Unusual Fluorine Substitution Effect on S···Cl Bonding between Sulfides and Atomic Chlorine

Comparison between Chlorine-Shared and π-Halogen Bonds Involving Substituted Phosphabenzene and ClF Molecules

Ab initio MP2/aug-cc-pVTZ calculations have been carried out in order to study the nature of P···Cl halogen bonding interaction between a phosphorus atom in an aromatic ring in para-substituted phosphabenzene (PPBZ) and ClF molecule. The interaction of PPBZ with ClF results in two different types of complexes: (i) complex formation through the chlorine-shared halogen bond (T1-X-PPBZ·ClF) and (ii) complex formation via halogen-π interaction (T2-X-PPBZ·ClF). T1-X-PPBZ·ClF complexes are found to be more stable than the T2-X-PPBZ·ClF complexes. This work also presents a general criterion to distinguish a chlorine-shared halogen bond from a traditional halogen bond and sheds light on the formation of the chlorine-shared halogen bond. The binding energy of T1-X-PPBZ·ClF complexes correlates well with the negative electrostatic potential of the P atom and PA value of the substituted PPBZ. The properties of both T1-X-PPBZ·ClF and T2-X-PPBZ·ClF complexes are analyzed using atom-in-molecule, natural bond orbital, and symmetry-adapted perturbation theory calculations. The variation of the Cl-F bond distances and the redshifts of the ν(ClF) vibration resulting from the interaction with PPBZs are discussed.

Nature of the Interaction of Pyridines with OCS. A Theoretical Investigation

Ab initio calculations were carried out to investigate the interaction between para-substituted pyridines (X-C₅H₄N, X=NH₂, CH₃, H, CN, NO₂) and OCS. Three stable structures of pyridine.OCS complexes were detected at the MP2=full/aug-cc-pVDZ level. The A structure is characterized by N…S chalcogen bonds and has binding energies between −9.58 and −12.24 kJ/mol. The B structure is bonded by N…C tetrel bond and has binding energies between −10.78 and −11.81 kJ/mol. The C structure is characterized by π-interaction and has binding energies between −10.76 and −13.33 kJ/mol. The properties of the systems were analyzed by AIM, NBO, and SAPT calculations. The role of the electrostatic potential of the pyridines on the properties of the systems is outlined. The frequency shift of relevant vibrational modes is analyzed.