Safety note: Some of the materials mentioned here are very dangerous. Ask a qualified chemist for advice before handling them. Qualified chemists should check the relevant safety literature before handling or giving advice about unfamiliar substances. NMR solvents are toxic and most are flammable. Specifically, silver salts are toxic (LD₅₀ for AgNO₃ is 7 g): wear protective gloves.

Silver NMR

Silver (Ag) has two NMR active spin ½ nuclei that yield very narrow signals over a wide chemical shift range. ¹⁰⁷Ag and ¹⁰⁹Ag both have very low sensitivity, ¹⁰⁹Ag being preferred as it has slightly higher sensitivity (fig. 1). In addition, ¹⁰⁷Ag has a resonant frequency beyond that of most standard NMR probes. However, it may be that ¹⁰⁷Ag yields sharper signals although it is difficult to determine for sure and resolution is not usually the major problem with silver NMR. Silver NMR is used for the study of silver salts and complexes. Its relaxation time is very long, of the order of hundreds of seconds for degassed samples and tens of seconds for air saturated samples, so the addition of a relaxation agent such as iron(III)nitrate may be used to speed acquisition.

Fig. 1. Comparison of the silver NMR isotopes for a sample of AgNO₃ (1 M) in D₂O

Both the isotopes have the same chemical shifts (fig. 2). The chemical shift is very sensitive to concentration and temperature.

Fig. 2. Chemical shift ranges for silver NMR

¹⁰⁷Silver NMR

(¹⁰⁷Ag) ¹⁰⁷Silver is a spin ½ nucleus that yields very sharp signals but is very insensitive (fig. 3). It is slightly less sensitive than ¹⁰⁹Ag so is not normally the preferred silver isotope for NMR. ¹⁰⁷Ag has a resonant frequency beyond that of most standard NMR probes. However, there is some evidence, although not certain, that the ¹⁰⁷Ag signal may be narrower than the ¹⁰⁹Ag signal.

Fig. 3. ¹⁰⁷Ag-NMR spectrum of AgNO₃ (1 M) in D₂O

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Properties of ¹⁰⁷Ag

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¹⁰⁹Silver NMR

(¹⁰⁹Ag) ¹⁰⁹Silver is a spin ½ nucleus that yields very sharp signals but is very insensitive (fig. 4). It is slightly more sensitive that ¹⁰⁷Ag and so is the preferred silver isotope for NMR.

Fig. 4. ¹⁰⁹Ag-NMR spectra of AgNO₃ (1 M) in D₂O

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Properties of ¹⁰⁹Ag

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References

1. C. W. Burges, R. Koschmieder, W. Sahm, and A. Schwenk, "Silver-107 and silver-109 nuclear magnetic resonance studies of silver ions in aqueous solutions", Z. Naturforsc. A, 28, 1753-1758 (1973).
2. P. M. Henrichs, S. Sheard, J. J. H Ackerman and G. E. Maciel, "Structural studies of organic silver complexes in dimethyl sulfoxide by carbon-13 and silver-109 NMR", J. Am. Chem. Soc., 101, 3222-3228 (1979).
3. A. F. M. J. Van der Ploeg, G. Van Koten, C. Brevard, "INEPT silver-109 NMR evidence for direct platinum-to-silver bonding in dinuclear [2,6-(Me₂NCH₂)₂C₆H₃][p-tolNC(H)NR]PtAgBr]", Inorg. Chem., 21, 2878-2881 (1982).
4. K. Endo, K. Matsushita, K. Deguchi, K. Yamamoto, S. Suzuki and K. Futaki, "Silver-109 NMR spectra of aqueous silver ions coordinated with nitroxide radical. Silver-tanol complex and tanol as a doping agent", Chem. Lett., 1497-1500 (1982).

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