Quantum‐chemical studies of the antioxidant effectiveness of para‐phenylene diamines

Abstract

The purpose of this review is to highlight how the antioxidant effectiveness (AE) of rubber additives can be quantitatively interpreted using results from quantum‐chemical calculations. The relationships between the AE of para‐phenylene diamines (PPD), evaluated through non‐isothermal differential scanning calorimetry measurements in styrene‐butadiene and polyisoprene rubber matrices, and various parameters obtained by quantum‐chemical calculations are reviewed. The N atom between both phenyl rings (A site) is more significant than the N atom between the phenyl ring and the alkyl chain (B site). The preferred formation of ketimine structures (instead of the quinonediimine ones) during dehydrogenation despite the higher stability of the NA‐centered radicals indicates a kinetic control of the antioxidant action. In most cases, the AE decreases with the strength of the NA–HA bond and increases with the chemical shifts of NA and HA. In hypothetical Cu(II) complexes, the AE rises with the affinity of NA to Cu, and the extent of electron density transfer from NA to Cu. Most deviations from linearity might be explained by steric hindrances. Reverse trends for the NA and NB chemical shifts are observed, despite the fact that similar reactions are supposed at both sites.

DFT studies of camptothecins cytotoxicity IV — active and inactive forms of irinotecan

“…Relative cytotoxicity of various forms of campto thecin and lactone forms of irinotecan and SN-38 have been investigated in a series of studies (Steklac and Breza, 2018, 2021, 2022a) by means of quantum chemistry. This treatment was originally developed for antioxidants Ghio, 2009, 2009a;Mammino, 2013;Kabanda et al, 2014;Tsiepe et al, 2015;Serobatse et al, 2016Serobatse et al, , 2016aBreza, 2016, 2017;Jelemenska and Breza, 2021;Breza and Jelemenska, 2022) and is based on the complexation ability of their various active sites to Cu(II) with subsequent electron density transfer (ligand oxidation and metal reduction). Metal ion affinity (MIA) data for the ligand active sites in hypothetical complexes can be obtained by DFT treatment.…”