BIMOLECULAR INTERACTIONS IN (ET)(3)SIOH-BASE-CCL4 HYDROGEN-BONDED SOLUTIONS STUDIED BY DEACTIVATION OF THE FREE OH-STRETCH VIBRATION

Picosecond infrared (IR) pump-probe measurements of the OH-stretch (nu = 1) population lifetime were performed for uncomplexed (Et)(3)SiOH i n room temperature, tertiary (Et)(3)SiOH:base:CCl4 hydrogen-bonded sol utions (base = acetonitrile, tetrahydrofuran, and pyridine). When base is present in solution, the intrinsic OH-stretch T-1 vibrational popu lation lifetime (183 +/- 6 (1 sigma) ps for (Et)(3)SiOH in CCl4) is re duced by bimolecular (Et)(3)SiOH:base hydrogen-bonding encounters. The base concentration dependence of the ''free'' OH-stretch vibrational deactivation rate is analyzed by a Stem-Volmer kinetic model and a lea st-squares fit to all the data yielded a single rate constant k(BM) = 1.2 +/- 0.2 X 10(10) dm(3) mol(-1) s(-1) for (Et)(3)SiOH:base bimolecu lar encounters. This value is in agreement with estimates for the bimo lecular diffusion limit. k(BM) was found to be the same for all (Et)(3 )SiOH:base interactions studied, suggesting that the bimolecular OH-st retch deactivation mechanism is relatively insensitive to the proton-a ccepting strength of the base.