The aim of this study is to investigate the influence of a hydrogen- or lithium-bonding interaction on the cooperativity of chalcogen bonds in linear NCH•••(OCX)2-5 and NCLi•••(OCX)2-5 clusters (X=S, Se). The nature of interactions in the optimized structures is analyzed by means of molecular electrostatic potential, quantum theory of atoms in molecules, natural bond orbital and electron density difference methods. According to our results, the formation of a lithium-bonding interaction in NCLi•••(OCX)2-5 clusters induces a large increase in the strength of X•••O chalcogen bonds, and hence their cooperativity. This can be mainly rationalized in terms of the electrostatic nature of chalcogen bonds as well as the fundamental orbital interaction between the interacting OCX subunits. The results of this study provide a theoretical evidence for the tuning of chalcogen bonds cooperativity by a hydrogen- or lithium-bonding.
