A quantum chemical study of the interaction of carboxylic acids with DMSO

Abstract

Quantum chemical computational methods, which use quantum mechanics and molecular dynamics theory, have developed rapidly in the past few decades, and quantum chemical computation has penetrated almost all fields of chemistry. Hydrogen bonds are ubiquitously common weak intermolecular interactions. Moreover, the bonding mechanism of hydrogen bonds is considered to be different from that of chemical bonding. Because of the difficulty of experimental studies, a more accurate calculation of hydrogen bonding from theory is a more convenient and direct method to understand hydrogen bonding. Density functional theory (DFT) is the most widely used general function in quantum chemical calculations, giving accurate results for most chemical systems. In this paper, the geometries of the hydrogen-bonded dimer complex of acetic acid and DMSO was structurally optimized and potential energy surface was determined. The geometries of four related hydrogen-bonded dimer complexes were fully optimized using the M06-2X/6-311++G (3d, 2p) exchange-correlation functional with DFT-D3(BJ) empirical dispersion correction. We found that hydrogen bonding is a mixture of electrostatic interactions and covalent bonding, and that hydrogen bonding is a kind of force with different percentages of electrostatic and covalent character, rather than a special force independent of chemical bonding. Thus, more clearly defining our inherent classification of forces between substances provides a new perspective for our future study of weak interactions such as hydrogen bonding.

Characterization of the absorption properties of 5 nm spherical gold nanoparticles functionalized with dodecanothiol and without functionalization with potential therapeutic applications

“…It was not possible to compare in which of the two suspensions the effect of irradiation on λ max is greater because the number of irradiated nanoparticles is different. When switching from aqueous to organic medium the ABMA maxima at t = 0 (360 nm, 380 nm and 402 nm) showed a slight bathochromic shift of 4 nm (364, 384 and 406 nm) related, probably to: (a) variation of the dielectric constant of the medium (m); (b) formation of H bridges between the −S=O group of DMSO and the −COOH groups of ABMA (Ren et al 2022); or (c) synergy of both processes (figures 2(e) and (f)). Irradiation at 532 nm produced no subsequent changes in either the position or intensity of these maxima (figure 2(e)), due to the known stability of ABMA.…”

“…The 384 nm maximum remained unchanged in position in the first 5 min of irradiation and then ran at 382 nm until the end. These variations could be related to the formation of new structures in solution because ABMA molecules undergo electronic redistribution in the presence of DMSO (Ren et al 2022). The higher irradiation intensity at 1064 nm could intensify the electronic redistribution leading to new structures in solution.…”

“…However, when irradiated at 1064 nm in the presence of DMSO the absorption of ABMA increases (figure 2(f)) while that of DCPIP decreases (figure 2(h)). This increase in ABMA absorption, together with slight shifts of its absorption bands during irradiation at 1064 nm is assumed to be associated with molecular variations due to stronger interactions between the −COOH groups of ABMA and the −S=O group of DMSO (Ren et al 2022) than those occurring when irradiated at 532 nm and lower laser fluence. Interactions between the −S=O groups of DMSO and −COOH groups can cause bond rotation or vibration and even lead to dimer formation (Takis et al 2017).…”