The physicochemical parameters including Hf, the
energy of the highest occupied molecular orbital (Ehomo)
and the energy of the lowest unoccupied molecular orbital
(Elumo) were calculated with HyperChem molecular
modeling software [17] after performing geometry optimization
and energy minimization using the AM1 semiempirical
method. Polak-Ribiere conjugate gradient with
RHF spin pairing, 0.01 convergence limit in vacuo, and
RMS gradient of 0.1 kcal/[Å mol] were used during