Turning to PD correlations with the three-way interaction energy E(Li-N 2 -PD), polarity and acceptor number also appear to be moderately correlated (Fig. ). While we have focused on the nitrogen-lithium adsorption energy E(Li-N 2 ) so far as it quantifies how much more the PD stabilizes the interaction, this energy quantifies the stability of the overall system. Thus, the negative correlation seen across all states suggests increasing polarity and Lewis acidity of the PD decreases the energy of the threeway interaction, thus making the overall system more stable. As expected, this results in moderately positive correlating pKa values for all our states ranging from 0.42 to 0.55. These results taken with the correlations for E(Li-N 2 ) suggest that while strong Lewis acids and electrophiles weaken the nitrogenlithium interaction by withdrawing electrons from the nitrogen molecule, the PD stabilizes the overall interaction. This explains why the embedded and buried were not seen in the absence of the PD.