The many-body expansion for aqueous systems revisited: III. Hofmeister ion–water interactions

Herman, Kristina M.; Heindel, Joseph P.; Xantheas, Sotiris S.

doi:10.1039/d1cp00409c

Cited by 20 publications

(20 citation statements)

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“…Hence, the occurrence of a higher energy configuration of the water molecules may have been responsible for accelerating the evaporation process for chaotropes. The present argument of lower/higher energy configuration of water molecules in the presence of Hofmeister ions is further supported by the computational studies by Herman et al and Heindel et al, where the kosmotropic and chaotropic anions are involved in enhancing and reducing the binding energies of the aqueous clusters (Table S5).…”

Section: Resultssupporting

confidence: 79%

“…The ability of kosmotropes and chaotropes to make strong/weak H-bonded water structure can be understood as follows: It is known that due to the small size and low polarizability, the kosmotrope anions are repelled from the interface and are strongly hydrolyzed . Because of the high charge density of kosmotropes, the water molecules in their surroundings are closely packed and thus use the configuration to make a strongly H-bonded network. , However, with the large size and high polarizability, the chaotropes are known to get adsorbed at the interface where the ions lose part of their hydration sheath, resulting in weakly H-bonded water molecules. ,, …”

Section: Resultsmentioning

confidence: 99%

“…45 Because of the high charge density of kosmotropes, the water molecules in their surroundings are closely packed and thus use the configuration to make a strongly H-bonded network. 46,47 However, with the large size and high polarizability, the chaotropes are known to get adsorbed at the interface where the ions lose part of their hydration sheath, resulting in weakly H-bonded water molecules. 45,46,48 Figure 4f demonstrates the variation in free OH peak area as a function of various ions.…”

Section: Journal Of the American Chemical Societymentioning

confidence: 99%

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Investigation of Water Evaporation Process at Air/Water Interface using Hofmeister Ions

2022

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Evaporation is an interfacial phenomenon in which a water molecule breaks the intermolecular hydrogen (H−) bonds and enters the vapor phase. However, a detailed demonstration of the role of interfacial water structure in the evaporation process is still lacking. Here, we purposefully perturb the H-bonding environment at the air/water interface by introducing kosmotropic (HPO4 –2, SO4 –2, and CO3 –2) and chaotropic ions (NO3 – and I–) to determine their influence on the evaporation process. Using time-resolved interferometry on aqueous salt droplets, we found that kosmotropes reduce evaporation, whereas chaotropes accelerate the evaporation process, following the Hofmeister series: HPO4 –2 < SO4 –2 < CO3 –2 < Cl– < NO3 – < I–. To extract deeper molecular-level insights into the observed Hofmeister trend in the evaporation rates, we investigated the air/water interface in the presence of ions using surface-specific sum frequency generation (SFG) vibrational spectroscopy. The SFG vibrational spectra reveal the significant impact of ions on the strength of the H-bonding environment and the orientation of free OH oscillators from ∼36.2 to 48.4° at the air/water interface, where both the effects follow the Hofmeister series. It is established that the slow evaporating water molecules experience a strong H-bonding environment with free OH oscillators tilted away from the surface normal in the presence of kosmotropes. In contrast, the fast evaporating water molecules experience a weak H-bonding environment with free OH oscillators tilted toward the surface normal in the presence of chaotropes at the air/water interface. Our experimental outcomes showcase the complex bonding environment of interfacial water molecules and their decisive role in the evaporation process.

