Diffusion NMR spectroscopy applied to coordination and organometallic compounds

Abstract

Abstract This chapter illustrates an extensive review of the application of diffusion NMR techniques on coordination compounds and organometallic systems that gives an idea of the extraordinary progress that this field has achieved, whether using PGSE or DOSY methodologies. The estimation of diffusion parameters using all the advantages of high-resolution NMR spectroscopy specially with modern probeheads, that allow the use of intense gradient fields and the tuning of less conventional nuclei, have begun new perspectives to determine the size and shape of many molecular systems in solution. In both, supramolecular architectures or smaller metallic complexes, this type of measurements allows one to assess their aggregation state, character of intermolecular interactions, stability or association constants between different hosts and guests, among many other interesting features. The main aim of this review is to present an overview of the PGSE and DOSY NMR mapping and its applications in inorganic systems, specifically coordination compounds based on transition metals, alkaline, alkaline-earth, main-group, and rare earth metal centres, as well as cluster complexes and metal-based supramolecular structures. A brief introduction to pulse-field gradient NMR is also given, with special emphasis on the methodological procedures that can be used to obtain good quality data, providing different possibilities when choosing different variables, such as the correct pulse sequence or the right equation that govern both the friction and/or shape factor. The material given in this review are appealing in its simplicity, offer chemically useful results and we believe they should significantly boost the use of diffusion NMR measurements.