biostudies-literatureJin SAustrian Science Fund FWFMinisterio de Ciencia, Innovaci?n y UniversidadesUniversidad de Valladolid3455-3465https://www.ebi.ac.uk/biostudies/studies/S-EPMC12010328biostudies-literatureUnknown129(15)Although iron is the most abundant transition metal in the interstellar medium, its interaction with hydrogen─by far the most abundant element─in small gas-phase molecules or complexes is poorly understood. Herein, we study the infrared spectroscopy of cationic iron complexes with one and two dihydrogen ligands, Fe<sup>+</sup>(H<sub>2</sub>)<sub>1,2</sub>, as well as their deuterated counterparts, Fe<sup>+</sup>(D<sub>2</sub>)<sub>1,2</sub>, using infrared multiple photon dissociation (IRMPD) spectroscopy. Quantum chemical calculations, including multireference configuration interaction (MRCI) with spin-orbit coupling, are used to simulate the electronic and vibrational contributions to the spectra. Broad electronic transitions are observed in the studied energy range of 2230-4000 cm<sup>-The journal of physical chemistry. AInfrared Multiple Photon Dissociation Spectroscopy of the H-H Stretching Mode and Low-Lying Electronic Transitions in Fe&lt;sup&gt;+&lt;/sup&gt;(H&lt;sub&gt;2&lt;/sub&gt;)&lt;sub&gt;1,2&lt;/sub&gt; and Fe&lt;sup&gt;+&lt;/sup&gt;(D&lt;sub&gt;2&lt;/sub&gt;)&lt;sub&gt;1,2&lt;/sub&gt;.PMC1201032810.55776/W125910.55776/P35013CONREC-2021-265Juanes MJin Svan der Linde COncak MBeyer MKfalseInfrared Multiple Photon Dissociation Spectroscopy of the H-H Stretching Mode and Low-Lying Electronic Transitions in Fe&lt;sup&gt;+&lt;/sup&gt;(H&lt;sub&gt;2&lt;/sub&gt;)&lt;sub&gt;1,2&lt;/sub&gt; and Fe&lt;sup&gt;+&lt;/sup&gt;(D&lt;sub&gt;2&lt;/sub&gt;)&lt;sub&gt;1,2&lt;/sub&gt;.Although iron is the most abundant transition metal in the interstellar medium, its interaction with hydrogen─by far the most abundant element─in small gas-phase molecules or complexes is poorly understood. Herein, we study the infrared spectroscopy of cationic iron complexes with one and two dihydrogen ligands, Fe<sup>+</sup>(H<sub>2</sub>)<sub>1,2</sub>, as well as their deuterated counterparts, Fe<sup>+</sup>(D<sub>2</sub>)<sub>1,2</sub>, using infrared multiple photon dissociation (IRMPD) spectroscopy. Quantum chemical calculations, including multireference configuration interaction (MRCI) with spin-orbit coupling, are used to simulate the electronic and vibrational contributions to the spectra. Broad electronic transitions are observed in the studied energy range of 2230-4000 cm<sup>-2025-01-01T00:00:00Z2025 Apr2025-07-07T03:10:04.214Z2025-07-07T03:10:04.214ZS-EPMC120103284017335610.1021/acs.jpca.5c00196