[Show abstract][Hide abstract] ABSTRACT: The vibrational energy relaxations (VERs) of the CO stretching mode of acetone and its complex with alcohols are investigated by sub-picosecond pump-probe spectroscopy and molecular dynamics simulation. The time constants of the vibrational energy relaxation of the free acetone and that of the 1:1 complex are 4.4 ps and 2.3 ps for methanol solvent and 5.2 ps and 1.8 ps for 1-proponal solvent, respectively. The VER rate is accelerated a few times by formation of the hydrogen bond. This acceleration of the vibrational energy relaxation is successfully reproduced by the Landau-Teller method calculated from the molecular dynamics simulation. Molecular dynamics simulations reveal that the VER time of acetone with the hydrogen bond is largely affected by the solute polarization induced by solvent molecules.
No preview · Article · Jan 2013 · The Journal of Physical Chemistry B
[Show abstract][Hide abstract] ABSTRACT: The vibrational dynamics of the CO stretching mode of 9-fluorenone (FL) in CD3CN and CD3OD were studied by subpicosecond UV-pump and IR-probe spectroscopy. We found that the CO stretching band is blue-shifted by hydrogen-bond formation in the SI state but red-shifted in the So state. In both CD3CN and CD3OD, the time evolution of the transient absorption spectrum was observed on a picosecond time scale, likely because of vibrational cooling and hydrogen-bond dynamics.
No preview · Article · Sep 2010 · Chemistry Letters
[Show abstract][Hide abstract] ABSTRACT: In aqueous solution, the basis of all living processes, hydrogen bonding exerts a powerful effect on chemical reactivity. The vibrational energy relaxation (VER) process in hydrogen-bonded complexes in solution is sensitive to the microscopic environment around the oscillator and to the geometrical configuration of the hydrogen-bonded complexes. In this Account, we describe the use of time-resolved infrared (IR) pump−probe spectroscopy to study the vibrational dynamics of (i) the carbonyl CO stretching modes in protic solvents and (ii) the OH stretching modes of phenol and carboxylic acid. In these cases, the carbonyl group acts as a hydrogen-bond acceptor, whereas the hydroxyl group acts as a hydrogen-bond donor. These vibrational modes have different properties depending on their respective chemical bonds, suggesting that hydrogen bonding may have different mechanisms and effects on the VER of the CO and OH modes than previously understood.
No preview · Article · Sep 2009 · Accounts of Chemical Research
[Show abstract][Hide abstract] ABSTRACT: The vibrational energy relaxation of 9-fluorenone and its complex with alcohols has been investigated by sub-picosecond pump–probe spectroscopy. The infrared absorption spectrum of 9-fluorenone in alcohol shows three distinct contributions from the free 9-fluorenone, its complex with one alcohol molecule, and that with two molecules. The time constant of the vibrational energy relaxation of the free 9-fluorenone is 4.7±0.1ps, and that of the 1:1 complex is 2.3±0.1ps. The acceleration of the vibrational energy relaxation due to hydrogen-bond formation is discussed in terms of the Fermi golden rule.
No preview · Article · Dec 2007 · Chemical Physics Letters