If I were to look at the same Li salt in a series of solvents would I expect to observe a trend in which the 7Li NMR signal shifts up field (becomes more shielded) as the Gutmann donor number of the solvent is increased? What other important characteristics of the solvents should I consider when analyzing the results of said experiment?
Please see ....
1: Measurement of solvent polarity by nuclear magnetic resonance and electron spin resonance spectral probes
Orland W. Kolling
Anal. Chem., 1977, 49 (4), pp 591–594
DOI: 10.1021/ac50012a022
2: Spectroscopic studies of ionic solvation. XVI. Lithium-7 and chlorine-35 nuclear magnetic resonance studies in various solvents
Yves M. Cahen, Paul R. Handy, Eric T. Roach, Alexander I. Popov
J. Phys. Chem., 1975, 79 (1), pp 80–85
DOI: 10.1021/j100568a018
Ahmed, thank you for your response. Reading of the second paper you suggested was one of the reasons I asked this question. Near the end of the Cahen paper they mention that the case for Li is different from that of Na. In 23Na the diamagnetic screening dominates, whereas in 7Li it is cancelled by the paramagnetic screening. If you look at literature on 23Na chemical shifts one notices a near linear trend up field with increasing the solvent donor number (see attached paper). This seems intuitive to me but clearly something more complicated is going on with 7Li, and perhaps other nuclei as well. I'm trying to wrap my mind around the various effects in play here. I will read the first paper you suggested to see what I can gather from that. Do you have any other good reading suggestions for what will affect the chemical shift of a metal cation in solution? I'm thinking of both solvent characteristics as well as characteristics of the NMR nucleus of interest (i.e. spin states etc.). At the moment I have a somewhat fuzzy understanding of the physics and am really trying to crystallize these concepts in my mind.
Thanks again,
Tylan
- Badges
- Science topic
- Similar topics
- Chemistry
- Sulfites
- Inorganic Chemistry
- Inorganic Chemicals
- Salts