Discussion of photochemistry / photophysics as related to solar energy:
Accounts of Chemical Research 2003, 36, 876-887. Read the stuff in the red boxes, and read the figure captions in order to understand the figures.
Slides: Nov_28_inked
Goals: interpret electronic spectra of coordination compounds (dd/LMCT/MLCT); interpret reactions of Ru(bpy)32+* in context of ground states and excited states.
I have a question about 10.23)a. The answer key labels the ground state term for [Co(NH3)6]3+ as I1. But for the [Co(CO4)]- it is labeled as S1. These are both low spin complexes, so shouldn’t they have the same Orbital Momentum (S)?
Actually, 10.23a didn’t ask about term symbols… But if you want them:
Co(III) has six d-electrons.
Since there is a lot of CFSE for a low-spin d6 configuration, the medium-field ligands (NH3) are enough the make Co(III) go low-spin.
Co(III) LS has 0 upe. 2S+1 = 1 Sum(ml) = 2+2+1+1+0+0 = 6
So the ground state ‘free ion’ term symbol should be singlet-eye, 1I
What about Co(CO)4-? That has a Co(-I)! so it is a d10 complex. (I almost got suckered into mis-counting it as a d8….). Anyway, fill up the d-orbitals with 2 electrons each.
2S+1 = 1 Sum(ml) = 0
So this ground state should be singlet-ess, 1S.
Incidentally, you’ll get an S state anytime the subshell is half-filled (d5 high spin) or fully filled (d10) or fully empty (d0). “S” is kinda like ‘A1g’ symmetry, in that it is totally symmetric…