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Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Section: Journal Of the American Chemical Societymentioning

confidence: 99%

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Investigation of Water Evaporation Process at Air/Water Interface using Hofmeister Ions

2022

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“…Here, the latter is understood as a many-body contribution consisting of the sum of all contributions from three-body to n-body, depending on the number of bodies (molecules), n , in the molecular chain. For more about the many-body approach, see a collection of papers and references therein [ 77 , 78 , 79 , 80 , 81 ]. There are a few extensions of BSSE correction (basis set superposition error) to the many-body approach, but in general they give several numerical problems, including negative values of some n-body BSSE corrections.…”

Section: Methodsmentioning

confidence: 99%

Resonance-Assisted Hydrogen Bond—Revisiting the Original Concept in the Context of Its Criticism in the Literature

Domagała

Simon

2021

IJMS

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In the presented research, we address the original concept of resonance-assisted hydrogen bonding (RAHB) by means of the many-body interaction approach and electron density delocalization analysis. The investigated molecular patterns of RAHBs are open chains consisting of two to six molecules in which the intermolecular hydrogen bond stabilizes the complex. Non-RAHB counterparts are considered to be reference systems. The results show the influence of the neighbour monomers on the unsaturated chains in terms of the many-body interaction energy contribution. Exploring the relation between the energy parameters and the growing number of molecules in the chain, we give an explicit extrapolation of the interaction energy and its components in the infinite chain. Electron delocalization within chain motifs has been analysed from three different points of view: three-body delocalization between C=C-C, two-body hydrogen bond delocalization indices and also between fragments (monomers). A many-body contribution to the interaction energy as well as electron density helps to establish the assistance of resonance in the strength of hydrogen bonds upon the formation of the present molecular chains. The direct relation between interaction energy and delocalization supports the original concept, and refutes some of the criticisms of the RAHB idea.

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“…Experiments and computations of NaCl ion-pairs in clusters have been mainly performed in systems composed of up to a few tens of H 2 O molecules. − Fourier transform microwave spectroscopy has shown that the distance between the ions in a NaCl pair increases by gradually adding up to 3 H 2 O molecules and reaches the value of 2.9 Å, which is the contact-ion pair (CIP) distance found in the bulk solution. Anion photoelectron spectroscopy of clusters comprising NaCl and up to 12 H 2 O molecules found that at 9–12 H 2 O molecules, the CIP and SSIP (solvent-separated ion pair) formations are almost degenerate in energy.…”

Section: Introductionmentioning

confidence: 99%

Salt Enrichment and Dynamics in the Interface of Supercooled Aqueous Droplets

et al. 2022

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The interconversion reaction of NaCl between the contact-ion pair (CIP) and the solvent-separated ion pair (SSIP) as well as the free-ion state in cold droplets has not yet been investigated. We report direct computational evidence that the lower is the temperature, the closer to the surface the ion interconversion reaction takes place. In supercooled droplets the enrichment of the subsurface in salt becomes more evident. The stability of the SSIP relative to the CIP increases as the ion-pairing is transferred toward the droplet’s outer layers. In the free-ion state, where the ions diffuse independently in the solution, the number density of Cl– shows a broad maximum in the interior in addition to the well-known maximum in the surface. In the study of the reaction dynamics, we find a weak coupling between the interionic NaCl distance reaction coordinate and the solvent degrees of freedom, which contrasts with the diffusive crossing of the free energy barrier found in bulk solution modeling. The H2O self-diffusion coefficient is found to be at least an order of magnitude larger than that in the bulk solution. We propose to exploit the enhanced surface ion concentration at low temperature to eliminate salts from droplets in native mass spectrometry ionization methods.

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The many-body expansion for aqueous systems revisited: III. Hofmeister ion–water interactions

Abstract: We report a Many Body Energy (MBE) analysis of aqueous ionic clusters containing anions and cations at the two opposite ends of the Hofmeister series, viz. the kosmotropes Ca2+, SO42-...

Cited by 20 publications

References 87 publications

Investigation of Water Evaporation Process at Air/Water Interface using Hofmeister Ions

Investigation of Water Evaporation Process at Air/Water Interface using Hofmeister Ions

Resonance-Assisted Hydrogen Bond—Revisiting the Original Concept in the Context of Its Criticism in the Literature

Salt Enrichment and Dynamics in the Interface of Supercooled Aqueous Droplets

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