Photoionization contact approximation

The linear free energy relationship observed for arene donors relates the activation barrier AG for aromatic substitution directly to the CT transition energy hver of the EDA complex. Since Aver pertains to the energetics of the photoionizations in equations (27) and (28), the correlation suggests that tiiese arene contact ion pairs are reasonable approximations to the transition states for both mercuration and thallation, e.g. Scheme 6. 

---