3+/2+) were close to those for [Fe(bpy)(3)](3+/2+), suggesting the outer components of reorganization energies for both complexes are similar to each other. On the other hand, the apparent reaction entropies for [Fe(phen)(3)](3+/2+) were smaller than those for [Fe(bpy)(3)](3+/2+), reflecting the difference in the charge densities of complexes. (C) The Author(s) 2015. Published by ECS. All rights reserved.