Charge distribution of poly (p-phenylene benzobisoxazole) investigated by quantum chemical simulation

The electrostatic potential fit (ESP) charges of the atoms of PBO model compound were evaluated by quantum chemical simulation. The geometry optimization with B3LYP functional and STO-3G, 6-31G(d), 6-311++G(2d,p), cc-pVTZ basis sets were applied, respectively. The charge distributions at these basis sets all indicate the N atoms to own the highest electronegativity, which are much stronger than that of O atoms. The result possesses successful representation of the electrostatic potential and deformation electron density. Moreover, the ESP charges fit well with the chemical trend exhibited by the protonation of PBO. Compared to the those derived from Mulliken, Hirshfeld and Natural Population Analysis (NPA) schemes, the charge distribution derived from electrostatic potential has the best performance both theoretically and experimentally.