O–H anharmonic vibrational motions in Cl−⋯(CH3OH)1−2 ionic clusters. Combined IRPD experiments and AIMD simulations
Résumé
The structures of Cl−–(Methanol)1,2 clusters have been unraveled combining Infrared Predissociation (IR-PD) experiments and DFT-based molecular dynamics simulations (DFT-MD) at 100 K. The dynamical IR spectra extracted from DFT-MD provide the initial 600 cm−1 large anharmonic red-shift of the O–H stretch from uncomplexed methanol (3682 cm−1) to Cl−–(Methanol)1 complex (3085 cm−1) as observed in the IR-PD experiment, as well as the subtle supplementary blue- and red-shifts of the O–H stretch in Cl−–(Methanol)2 depending on the structure. The anharmonic vibrational calculations remarkably provide the 100 cm−1 O–H blue-shift when the two methanol molecules are simultaneously organized in the anion first hydration shell (conformer 2A), while they provide the 240 cm−1 O–H red-shift when the second methanol is in the second hydration shell of Cl− (conformer 2B). RRKM calculations have also shown that 2A/2B conformers interconvert on a nanosecond time-scale at the estimated 100 K temperature of the clusters formed by evaporative cooling of argon prior to the IR-PD process.
Mots clés
Anharmonic vibrational calculations
Anharmonicities
DFT-MD
Evaporative cooling
First hydration shell
IR-PD
Molecular dynamics simulations
Vibrational motions
Evaporative cooling systems
Experiments
Hydration
Chlorine compounds
anion
methanol
article
chemistry
Dynamical spectra
infrared spectrophotometry
molecular dynamics
Vibrational anharmonicities
vibrational spectroscopy
Anions
Chlorine
Molecular Dynamics Simulation
Motion
Quantum Theory
Spectrophotometry
Infrared