Sm. Arrivo et Ej. Heilweil, CONSERVATION OF VIBRATIONAL-EXCITATION DURING HYDROGEN-BONDING REACTIONS, Journal of physical chemistry, 100(29), 1996, pp. 11975-11983
We report novel transient infrared ''tag and probe'' investigations of
the equilibrium kinetics and vibrational energy transfer between the
free acid Et(3)SiOH and its 1:1 hydrogen-bonded complex with acetonitr
ile, Et(3)SiOH ... N=CCH3, in dilute (0.1 mol/dm(3) acid) CCl4 solutio
ns at 293 K. Picosecond time-resolved infrared double-resonance spectr
oscopy measures the vibrational population of the OH-stretching mode (
via upsilon = 1 --> 2 absorption) after IR excitation of either the fr
ee acid or the homogeneously broadened OH(upsilon = 0 --> 1) absorptio
n of the complex. The free acid and 1:1 complex OH(upsilon = 1) popula
tion lifetimes (TI) and equilibrium reaction rate constants affecting
hydrogen-bond formation and dissociation are unambiguously determined
for this system. Tagged free acid OH(upsilon = 1) leads to complex for
mation with OH(upsilon = 1) excitation, indicating OH(upsilon = 1) pop
ulation is maintained during collision and formation of hydrogen bonds
. This is the only known example where OH(upsilon = 1) vibrational pop
ulation of a polyatomic reactant is prepared and that excitation is fo
llowed during a condensed-phase bimolecular reaction which leads to an
excited hydrogen-bonded product.