Infrared Multiple Photon Dissociation Spectroscopy Confirms Reversible Water Activation in Mn⁺(H₂O)_n, n ≤ 8

Abstract

Controlled activation of water molecules is the key to efficient water splitting. Hydrated singly charged manganese ions Mn + (H 2 O) n exhibit a size-dependent insertion reaction, which is probed by infrared multiple photon dissociation spectroscopy (IRMPD) and FT-ICR mass spectrometry. The noninserted isomer of Mn + (H 2 O) 4 is formed directly in the laser vaporization ion source, while its inserted counterpart HMnOH + (H 2 O) 3 is selectively prepared by gentle removal of water molecules from larger clusters. The IRMPD spectra in the O–H stretch region of both systems are markedly different, and correlate very well with quantum chemical calculations of the respective species at the CCSD(T)/aug-cc-pVDZ//BHandHLYP/aug-cc-pVDZ level of theory. The calculated potential energy surface for water loss from HMnOH + (H 2 O) 3 shows that this cluster ion is metastable. During IRMPD, the system rearranges back to the noninserted Mn + (H 2 O) 3 structure, indicating that the inserted structure requires stabilization by hydration. The studied system serves as an atomically defined single-atom redox-center for reversible metal insertion into the O–H bond, a key step in metal-centered water activation.

Size-dependent H and H2 formation by infrared multiple photon dissociation spectroscopy of hydrated vanadium cations, V+(H2O)n, n = 3–51

“…IRMPD yields are calculated from the corrected ion intensities, normalized by the wavelength-specific laser power and re-normalized for display as described before. 75 …”

Viewpoints on the 11th International Meeting on Atomic and Molecular Physics and Chemistry

“…In his invited talk, Hans Christian Schewe reported on experimental studies of electrolyte-to-metal transition in liquid alkali-metal ammonia solutions using liquid microjets and droplets in vacuum as developed in his laboratory in Prague, as well as on his recent experiments showing spectroscopic evidence of a metallic water solution . The invited talk of Milan Ončák focused on the modeling of excited-state dynamics of hydrated metal ions in the gas phase, M + (H 2 O) n , M + = Mg + , V + , and Al + . , …”

“…23 The invited talk of Milan Oncǎḱ focused on the modeling of excited-state dynamics of hydrated metal ions in the gas phase, M + (H 2 O) n , M + = Mg + , V + , and Al + . 24,25 The Wednesday program was opened by the talk of Dr. Jun Ye, who presented an overview of the recent state of the art experimental techniques to control molecules in optical lattices as well as using these techniques to reveal the quantum stateresolved reaction dynamics. The talk was followed by the hot topic of Adam Koza, theoretically investigating intermolecular interactions in ultracold mixtures using highly correlated ab initio electronic structure techniques.…”

Thermally Activated vs. Photochemical Hydrogen Evolution Reactions–A Tale of Three Metals

“…[32] Water activation may proceed without subsequent hydrogen evolution, as documented for [Mn(H 2 O) n ] + . [33,34] This reductionist approach of course comes at a price. The reaction mechanisms obviously cannot be directly transferred to electrochemical environments, where controlled electric potentials are applied, and interface effects at extended surfaces play an important role.…”