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Isomer‐Specific Vibrational Spectroscopy of Microhydrated Lithium Dichloride Anions: Spectral Fingerprint of Solvent‐Shared Ion Pairs
Author(s) -
Chakraborty Arghya,
Schmahl Sonja,
Asmis Knut R.
Publication year - 2021
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.202100170
Subject(s) - chemistry , molecule , ion , spectroscopy , infrared spectroscopy , aqueous solution , lithium (medication) , solvent , hydrogen bond , population , electrolyte , analytical chemistry (journal) , organic chemistry , medicine , physics , quantum mechanics , endocrinology , demography , electrode , sociology
The vibrational spectroscopy of lithium dichloride anions microhydrated with one to three water molecules, [LiCl 2 (H 2 O) 1–3 ] − , is studied in the OH stretching region (3800–2800 cm −1 ) using isomer‐specific IR/IR double‐resonance population labelling experiments. The spectroscopic fingerprints of individual isomers can only be unambiguously assigned after anharmonic effects are considered, but then yield molecular level insight into the onset of salt dissolution in these gas phase model systems. Based on the extent of the observed frequency shifts Δν OH of the hydrogen‐bonded OH stretching oscillators solvent‐shared ion pair motifs (<3200 cm −1 ) can be distinguished from intact‐core structures (>3200 cm −1 ). The characteristic fingerprint of a water molecule trapped directly in‐between two ions of opposite charge provides an alternative route to evaluate the extent of ion pairing in aqueous electrolyte solutions.