Investigation of the Molecular Level Interaction in [CH3OH-CH2X2] Complexes (X=I, Br, and Cl) using Matrix-Isolation IR Spectroscopy.

The CH 3 OH - CH 2 X 2 ${\left[ {{\rm{CH}}_{\rm{3}} {\rm{OH}} - {\rm{CH}}_{\rm{2}} {\rm{X}}_{\rm{2}} } \right]}$ (X=Cl, Br, and I) complexes have been studied to understand the tendency towards the formation of hydrogen bonds and halogen bonds. Three different types of interactions viz., C-X · · · ${ \cdot \cdot \cdot }$ O, C-H · · · ${ \cdot \cdot \cdot }$ O, and O-H · · · ${ \cdot \cdot \cdot }$ X, are possible between the CH 3 OH ${{\rm{CH}}_{\rm{3}} {\rm{OH}}}$ and CH 2 X 2 ${{\rm{CH}}_{\rm{2}} {\rm{X}}_{\rm{2}} }$ . Experiments have been carried out in low temperature N 2 ${{\rm{N}}_{\rm{2}} }$ matrix using Fourier Transform Infrared spectroscopy. Electronic structure calculations have been performed to identify the possible binding motifs between CH 2 X 2 ${{\rm{CH}}_{\rm{2}} {\rm{X}}_{\rm{2}} }$ and CH 3 OH ${{\rm{CH}}_{\rm{3}} {\rm{OH}}}$ . Formation of more than one complex has been confirmed in CH 3 OH - CH 2 X 2 ${\left[ {{\rm{CH}}_{\rm{3}} {\rm{OH}} - {\rm{CH}}_{\rm{2}} {\rm{X}}_{\rm{2}} } \right]}$ (X=Br and I) mixture, using the experimental and simulated IR spectra, whereas only one type of complex is found in CH 3 OH - CH 2 Cl 2 ${\left[ {{\rm{CH}}_{\rm{3}} {\rm{OH}} - {\rm{CH}}_{\rm{2}} {\rm{Cl}}_{\rm{2}} } \right]}$ mixture. Energy decomposition analysis, quantum theory of atoms in molecules, and non-covalent interaction analysis have been performed to understand the nature of interaction and the driving force for complexation under experimental conditions.