FTIR studies and DFT calculations on the associative nature of methyl cellosolve in binary solutions with acetonitrile

•MCS molecules don't exist as monomers, dimers and trimers.•Pure MCS exists as tetramers of closed geometry.•(MCSmethyl/methylene)C−H⋯N(AN), (ANmethyl)C−H⋯O(hydroxyland/oretheroxygenofMCS).•1:4 (AN:MCS) and 2:4 (AN: MCS) complexation of AN with MCS.•2:4 (AN: MCS) complex is the most stable one. From the FTIR spectral studies on neat acetonitrile (AN), methyl cellosolve (MCS) and their binary solutions at different compositions, (MCS)O−H⋯N(AN),(MCSmethyland/ormethylene)C−H⋯N(AN) and(ANmethyl)C−H⋯O(MCShydroxyland/orethereal) heterointeractions have been identified. DFT calculations show that MCS multimerization and AN dimerization are through (MCShydroxyl)O−H⋯O(ethericoxygenofMCS) and (ANmethyl)C−H⋯N(AN) interactions, respectively. Two different geometries of 1:4 (AN: MCS) complexes and 1 type of 2:4 (AN: MCS) complex have been formed in the solutions. Of the three, 2:4 (AN:MCS) complex is the most stable one as suggested by the interaction energies. 2:4 complexation occurs in the binary solution in which AN concentration is one fourth of the MCS concentration. Of the three complexes, two 1:4(AN:MCS) complexes and one 2:4 complex, this 2:4 complex is the most stable one. [Display omitted]