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Between [cr(h2o)6]3+, [crcl6]3-, [cr(en)3]3+ and [cr(ox)3]3- which would present the peak of shortest wavelength
Accepted Answer
The complex with the shortest wavelength absorption peak would be [CrCl6]3-. Here's why:
Ligand Field Theory: The color of a transition metal complex arises from the absorption of light, which causes an electron to transition from a lower energy d-orbital to a higher energy d-orbital. The energy difference between these orbitals, and thus the wavelength of light absorbed, is influenced by the ligands surrounding the metal.
Spectrochemical Series: The spectrochemical series ranks ligands based on their ability to split the d-orbitals. Strong-field ligands (like Cl-) cause a large splitting, resulting in higher energy transitions and shorter wavelengths of light absorbed.
Comparison:
[CrCl6]3- has chloride ions as ligands, which are relatively weak-field ligands. This leads to a smaller splitting of the d-orbitals, resulting in the shortest wavelength absorption.
[Cr(H2O)6]3+ has water molecules as ligands, which are also weak-field ligands but slightly stronger than chloride.
[Cr(en)3]3+ and [Cr(ox)3]3- have ethylenediamine (en) and oxalate (ox) ligands, respectively, which are both strong-field ligands. These complexes would absorb longer wavelengths of light.
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