Theoretical structural and vibrational properties of the artificial sweetener sucralose

The structural and vibrational properties of sucralose were predicted by combining the available experimental infrared spectrum in the solid phase and ab initio calculations based on density functional theory (DFT). The highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps HOMO-LUMO frontier orbitals, Natural Bond Orbital (NBO) and Atoms in Molecules (AIM) theory calculations were employed to study the stability, bond order, possible charge transfer and the topological properties of the glucopyran and glucofuran rings. To perform a complete assignment of the vibrational spectra, the density functional theory (DFT) calculations were combined with Pulay's Scaled Quantum Mechanics Force Field (SQMFF) methodology. The calculations were also used to predict the Raman spectrum of sucralose. A complete assignment of the 120 normal vibrational modes for sucralose was performed. Four strong bands in the infrared spectrum at 1093, 1040, 1025 and 990cm^-1 are characteristic of sucralose in the solid phase. In this work, the calculated structural and vibrational properties of sucralose were analysed and compared with those of sucrose. The high stability of sucrose in relation to sucralose was justified by means of NBO and AIM analyses.