Supplementary Material
Solute Anisotropy Effects in Hydrated Anion and Neutral Clusters
Hui Wen,1 Gao-Lei Hou,2 Shawn M. Kathmann,1 Marat Valiev, 2,a) Xue-Bin Wang1,a)
1
Chemical & Materials Sciences Division, Pacific Northwest National Laboratory, 902 Battelle
Boulevard, P. O. Box 999, Richland, Washington 99352,
2
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P. O.
Box 999, Richland, Washington 99352
*Correspondence to: xuebin.wang@pnnl.gov; marat.valiev@pnnl.gov
Materials and Methods:
Photoelectron Spectroscopy
A low temperature photoelectron spectrometer coupled to an electrospray ion source and a
cryogenic ion-trap was used to obtain photoelectron spectra at 20 K.19 In this work, sodium and
potassium iodate salts were dissolved in acetonitrile : water (7:3 v/v) and the above solutions
were directly used for spraying. The IO3–(H2O)n cluster anions generated were trapped and
cooled for 20-80 ms before being transferred into the extraction zone of a time-of-flight mass
spectrometer. These anions were then mass-selected and decelerated before being photodetached
with a 157 nm F2 excimer laser. The laser was operated at a 20 Hz repetition rate with the ion
beam off at alternating laser shots to enable shot-to-shot background subtraction to be carried
S1
out. Photoelectrons were collected at ~100% efficiency with the magnetic bottle and analyzed in
a 5.2 m long electron flight tube. The time-of-flight photoelectron spectra were collected and
converted to kinetic energy spectra, calibrated using I–, ClO2–, and Cu(CN)2–. The electron
binding energy spectra were obtained by subtracting the kinetic energy spectra from the
detachment photon energy, and had a resolution (E/E) of ~2% or 20 meV at 1 eV as measured
for I– at 355 nm. Electron binding energy was obtained by drawing a straight line along the rising
edge of each spectrum and adding instrumental resolution to the crossing point with the binding
energy axis.
Theoretical Details
Calculations were performed using NWChem computational chemistry package.21 We have used
6-31++G** basis set
s1
for solvent water molecules. The basis set for iodate consisted of SDB-
aug-cc-pVTZ basis for iodine,s2 and cc-pvtz basis set for oxygen atoms.s3 All optimizations were
performed at DFT/B3LYP level of theory.s4 Electron binding energies calculated by taking the
difference between anion (singlet) and neutral (doublet) species at the optimized anion geometry.
For each iodate-water cluster, numbers of different isomers were investigated (up to 30-40
candidates per structure).
References
S1
J. D. Dill, J. A. Pople, J. Chem. Phys. 62, 2921 (1975).
S2
J. M. L. Martin, A. Sundermann, J. Chem. Phys. 114, 3408 (2001).
S3
J.T. H. Dunning, J. Chem. Phys. 90, 1007 (1989).
S4
A. D. Becke, J. Chem. Phys. 98, 1372 (1993); C. Lee, W. Yang, R. G. Parr, Phys. Rev. B 37,
785 (1988).
S2
Table 1S. Electron binding energy (EBE in eV) measured from the maximum of the first spectral
feature and calculated from the lowest minimum of each IO3–(H2O)n (n = 0-12) clusters. The
threshold detachment energy, TDE, estimated from each spectral threshold is also listed.
Number of water molecules, n
Experiment
Calculation*
TDE (EBE)
EBE
0
4.70 (4.75)
4.55
1
5.21 (5.32)
5.15
2
5.66 (5.76)
5.62
3
5.85 (5.98)
5.88
4
6.05 (6.27)
6.06
5
6.29 (6.57)
6.30
6
6.53 (6.83)
6.43
7
6.68 (7.02)
6.56
8
6.92 (7.29)
6.68
9
7.12 (7.54)
6.90
10
6.97 (7.38)
6.85
11
7.02 (7.45)
7.01
12
7.12 (7.50)
7.10
*Calculated from the lowest isomer for each cluster shown in Fig.2. The other low lying isomers
and their EBEs are given in Figs. 1S-11S.
S3
FIG. 1S: Lowest isomers for n=2 cluster
S4
FIG. 2S: Lowest isomers for n=3 cluster
S5
FIG. 3S: Lowest isomers for n=4 cluster
S6
FIG. 4S: Lowest isomers for n=5 cluster
S7
FIG. 4S: Lowest isomers for n=5 cluster
S8
FIG. 5S: Lowest isomers for n=6 cluster
S9
FIG. 5S: Lowest isomers for n=6 cluster
S10
FIG. 5S: Lowest isomers for n=6 cluster
S11
FIG. 5S: Lowest isomers for n=6 cluster
S12
FIG. 6S: Lowest isomers for n=7 cluster
S13
FIG. 6S: Lowest isomers for n=7 cluster
S14
FIG. 7S: Lowest isomers for n=8 cluster
S15
FIG. 7S: Lowest isomers for n=8 cluster
S16
FIG. 8S: Lowest isomers for n=9 cluster
S17
FIG. 8S: Lowest isomers for n=9 cluster
S18
FIG. 9S: Lowest isomers for n=10 cluster
S19
FIG. 9S: Lowest isomers for n=10 cluster
S20
FIG. 9S: Lowest isomers for n=10 cluster
S21
FIG. 10S: Lowest isomers for n=11 cluster
S22
FIG. 10S: Lowest isomers for n=11 cluster
S23
FIG. 10S: Lowest isomers for n=11 cluster
S24
FIG. 11S: Lowest isomers for n=12 cluster
S25
FIG. 11S: Lowest isomers for n=12 cluster
S26
FIG. 11S: Lowest isomers for n=12 cluster
S27