Figure 1.

Definition of 1^st and 2^nd shell molecular motifs based on a spin system. The proton spin system together with its directly bonded carbon atoms defines the molecular spin system or “0^th shell molecular motif” (red). The “1^st shell molecular motif” (dashed orange box) is obtained after inclusion of the heavy atoms that are directly bonded to the spin system (orange). The additional inclusion of heavy atoms that are up to two bonds away from the spin system yields the “2^nd shell molecular motif” (dashed green box).