Question

Answer all parts please! :)

Sketch the d-orbital splitting for [Ru(bpy)₃]²⁺, and populate it with electrons.

From part c (and consulting an appropriate Tanabe-Sugano diagram), how many d-d transitions are spin-allowed? List them.

Sketch the excited-state d-orbital splitting.

What is the ground-state term symbol for [Ru(bpy)₃]²⁺?

Would you expect to see a Jahn-Teller distortion? Explain.

Answer 1

[Ru(bpy)₃]²⁺ is a coordination compound of Ru²⁺ with bidentate ligand bpy(bipyridine). The crystal field splitting energy becomes higher for heavier metals inspite of the ligand being a weak one, thus the metal is in low- spin d⁶ configuration i.e. t_2g⁶.

d-orbital splitting:

Tanabe-sugano diagram for low-spin d⁶ complex

The spin allowed transitions are those in black lines: ¹T_1g<--¹A_1g   and ¹T_2g <--¹A_1g

Those in red lines are spin-forbidden transitions. List all the lines, the transition has to be denoted with the higher state followed by ground state, i.e., ¹T_1g<--¹A_1g and not ¹A_1g --> ¹T_1g.

The excited state d-orbital splitting: excited electron can go to the d_z² or d_x²-y² state

In ground-state all the electrons are paired, i.e. symmetric thus the term symbol is A_1g

A Jahn-Teller ditortion can be expected in the excited state where the electron can occupy either the d_z² or d_x^2-y² state. Whereas, the ground state has all electrons in the degenerate energy levels, so there won't be any distortion in ground state.