Insights into the cooperativity between multiple interactions of dimethyl sulfoxide with carbon dioxide and water.

Interactions of dimethyl sulfoxide with carbon dioxide and water molecules which induce 18 significantly stable complexes are thoroughly investigated. An addition of CO2 or H2 O molecules into the DMSO⋯1CO2 and DMSO⋯1H2 O systems leads to an increase in the stability of the resulting complexes, in which it is larger for a H2 O addition than a CO2 . The overall stabilization energy of the DMSO⋯1,2CO2 is mainly contributed by the S=O⋯C Lewis acid-base interaction, whereas the O - H⋯O hydrogen bond plays a significant role in stabilizing complexes of DMSO⋯1,2H2 O and DMSO⋯1CO2 ⋯1H2 O. Remarkably, the complexes of DMSO⋯2H2 O are found to be more stable than DMSO⋯1CO2 ⋯1H2 O and DMSO⋯2CO2 . The level of the cooperativity of multiple interactions in ternary complexes tends to decrease in going from DMSO⋯2H2 O to DMSO⋯1CO2 ⋯1H2 O and finally to DMSO⋯2CO2 . It is generally found that the red shift of the O - H bond involved in an O - H⋯O hydrogen bond increases while the blue shift of a C - H bond in a C - H⋯O hydrogen bond decreases when a cooperative effect occurs in ternary complexes as compared to those of the corresponding binary complexes. © 2018 Wiley Periodicals, Inc.