Question
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The purple colour of \[KMn{O_4}\] is due to the charge transfer transition.
Reason- The intense colour is most of the transition metal complexes is due to d-d transition.
A. Both assertion and reason are correct and reason is the correct explanation for assertion.
B.Both assertion and reason are correct but reason is not the correct explanation for assertion.
C.Assertion is correct but reason is incorrect
D.Both assertion and reason are incorrect

Answer
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Hint:
\[KMn{O_4}\] has a deep purple color because of the charge transfer from the ligand \[\;\left( {{O_2} - } \right)\] to the metal center. This is called ligand to metal charge transfer.

Complete step by step answer:
-Ligand to metal charge transfer complexes arise from transfer of electrons from MO with ligand like character to those with metal like character.
-This type of transfer is predominant if complexes have ligands with relatively high energy lone pairs (example O, S or Se) or if the metal has low lying empty orbitals.
-Hence, due to electronic transition, potassium permanganate is purple in colour. It is not due to d-d transition as Mn in \[KMn{O_4}\] exists with +7 oxidation state and it has no d electrons.
-Due to the charge transfer reactions within the molecule, photons promote an electron from the highest energy MO orbital in one of the MO bonds to an empty d orbital of Mn.
Therefore, both assertion and Reason are correct but reason is not the correct explanation for assertion.

Hence, option B is correct.

Note:
The nature of attraction in a charge transfer complex is not a stable chemical bond, and is thus much weaker than covalent forces. Charge transfer complexes exist in many types of molecules, inorganic as well as organic, and in solids, liquids, and solutions. Example, the complex formed by iodine when combined with starch, which exhibits an intense blue charge-transfer band.