- L1 absorbs red light (longest wavelength, weakest ligand).
- L4 absorbs blue light (shortest wavelength, strongest ligand).
Thus, L1 is the weakest and L4 is the strongest, with L3 and L2 in between.
The octahedral complex of a metal ion M3+ with four monodentate ligands L1, L2, L3, and L4 absorb wavelengths in the region of red, green, yellow and blue respectively. The increasing order of ligand strength of the four ligands is:
L4 < L3 < L2 < L1
L1 < L3 < L2 < L4
L3 < L2 < L4 < L1
L1 < L2 < L3 < L4
L1 < L3 < L2 < L4
Explanation:
Thus, L1 is the weakest and L4 is the strongest, with L3 and L2 in between.