A simple example demonstrating this is shown in Fig. using free-base subporphyrin monoanion. Species 8a represents a 2S structure and has the highest energy on its PES. Previous methods looking at isomers would not consider such a species. Replacing the H-atom bonder with BF inverts the energetic nature of its PES such that species 37athe BF-analogue of 8a represent a LM structure. Despite the contrasting energetics of each PES, their graph topologies (white lines) are identical. Consequently, the atom-connection configurations of the formalism can be thought of as "structural motifs". 12 | J. Name., 2012, 00, 1-3 This journal is © The Royal Society of Chemistry 20xx With this structural-motif principle in mind, the application of 𝒮 4 ℬ 𝑛 partitioning to the more extensively known chemistry of porphyrins and related macrocycle systems yields new insights and will be presented in a subsequent paper. Systems of five or more 𝒮-sites such as sapphyrins and texaphyrins (𝒮 5 ℬ 3 ), smaragdyrins (𝒮 5 ℬ 4 ), rosarins (𝒮 6 ℬ 3 ) and higher homologs will also be dealt with elsewhere.