Unexpected change in NOE with increasing temperature: Crosstalk between chemical exchange and cross relaxation in a NiN2S2 complex

[Display omitted] •Unexpected increase in nuclear Overhauser effect (NOE) enhancement between spins with increasing temperature.•Explanation of the observation using due to crosstalk between exchange and NOE.•Dynamic events in NiN2S2 metal complexes. Typically, with increasing sample temperature the...

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Bibliographic Details
Published in:Chemical physics letters 2019-01, Vol.715, p.160-165
Main Authors: Dougherty, Ryan J., Golden, Melissa L., Krishnan, V.V.
Format: Article
Language:English
Subjects:
Chemical exchange
Metal-ligand complexes
NMR
Nuclear Overhauser Effect (NOE)
Tetradentate complexes
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Summary:[Display omitted] •Unexpected increase in nuclear Overhauser effect (NOE) enhancement between spins with increasing temperature.•Explanation of the observation using due to crosstalk between exchange and NOE.•Dynamic events in NiN2S2 metal complexes. Typically, with increasing sample temperature the rotational correlation time of the molecule decreases, leading to a decrease in the relative nuclear Overhauser effect (NOE) enhancement. In characterizing the (O-ethyl-L-cysteinato)-Ni(II) in the solution state, the measured NOE enhancement increases with increasing sample temperature. This unexpected change is explained via crosstalk between nuclear spin cross relaxation and an additional chemical exchange phenomenon between the amino protons of the molecule. The case study using a relaxation matrix approach, with both cross relaxation and chemical exchange, could be essential to understanding a metal complex with a bidentate amino acid derived ligands.
ISSN:0009-2614
1873-4448
DOI:10.1016/j.cplett.2018.11.010