4,4′-Dipyridyl Dioxide·SbF3 Cocrystal: Pnictogen Bond Prevails over Halogen and Hydrogen Bonds in Driving Self-Assembly

The SbF3·4,4′-dipyridyl N,N′-dioxide cocrystal is prepared and characterized via infrared spectroscopy and 121Sb and 123Sb nuclear quadrupole resonance. Single crystal X-ray analysis proves that a major role in cocrystal formation is played by Sb···O pnictogen bonds, the attractive interactions wherein antimony and oxygen act as the electrophilic and nucleophilic sites, respectively. Molecular electrostatic potential and natural bond orbital analyses confirm the relevance of this interaction in the self-assembly process. Dipyridyl dioxide also forms hydrogen bonded and halogen bonded cocrystal, e.g., when water and 1,4-diiodo-tetrafluoro-benzene function as acceptors of electron density. Experiments of competitive cocrystal formation indicate that under the adopted conditions the pnictogen bond prevails over the halogen bond and the hydrogen bond in identifying the tecton involved in cocrystal formation with dipyridyl dioxide.