INVESTIGADORES
MARCECA Ernesto Jose
artículos
Título:
Is Ammonia a Better Solvent Than Water for Contact Ion Pairs?
Autor/es:
GERMÁN SCIAINI; ERNESTO MARCECA; ROBERTO FERNÁNDEZ PRINI
Revista:
JOURNAL OF PHYSICAL CHEMISTRY B
Editorial:
American Chemical Society
Referencias:
Año: 2008 vol. 112 p. 11990 - 11995
ISSN:
1089-5647
Resumen:
The existence of a charge-transfer-to-solvent process when a KI contact
ion pair (CIP) dissolved in supercritical water (SCW) is excited by UV
light was confirmed by use of electronic structure calculations applied
to molecular dynamics trajectories. We observed similar behavior with
fluid density as that found for the KICIP in supercritical ammonia
(SCA); nevertheless, there are some distinct features in the two
supercritical solvents. First, the effect of the solvent field due to
the molecules lying beyond the first solvation shell is very different
in SCW compared with that observed in SCA; in SCW it actually has a
destabilizing effect over the ground and excited states. Second, our
results for the thermodynamic behavior of the CIP indicate that SCA is
better solvent than SCW for this species. The differences found can be
attributed to the solvent molecules surrounding the CIP and bridging the
two ions; they shield more efficiently the ion pair from long-range
solvent effects in SCA. The different behavior is partially attributed
to a stronger solvent-solvent interaction in SCW than in SCA.