NMR properties of lanthanide(III) complexes of the macrocyclic ligand C22H26N6

The nuclear magnetic resonance properties of a series of complexes with general formula [Ln(CH3COO)2L]Cl·nH2O, where L is the hexadentate macrocyclic ligand C22H26N6, Ln is La(III)Lu(III) and Y(III), and n=4–6, have been investigated. 1H and 13C NMR spectra were recorded for all members of the series; whenever possible, assignments were confirmed by heteronuclear correlation spectroscopy. The proton chemical shifts varied significantly with the metal center, the solvent, and the counterion; they were unaffected by changes in concentration. An analysis of the paramagnetic shifts for the proton acetate resonances of several complexes revealed the presence of a significant contact shift, which was dominant in the case of the Eu(III) complex.