Probing the behavior of confined water by proton-transfer reactions.
The picosecond dynamics of a bifunctional and H-bonding molecule, 7-hydroxyquinoline (7HQ), has been studied in a reverse micelle with increasing water content. The fluorescence kinetics has a complex behavior as the water content is changed. All reactions are irreversible, and a two-step mechanism is invoked to explain the observations. H2O/D2O exchange and excitation energy effects show that the second step has a higher barrier and that the corresponding reaction occurs through tunneling. The results clearly indicate two regimes of water nanopool behavior switching at W0 approximately 5 (W0 = [water]/[surfactant]). Water collective dynamics explains these observations. The lower fluidity of confined water within the reverse micelle with respect to normal bulk water alters the related H-bond network dynamics and therefore is responsible for the slower proton-transfer processes.
Angulo
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G
Departamento de Química Física, Sección de Químicas, Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Avenida Carlos III, S.N., 45071 Toledo, Spain.
Organero
J A
JA
Carranza
M A
MA
Douhal
A
A
D017666:Deuterium Oxide / Q000737:chemistry; D005453:Fluorescence; D006860:Hydrogen Bonding; D006912:Hydroxyquinolines / Q000737:chemistry*; D007700:Kinetics; D008823:Micelles; D011522:Protons; D012997:Solvents / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013501:Surface-Active Agents / Q000737:chemistry*; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
D006912:Hydroxyquinolines; D008823:Micelles; D011522:Protons; D012997:Solvents; D013501:Surface-Active Agents; D014867:Water; D017666:Deuterium Oxide