Hydrogen bonding induced distortion of CO3 units and kinetic stabilization of amorphous calcium carbonate

results from 2D 13C NMR spectroscopy

Sabyasachi Sen*, Derrick C. Kaseman, Bruno Colas, Dorrit E. Jacob, Simon M. Clark

*Corresponding author for this work

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Systematic correlation in alkaline-earth carbonate compounds between the deviation of the CO3 units from the perfect D3h symmetry and their 13C nuclear magnetic resonance (NMR) chemical shift anisotropy (CSA) parameters is established. The 13C NMR CSA parameters of amorphous calcium carbonate (ACC) are measured using two-dimensional 13C phase adjusted spinning sidebands (PASS) NMR spectroscopy and are analyzed on the basis of this correlation. The results indicate a distortion of the CO3 units in ACC in the form of an in-plane displacement of the C atom away from the centroid of the O3 triangle, resulting from hydrogen bonding with the surrounding H2O molecules, without significant out-of-plane displacement. Similar distortion for all C atoms in the structure of ACC suggests a uniform spatial disposition of H2O molecules around the CO3 units forming a hydrogen-bonded amorphous network. This amorphous network is stabilized against crystallization by steric frustration, while additives such as Mg presumably provide further stabilization by increasing the energy of dehydration.

Original languageEnglish
Pages (from-to)20330-20337
Number of pages8
JournalPhysical Chemistry Chemical Physics
Volume18
Issue number30
DOIs
Publication statusPublished - 14 Aug 2016

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