European Commission logo
English English
CORDIS - EU research results

Structure and dynamics of catalytically active species from Residual Dipolar Couplings

Final Report Summary - RDC@CATALYSIS (Structure and dynamics of catalytically active species from Residual Dipolar Couplings)

Nowadays it is generally accepted, that the three dimensional structure is the key to success if molecules or materials shall exhibit specific functions. Recently a new theory on molecular recognition has been proposed, which addresses the question whether a structural change is induced by the binder as in the Induced-Fit Theory, or if the active conformation is already a member of the ensemble of conformations present in solution and is selected by the binder (Conformational Selection). The investigation of structures and their dynamics in solution is thus a fascinating field of science, which quite frequently allows deducing structure activity relationships and gives hints for the rational design of functional molecules.
One class of functional molecules are catalysts. It was the objective of the current project to establish methods to investigate the solution structure and dynamics of catalytically active species in order to understand their reactivity and selectivity.
Of special interest for synthesis are enantioselective processes. Knowledge about the origins of enantio¬selection in homogeneously catalysed processes is still limited though. If the origins of enantioselection are to be investigated one crucial step is to obtain knowledge about the spatial relationship between the catalyst (composed of metal and ligands in metal catalysed processes and of the catalyst only in organo¬catalytic processes) and the substrate. If an intermediate can be isolated this spatial relationship can - in principle - be obtained either from X-ray crystallography or from NMR-spectroscopy (nuclear magnetic resonance). It has to be pointed out that the structure in the solid state does not necessarily resemble the one in solution and that dynamic processes, which we believe to be crucial for the function of catalysts, are not easily accessible from X-ray data. High-resolution solution state NMR spectroscopy on the contrary cannot only be used to determine the spatial relationship, but also for the investigation of dynamic processes.
We have used conventional NMR –parameters such as the Nuclear Overhauser Effect (NOE) together with the recently (re)introduced Residual Dipolar Couplings (RDCs) to investigate the solution structures of metal-based and organocatalysts and have obtained significant insights into two classes of reactions – a palladium catalysed allylic substitution reaction and a kinetic resolution of diols with a peptide catalyst.
To achieve these goals it was also necessary to develop methods for the treatment of flexibility, to develop software and to implement state-of the art NMR techniques, such as ultra-fast NMR, non-uniform sampling and pure-shift NMR etc.