Chalcogen bonds tuned by an N-H•••π or C-H•••π interaction: investigation of substituent, cooperativity and solvent effects

In the present work, ab-initio calculations are performed to investigate cooperativity effects between chalcogen bond and H center dot center dot center dot pi interactions in XHY center dot center dot center dot NCH center dot center dot center dot C6H6 and XHY center dot center dot center dot CNH center dot center dot center dot 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 atomsin molecules, noncovalent interaction index, many body analysis of interaction energy and electron density shift analysis. For each ternary complex, the shortening of the Y center dot center dot center dot N(C) distance is more pronounced than that of the H center dot center dot center dot pi. The cooperative energies of these complexes are all negative which demonstrate a positive cooperativity between the Y center dot center dot center dot N(C) and H center dot center dot center dot pi 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 center dot center dot center dot CNH center dot center dot center dot C6H6 complexes indicate a larger sensitivity on the polarity of solvent than XHY center dot center dot center dot NCH center dot center dot center dot C6H6 ones. [GRAPHICS] .