Margarita I. Bernal-Uruchurtu

Performance of local correlation methods for halogen bonding: The case of Br2–(H2O)n,n = 4,5 clusters and Br2@51262 clathrate cage

The performance of local correlation methods is examined for the interactions present in clusters of bromine with water where the combined effect of hydrogen bonding (HB), halogen bonding (XB), and hydrogen-halogen (HX) interactions lead to many interesting properties. Local methods reproduce all the subtleties involved such as many-body effects and dispersion contributions provided that specific methodological steps are followed. Additionally, they predict optimized geometries that are nearly free of basis set superposition error that lead to improved estimates of spectroscopic properties. Taking advantage of the local correlation energy partitioning scheme, we compare the different interaction environments present in small clusters and those inside the 5(12)6(2) clathrate cage. This analysis allows a clear identification of the reasons supporting the use of local methods for large systems where non-covalent interactions play a key role.

Intramolecular hypervalent CO⋯S interactions in a series of 1,3-benzothiazole derivatives

Seven compounds derived from 2-(4-chlorophenoxy)-2-methylpropionic acid and 2-aminobenzothiazole, 2-amino-6-methylbenzothiazole, 2-amino-6-methoxybenzothiazole, 2-amino-6-ethoxybenzothiazole, 2-amino-6-chlorobenzothiazole, 2-amino-6-nitrobenzothiazole, and 2-amino-6-(methylsulfonyl) benzothiazole have been prepared and structurally characterized. This set of 1,3-benzothiazole derivatives (1–7) has been studied by means of elemental analysis, mass spectrometry, IR, NMR (1H, 13C) spectroscopy, and single-crystal X-ray diffraction analysis. This work focuses on the description of the hypervalent contacts (CO⋯S, S⋯S), hydrogen bonds Y–H⋯X (Y = O, N, C; X = O, N, Cl, π) and van der Waals contacts (Cl⋯π, S⋯π, H⋯H) that are found to be the driving forces for the supramolecular arrangements present in the crystal structures.

Is Br2 hydration hydrophobic

The spectroscopic properties of bromine in aqueous systems suggest it can behave as either hydrophilic or hydrophobic solute. In small water clusters, the halogen bond and the hydrogen-halogen interaction are responsible for its specific way of binding. In water hydrates, it is efficiently hosted by two different cages forming the crystal structure and it has been frequently assumed that there is little or no interaction between the guest and the host. Bromine in liquid solution poses a challenging question due to its non-negligible solubility and the large blue shift measured in its absorption spectra. Using a refined semi-empirical force field, PM3-PIF, we performed a Born-Oppenheimer molecular dynamics study of bromine in liquid water. Here we present a detailed study in which we retrieved the most representative hydration structures in terms of the most frequent positions around bromine and the most common water orientations. Albeit being an approximate description of the total hydration phenomenon, it captures the contribution of the leading molecular interactions in form of the recurrent structures. Our findings confirm that the spectroscopic signature is mainly caused by the closest neighbors. The dynamics of the whole first hydration shell strongly suggests that the external molecules in that structure effectively isolate the bulk from the presence of bromine. The solvation structure fluctuates from a hydrophilic to a hydrophobic-like environment along the studied trajectory.