method was used for quantum
chemical calculation using the Dmol3 package combined with the
standard 6-311G (d, p) basis sets. DFT calculations employed the
B3LYP keyword invoking Becke's three parameter hybrid method
under correlation function of Lee et al. [23,24]. Optimization of
structural parameters is used to describe all stationary vibration
frequency calculation at DFT level with all stationary points as
minimum. Theoretical parameters are calculated, including the
energies of the highest occupied orbital (EHOMO), energies of lowest
unoccupied molecular orbitals (ELUMO) and energy gap (DE) as well
as dipole moment (m).