(c)
Scheme 2. The variation of the relative energy ∆E of the torsional θ C1-N7 BCP (left panel) and C1-C2 BCP (right panel) with the CW (-180.0º ≤ θ ≤ 0.0º) and CCW (0.0º ≤ θ ≤ 180.0º) torsions in sub-figure (a) . The variations of the bond-path lengths (BPL) in sub-figure (b) with the C1-N7 BCP (left panel) and C1-C2 BCP (right panel). The corresponding plots for the ellipticity ε are provided in sub-figure (c) .