Couldn't agree more - the only time I use a 1D 89Y spectrum is for pulse
calibration and that's it.
89Y is 100% abundant and although nJYH is usually so small that's not resolved
in the 1D proton, you can still get enough signal to see something with a 10
minute 1H,89Y-HMBC. How small you set the nominal J is going to depend on how
fast relaxation is in your system, but 3 Hz isn't a bad place to start.
See
https://pubs.acs.org/doi/10.1021/om060695y for a modest selection of 89Y
shifts so you can figure out what sweep width etc. to use. If you need a test
molecule then you could do worse than yttrium bis(trimethylsilyl)amide
(e.g.
https://www.strem.com/catalog/v/39-1500/83/yttrium_41836-28-6
I've tried the same with 109Ag but didn't seem to get very far, possibly because
the only commercially-available silver complexes I could find at the time didn't
have the right couplings. Any suggestions for a reliable test molecule?
Thanks
________________________________
> From: main_at_ammrl.groups.io <main_at_ammrl.groups.io> on behalf of CHARLES G FRY via groups.io <fry=chem.wisc.edu_at_groups.io>
> Sent: Thursday, August 31, 2023 18:06
> To: main_at_ammrl.groups.io <main_at_ammrl.groups.io>
> Subject: [External] Re: [AMMRL] Y89 measurement
I was about to respond similar to Dave's email stating that getting to low
gamma nuclei via 1H (and perhaps 31P) HMBC has been the most successful route
we've used. The combination of polarization enhancement and T1 savings is
very powerful and makes many of our studies viable that otherwise would not
have been. 103Rh and 183W are just a couple of other nuclei we've had 1H-X
successes with, in addition to 89Y.
On 8/31/2023 11:49 AM, Vander Velde, David wrote:
1H-89Y HMBC is pretty straightforward and 89Y sits just above 109Ag which is
the nominal low frequency limit of many Bruker broadband probes. Setting it
up from scratch, you can guess the length of a 89Y pulse by extrapolating
from anything which is calibrated nearby assuming the pulse voltage is constant
and then the pulse just scales with the gyromagnetic ratio. The simplest
version of an HMBC is pretty forgiving (starting from the 1H-15N parameters
with no 1 bond couplings suppressed, no filters on the size of the J). That
pulse estimate is enough to get started. You can refine the parameters by
running arrays of just the first block of the HMBC. If you don't know where
they X signal is (a problem especially for something like 195Pt), you can
find it quickly with an array of X nucleus carrier frequencies. With the
X signal frequency known, the low gamma pulse width can be calibrated with
an array. Likewise, if the 1H-X J coupling is not resolved in the 1H, you
can find the value that gives the most signal.
Our experience here is limited to a few 89Y organometallics and the 89Y shifts
calculated by absolute referencing were bigger than we expected, but that
was the outcome. We never saw any 89Y signals by direct observation, very
long T1's and low concentration likely weren't helping.
The same approach has worked for some really low gamma nuclei. We have a newer
type Bruker iProbe that is rated to reach 109Ag, and that is the lowest frequency
it will reach. However we have a previous generation Bruker probe that will go
to lower frequencies. It will tune but not quite match the 12.5 MHz frequency
for 103Rh, close enough for HMBC. I got an HMBC signal from Rh(acac)3 even
though there is no resolved Rh multiple bond coupling in the 1H spectrum. To
get this going, we got some valuable help from Brian Andrew at Bruker with
putting firmware entries for these wacky nuclei into that probe.
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Received on Thu Aug 31 2023 - 11:19:05 MST