DFT Investigation of a Charge-Transfer Complex Formation Between p-Phenylenediamine and 3,5-Dinitrosalicylic Acid

This study presents a computational investigation of p-phenylenediamine (PPD) interaction with 3,5-dinitrosalicylic acid (DNS) within PPD/DNS charge transfer (CT) complex. All calculations were performed by M06-2X/6-311+G(d,p) levels of theory in vacuum, water and methanol. EDA analysis was used to control the complexation process and suggested that electrostatic and dispersion energies contributes greatly in stabilizing PPD/DNS CT complex. The results of energy optimization showed that PPD/DNS CT complex is stable with negative complexation energy; the obtained geometries showed that ammonium group of PPD is closed to carboxylate one of DNS enabling the establishment of large number of interactions. Additionally, different analyses were performed on obtained optimized structures: TD-DFT, NBO, QTAIM and NCI. Consequently, NBO, QTAIM and NCI analysis give that PPD/DNS CT complex is stabilized by hydrogen bonding and van der Waals interactions.