Ion pair and partially hydrated Li+NO3− ion pair structures: Correlation of molecular orbital results with matrix isolation data

Abstract

The results of a molecular orbital study for the ion pair Li+NO3−, alone and hydrated, have been related to the vibrational data for the same species matrix isolated in argon. Initially it was established that a plot of the N–O bond overlap population vs empirical FNO force constants, for fourteen molecules, is impressively linear. Subsequently this plot has been used to convert the Gaussian 70-derived N–O overlap populations for the N–O bonds of Li+NO3−, alone or hydrated, to FNO values for the particular species. In the simple Li+NO−3 pair, for example, the minimum energy bidentate structure has a significantly smaller overlap population in the two metal-coordinated N–O bonds. These overlap populations indicate an N–O stretching force constant difference of 3.94×102 N m−1 which can be converted to a 245 cm−1 splitting of the otherwise degenerate ν3 antisymmetric stretching mode. The latter value compares well with the experimental value of 265 cm−1 and, together with equally encouraging comparisons for the hydrated ion pair, suggests that the Gaussian 70 results for these systems, even using the STO-3G minimum basis set, realistically depict the bonding for Li+NO3− as well as the influence of hydration on that bonding.

On the nature of tetraalkylammonium ions in common electrochemical solvents: General and specific solvation – Quantitative aspects

“…It can be seen that in general the free energy of coordination with a tetraalkylammonium salt increases as the number of solvent molecules increases from one to four, which seems to be as many as can be accommodated sterically around an R 4 N + ion. Similar effects of increasing stabilization as the number of solvent molecules increase up to a maximum are found with inorganic ions [12,38,40]. X-ray crystallographic data [8][9][10] and our earlier computational study [2] agree that lithium coordinates to four solvent molecules in THF.…”

Enthalpies of Transfer of Amino Acids from Water to Aqueous Solutions of Alkali Metal Nitrates

“…Raman and infrared spectra studies of alkali metal nitrates solutions found that, when the concentration rises above 1.5 mol·dm -3 , there is evidence of cation−anion contact with the increasing concentration of LiNO 3 . Molecular orbital results also substantiate the bidentate structure of Li + NO 3 - with a high percent covalency for the Li−O bonds association …”

“…Molecular orbital results also substantiate the bidentate structure of Li + NO 3with a high percent covalency for the Li-O bonds association. 25 The results of our study suggest that the contact between cations and anions decreases electrostatic interaction and hydrophilic-hydrophilic interaction between L-serine and LiNO 3 more than that between glycine and LiNO 3 .…”

Formation of Contact Ion Pairs and Solvation of Li+Ion in Sulfones: Phase Diagrams, Conductivity, Raman Spectra, and Dynamics

“…53 On the other hand, the peak frequency of the low-frequency line appears quite close to that of the contact ion pair Li + NO 3 isolated in an argon matrix. 54,55 Therefore, it is tempting to suggest that, in the LiNO 3 + (CH 3 ) 2 SO 2 system, unlike other systems studied to date, 13 the totally symmetric ν 1 (A′ 1 ) vibrations of the free NO 3 are represented by the highfrequency lines, and the low-frequency lines correspond to vibrations of NO 3 in the ion pairs. If this assumption is true, one may claim that, in the LiNO 3 + (CH 3 ) 2 SO 2 system, both components do not significantly interact and prefer to keep the molecular structure characteristic to the neat liquids.…”