*2.8. DFT Calculations*

DFT method (Density Functional Theory method) with B3LYP/6-311G(d,p) was used to optimize the geometries of the molecules. The optimized stable conformation was confirmed to be real minima by frequency calculation (no imaginary frequency). Additionally, HOMO, E-gap (expressed by ELUMO-HOMO = ELUMO − EHOMO) [24], and Fukui functions were applied to predict reactivity sites. Fukui functions (f−, f+, f0) were calculated using Equations (4)–(6) [25]. q from Equations (4)–(6) represents the atomic charge at the rth atomic site with the neutral (N), anionic (N + 1), and cationic (N-1) chemical species [26]. All calculations were performed using the Gaussian 09, Revision D.01 program package (Gaussian, Inc., Wallingford, CT, USA) [27].

$$\mathbf{f}^+ = \mathbf{q}(\mathbf{N}+1) - \mathbf{q}(\mathbf{N}) \quad \text{for nucleophile attack} \tag{4}$$


$$\mathbf{f}^{\mathrm{d}} = (\mathbf{q}(\mathbf{N} + 1) - \mathbf{q}(\mathbf{N} - 1))/2 \quad \text{for radical attack} \tag{6}$$
