PMID- 19292492
OWN - NLM
STAT- PubMed-not-MEDLINE
DCOM- 20090612
LR  - 20090318
IS  - 1520-5126 (Electronic)
IS  - 0002-7863 (Linking)
VI  - 131
IP  - 11
DP  - 2009 Mar 25
TI  - Structures of thermal, mass-selected water clusters probed with hydrophobic ion 
      tags and infrared photodissociation spectroscopy.
PG  - 4110-9
LID - 10.1021/ja809414a [doi]
AB  - The structures of tetramethylammonium (TMA(+)) and phenyltrimethylammonium 
      (PTMA(+)) with 1-8 water molecules attached were investigated using infrared 
      photodissociation spectroscopy (IRPD), blackbody infrared radiative dissociation, 
      and theory to elucidate the effects of ion-water interactions and water-water 
      hydrogen bonding in clusters containing these hydrophobic ions. Several pieces of 
      evidence suggest that these ions have only a small effect on water structure. The 
      binding energy of a water molecule to TMA(+) is 44 kJ/mol, a value that is 
      significantly lower than that reported for other cations and close to the 
      condensation energy of bulk water. The OH asymmetric stretch of the water 
      molecule in TMA(+).(H(2)O)(1) at 3718 cm(-1) is less red-shifted from that of an 
      isolated water molecule (3756 cm(-1)) than for those of other cations, and 
      water-water hydrogen bonding is extensive for all clusters with two or more water 
      molecules. These results indicate that charge transfer from water to these 
      hydrophobic ions is much less than that for other cations. There are two 
      predominant structures for these ions with three water molecules: one in which 
      water molecules form a chain and one with a cyclic structure analogous to that of 
      neutral water trimer. With four water molecules attached, water forms a cyclic 
      structure similar to that of neutral water tetramer. The spectra of the larger 
      clusters follow trends reported for neutral water molecule clusters, which 
      indicates that these hydrophobic ions have only a minimal effect on the structure 
      of water in clusters with four or more water molecules. These results suggest 
      that these hydrophobic ions can be used as "tags" that could make possible 
      acquisition of IRPD spectra of even larger clusters, such as clathrates, for 
      which precise mass selection of neutral clusters is not possible by other 
      methods.
FAU - Prell, James S
AU  - Prell JS
AD  - Department of Chemistry, University of California, Berkeley, California 
      94720-1460, USA.
FAU - Williams, Evan R
AU  - Williams ER
LA  - eng
PT  - Journal Article
PL  - United States
TA  - J Am Chem Soc
JT  - Journal of the American Chemical Society
JID - 7503056
EDAT- 2009/03/19 09:00
MHDA- 2009/03/19 09:01
CRDT- 2009/03/19 09:00
PHST- 2009/03/19 09:00 [entrez]
PHST- 2009/03/19 09:00 [pubmed]
PHST- 2009/03/19 09:01 [medline]
AID - 10.1021/ja809414a [doi]
PST - ppublish
SO  - J Am Chem Soc. 2009 Mar 25;131(11):4110-9. doi: 10.1021/ja809414a.