title: The effect of halide and iodate anions on the hydrogen-bonding network of water in aqueous nanodrops.
abstract: The hydration of halide and iodate anions was investigated using electrospray ionization (ESI) mass spectrometry and infrared photodissociation (IRPD) spectroscopy. The average cluster sizes, determined from the abundances of X-(H2O)n(X-= F-, Cl-, Br-, I-, IO3-) in the ESI mass spectra, follow the order F-> IO3-≈ Cl-> Br-> I-. The average cluster sizes and solution hydration enthalpies of the halides increase linearly with decreasing ionic radii, but IO3-does not fit this trend. The correlation between average cluster sizes and solution hydration enthalpies indicates that there is a similar relationship between ion-water interactions in these large gas-phase clusters and in bulk solution. The abundances of odd number clusters between n = 49 and 55 for I-, Br-and Cl-are enhanced but those for F-and IO3-are not. I-and IO3-have nearly the same ionic radii, but evidence suggests that these ions interact with water molecules differently both in solution and in small clusters. IRPD spectra of I-(H2O)nand IO3-(H2O)n, measured for select cluster sizes between n = 30 and 75 reveal differences in the hydrogen-bonding network of water molecules in these two ions even for sizes around n = 50. This indicates that differences in hydration motifs reported previously for the first hydration shells of I-and IO3-propagate to water molecules past the second solvation shell, a phenomenon that has not been reported previously for singly charged anions.
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720-1460, USA. erw@berkeley.edu.
authors.forename: Satrajit
authors.initials: S
authors.lastname: Chakrabarty
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720-1460, USA. erw@berkeley.edu.
authors.forename: Evan R
authors.initials: ER
authors.lastname: Williams