Clearly the fits are providing faithful representation of this high diverse and high energy dataset. The red points are the predictions of F-PES, whereas the black × markers are the predictions of MB-PES. TS2 is the barrier to free rotation in which the C11-C12-C13-C14 are all in the same plane in a "u"-shape, whereas TS1 is the barrier between minima in the zig-zag form (GM) and a partially rotated form (LM). The DFT energies are GM = 0 cm -1 , TS1 = 1226 cm -1 , LM = 359 cm -1 , TS2 = 2725 cm -1 . )