Figure 4.

(A) The 2D free energy surface obtained from set A, where Mg²⁺ is bound at the catalytic site, projected in the (r1 – r2) and (r3 – r4) space. The initial string (dashed black line) corresponds to the MEP obtained in our previous study.¹⁹ The converged string (solid black line) corresponds to the MFEP obtained from set A. Both the MEP and MFEP correspond to a concerted mechanism with a phosphorane-like TS, but the MFEP is more synchronous than the previously obtained MEP. Each circle corresponds to an image along the string. The color scale denotes free energy in units of kcal/mol. (B) The 1D free energy profile along the MFEP obtained from set A, where Mg²⁺ is bound at the catalytic site. (C) Values of the most important reaction coordinates, r1, r2, r3, and r4, along the MFEP. Each circle corresponds to an image along the string.