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Using density functional theory, polyols were used as model ligands for Cu+/Cu2+ complexes to study the role of the hydrogen bond network on the metal binding affinity. In addition to the gas phase studies, the calculations were performed in 1‐decanol and DMSO solvents. The Cu2+ complexes were the most stable complexes with the highest bond dissociation energies (BDE). The presence of three H‐bonds in the first shell increased BDE values up to 17.99 and 57.07 kcal/mol for Cu+ and Cu2+ complexes in the gas phase, respectively, whereas the presence of another three H‐bonds in the second shell increased BDE values up to 7.27 and 24.35 kcal/mol for Cu+ and Cu2+ complexes in the gas phase, respectively. Therefore, this H‐bond network caused, for example, a more stable Cu+ complex with a formation constant of 1.4 × 1017 times. The natural bond orbital (NBO), atoms in molecules (AIM), and reduced density gradient (RDG) analyses showed that the intramolecular hydrogen bond network led to the enhancement of metal‐binding affinity. [ABSTRACT FROM AUTHOR]

In our previous report (J. Phys. Org. Chem., 2017), we discussed the dual behavior of gold nanocluster (Au3 NC), where it scavenged reactive oxygen species (ROS) while promoted their generation to a lesser extent. Continuing this quest, we investigate the effects of Au3 NC on common reactive nitrogen species (RNS: ON˙ and ON˙O) and their precursors (ONH and ONOH, respectively), at B3LYP/LACVP+* level of theory. We compare the results with those of prevalent ROS (HO˙ and HOO˙) and their precursors (HOH and HOOH, respectively). To this end, various parameters are probed such as binding energy (Eb), bond dissociation energy (BDE), bond lengths, Mullikan spin density (MSD), critical point (CP) eigenvalues (atoms in molecules [AIM] analysis), and natural bond orbital (NBO) analysis including natural population analysis (NPA) and change of charge transfer energy (ΔECT). Our results show that in the presence of Au3 NC, BDEs of the NH and OH bonds increase in both ONHAu3 (1) and ONOHAu3 (2) compared with their free forms (ONH and ONOH, respectively). In other words, the tendency to dissociate these bonds and form their corresponding RNS (1′ and 2′) decreases in the presence of gold. This is exactly the opposite of what is observed for the OH bonds in HOHAu3 (3), HOOHAu3 (4), and their corresponding ROS (3′ and 4′). Therefore, we can conclude that gold shows a different behavior in the face of RNS compared with ROS where it is a better scavenger of ROS than RNS. [ABSTRACT FROM AUTHOR]

Density functional theory method and B3LYP/6-311++G(d,p) level of theory were used to determine the acidity of alkyl and polyolalkyl in the gas and solution (H2O, DMSO, and CH3CN) phase. Polarized continuum model was applied to calculate p Ka values of alkyl and polyolalkyl . A comparison between acidity of alkyl and polyolalkyl in the gas and solution phase indicates that the acidity strength of polyolalkyl enhances with the increase of the cooperativity effect of hydrogen bonds in polyolalkyl . Natural bond orbital and quantum theory of atoms in molecules analyses also confirm the role of cooperativity effect on the acidity of polyolalkyl . Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In this study, the effects of the remote intramolecular hydrogen bonding on the acidity of hydroxy‐1,4‐benzoquinone derivatives have been investigated ab initio by employing density functional theory (DFT) methods. The computational studies were performed for both gas and solution (H2O, DMSO, and MeCN solutions) phases. Our results indicated that remote hydrogen bonding could play an important role in increasing the acidity of hydroxy‐1,4‐benzoquinone. Noncovalent interaction reduced density gradient (NCI‐RDG) methods were used to visualize the attractive and repulsive interactions in the studied acids and their conjugate bases. Natural bond orbital (NBO) analysis was performed to confirm intramolecular hydrogen bonding effect on acidity. Quantum theory of atoms in molecules (QTAIM) was also used to study the nature of hydrogen bonds. QTAIM results showed that the intramolecular hydrogen bonds in these structures are electrostatic (closed‐shell) interactions in nature. In this study, the effects of the remote intramolecular hydrogen bonding on the acidity of hydroxy‐1,4‐benzoquinone derivatives are explored by using ab initio and density functional theory (DFT) calculations. It was found that remote hydrogen bonding could play a surprisingly role in increasing the acidity of hydroxy‐1,4‐benzoquinone. [ABSTRACT FROM AUTHOR]