EOM-CCSD Ω(T1)-Ω(S1) This correlation also extends to multi-substituted systems (Figure middle, right) with R 2 values of 0.84 and 0.89 for di-and tri-substituted systems, respectively. The values consistently show that Ω(S 1 ) is typically less than Ω(T 1 ), indicating greater deviation from single-excitation character in the singlet excited state, consistent with findings by Drwal et al. The strong correlations between wavefunction character metrics and ∆E ST across all substitution patterns reveal that structural modifications primarily alter the T 1 wavefunction character, providing a mechanism to tune ∆E ST . The extremes in our dataset-particularly the ability of NH 2 groups to produce both the most positive and most negative gaps in different combinations-can be explained through these electronic effects on wavefunction character.