The electronic transitions responsible for the colour of K₂ Cr₂ O₇ and porphyrin in their solid state… · ABC26IN0628

Subject: Inorganic Chemistry · Chapter: Coordination Chemistry · Topic: Coordination Compounds – General · Exam: JAM 2005-2022 · Marks: 2 · Difficulty: Medium

The electronic transitions responsible for the colour of $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$ and porphyrin in their solid state respectively are:
(a)$\mathrm{d} \rightarrow \mathrm{d} ; \pi \rightarrow \pi^{*}$
(b)$\mathrm{M} \rightarrow \mathrm{L}$ charge transfer; $\pi \rightarrow \pi^{*}$
(c)$\mathrm{L} \rightarrow \mathrm{M}$ charge transfer; $\pi \rightarrow \pi^{*}$
(d)$\mathrm{L} \rightarrow \mathrm{M}$ charge transfer; $\mathrm{d} \rightarrow \mathrm{d}$
Answer
Answer: C ✓ checked by 4AB · confidence high
Explanation
K₂Cr₂O₇: Cr(VI) is d⁰, colour from O→Cr LMCT. Porphyrin (free base): intense π→π* (Soret/Q) bands of the conjugated macrocycle.

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