Density Functional Theory Study of Acetonitrile -Water Clusters: Structures and Infrared Frequency Shifts

Abstract

We present calculations for the acetonitrile -water clusters to examine the nature of interactions in the mixed clusters. We calculate conformers of various composition, either of σ-type (-OH and -CN binding linearly) or π-type (-OH and -CN interacting perpendicularly) structures for the acetonitrile -water clusters. We predict that the IR frequency of the proton-accepting C≡N stretching mode red-shifts in the σ-type clusters and blueshifts in π-type conformers, whereas the proton-donating -OH stretching frequency red-shifts in all cases. We find that this intriguing pattern also applies to the acetonitrile -water clusters of various molar ratio.

Binary-Phase Acetonitrile and Water Aerosols: Infrared Studies and Theoretical Simulation at Titan Atmosphere Conditions

“…Most evident in the 130 K x (CH 3 CN) = 0.8 binary ice shown in Figure , a pronounced satellite peak is observed toward the red edge at 2245 cm –1 . This peak likely indicates that a portion of the CH 3 CN component interacts with H 2 O via side-directed π-type hydrogen bonding, as a similar satellite peak is computed for the (H 2 O) 2 –(CH 3 CN) 2 cluster . Other studies have assigned the CH 3 CN···HOH complex by way of a red-shifted CN satellite band arising from strong dipole–dipole interactions (Figure S-6e).…”

Computational Study of Hydrogen Bonding in CH3CN•••H-X (X=OH, F, Cl, NH2) Complexes

“…They studied acetonitrile complex with phenol. Like previous works [14,15], they also concentrated on C N stretching mode in both  type (OH and CN linear interaction) and  (OH and CN perpendicular interaction) hydrogen bonds.…”

“…So far there are few reports regarding computational studies of acetonitrile complex [14][15][16][17][18][19][20][21]. In almost all studies acetonitrilewater complexes have been reported.…”

“…One of the previous works on the acetonitrile complex is by Doo-Sik Ahn and Sungyul Lee. They have two works on this system [14,15]. They examined CH 3 CN•••(H 2 O) n clusters (n=1-4 for fi rst work and n= 4, 8 for second work) and found two isomers.…”

Application of the Approximate 3D-Reference Interaction Site Model (RISM) Molecular Solvation Theory to Acetonitrile as Solvent

“…The first peak belongs to the formation of H-bonds between acetonitrile and water molecules (N···H water or O···H ACN ). A presence of such hydrogen bonded complexes was reported from density functional theory based calculations, although exact structural details were absent in the literature . The other total distribution functions involving H···O (or N) interactions showed the presence of multiple small clusters in the binary mixtures of different concentrations of ACN.…”