Theoretical study on cooperative effects between X⋯N and X⋯Carbene halogen bonds (X = F,Cl,Br and I).

Quantum chemical calculations are performed to study the interplay between halogen⋯nitrogen and halogen⋯carbene interactions in NCX⋯NCX⋯CH2 complexes, where X = F, Cl, Br and I. Molecular geometries and interaction energies of dyads and triads are investigated at the MP2/aug-cc-pVTZ level of theory. It is found that the X⋯N and X⋯Ccarbene interaction energies in the triads are larger than those in the dyads, indicating that both the halogen bonding interactions are enhanced. The estimated values of cooperative energy E coop are all negative with much larger E coop in absolute value for the systems including iodine. The nature of halogen bond interactions of the complexes is analyzed using parameters derived from the quantum theory atoms in molecules methodology and energy decomposition analysis.