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The HXeY⋯H2O complexes (Y = Cl, Br, and I) are studied theoretically and experimentally. The calculations at the CCSD(T)/def2-TZVPPD level of theory predict two stable structures for Y = Cl and Br and one structure for Y = I, with interaction energies up to about -7 kcal mol-1. In the experiments, we have identified several infrared absorption bands originating from the H-Xe stretching mode of these complexes in a xenon matrix. The monomer-to-complex frequency shifts of this mode are up to +82 cm-1 (Y = Cl), +101 cm-1 (Y = Br), and +138 cm-1 (Y = I), i.e., the shift is smaller for more strongly bound molecules. Based on the agreement of the experimental and theoretical results, the observed bands are assigned to the most stable planar structure with an O-H⋯Y–Xe hydrogen bond. [ABSTRACT FROM AUTHOR]

Lithium bonding in lithium 2-pyridyl-N-oxide acetate has been investigated using classic Car–Parrinello molecular dynamics (CPMD) and the path integral approach [path integrals molecular dynamics (PIMD)]. The simulations have been performed in 300 K. Structures, energies, and lithium trajectories have been determined. The CPMD results show that the lithium atom is generally equidistant between heavy atoms in the (O...Li...O) bridge. Applying quantum effects through the PIMD leads to similar conclusion. The theoretical lithium 2-pyridyl-N-oxide acetate infrared spectrum has also been determined using the CPMD calculations. This shows very good agreement with available experimental results and reproduces well the broad low-frequency band observed experimentally. In order to gain deeper understanding of the nature of the lithium bonding topological analysis of the electron localization function has been applied. [ABSTRACT FROM AUTHOR]

Car‐Parrinello and path integrals molecular dynamics (CPMD and PIMD) simulations were carried out for the 10π‐electron aromatic systems: 2‐hydroxy‐2,4,6‐cycloheptatrien‐1‐one, commonly known as Tropolone (I) and 2‐hydroxy‐2,4,6‐cycloheptatriene‐1‐thione, called Thiotropolone (II) in vacuo and in the solid state. The extremely fast proton transfer (FPT) and "prototropy" tautomerism in the keto‐enol (thione‐enethiol) systems have been analyzed on the basis of CPMD and PIMD methods level. Comparisons of two‐dimensional (2D) free‐energy landscapes of reaction coordinate δ‐parameter and RO...O or RO...S distances shows that the OH... tautomer to be more favorable in the Thiotropolone. The hydrogen between the oxygen and the sulfur atoms adopts a starkly asymmetrical position in the double potential well. The values of the energy barriers for the FPT were calculated and suggested a strong hydrogen bond with low barrier for FPT mechanism. These studies and the 2D average index of π‐delocalization 〈λ〉 landscape of time evolutions of RO1...O2 and RC7O2 or RC7S1 distances for the both crystals indicate that hydrogen bonds in the crystals of Tropolone (I) and Thiotropolone (II) have characteristic properties for the type of bonding model resonance‐assisted hydrogen bonds and also low‐barrier hydrogen bonds. In the crystal of the Thiotropolone (II), we found the hydrogen bond OH...S existing without the equilibrium of the two tautomers whereas in the crystal of the Tropolone (I) has been confirmed the hydrogen bond OH...O existing with the equilibrium of the two tautomers. It was also found the significant differences in frequency, speed, and the image of the FPT in the studied crystals. © 2018 Wiley Periodicals, Inc. Hydrogen bond is the most important of all directional intermolecular interactions. Hydrogen bonded systems play also a very important role in many physical, chemical and biological processes. The extremely fast proton transfer (FPT) and 'prototropy' tautomerism in the keto‐enol (thione‐enethiol) 10ϕ‐electron aromatic systems have been analyzed on the basis of CPMD and PIMD methods level for the 2‐hydroxy‐2,4,6‐cycloheptatrien‐1‐one, commonly known as Tropolone (I) and 2‐hydroxy‐2,4,6‐cycloheptatriene‐1‐thione, called Thiotropolone (II) in vacuo and in the solid state. [ABSTRACT FROM AUTHOR]