Microhydration of Nitromethane Anions from Both a Solute and Solvent Perspective

Abstract

We present experimental infrared spectroscopic data on mass-selected, hydrated nitromethane anion clusters with up to four water ligands. The vibrational bands in the OH stretching region encode the solvent structure, while the CH stretching bands contain information on the influence of the hydration shell on the solute ion. We interpret our findings using density functional theory calculations. The first water molecule binds symmetrically to the two oxygen atoms of the nitro group but couples to low-frequency vibrational modes that impart a very complicated structure on the OH stretching region. Competition between water-ion and water-water interaction makes the dihydrate very floppy and precludes unambiguous structural assignment. The tri- and tetrahydrate spectra can be interpreted on the basis of H-bonded ring structures. The excess electron is polarized by hydration, which can clearly be seen by shifting CH stretching frequencies.

Molecular-level origin of the carboxylate head group response to divalent metal ion complexation at the air–water interface

“…S3. These structures largely follow those reported by Marcum and Weber (45) and Motegi et al (46) for the CH 3 NO 2 − (H 2 O) n clusters. An exception, however, is the n = 5 arrangement that is calculated to exhibit the observed discontinuity in the splitting between the 2 CO stretching bands.…”

Effect of microhydration on the atmospherically important metastable carbonyl sulfide anion: Structure, energetic, and infrared study

“…Infrared (IR) photo‐dissociation spectroscopy of size‐selected clusters along with mass spectroscopic techniques have been important experimental tools to probe the structure of anions at various level of hydration . Experimental and theoretical tools have been combindely applied for the microhydration study of various triatomic and more complex organic anions which feature a triatomic binding site …”

“…[1,2] Hydration of anion modifies the hydrogen-bonded network between water molecules and the extent of modification depends on the nature of anions. [3][4][5][6] Various experimental and theoretical studies have been performed to acquire the molecular level understanding about the hydration of ions. [7][8][9][10][11][12] Infrared (IR) photo-dissociation spectroscopy of size-selected clusters along with mass spectroscopic techniques have been important experimental tools to probe the structure of anions at various level of hydration.…”

“…[13][14][15][16][17][18][19][20] Experimental and theoretical tools have been combindely applied for the microhydration study of various triatomic and more complex organic anions which feature a triatomic binding site. [3][4][5][18][19][20][21][22][23][24][25][26][27][28][29] Carbonyl sulfide (OCS) is the most abundant and stable sulfur-containing triatomic gas in the atmosphere which plays an important role in the aerosol formation. [30,31] However, its anionic form (OCS 2 ) is a metastable species.…”

“…A detailed molecular level understanding of the ion–water interaction, especially of anion–water, is important due to its occurrence as an important reactive intermediate in many chemical processes ranging from atmospheric, biological to chemical reactions . Hydration of anion modifies the hydrogen‐bonded network between water molecules and the extent of modification depends on the nature of anions . Various experimental and theoretical studies have been performed to acquire the molecular level understanding about the hydration of ions .…”