In which of the following ions , the colour is not due to d-d transition ?

A. [Ti(H₂O)₆]³⁺

B. [CoF₆]³⁺

C. [CrO₄]²⁻

D. [Cu(NH₃)₄]²⁺

Answer: Option C

Solution(By Examveda Team)

The colour of transition-metal compounds is normally associated with d-d transitions. However, some transition metal compounds show intense colour in solution in spite of absence of d-electrons. For example, the orange colour of TiBr₄, yellow colour of CrO₄^2-, orange colour of Cr₂O₂^7-, intense red colour of [Fe(SCN)₄] and deep purple of MnO₄ are not due to d—d transitions. In the case of MnO₄ ion, the color is due to charge transfer and not due to d-d transitions.