Why the colour of trans [ Co (en)2 F2 ] + is less intense than that of cis [ Co (en)2 F2 ] + ?
Why the colour of trans [ Co (en)2 F2 ] + is less intense than that of cis [ Co (en)2 F2 ] + ?
In the given two complexes [ cis and trans form of diflouridobis( ethylene diamine ) cobalt (III) ion ] both the ligands and the geometry of the complex are same but in the above octahedral complexes arrangements are different one is cis and other is trans.
According to
crystal field theory the colour of transition metal complexes arises due to the
d-d transition of electrons from lower energy d-orbitals to higher energy
d-orbitals , that takes place with the help of visible photons.
Again, according
to crystal field theory the magnitude of Δ0
in octahedral complexes depends on the nature of ligands and also on the nature
of arrangements of ligands.
Since arrangement of ligands are different , the Δ0 values for the given two complexes are also different .
The Δ0
value for the complex, cis [ Co (en)2 F2
] + lies totally in the visible region and the transition is of
allowed type and so it is intensely coloured .
But that of
in trans complex is shifted towards the border of visible and invisible region
. So it is less intensely coloured.
Summary
- Why the colour of trans [ Co (en)2 F2 ] + is less intense than that of cis [ Co (en)2 F2 ] + ?
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