Combined σ- and π-Hole Donor Properties of Perfluorinated Iodo(or bromo)benzenes: Halogen Bonding and π-Hole Interactions in Cocrystals Including Cu4I4 Clusters

Cocrystallization of CuI with NCNMe2 in the presence of 1,4-diiodotetrafluorobenzene (1,4-FIB) and 1,4-dibromotetrafluorobenzene (1,4-FBrB) in MeCN gave cocrystals [Cu4I4(NCNMe2)(4)]center dot 1,4-FIB, [Cu4I4(NCNMe2)(2)(NCMe)(2)]center dot 1,4-FIB, and [Cu4I4(NCNMe2)(4)]center dot 1,4-FBrB, whose solid-state structures were studied by X-ray diffraction. In these three cases, the perfluorinated haloarenes function as combined sigma- and pi-hole donors, and their crystal structures exhibit intermolecular contacts, including halogen bonding (HaB) and pi-hole interactions with the iodine ligands of the copper clusters. Analysis of the theoretical calculation data indicated that the formation of (cubane)center dot(perfluorinated haloarene) pi-hole dimer is slightly energetically more favorable than (cubane)center dot(perfluorinated haloarene) HaB-based sigma-hole dimer. The pi-hole contacts and HaBs are accompanied by additional hydrogen bonding and also pi-hole(N-CN)center dot center dot center dot X (X = Br, I) contacts. Altogether, these interactions lead to the occurrence of moderately strong noncovalent binding between copper clusters and the aromatic HaB donors.

Automated summary

Cocrystallization of CuI with NCNMe2 in the presence of 1,4-diiodotetrafluorobenzene (1,4-FIB) and 1,4-dibromotetrafluorobenzene (1,4-FBrB) in MeCN resulted in the formation of three cocrystals. The solid-state structures of these cocrystals were studied using X-ray diffraction. Perfluorinated haloarenes act as combined sigma- and pi-hole donors and form intermolecular contacts with the copper clusters through halogen bonding and pi-hole interactions with the iodine ligands. Theoretical calculations suggest that the formation of (cubane)•(perfluorinated haloarene) pi-hole dimer is slightly more energetically favorable than (cubane)•(perfluorinated haloarene) HaB-based sigma-hole dimer. These interactions involve additional hydrogen bonding and pi-hole(N-CN)•••X (X = Br, I) contacts, leading to moderately strong noncovalent binding between the copper clusters and the aromatic HaB donors.