The cooperativity between pnicogen bond and dihydrogen bond interactions in HMH⋯HCN⋯PH2X (M = Be, Mg, Zn; X = H, F, Cl) complexes is studied by ab initio calculations. To understand the properties of the systems better, the corresponding dyads are also investigated. The cooperative effects are analyzed in terms of geometric, energetic and electron charge density properties of the complexes. The estimated values of cooperative energy Ecoop are all negative with much larger Ecoop in absolute value for the systems including PH2F. It is seen that the electrostatic interaction is a dominant factor in enhancing both types of interactions. The electron density at the P⋯N and H⋯H bond critical points can be regarded as a good descriptor of the degree of cooperative effects.
