Macrocyclic coordination chemistry

Abstract

This chapter reviews the literature published on macrocyclic coordination chemistry during 2011. The aim is to describe the key advances, focusing predominantly on complexes formed with transition metal and lanthanide ions. Porphyrin ligands and supramolecular chemistry are not covered. Trends in the development of macrocyclic chelator design and the impact of the coordination chemistry of the chelators on both existing and emerging applications are discussed. HighlightsThere were some interesting and important advances in this field reported in 2011. The progressing development of the immobilisation of macrocycles on surfaces and as components of supramolecular species are particularly important with catalytic complexes on nanoparticles participating in highly effective oxidation reactions 1 and also the formation of constructs for multi-modal imaging in vivo. 2,3 Similarly the incorporation of functionalised macrocyclic complexes into micelles and vesicles facilitated enhanced DNA cleavage properties. 4 MRI imaging is the source of the greatest number of publications in this area but often the same types of chelators and techniques are employed. Deviations from the normal approach include continued efforts to design macrocyclic complexes for PARACEST MR imaging; this can be carried out by optimising slow water exchange with appropriate donor choice, or incorporating the functional macrocyclic component into micelles for sensing, and has resulted in key advances in 2011. [5][6][7] Another imaging paper reports optimised methods for efficient dynamic nuclear polarisation of 89 Y which could ultimately lead to clinical use of targeted complexes in MR imaging with the significant signal enhancement offered by this technique.

Amide conjugates of the DO3A‐N‐(α‐amino)propionate ligand: leads for stable, high relaxivity contrast agents for MRI?

“…Nonetheless, the high relaxivities predicted theoretically have not yet been achieved in spite of the tremendous efforts and developments in the field . The main approaches to enhancing detection sensitivity involve optimizing the relaxivity of individual chelates, clustering a high number of (high relaxivity) chelates into (bio)macromolecular carriers or self‐assembling monomeric chelates into supramolecular structures, and directing chelate constructs to the sites of interest by attaching targeting moieties recognized specifically by cellular receptors . All these approaches require chemical modification of the basic chelator structure in order to introduce ‘handles’ for chemical functionalization.…”