Theoretical Exploration of Enhanced Antioxidant Activity in Copper Complexes of Tetrahydroxystilbenes: Insights into Mechanisms and Molecular Interactions.

A theoretical investigation was conducted using DFT/PW91/TZP/DMSO calculations on a complete set of exhaustive lists of 18 compounds resulting from the complexation of trans-2,4,3',5'-tetrahydroxystilbene (T-OXY) and cis-2,4,1',3'-tetrahydroxystilbene (C-OXY) with copper metal cations (Cu+ and Cu2+). The ligand-binding sites are the critical points of Quantum Theory of Atoms in Molecules (QTAIM) analysis on neutral and deprotonated ligands. Various mechanisms, including hydrogen atom transfer (HAT), sequential proton loss electron transfer (SPLET), single electron transfer followed by proton transfer (SET-PT), and bond dissociation energy (BDE(E0)) calculations, were employed to quantify the antioxidant activity. The BDE(E0) mechanism emerged as the most suitable approach for such analyses to evaluate the departure of hydrogen atoms since the results show the HAT mechanism is the most likely occurring. Particularly intriguing were the anionic Cu+ complexes with ligands adopting trans configurations and deprotonated conformations, displaying superior antioxidant activity compared to their counterparts. Remarkably, a single ligand within the Cu+ complex exhibited exceptional antioxidant prowess, yielding a BDE(E0) value of 91.47 kcal/mol. Furthermore, a complex involving two deprotonated ligands demonstrated antioxidant activity of 31.12 kcal/mol, signifying its potential as a potent antiradical agent, surpassing T-OXY by a factor of 3.91 and even surpassing the antioxidant efficiency of Vitamin C.

Use of a Metal Organic Framework for the Adsorptive Removal of Gaseous HCl: A New Approach for a Challenging Task.

In this work, the potentialities of the amino-functionalized, chromium-based MIL-101 metal organic framework (NH2-MIL-101) as a high capacity, fully regenerable hydrogen chloride adsorbent have been proved by a thorough adsorption thermodynamics investigation. The chosen adsorbent showed high gaseous HCl adsorption capacities and, to the best of our knowledge, it is the first example of a totally regenerable substrate for this kind of adsorbate, as evidenced by both experimental and modeling results. This paves the way to the implementation of greener, more energetically efficient pressure/temperature swing adsorption processes to purify biogas feeds for high-temperature fuel cells.