Hydrogen bond dynamics of superheated water and methanol by ultrafast IR-pump and EUV-photoelectron probe spectroscopy

Abstract

Supercritical water and methanol have recently drawn much attention in the field of green chemistry. It is crucial to an understanding of supercritical solvents to know their dynamics and to what extent hydrogen (H) bonds persist in these fluids. Here, we show that with femtosecond infrared (IR) laser pulses water and methanol can be heated to temperatures near and above their critical temperature T c and their molecular dynamics can be studied via ultrafast photoelectron spectroscopy at liquid jet interfaces with high harmonics radiation. As opposed to previous studies, the main focus here is the comparison between the hydrogen bonded systems of methanol and water and their interpretation by theory. Superheated water initially forms a dense hot phase with spectral features resembling those of monomers in gas phase water. On longer timescales, this phase was found to build hot aggregates, whose size increases as a function of time. In contrast, methanol heated to temperatures near T c initially forms a broad distribution of aggregate sizes and some gas. These experimental features are also found and analyzed in extended molecular dynamics simulations. Additionally, the simulations enabled us to relate the origin of the different behavior of these two hydrogen-bonded liquids to the nature of the intermolecular potentials. The combined experimental and theoretical approach delivers new insights into both superheated phases and may contribute to understand their different chemical reactivities.

Quantitative decomposition of resonance‐assisted hydrogen bond energy in β‐diketones into resonance and hydrogen bonding (π‐ and σ‐) components using molecular tailoring and function‐based approaches

“…However, the values of the V local potential energy of the electrons at the critical point of the H‐bond, which is the most popular descriptor of H‐bond, were not presented in these papers by Rusinska‐Roszak. The V values were widely used for estimation of the H‐bond energy by means of the Espinosa's equation and its modified versions . For this reason, we had to calculate this parameter additionally.…”

“…The V values were widely used for estimation of the H-bond energy by means of the Espinosa's equation [21][22][23][24][25][26] and its modified versions. [27][28][29][30][31] For this reason, we had to calculate this parameter additionally.…”

Benchmark calculations of intramolecular hydrogen bond energy based on molecular tailoring and function‐based approaches: Developing hybrid approach

“…Similar linear relations between E HB and ρ BCP were obtained in the Nikolaienko et al and Brovarets et al presents the well‐known Espinosa‐Molins‐Lecomte equation, which relies on the X‐ray diffraction data and calculations of the topological parameters of H‐bonds in the framework of QTAIM. It is the most widely used relation for estimating the H‐bond energy due to its exceptional simplicity ( E HB = | V |/2, if V in kcal mol −1 ) . However, some evidence suggests that the use of Equation results in a significant overestimation in energy of intramolecular interactions .…”

“…It is the most widely used relation for estimating the H-bond energy due to its exceptional simplicity (E HB = |V|/2, if V in kcal mol −1 ). [36][37][38][39][40][41] However, some evidence suggests that the use of Equation (8) results in a significant overestimation in energy of intramolecular interactions. [22,32,42,43] For this reason, the Espinosa-Molins-Lecomte equation was modified to obtain more reliable values of estimated energy.…”

Deeply cooled and temperature controlled microjets: Liquid ammonia solutions released into vacuum for analysis by photoelectron spectroscopy

“…Under extreme non-equilibrium conditions (IR laser heating, 400 K) H-bonding dynamics in water and methanol has been tracked by time resolved PES. [56,57] IV. SUMMARY…”