Isotopic Preferential Solvation of I(-) in Low-Temperature Water Nanoclusters.
We present results from ring polymer molecular dynamics experiments that provide microscopic insights into the characteristics of the isotopic stabilizations of H and D aqueous species in the first solvation shell of a halide I(-) ion in water nanoclusters at low temperatures. The analysis of the simplest I(-)·(HOD) dimer shows a clear propensity for the light isotope to lie at the non-hydrogen-bonded dangling position. Our results predict that, at T ∼ 50 K, I(-)·(DOH) isomers are three times more abundant than I(-)·(HOD) ones. The reasons for such stabilization can be traced back to differences in the nuclear kinetic energy projected along directions perpendicular to the plane of the water molecule. Dynamical implications of these imbalances are shown to be reflected in the characteristics of the corresponding bands of the infrared spectroscopic signals. A similar analysis performed in larger aggregates containing ∼20 water molecules reveals, in contrast, a stabilization of the light isotope along I(-)···HO hydrogen bonds. Effects derived from the consideration of smaller halide anions with larger electric fields at the surface are also examined.
Departamento de Química Inorgánica Analítica y Química-Física e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires , Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina.
Pablo E
PE
Videla
Department of Chemistry, Rice University , Houston, Texas 77005-1892, United States.
Peter J
PJ
Rossky
Departamento de Química Inorgánica Analítica y Química-Física e INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires , Ciudad Universitaria, Pabellón II, 1428 Buenos Aires, Argentina.|Departamento de Física de la Materia Condensada, Comisión Nacional de Energía Atómica , Avenida Libertador 8250, 1429 Buenos Aires, Argentina.
Daniel
D
Laria