*2.2. DFT Calculation*

The molecular building and geometric optimization of all 18 compounds was performed by DFT using Gaussian 03W software package with basis set method B3LYP/6-31 + G(d,p). The Gauss-view program was used for molecular visualization. Geometrical, energetic and electronic parameters were calculated using structures optimized at 298 K and 1 atm. The Gibbs free energy equation (ΔG = −RT ln K) was used to search conformational space.
