text: One consequence of geometric strain on both the boron and the porphyrin moieties is unique reactivity. The Brothers group was able to demonstrate reductive coupling, wherein two BX units inside the porphyrin pocket become X-B-B-X, only occurs with X=Br and when the substrates are within the porphyrin pocket. DFT calculations show that for X=Cl or F, the reaction is endothermic and non-spontaneous. However, for X=Br, the reduction is spontaneous, which was consistent with experimental findings. Further, when the same reaction is simulated with two porphyrin halves ((dipyrromethene)BX), it is non-spontaneous even for X=Br, suggesting the steric strain of the porphyrin ring to be the driving force behind the reduction reaction.