Ab initio calculations of cooperativity effects on chalcogen bonding: linear clusters of (OCS)2-8 and (OCSe)2-8

Chalcogen bonding, a Lewis acid-Lewis base attractive interaction in which a chalcogen atom (O, S, Se or Te) acts as the Lewis acid, plays a critical roles in fields as diverse as molecular biology, drug design and material engineering. In this work, ab initio calculations are performed to analyze the cooperative effects in linear (OCS)(n) and (OCSe)(n) clusters, where n = 2-8. These cooperative effects are analyzed in terms of geometric, energetic and O-17 nuclear magnetic resonance (NMR) parameters and electron charge density properties of the clusters. The results of electron density analysis reveal that the capacity of the OCS and OCSe clusters to concentrate electrons at the S center dot center dot center dot O and Se center dot center dot center dot O critical points, respectively, enhances considerably with cluster size. The results also indicate that the magnitude of cooperative effects is more important for OCSe than for OCS clusters.