[MnO₄]⁻is deep purple in colour whereas [ReO₄]⁻is colourless. This is due to greater energy required for · ABC26IN0114
Subject: Inorganic Chemistry · Chapter: Coordination Chemistry · Topic: Charge Transfer Spectra · Exam: CSIR NET 2015 · Marks: 2 · Difficulty: Medium
$\left[\mathrm{MnO}_{4}\right]^{-}$is deep purple in colour whereas $\left[\mathrm{ReO}_{4}\right]^{-}$is colourless. This is due to greater energy required for
(a)d-d transitions in the Re compound compared to the Mn compound
(b)d-d transitions in the Mn compound compared to the Re compound
(c)charge transfer from O to Re compared to O to Mn
(d)charge transfer from O to Mn compared to O to Re
Answer
Answer: C ✓ checked by 4AB · confidence high
Explanation
Both ions are d⁰, so the colour must be O→M LMCT. Re(VII) 5d orbitals lie higher than Mn(VII) 3d, so the O→Re transfer needs more energy, falls in the UV and ReO₄⁻ is colourless, while O→Mn absorbs in the visible and MnO₄⁻ is purple.