In the present work, ab initio calculations are performed to investigate cooperativity effects between chalcogen bond and H∙∙∙π interactions in XHY•••NCH•••C6H6 and XHY•••CNH•••C6H6 complexes, where X=F, Cl, Br, CN, NC and Y=S, Se. The nature of these interactions and the mechanism of cooperativity are studied by means of quantum theory of atoms in molecules, noncovalent interaction index, many-body analysis of interaction energy and electron density shift analysis. For each ternary complex, the shortening of the Y•••N(C) distance is more pronounced than that of the H∙∙∙π. The cooperative energies of these complexes are all negative which demonstrates a positive cooperativity between the Y•••N(C) and H∙∙∙π interactions. The many-body analysis of interaction energy reveals that the two-body energy term has the largest contribution to the total interaction energies of ternary complexes. A good linear correlation is established between the three-body energy and cooperative energy values in the ternary systems. The cooperative energies of XHY•••CNH•••C6H6 complexes indicate a larger sensitivity on the polarity of solvent than XHY•••NCH•••C6H6 ones.
