Conclusions

1. Electronic (e.g. π vs σ) as well as Spin state may play a wider role in di-imino Fe catalytic systems
2. The correlation of (X-Ray) Structure, Spin state, Electronic (Oxidation) state and Substituent is a challenging informatics problem!
3. Whilst theory cannot (reliably) model absolute Quartet/Sextet energy difference, it can model trends
4. Co-operative 1,4 Substituents can modify (tune) the electronic role of 2,3 substituents via steric buttressing
5. Understanding the orbital occupancy is vital for understanding Structure and Reactivity
6. But: Major changes in substituent may qualitatively change these occupancies (Y=H vs Y=Ph)
7. Theory CAN (quantitatively) model all the experimental observations, and can be used to predict new experiments!