Ion−Solvent Interactions in Acetonitrile Solutions of Lithium, Sodium, and Tetraethylammonium Perchlorate Using Attenuated Total Reflectance FTIR Spectroscopy

Abstract

A vibrational spectroscopic study of ion solvation in LiClO 4 -, NaClO 4 -, and tetraethylammonium perchlorateacetonitrile solutions has been performed using attenuated total reflection FTIR spectroscopy. Spectra were curve fitted in the CtN stretching and C-CtN bending regions of the solvent using a multiple-dimensional fitting routine that factors an entire set of solution spectra into their physically real basis spectra according to a user supplied mathematical model. The spectra of the solutions of tetraethylammonium perchlorate in acetonitrile were shown to be a linear combination of one physically real basis spectrum that accounts for self-associated acetonitrile and another that accounts for the spectrum of the acetonitrile molecules associated with the perchlorate anion. It is demonstrated for the first time that the CtN stretching band of acetonitrile molecules associated with ClO 4anions has a significantly different molar absorption coefficient from the same band for self-associated acetonitrile. The spectra of LiClO4 and NaClO4 solutions in acetonitrile were shown to be a linear combination of one physically real basis spectrum that accounts for the spectrum of self-associated acetonitrile and another that accounts for the spectrum of the acetonitrile molecules associated with both the cation and the anion. The fractional contribution of these physically real basis spectra to the solution spectra depends on the total electrolyte concentration, rather than on the extent of ion pairing. Two possible rationalizations for this phenomenon are discussed.

Solvation of monovalent anions in acetonitrile and N,N-dimethylformamide: Parameterization of the IEF-PCM model

“…Studies on ion-solvent interactions in AN solutions of lithium and sodium perchlorate indicate the formation of ion pairs over a wide range of concentrations [65]. Thus, the ion-ion interactions complicate the separation of the individual ionic contributions to thermodynamic transfer functions for the electrolytes.…”

Ligand‐Exchange Processes on Solvated Lithium Cations: Acetonitrile and Hydrogen Cyanide

“…[24,26] Since an ion in solution strongly disturbs the local solvent structure, [27] a detailed knowledge of the environment is an essential prerequisite for understanding reactions in the neighbourhood of the ion. Several studies investigated solvated Li + ions in acetonitrile both experimentally with various spectroscopic techniques [28][29][30][31] and computationally with different classical molecular dynamics (MD) methods [32][33][34][35] and Monte Carlo simulations of solvated alkali and halide ions in CH 3 CN. [36] Over the past decade, DFT and ab initio calculations on [Li(CH 3 CN) n ] + and related clusters were also performed by different groups.…”

Electronic absorption spectra of ascorbic acid in water and water–dialkylsulfoxide mixtures

“…It is noteworthy that the analysis of overlapping bands in UV-Vis absorption spectroscopy is a common technique [10][11][12][13]. The spectral bands were deconvoluted using a modified version of the Loring LinkFit program [14], the spectral analysis of which is based on the use of a Gaussian function. The program enabled contributions of neutral and ionic AA species to be found in both distilled water and the buffer solutions at different pH values.…”