Design principles and theory of paramagnetic fluorine-labelled lanthanide complexes as probes for19F magnetic resonance: a proof-of-concept study

Kirsten H. Chalmers, Elena De Luca, Naomi H.M. Hogg, Alan M. Kenwright, Ilya Kuprov, David Parker, Mauro Botta, J. Ian Wilson, Andrew M. Blamire

Risultato della ricerca: Contributo su rivistaArticolo in rivistapeer review

Abstract

The synthesis and spectroscopic properties of a series of CF 3-labelled lanthanide(III) complexes (Ln = Gd, Tb, Dy, Ho, Er, Tm) with amidesubstituted ligands based on 1,4,7,10tetraazacyclododecane are described. The theoretical contributions of the 19F magnetic relaxation processes in these systems are critically assessed and selected volumetric plots are presented. These plots allow an accurate estimation of the increase in the rates of longitudinal and transverse relaxation as a function of the distance between the LnIII ion and the fluorine nucleus, the applied magnetic field, and the re-rotational correlation time of the complex, for a given LnIII ion. Selected complexes exhibit pH-dependent chemical shift behaviour, and a pKa, of 7.0 was determined in one example based on the holmium complex of an orthocyano DO3A-monoamide ligand, which allowed the pH to be assessed by measuring the difference in chemical shift (varying by over 14ppm) between two 19F resonances. Relaxation analyses of variable-temperature and variable-field 19F, 17O and 1HNMR spectroscopy experiments are reported, aided by identification of salient lowenergy conformers by using density functional theory. The study of fluorine relaxation rates, over a field range of 4.7 to 16.5 T allowed precise computation of the distance between the LnIII ion and the CF3 reporter group by using global fitting methods. The sensitivity benefits of using such paramagnetic fluorinated probes in 19FNMR spectroscopic studies are quantified in preliminary spectroscopic and imaging experiments with respect to a diamagnetic yttrium(III) analogue.

Lingua originaleInglese
pagine (da-a)134-148
Numero di pagine15
RivistaChemistry - A European Journal
Volume16
Numero di pubblicazione1
DOI
Stato di pubblicazionePubblicato - 4 gen 2010

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