I want to thank everyone who replied to my questions on Se-77. They were
all very helpful and I now know what to use to set up the instrument and do
my experiments. AMMRL is truly a great organization to belong to. I have
summarized the responses below.
Thanks again.
Mazi.
I have done some SS NMR on Se. Great nucleus, easy to deal with. I used
H2SeO3 as reference material to set up the spectrometer, and then went
right ahead and got great signal. T1 was on the order of hundreds of ms if
I remember correctly. I published one paper on P-31 to Se-77 CP, it's in SS
NMR.
In general, Se compounds smell foul and are toxic, worse than sulfides. At
CSU I had a sealed ampule of liquid Me2Se for a chemical shift reference,
and I used solid (NH4)2SeO4 as a nonvolatile (nonsmelly) working reference.
Line width is normal for S=1/2, but CSA and T1 are often large. Do CP if
you can.
Please see our recent publication below for some info of 77Se:
NMR Analysis of Surfaces and Interfaces in 2-nm CdSe
Mia G. Berrettini, Gary Braun, Jerry G. Hu, and Geoffrey F. Strouse
pp 7063 - 7070; (Article) DOI:
<
http://dx.doi.org/10.1021/ja037228h>10.1021/ja037228h
We used SeO2 solution and solid for pulse length calibration and hahnecho
expt setup, (NH4)3SeO4 for CPMAS setup. Please let me know if you need more
details.
Let me call your attention to two papers which may be of interest:
1. Harris and Sebald: Magn.Res.Chem. 25, 1058 (1987)
2. M.Potrebowsky et al. Solid State NM Resonance, 11, 215-224 (1998)
Paul Ellis (now at Batelle, or Pacific Northwest Labs, PNL), has published
much of the seminal work on 77Se NMR. In general, 77Se is a great nucleus
to study, with good sensitivity, decent natural abundance, and mercifully
short T1's. It's principal drawback lies in its toxicity. Be very careful
when handling samples!
We're doing quite a bit of work on Se-77, and I'd be happy to share
our library of references with you. We're doing liquids work at
the moment, but we're trying to get some solid-state work going on
several systems (with narrower CSA's)
There is a great review article by Duddeck, but it focuses mainly on
Se-77 in liquids.
I've done solution based Se-77. T1's are long, very long, as I recall.
Sensitivity was quite good aside from that. I don't recall what the
reference material was and for SSNMR it will probably be different. I
imagine that it will be straightforward for you except for the T1 problem
in the solid state. Don't know if you have any thing to cross polarize
with. That would likely help.
I only did one series of experiments with this nucleus, on Se=PPh3, but I
recall that it was very straighforward. I used this sample to set up as
well, but the recommended solid setup sample is (NH4)2Se)4 which should
appear at 1040.2 ppm relative to the primary reference, (CH3)2Se (see
Collins, Ratcliffe and Ripmeester, J. Magn. Reson. V. 28, p. 105 (1986)).
Most of my spectra were collected with CP , so T1s were not a factor. I
have one that I collected with a single pulse (and decoupling); I obtained
a reasonable spectrum with 32 scans and a 10 s recycle delay, but I don't
think I checked the T1s closely in this case. Linewidths were about 20 Hz.
There is an extensive review article on Se NMR in
Progress in Nuclear Magnetic Resonance Spectroscopy, Volume 27, Issues 1-3,
1995, Pages 1-323 ,Helmut Duddeck,Selenium-77 nuclear magnetic resonance
spectroscopy
The file is some 15 ,000K large
Great minds must think alike. A friend of mine is synthesizing some
Se-containing materials, and we've talked about doing solid-state 77Se on
them. So, I've been asking similar questions. There doesn't seem to be much
information out there, but I did find this article: Collins, Ratcliffe, and
Ripmeester, "CP/MAS 77Se NMR in Solids. Chemical Shift Tensors and
Isotropic Shifts", J. Mag. Res., 68, 172 (1986). I haven't done a
comprehensive search, so there may be more.
>Dear AMMRL Colleagues,
>I have been asked to do some Se-77 solid-state work. Have any of you done
>this before, and if so what is a good reference material to set up the
>instrument with, and what are the major problems (i.e. sensitivity,
>linewidth, T1's, etc.)?
>
>I would also appreciate any good literature reference you may have on
>Se-77 (solids or liquids).
>
>Thank you in advance.
>
>Mazi
>
>Mazi Sardashti
>ConocoPhillips
>150 PL, BTC
>Bartlesville, OK 74004
>Phone:(918) 661-4129
>FAX:(918) 662-2888
>e-mail:mazi.sardashti_at_conocophillips.com
Mazi
Mazi Sardashti
ConocoPhillips
150 PL, BTC
Bartlesville, OK 74004
Phone:(918) 661-4129
FAX:(918) 662-2888
e-mail:mazi.sardashti_at_conocophillips.com
Received on Fri Jun 04 2004 - 17:02:14 MST