Theoretical molecular structures for weakly bound complexes HX⋯·SO3 (X=F, Cl, Br): ab initio and DFT calculations

The molecular structures of HX⋯·SO3 (X=F, Cl, Br) have been calculated by ab initio and density functional theory (DFT) methods. Calculations show that they are weakly bound van der Waals complexes rather than genuine electron donor–acceptor complexes since they have long intermolecular distances. At the MP2/6-311++G(3df, 3pd) level, the intermolecular bond distances S⋯·F, S····Cl, and S⋯·Br are computed to be 2.667, 3.112, and 3.230 Å, respectively, while the angles ∠H–F–S, ∠H–Cl–S, and ∠H–Br–S are computed to be 108.4°, 87.4°, and 85.6°, respectively.