Structures, properties and nature of DMSO-XY (XY=ClF and BrF) complexes: redshift and blueshift of S=O stretch.

The DMSO-XY (XY=ClF and BrF) complexes have been investigated with quantum chemical calculations. In general, two minima complexes were found, one with an O···X halogen bond and the other one with a S···X halogen bond. The former is more stable than the latter. Additionally, one first order saddle point complex was also observed. The interaction energies in the S complexes suffer a prominent influence from the calculation methods. At the CCSD(T)/aug-cc-pVDZ level, the interaction energies are calculated to be -9.19 and -12.73 kcal/mol for the Cl and Br global minima, respectively. Both complexes have also been evidenced to be stable at room temperature. The SO stretch vibration exhibits a red shift at the global minimum but a blue shift at the local minimum, whereas the CSC and CH stretch vibrations move to high frequency in both cases. The energy decomposition analyses indicate that the electrostatic interaction plays a dominant role in stabilizing these halogen-bonded complexes.