pH-Dependent Interactions between Keggin Heteropolyanions in Dilute Solutions: pH-Dependent Interactions between Keggin Heteropolyanions in Dilute Solutions
Journal Article
·
· European Journal of Inorganic Chemistry
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Univ. of Chicago, IL (United States)
Previously, Keggin phosphotungstate heteropolyanions (HPA), PW12O403–, are known to interact via short-range attraction and long-range repulsion (SALR) at moderate and high solution concentrations and low-pH (pH = 1). These interactions were identified through the observation of structure factor peaks in small-angle X-ray scattering (SAXS) data reported previously (J. Phys. Chem. C 2016, 120, 1317). Here we describe the interactions between the same heteropolyanions with extremely low concentrations at low (pH = 0) and high pH (pH = 4.7) conditions. The solution chemistry of Keggin heteropolyanions at these two pH values offers a unique way to change the charge of the cluster anions without changing the structure (from the perspective of SAXS) and, at the same time, changing the hydrogen bonding interactions. The structure factors obtained from concentration dependent SAXS data reveal that the change in pH changes the nature of SALR interactions, consistent with the presence of the plenary PW12O403– anion at pH = 0 and the monovacant lacunary PW11O397– anion at pH = 4.7. At the low pH condition, the attractive interactions dominate to provide a peak near Q = 0 Å–1 momentum transfer in the structure factors, whereas at pH = 4.7 the repulsive interactions dominate, thereby eliminating the peak near Q = 0 Å–1. The experimental findings presented here are in agreement with the recent liquid state theory and computer simulation predictions on SALR interactions.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- National Science Foundation (NSF); USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- Grant/Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1494561
- Alternate ID(s):
- OSTI ID: 1488961
- Journal Information:
- European Journal of Inorganic Chemistry, Journal Name: European Journal of Inorganic Chemistry Journal Issue: 3-4 Vol. 2019; ISSN 1434-1948
- Publisher:
- ChemPubSoc EuropeCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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