title: Coordination-Dependent Spectroscopic Signatures of Divalent Metal Ion Binding to Carboxylate Head Groups: H2- and He-Tagged Vibrational Spectra of M2+·RCO2¯ (M = Mg and Ca, R = -CD3, -CD2CD3) Complexes.
abstract: We explore the intramolecular distortions present in divalent metal ion-carboxylate ion pairs using vibrational spectroscopy of the cryogenically cooled, mass-selected species isolated in the gas phase. The spectral signatures of the C-O stretching modes are identified using the perdeutero isotopologues of the acetate and propionate anions to avoid congestion arising from the CH2fundamentals. Both Ca2+and Mg2+are observed to bind in a symmetrical, so-called "bidentate" arrangement to the -CO2¯ group. The very strong deformations of the head groups displayed by the binary complexes dramatically relax when either neutral water molecules or counterions are attached to the Mg2+RCO2¯ cation. These results emphasize the critical role that local coordination plays when using the RCO2¯ bands to deduce the metal ion complexation motif in condensed media.
authors.affiliation: Sterling Chemistry Laboratory, Department of Chemistry, Yale University , 225 Prospect Street, New Haven, Connecticut 06520, United States.
authors.forename: Joseph W
authors.identifier: http://orcid.org/0000-0002-8759-3288
authors.initials: JW
authors.lastname: DePalma
authors.affiliation: Sterling Chemistry Laboratory, Department of Chemistry, Yale University , 225 Prospect Street, New Haven, Connecticut 06520, United States.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Kelleher
authors.affiliation: Instituto de Química, Universidade de São Paulo , Caixa Postal 26077, São Paulo, CEP 05508-900, Brazil.
authors.forename: Laís C
authors.initials: LC
authors.lastname: Tavares
authors.affiliation: Sterling Chemistry Laboratory, Department of Chemistry, Yale University , 225 Prospect Street, New Haven, Connecticut 06520, United States.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Johnson