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Wednesday, December 19, 2007

31P - 109Ag HMQC

Silver has two spin I = 1/2 isotopes (109Ag and 107Ag) with natural abundances of 48.18% and 51.82%, respectively. Although 109Ag has a lower natural abundance, it is the preferred isotope to observe as its gyromagnetic ratio is slightly higher than that of 107Ag. Direct observation of 109Ag is problematic in that the Larmor frequency is low, the NOE's to protons are negative and most importantly, the T1's are very long (minutes to hours). In some silver phosphine complexes with 109Ag - 31P coupling, the problems of observing silver directly can be circumvented by using indirect detection via a 31P detected 31P - 109Ag HMQC. The advantages of using this approach are that the directly observed 31P frequency is 8.7 times higher than that of 109Ag and the relaxation delay in the experiment depends on the 31P T1's which tend to be orders of magnitude shorter than those of 109Ag.
Below is an example of a 31P detected 31P - 109Ag HMQC for a silver phosphine complex. These data were acquired without 109Ag decoupling. In the 31P trace on the top of the spectrum one can see a single 31P resonance with coupling to both 109Ag and 107Ag. The 109Ag is indirectly observed in the F1 domain.

4 comments:

Egon Willighagen said...

Glenn, do you have some more information on the Ag-P complex? Maybe a pointer to the crystal structure, or paper describing the compound?

Glenn Facey said...

Egon,

I ran this spectrum for a researcher here at the University of Ottawa. I left out any details of the specific complex from the BLOG entry as it is part of some work that is as yet unpublished. However, you can find more info about similar complexes from the following paper.

JACS Vol 124, pp 3946-3950 (2002).

cheers,

Glenn

nmrfreak said...

Glenn, out of curiousity, what kind of probe did you use to acquire this spectrum?

Mike

Glenn Facey said...

Mike,

This spectrum was acquired on a 3 channel Bruker AVANCE 500 with a triple resonance 5 mm probe. The probe has one broadband channel, a fixed 31P channel and a proton channel. Although the very large 31P coil was meant for decoupling, it was used to observe 31P here.

cheers,

Glenn