Interplay between the N→C Dative Bond, Intramolecular Chalcogen Bond and π Conjugation in the Complexes Formed by Cyclo[18]carbon and C14 Polyyne with 1,2,5-Chalcogenadiazoles

The N→C dative bond (DB), intramolecular chalcogen bond and π conjugation play important roles in determining the structures and properties of some molecular carbon materials and organic/polymeric photovoltaic materials. In this work, the interplay between the N→C dative bond, intramolecular chalcogen bond and π conjugation in the complexes formed by cyclo[18]carbon and C14 polyyne with 1,2,5-chalcogenadiazoles has been investigated in detail by using reliable quantum chemical calculations. This study has made four main findings. First, only the Te-containing complexes bound by N→C dative bonds are much more stable than their corresponding van der Waals (vdW) complexes. Second, in addition to through-bond π conjugations, through-space π conjugations also exist in some Se/Te-containing complexes bound by N→C dative bonds. Third, the cooperativity between intramolecular chalcogen bond, π conjugation between two monomers and N→C dative bond is not very strong and can be ignored. Fourth, compared to π conjugations, intramolecular Ch···C (Ch = O, S, Se, Te) chalcogen bonds play a secondary role in stabilizing the complexes bound by N→C dative bonds. These findings clearly indicate that the role of “conformational lock”, popular in the field of organic optoelectronic materials, may have been greatly overestimated.