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Threshold Collision‐Induced Dissociation of Hydrated Magnesium: Experimental and Theoretical Investigation of the Binding Energies for Mg 2+ (H 2 O) x Complexes ( x =2–10)
Author(s) -
Carl Damon R.,
Armentrout Peter B.
Publication year - 2013
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.201200860
Subject(s) - chemistry , dissociation (chemistry) , collision induced dissociation , bond dissociation energy , thermochemistry , molecule , analytical chemistry (journal) , mass spectrometry , ionization , ion , kinetic energy , binding energy , fragmentation (computing) , tandem mass spectrometry , crystallography , atomic physics , organic chemistry , chromatography , operating system , physics , quantum mechanics , computer science
The sequential bond energies of Mg 2+ (H 2 O) x complexes, in which x =2–10, are measured by threshold collision‐induced dissociation in a guided ion beam tandem mass spectrometer. From an electrospray ionization source that produces an initial distribution of Mg 2+ (H 2 O) x complexes in which x =7–10, complexes down to x =3 are formed by using an in‐source fragmentation technique. Complexes smaller than Mg 2+ (H 2 O) 3 cannot be formed in this source because charge separation into MgOH + (H 2 O) and H 3 O + is a lower‐energy pathway than simple water loss from Mg 2+ (H 2 O) 3 . The kinetic energy dependent cross sections for dissociation of Mg 2+ (H 2 O) x complexes, in which x =3–10, are examined over a wide energy range to monitor all dissociation products and are modeled to obtain 0 and 298 K binding energies. Analysis of both primary and secondary water molecule losses from each sized complex provides thermochemistry for the sequential hydration energies of Mg 2+ for x =2–10 and the first experimental values for x =2–4. Additionally, the thermodynamic onsets leading to the charge‐separation products from Mg 2+ (H 2 O) 3 and Mg 2+ (H 2 O) 4 are determined for the first time. Our experimental results for x =3–7 agree well with quantum chemical calculations performed here and previously calculated binding enthalpies, as well as previous measurements for x =6. The present values for x =7–10 are slightly lower than previous experimental results and theory, but within experimental uncertainties.