If a didentate ligand ethane -1,2- diamine is progressively added in the molar ratio en : Ni :: 1 : 1, 2 : 1, 3 : 1 to [Ni(H2O)6]2+ aq solution, following co-ordination entities are formed.
I. [Ni(H2O)4en]2+(aq) - pale blue
II. [Ni(H2O)2(en)2]2+(aq) - blue/purple
III. [Ni(en)3]2+(aq) - violet
The wavelength in nm of light absorbed in case of I and III are respectively