Search

Hydrated singly charged aluminum ions eliminate molecular hydrogen in a size regime from 11 to 24 water molecules. Here we probe the structure of HAlOH+(H2O)n−1, n=9–14, by infrared multiple photon spectroscopy in the region of 1400–2250 cm−1. Based on quantum chemical calculations, we assign the features at 1940 cm−1 and 1850 cm−1 to the Al−H stretch in five‐ and six‐coordinate aluminum(III) complexes, respectively. Hydrogen bonding towards the hydride is observed, starting at n=12. The frequency of the Al−H stretch is very sensitive to the structure of the hydrogen bonding network, and the large number of isomers leads to significant broadening and red‐shifting of the absorption of the hydrogen‐bonded Al−H stretch. The hydride can even act as a double hydrogen bond acceptor, shifting the Al−H stretch to frequencies below those of the water bending mode. The onset of hydrogen bonding and disappearance of the free Al−H stretch coincides with the onset of hydrogen evolution. [ABSTRACT FROM AUTHOR]

Materials based on molybdenum sulfide are known as efficient hydrogen evolution reaction (HER) catalysts. As the binding site for H atoms on molybdenum sulfides for the catalytic process is under debate, [HMo3S13]− is an interesting molecular model system to address this question. Herein, we probe the [HMo3S13]− cluster in the gas phase by coupling Fourier‐transform ion‐cyclotron‐resonance mass spectrometry (FT‐ICR MS) with infrared multiple photon dissociation (IRMPD) spectroscopy. Our investigations show one distinct S−H stretching vibration at 2450 cm−1. Thermochemical arguments based on DFT calculations strongly suggest a terminal disulfide unit as the H adsorption site. [ABSTRACT FROM AUTHOR]

We investigate activation of carbon dioxide by singly charged hydrated magnesium cations Mg.+(H2O)n, through infrared multiple photon dissociation (IRMPD) spectroscopy combined with quantum chemical calculations. The spectra of [MgCO2(H2O)n].+ in the 1250–4000 cm−1 region show a sharp transition from n=2 to n=3 for the position of the CO2 antisymmetric stretching mode. This is evidence for the activation of CO2 via charge transfer from Mg.+ to CO2 for n≥3, while smaller clusters feature linear CO2 coordinated end‐on to the metal center. Starting with n=5, we see a further conformational change, with CO2.− coordination to Mg2+ gradually shifting from bidentate to monodentate, consistent with preferential hexa‐coordination of Mg2+. Our results reveal in detail how hydration promotes CO2 activation by charge transfer at metal centers. [ABSTRACT FROM AUTHOR]

We report the observation of chemical reactions in gas-phase Rhn(N2O)m+ complexes driven by absorption of blackbody radiation. The experiments are performed under collision-free conditions in a Fourier transform ion cyclotron resonance mass spectrometer. Mid-infrared absorption by the molecularly adsorbed N2O moieties promotes a small fraction of the cluster distribution sufficiently to drive the N2O decomposition reaction, leading to the production of cluster oxides and the release of molecular nitrogen. N2O decomposition competes with molecular desorption and the branching ratios for the two processes show marked size effects, reflecting variations in the relative barriers. The rate of decay is shown to scale approximately linearly with the number of infrared chromophores. The experimental findings are interpreted in terms of calculated infrared absorption rates assuming a sudden-death limit. [ABSTRACT FROM AUTHOR]