Based on the role of H-bond donor-acceptor pairing in
DES, three metal salt hydrates were evaluated for the synthesis of new solvents. LiCl·3H2O, MgCl2·3H2O, ZnCl2·3H2O are denoted as MS1, MS2, MS3, respectively. The structure of
cellobiose and
molecular interactions between the solvent and cellobiose in this work were studied using the Gaussian 16 package, with all samples optimized at the M06-2X/6-311+G⁎⁎ level. Frequency analyses were carried out for the optimized structures to verify energy minima and provide zero-point energy corrections. Thermochemical characteristics were also assessed to ensure consistency and reproducibility. To eliminate the dispersion effect, the empirical dispersion keyword = gd3 was added to the route section and the calculations were optimized without symmetry restrictions. MultiWFN code (Lu and Chen, 2012) was used to analyze the calculation results.
Acid dissociation constant (pKa) was used to quantitatively measure the strength of an acid in solution (the low the
pKa value, the stronger acidity the solvent) (Shokri et al., 2013). The pKa calculations were also performed using the Gaussian 16 package, and the geometry and harmonic frequencies of each species were optimized employing the B3LYP/6-311+G⁎⁎ method. Zero-point vibrational energy corrections were obtained by using the same method while single-point electronic energy values were calculated at the B2PLYPD3/def2TZVP and B3LYP/6-311+G⁎⁎ levels. The detailed calculation methods see Note S2.