One DMANH molecule, shown in Fig. , was solvated in a TIP3P water sphere with a radius of 25 Å using the LEaP module in the AmberTools19 package. One chlorine ion was added for neutralization. The QM region contained only the DMANH molecule, and the MM region comprised all the solvent molecules and the counter ion. In the MM region, the SHAKE algorithm was applied to constrain all the bonds involving hydrogen atoms.