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.
>
> ------------------------------------------------------------------------
> *From:* main_at_ammrl.groups.io <main_at_ammrl.groups.io> on behalf of Craig Grimmer <craig.grimmer_at_gmail.com>
> *Sent:* Thursday, August 31, 2023 5:29 AM
> *To:* main_at_ammrl.groups.io <main_at_ammrl.groups.io>
> *Subject:* Re: [AMMRL] Y89 measurement
> Good afternoon Stephen
>
> For 89Y (transmitter frequency 24.5013454) on a 5 mm broadband probe
> on a "500" magnet, I use a 3 M solution of Y(NO3)3.6H2O and I get a
> reasonable signal from 4 scans (transients) with d1 = 720 seconds with
> pw = 18 us at 150 W. I've not measured the T1 of this sample but 720
> seconds seemed a reasonable figure based on the information in Brevard
> & Granger's book that reads "/T1 typical value (s): > 50/"). If
> you're struggling to find a signal from a multi-molar solution, set a
> wide sweep width to start with, ~1000 ppm.
>
> Kind regards,
> Craig.
>
>
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Received on Thu Aug 31 2023 - 10:06:23 MST