A theoretical evidence for cooperativity effects in fluorine-centered halogen bonds: linear (FCN)2–7 and (FNC)2–7 clusters

A theoretical investigation was performed to study cooperative effects in fluorine-centered halogen bond interactions. We investigated geometry, strength, and origin of the interactions in linear (FCN)_2–7 and (FNC)_2–7 clusters by means of MP2 and CCSD(T) methods. Our results strongly suggest that cooperative effects induced by fluorine-centered halogen bonds are significant in both linear FCN and FNC clusters. CCSD(T)/6-311++G** calculations reveal that for (FCN)_2–7 clusters, the average halogen-bonding energy per monomer increases from ?0.76 kcal/mol in dimer to ?0.92 kcal/mol in heptamer. The results of electron density analysis suggest that the capacity of the linear FCN and FNC clusters to concentrate electrons at the F···N and F···C BCPs enhance considerably with cluster size. The results also indicate that the magnitude of cooperative effects is more important for FCN than for FNC clusters. According to energy decomposition analysis, attractive electrostatic and dispersion components make the major contribution to the F···N and F···C halogen bond interactions. An acceptable correlation is found between different energy terms and total interaction energies, revealing the main role of these interactions for stability of linear (FCN) _n and (FNC) _n clusters.