Infrared photodissociation spectra of the D2-tagged microhydrated sulfate dianions with three to eight water molecules are presented over a broad spectral range that covers the OH stretching and H2O bending modes of the solvent molecules at higher energies, the sulfate stretching modes of the solute at intermediate energies and the intermolecular solute librational modes at the lowest energies. A low ion temperature combined with messenger-tagging ensures well-resolved vibrational spectra that allow for structure assignments based on a comparison to harmonic and anharmonic IR spectra from density functional theory (DFT) calculations. DFT ab initio molecular dynamics simulations are required to disentangle the broad and complex spectral signatures of microhydrated sulfate dianions in the OH stretching region and to identify systematic trends in the correlation of the strength and evolution of the solute-solvent and solvent-solvent interactions with cluster size. The onset for the formation of the second solvation shell is observed for n = 8.
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http://dx.doi.org/10.1039/d0cp04386a | DOI Listing |
J Phys Chem A
February 2022
EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, U.K.
We report a computational study of the little-studied neutral bisulfite, bisulfate, dihydro-phosphite, and dihydro-phosphate radicals (HSO, HPO, = 3,4), calling special attention to their various tautomeric structures together with p values estimated from the Gibbs free energies of their dissociations (at the G4 and CAM-B3LYP levels of density functional theory). The energetics of microhydration clusters with up to four water molecules for the S-based species and up to eight water molecules for the P-based species were investigated. The number of microhydrating water molecules needed to induce spontaneous de-protonation is found to correlate the acid strength of each radical.
View Article and Find Full Text PDFPhys Chem Chem Phys
December 2020
Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstr. 2, 04103 Leipzig, Germany.
Infrared photodissociation spectra of the D2-tagged microhydrated sulfate dianions with three to eight water molecules are presented over a broad spectral range that covers the OH stretching and H2O bending modes of the solvent molecules at higher energies, the sulfate stretching modes of the solute at intermediate energies and the intermolecular solute librational modes at the lowest energies. A low ion temperature combined with messenger-tagging ensures well-resolved vibrational spectra that allow for structure assignments based on a comparison to harmonic and anharmonic IR spectra from density functional theory (DFT) calculations. DFT ab initio molecular dynamics simulations are required to disentangle the broad and complex spectral signatures of microhydrated sulfate dianions in the OH stretching region and to identify systematic trends in the correlation of the strength and evolution of the solute-solvent and solvent-solvent interactions with cluster size.
View Article and Find Full Text PDFPhys Chem Chem Phys
January 2016
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
We report infrared multiple photon dissociation spectra of cryogenically-cooled (NaSO4(-))2(H2O)n dianions (n = 0-6, 8) in the spectral range of the sulfate stretching and bending modes (580-1750 cm(-1)). Characteristic absorption bands and structural trends are identified based on a comparison to harmonic spectra of minimum-energy structures. The bare quarternary complex (NaSO4(-))2 exhibits a C2h structure containing two fourfold-coordinated sodium cations in-between the two chelating sulfate dianions.
View Article and Find Full Text PDFJ Chem Theory Comput
May 2015
School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
The sulfate ion is the most kosmotropic member of the Hofmeister series, but the chemical origins of this effect are unclear. We present a global optimization and energy landscape mapping study of microhydrated sulfate ions, SO4(2-)(H2O)n, in the size range 3 ≤ n ≤ 50. The clusters are modeled using a rigid-body empirical potential and optimized using basin-hopping Monte Carlo in conjunction with a move set including cycle inversions to explore hydrogen bond topologies.
View Article and Find Full Text PDFJ Phys Chem B
August 2012
Department of Chemistry, University of California, Davis, Davis, California 95616, USA.
Sulfate-water clusters play an important role in environmental and industrial processes, yet open questions remain on their physical and chemical properties. We investigated the smallest hydrated sulfate anion clusters believed to have a full solvation shell, with 12 or 13 water molecules. We used ab initio molecular dynamics and electronic structure calculations based on density functional theory, with semilocal and hybrid functionals.
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