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Choose the coordination complex which will give the peak of shortest wavelength: [crcl6)3- [cr(h2o)6]3+ [cr(en)2]3+ [cr(ox)3]3-
Accepted Answer
The complex with the shortest wavelength absorption peak will be [Cr(en)2]3+. Here's why:
Ligand Field Theory: The color of a coordination complex arises from the absorption of light, which causes an electron to transition between d-orbitals. The energy difference between these orbitals, known as the crystal field splitting energy (Δ), determines the wavelength of light absorbed.
Strong Field Ligands: Strong-field ligands, like ethylenediamine (en), cause a larger splitting of the d-orbitals, resulting in a higher Δ value. This means that the complex will absorb higher-energy (shorter wavelength) light.
Comparison:
Cl- is a weak-field ligand.
H2O is a weak-field ligand, but slightly stronger than Cl-.
en is a strong-field ligand.
ox (oxalate) is a moderately strong-field ligand.
Therefore, [Cr(en)2]3+ with its strong-field ligand, ethylenediamine, will have the largest Δ and absorb the shortest wavelength light.
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