Good day
Does anybody have experience with performing NMR on paramagnetic transition metal complexes, in particular Copper(II)? How large are the shifts? How hardcore is the mathematics involved? Is this something an average NMR user can perform or should I rather avoid it all together?
Kind regards,
Korban
The HNMR spectra of paramgnetic complexes cahracterized by
A wide range chemical shift. The position of signal totally different from the diamagnetic corresponding complexes for example the azomethine proton appear in the range 8.5____9.ppm but in paramgnetic complexes i think that appear at ~_22ppm
Also the broadinng of the signals
I do not have any experience with copper(II) particularly, but in general NMR of paramagnetics is characterised by (a) a wide chemical shift range, several hundreds of ppm even for 1H is possible, and (b) fast relaxation leading to broad and sometimes even unobservable signals. Moreover, chemical shifts are very temperature-sensitive and less reproducible than those of diamagnetics. There is at least one monograph dealing with the problems related to paramagnetism in NMR, "Solution NMR of paramagnetic molecules" by Ivano Bertini, Claudio Luchinat and Giacomo Parigi (1st edition 2001 by Elsevier). As far as I know, there is also a newer edition.
Read up on "shift reagents." Most of them use lanthanides (the most recent review from a quick search is Weisman, G. R. in Asymmetric Synthesis, Morrison, James, ed. (Elsevier/Academic) 1983, pp. 153–171 ISBN 9780323157360, and the review following it, by R. R. Fraser. For copper specifically there try:
"NMR of Organocopper Compounds," Gärtner, Tobias; Gschwind, Ruth M. in Rappaport, Zvi; Marek, Ilan; eds., The Chemistry of Organocopper Compounds (Wiley, Hoboken, NJ) 2009 ISBN 9780470772966
Vila, A. J.; Ramirez, B. E.; Di Bilio, A. J.; Mizoguchi, T. J.; Richards, J. H.; and Gray, H. B. "Paramagnetic NMR Spectroscopy of Cobalt(II) and Copper(II) Derivatives of Pseudomonas aeruginosa His46Asp Azurin," Inorganic Chemistry 1997, 36(20), 4567–4570 DOI: 10.1021/ic9703282
Ramadan, Saadallah; Hambley, Trevor W.; Kennedy, Brendan J.; Lay, Peter A. "NMR Spectroscopic Characterization of Copper(II) and Zinc(II) Complexes of Indomethacin," Inorganic Chemistry 2004, 43(9), 2943–2946 DOI: 10.1021/ic0352811
If you like learning new (and sometimes unexpected) things, GO FOR IT!
It is a bit off the beaten track, but for a newbie that should be a big pro!
copper (II) is diamagnetic in nature . NMR will not proide clear information.
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