Multinuclear structures applications

To develop a methodology applicable to the design of a wide range of multinuclear active sites on the backbones of insoluble polymers we prepared a molecular entity, composed of various catalytic elements, with a precisely defined structure and then attached it to a polymeric backbone. Thus, we synthesized catalytic modules containing one, two, or four metal-chelating sites, which were subsequently attached to a polystyrene derivative to produce 21-23 [55]. 

Simpson TJ. Applications of multinuclear NMR to structural and biosynthetic studies of polyketide microbial metabolites. Chem. Soc. Rev. 1987 16 123-160. 

NMR has been an integral part of the chemist s analytical toolbox for decades. The most common and fundamental experiment is the one-dimensional (ID) H experiment. The relatively high sensitivity of the H nucleus makes this a very useful start, but for a complex molecule the ID spectrum can be crowded and often uninterpretable. In these cases more advanced techniques can be used to provide increased resolution and specific types of structural information. In this section we will describe a range of NMR techniques from the simplest ID experiments to complex multidimensional, multinuclear experiments. The focus of this section will be on the general principles underlying these experiments and their applications to molecules of pharmaceutical interest. Further details on these experiments can be found in the references. 

The explosion of activity and subsequent literature in the polyoxometalate field during the past two decades may reflect the increasing access to reliable methods of characterization in solution (multinuclear NMR) and the solid state (X-ray diffraction), but is certainly stimulated by the realization that there are few fields of science to which these complexes do not have important applications. One result of this expansion has been the necessity to devote two chapters to the chemistry of polyoxometalates one focusing on structure and one on reactivity instead of the single chapter in the original Comprehensive Coordination Chemistry (CCC, 1987). 

Applications of multinuclear NMR to structural and biosynthetic studies of polyketide microbial metabolites, T.J. Simpson, Chem. Soc. Rev., 1987,16,123. Natural products of filamentous fungi enzymes, genes and their regulation, D. Hoffmeister and N.P. Keller, Nat. Prod. Rep., 2007, 24, 393. 

One of the more important current applications of high-resolution multinuclear NMR is in the determination of the three-dimensional structures of proteins and other macromolecules in solution. These techniques are complementary to crystallographic methods. A typical experimental procedure is described in Box 2.2. 

Prom a practical point of view, the application of biomimetic models to processes of synthetic, or industrial interest depends strongly on the transformation of the current stoichiometric reactions into catalytic reactions (e.g., in the phenol oxygenation reactions), the stability of the catalysts, and the introduction of stereoselectivity characteristics in the reactions, by using structurally more sophisticated and possibly chiral ligands. In addition, the biomimetic chemistry of the more complex multinuclear Cu sites, such as the trinuclear Cu sites of blue oxidases, is still in its infancy, and important contributions are expected in the next few years from the study of new and suitable model compounds. 

A wide range of proton and carbon NMR techniques, almost exclusively using Fourier Transform (FT) spectroscopy, are presented in applications to support proposed chemical structures, with multinuclear NMR being used where appropriate. Polarisation transfer experiments (e.g. DEPT) are used to indicate carbon multiplicity and the use of two-dimensional techniques, which facilitate signal assignment, is seen more frequently in applications. Typical techniques include H- H correlation (COSY and related phase-sensitive experiments) proton-carbon heteronuclear correlation (including inverse... 

R 627 B. Wrakmeyer, J. Weidinger, A. Pedall and W. Milius, N-Silylaminotitanium Chlorides - Synthesis, Structures, Multinuclear Magnetic Resonance, and Some Applications , Z. Anorg. Allg. Chem., 2003, 629, 862... 

A number of review articles have described the applications of multinuclear NMR methods for studying structures and internal rearrangements of metal clusters. The more specific cluster types covered were transition metal carbonyl clusters/ chiral clusters/ and mixed metal clusters containing carbyne or ketenylidene bridges. ... 

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