The use of infrared probes in solvation studies

Vibrational Solvatochromism in Vaska’s Complex Adducts

“…All solutions were prepared and studied at room temperature. The AN values for toluene, chlorobenzene, dichlorobenzene, and trichlorobenzene were not available in the literature, but were determined experimentally by monitoring the carbonyl stretching frequency of acetone . A small aliquot of acetone was added to each solvent (∼0.135 M solutions), and the FTIR spectra were collected following the procedure below.…”

“…Static and dynamic solvent–solute interactions have been implicated as key variables in some of the most important reaction types, from electron transfer to catalysis. − Developing a basic understanding of these interactions can often be achieved by monitoring chromatographic mobilities − or spectroscopic features, such as solvatochromic shifts of electronic absorption and emission spectra, − NMR chemical shifts, − and vibrational frequencies − across a range of solvent types. Using these approaches, the characteristics of the solvation environment can be correlated with a systematic change in a spectral feature to provide some insight into the origins of chemical reactivity in different solvents.…”

“…In other cases, a single solvent parameter has been shown to be sufficient to properly correlate measured values. For example, molecular vibrational frequencies have been shown in several studies to have a strong correlation with the Lewis acceptor number (AN), a scale that was developed by Gutmann from 31 P NMR chemical shifts of triethylphosphine oxide in a broad range of solvents. , Symons and co-workers reported that the carbonyl stretching vibration on acetone had a strong correlation with AN, with the CO frequency shifting to lower wavenumbers with increasing AN . The authors noted that the sensitivity to this parameter when other solvation metrics showed no correlation was due to the electron rich oxygen being particularly perturbed by the electrophilicity of the solvent.…”

“…The AN values for toluene, chlorobenzene, dichlorobenzene, and trichlorobenzene were not available in the literature, but were determined experimentally by monitoring the carbonyl stretching frequency of acetone. 18 A small aliquot of acetone was added to each solvent (∼0.135 M solutions), and the FTIR spectra were collected following the procedure below. The toluene, chlorobenzene, and o-dichlorobenzene ANs were determined to be 10, 9, and 14.1, respectively.…”

On the possible solvation of tetraalkyl-ammonium cations and tetraphenyl-boron anions by water

“…When a basic, aprotic solvent is added to water, it forms H-bonds, thereby reducing the concentration of OH free groups. 13,14 This can be estimated from the NIR spectra, which show a fall in the band. It is also manifest in the OH free rates of nucleophilic and electrophilic reactions, and the two sets of results agree quantitatively.11h14…”