Nature of Brønsted acid–noble atom contacts: A reevaluation of hydrogen bonding criteria

Abstract

Xenon atoms interact weakly and reversibly with different molecular systems and human body. In this report, we consider their participation in hydrogen bonding in relation to analogous interactions of Ne, Ar, and Kr. Acid-noble atom dimers, AAHÁÁÁRg, are examined by the quantum theory of atoms in molecules and the results are discussed using several independent parameters. Different factors of this complexation are recognized: (i) the AH acidity and the Rg basicity, (ii) the AH structure, (iii) the electronegativities of atoms A and Rg, and (iv) the charge transfer from Rg to the complex critical point and to the acidic H atom. AAHÁÁÁNe contacts are qualitatively different from the remaining complexes. Koch and Popelier's criteria of hydrogen bonding, developed for classic complexes, are usually fulfilled for these very weak systems with one main exception: the charge on the acidic H increases upon the complexation to bigger Rg atoms.

Participation of Xenon Guest in Hydrogen Bond Network of β-Hydroquinone Crystal

“…69,70 Recent studies on isolated, H-bonded-like Xe•••HA dimers (where AH are different acids: NCH, CNH, ClH, BrH, ClOH, BrOH, CHCOOH, CFCOOH, and CClCOOH) revealed very big δ( 129 Xe) sensitivity to AH acidity. 69 Calculated energy formation of the A−H•••Xe dimers and the 129 Xe deshielding, resulting from these contacts, are within 1.4−5.4 kJ/mol and 54−85 ppm, respectively. 69 For each Xe•••HA dimer, the shielding tensor principal component σ zz represents the highest shielding direction (z) parallel or almost parallel to the Xe•••H direction.…”

The hydrogen bond – practice and QTAIM theory

“…1. 35 Thus it can be concluded that the mutual interconnection between both theoretical r(r c ) and experimental DA 1/2 This journal is © The Royal Society of Chemistry 2014 parameters does exist. It is also clear from the Fig.…”

Bonding Motifs of Noble-Gas Compounds As Described by the Local Electron Energy Density

“…The Ng–HF (Ng = Ne, Ar, Kr, Xe) species were recently investigated within a general study on the formation of hydrogen bonding by Ng atoms. , Thus, while Kr–HF and Xe–HF were predicted to be stable and to feature properties typical of H-bonding contacts, Ne–HF and Ar–HF were even unstable when basis set superposition error and zero-point vibrational energy corrections were included. Interestingly, the study of the H mol ( r ) function actually confirms the different bonding situations of the lightest and the heaviest Ng–HF.…”

“…21 Following pioneering applications reported so far, 22-25 the AIM theory is extensively employed to analyze the bonding situation of noble-gas compounds. [26][27][28][29][30][31] In general, within the AIM theory, one explores the topology ρ(r) is relatively large and ∇ 2 ρ(r) < 0, while for typical non-covalent (closed-shell) interactions such as ionic bonds, hydrogen bonds, and van der Waals contacts, at the BCP ρ(r) is relatively small, and ∇ 2 ρ(r) > 0. 21 These criteria, however, must often contend with conflicting indications from independent evidence, and further analysis is required.…”

“…Over the years, this bonding versatility has been continuously assayed by various theoretical methods, including, in particular, the topological analysis of the electron localization function (ELF) − and of the electron density, the latter being performed within Bader’s theory of atoms in molecules (AIM) . From the pioneering applications reported so far, − the AIM theory has been extensively employed to analyze the bonding situation of noble-gas compounds. − In general, within the AIM theory, one explores the topology of the electron density ρ­( r ) and calculates the value of ρ­( r ) and its Laplacian ∇ 2 ρ­( r ) at the (3,–1) critical points (∇ρ­( r ) = 0) located on the gradient paths connecting the various bonded atoms (bond critical points, BCPs). Thus, for typical covalent bonds, at the BCP ρ­( r ) is relatively large and ∇ 2 ρ­( r ) < 0, while for typical noncovalent (closed-shell) interactions such as ionic bonds, hydrogen bonds, and van der Waals contacts, at the BCP ρ­( r ) is relatively small and ∇ 2 ρ­( r ) > 0 .…”