Question

Assertion (A): In $[Ti(H_{2}O)_{6}]^{3+}$ electronic spectra the observed absorption is unsymmetrical appears to be result of more than one absorption bands. Reason (R): Due to Jahn Teller effect energy of $d_{xy}$ is lowered so shown electronic jump $d_{xy}^{1} \rightarrow d_{x^{2}-y^{2}}$ and $d_{xy}^{1} \rightarrow d_{z^{2}}$ so give rise two absorption bands.}

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is NOT the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Hint:

Unsymmetrical peaks in $d^1, d^4$ (high spin), and $d^9$ complexes are almost always due to Jahn-Teller distortion.

Answer 1

The Correct Option is A

Step 1: Concept The Jahn-Teller effect describes the geometrical distortion of non-linear molecular systems in electronically degenerate states to remove the degeneracy and lower the energy.

Step 2: Meaning In $Ti^{3+}$ ($d^1$), the electron occupies the $t_{2g}$ set. This degeneracy causes distortion, splitting both the $t_{2g}$ and $e_g$ levels.

Step 3: Analysis Instead of a single $t_{2g} \rightarrow e_g$ transition, the splitting leads to multiple closely spaced transitions. This results in an unsymmetrical peak (a shoulder) in the UV-Vis spectrum. The Reason correctly identifies the splitting of orbitals due to this effect.

Step 4: Conclusion Both statements are correct, and the Jahn-Teller effect is indeed the reason for the unsymmetrical nature of the spectrum. Final Answer: (A)