Determining the 3D structure of ligands and their metal ligand complexes in solution by nuclear magnetic resonance (NMR) spectroscopy using Residual Dipolar Couplings (RDCs)

摘要

Residual Dipolar Couplings (RDCs) have been used in the structural determination of biomolecules, pharmaceutical molecules, and small organic molecules in solution. Determining the structure of metal-ligand complexes in solution may also benefit from the application of dipolar couplings. X-ray crystallography can be used to determine the structure of metal ligand complexes in solid state. Chiral catalyst ligands and biologically active ligands and their metal complexes are both most active in solution making structural determination in solution of direct interest for these applications.;This study focuses on determining the structure of NaphthoQuinoneSulfonic Acid Benzyl Thiosemicarbazone (NQSA-BTSC) ligand, NaphthoQuinoneSulfonic Acid Phenyl Thiosemicarbazone (NQSA-PTSC) ligand, (1R,2 R)-N,N'-1,2-Cyclohexanediylbis(2-pyridinecarboxamide) also known as (R,R)-DACH-pyridyl Trost ligand, and their metal complexes in solution. RDCs have been proved to be a useful method in determining molecular shapes in solution. This is achieved by using the strain aligned gel (SAG) method. Anisotropic media of poly methyl methacrylate (PMMA) and polyvinyl acetate (PVAC) were used to generate an anisotropic environment for examining ligands and metal ligand complexes. This anisotropic environment allows us to determine RDCs in solution by NMR spectroscopy and used to find the three dimensional structure of these complexes through the singular value decomposition (SVD) methodology currently employed for other molecules.