Experimental and theoretical vibrational investigation on the saccharinate ion in aqueous solution

We combined experimental vibrational spectroscopy (FTIR-Raman) and ab-initio calculations based on the density functional theory (DFT) to predict the structural and vibrational properties of sodium saccharinate in the solid and aqueous solution phases. The structural properties for the saccharinate ion and its dimer, such as the bond order, possible charge-transfer and the topological properties for both rings in the two media were studied by means of the Natural Bond Orbital (NBO) and the Atoms in Molecules theory (AIM) investigation. For a complete assignment of the IR and Raman spectra, the density functional theory calculations were combined with Pulay’s scaled quantum mechanics force field (SQMFF) methodology in order to fit the theoretical frequency values to the experimental ones. An agreement between theoretical and available experimental results was found. Four intense bands in the infrared spectrum characteristic of the dimeric species of the compound were detected.

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► A complete assignment of the observed spectral features is proposed.
► Four intense bands associated with the dimer were detected in the IR spectrum.
► The SQM force field was obtained for the saccharinate dimer.
► The topological properties for the saccharinate dimer were studied.
► The charge-transfers for the saccharinate dimer were studied.