Towards aqueous chiral heptadentate lanthanide complexes as selective shift and relaxation agents for MRS.

Magnetic resonance spectroscopy (MRS) is of prime importance in diagnostics and offers a means of analyzing, in vivo, the chemical content of living tissue, as a non-invasive alternative to biopsy. Several heptadentate, lanthanide complexes have been synthesized and their potential to act as shift and relaxation agents in MRS (for lactate, in particular) has been assessed through (1)H NMR analysis. The binding affinity and enantiopurity of the complexes have been modulated by systematic variation of the lanthanide ion and ligand structure, in particular the peripheral electrostatic charge of the complex (cationic versus neutral) and the local charge and steric demand at the metal centre.