To evaluate the performance of ML models trained on the data of CH 2 NH + 2 , taken from reference 9, with outof-training samples, we conducted quantum chemical reference calculations on a 2D-potential energy surface comprising 9191 points (101×91 points). This grid was constructed based on the geometry of CH 2 NH + 2 in the reference database with the lowest energy in the ground state. We scanned the distance of the C=N bond between 2.432 and 4.432 Bohr in steps of 0.020 Bohr (101 steps), and varied the HC=NH dihedral angle from 0 to 90 • in 1 • increments (91 steps). For each geometry, electronic properties were obtained at the SA(3)-MRCI(6,4)/aug-cc-pVDZ level of theory for the three lowest-lying singlet states, as detailed above (i).