Thank you to Dominique Duguay for providing the sample of ortho-carborane.
Tuesday, April 29, 2008
1H - 11B HMQC
HMQC and HSQC experiments are very commonly applied to 1H - 13C and 1H - 15N. These techniques can also be applied to other isotopes. The figure below shows the 1H - 11B HMQC spectrum or ortho-carborane. The top and side traces are separately acquired 1H [11B] and 11B [1H] spectra, respectively. These data, combined with the 11B COSY data, allow the complete assignment of the 1H [11B] spectrum.
Thank you to Dominique Duguay for providing the sample of ortho-carborane.
Thank you to Dominique Duguay for providing the sample of ortho-carborane.
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7 comments:
It's a powerful technique for the 1J proton-boron couplings. We used it quite a bit in Warren Piers' group to show direct boron-proton interactions.
Kevin Cook
March 2, 2009
The original figure in this post had proton positions 2 and 5 and boron positions A and D assigned incorrectly. The figure was changed to reflect the correct assignments. Thank you to Guangyu Li for bringing this to my attention and pointing out the following reference:
Siedle, Bodner, Garber, Deer and Todd, Inorganic Chemistry 13(10) p. 2321 (1974).
Glenn
Nice experiment. I am wondering which gradient ratio you are using to get such results
Thanks in advance
Anonymous,
The gradients were calculated using the Bruker au program "gradratio". This data was collected with hmqcgpqf pulse sequence with GPZ1=60, GPZ2=20 and GPZ3=65.67.
Glenn
Thanks a lot for your quick answer
Hello Glen,
i am not sure if you get updates about these posts but I hope you see this! I am currently trying to get an HMQC spectrum for the assignment of a BF3 containing molecule. The coupling is a 4J B-H which I do not know the coupling constant for. I am using an old pulse program on the II300 which was optimized for 158 Hz (pulse program below). what i am hoping to know is whether this coupling is too distant to see coupling with HMQC and whether there is an estimate for the constant i should be using for the program.
Thank you!
Eliza,
An HMQC may work in the case you describe if the long range proton - boron coupling constant is greater than a few Hz and the 1H resonances have a sufficiently long T2. If the long range coupling is close to zero, then an HMQC will not work. I would try running the simplest HMQC pulse program without gradients (probably hmqcqf) and set cnst2 to about 3 to 10 Hz.
Good luck
Glenn
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