Pnicogen bonds,1 i.e.non-covalent interactions between an electron donor and a covalently-bound pnicogen atom acting as an electron acceptor,have gained increased interest recently.It has been demonstrated that this new type of intermolecular interaction can act as a new molecular linker2 and would be useful for chiral discrimination.3 Like hydrogen and halogen bonds,this interaction also displays cooperativity,4 which is responsible for its applications in crystal structures.Similarly,the electron donors in pnicogen bonds can be molecules with lone pair electrons,unsaturated compounds with π electrons or metal hydrides.5 It has been evidenced that radicals can participate in hydrogen bond6 and halogen bond,7 which are much weaker than those with lone pair electrons as the electron donors.However,when we performed an ab initio study on the interaction between H3P and H3C radical (Figure 1),we found that the interaction between them is so strong that it is larger than those with lone pair electrons as the electron donors,and the binding energy amounts to more than 40 kcal/mol in some complexes.Thus we think H3P and its derivatives can serve as a good radical receptor.Compared to the single-electron hydrogen bond6 and halogen bond,7 we presumed that the single-electron pnicogen bond has a new formation mechanism.We also found some unexpected trends in the single-electron pnicogen bond.For example,with the increase of X electronegativity in the Lewis acid XH2P (X = F,Cl,Br),the binding energy with the methyl radical is decreased.