13C NMR of a single molecule magnet: analysis of pseudocontact shifts and residual dipolar couplings

Damjanovic, Marko (2013) 13C NMR of a single molecule magnet: analysis of pseudocontact shifts and residual dipolar couplings. [Laurea magistrale], Università di Bologna, Corso di Studio in Advanced spectroscopy in chemistry [LM-DM270], Documento ad accesso riservato.
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Paramagnetic triple decker complexes of lanthanides are promising Single Molecule Magnets (SMMs), with many potential uses. Some of them show preferable relaxation behavior, which enables the recording of well resolved NMR spectra. These axially symmetric complexes are also strongly magnetically anisotropic, and this property can be described with the axial component of the magnetic susceptibility tensor, χa. For triple decker complexes with phthalocyanine based ligands, the Fermi˗contact contribution is small. Hence, together with the axial symmetry, the experimental chemical shifts in 1H and 13C NMR spectra can be modeled easily by considering pseudocontact and orbital shifts alone. This results in the determination of the χa value, which is also responsible for molecular alignment and consequently for the observation of residual dipolar couplings (RDCs). A detailed analysis of the experimental 1H-13C and 1H-1H couplings revealed that contributions from RDCs (positive and negative) and from dynamic frequency shifts (negative for all observed couplings) have to be considered. Whilst the pseudocontact shifts depend on the average positions of 1H and 13C nuclei relative to the lanthanide ions, the RDCs are related to the mobility of nuclei they correspond to. This phenomenon allows for the measurement of the internal mobility of the various groups in the SMMs.

Tipologia del documento
Tesi di laurea (Laurea magistrale)
Autore della tesi
Damjanovic, Marko
Relatore della tesi
Correlatore della tesi
Corso di studio
Ordinamento Cds
Parole chiave
Single Molecule Magnets (SMMs), 1H NMR, 13C NMR, residual dipolar couplings (RDCs)
Data di discussione della Tesi
26 Luglio 2013

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