A cooperative mechanism as the main source of the marked structural differences between solid and gaseous HCN⋯BF3

The marked structural differences between the solid- and gas-phase structures of HCN⋯BF3 are reproduced by ab initio calculations employing the D95** and 6-31++G** basis sets. Specifically, the shortening in the B⋯N distance and the distortion in the N⋯B–F angle are reproduced to within 0.1 Å and 4°, respectively. The results suggest that a cooperative mechanism, where the nearest neighbour is deeply involved is responsible for the structural differences between the two states of HCN⋯BF3.