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 H2O molecules into the DMSO⋯1CO2 and DMSO⋯1H2O systems leads to an increase in the stability of the resulting complexes, in which it is larger for a H2O 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⋯1,2H2O and DMSO⋯1CO2⋯1H2O. Remarkably, the complexes of DMSO⋯2H2O are found to be more stable than DMSO⋯1CO2⋯1H2O and DMSO⋯2CO2. The level of the cooperativity of multiple interactions in ternary complexes tends to decrease in going from DMSO⋯2H2O to DMSO⋯1CO2⋯1H2O 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. Interactions of dimethyl sulfoxide with carbon dioxide and water molecules are thoroughly investigated, and the origin of interactions stabilizing the complexes is clarified. Addition of CO2 or H2O molecules into the DMSO⋯1CO2 and DMSO⋯1H2O systems leads to an increase in stability of resulting complexes. The strength of complexes is mainly contributed by the O − H⋯O hydrogen bond. The level of cooperativity of multiple interactions in ternary complexes decreases in going from DMSO⋯2H2O to DMSO⋯1CO2⋯1H2O and finally to DMSO⋯2CO2. O‐H red shift in O − H⋯O hydrogen bonds increases while C − H blue shift in C − H⋯O hydrogen bonds decreases when a cooperative effect occurs in ternary complexes.