Deliberate Design of Ligand Architecture Yields Dramatic Enhancement of Metal Ion Affinity

• DOI: 10.1021/ja025854t
• Publication Date: 2002-07-26T06:09:00Z
• Authors: Gregg J. Lumetta; Brian M. Rapko; Priscilla A. Garza; Benjamin P. Hay; Robert D. Gilbertson; Timothy J. R. Wea...; James E. Hutchison
• Keywords: 01 natural sciences; 0104 chemical sciences

Evaluation of the malonamide substructure with respect to binding site preorganization and complementarity for lanthanide metal ions suggests a new ligand architecture specifically designed enhance ion affinity. Consideration conformational reorganization, restricted bond rotation, donor group orientation that typical structures, example, N,N,N‘N‘-tetrahexylpropane-1,3-diamide (1), N,N‘-dibutyl-N,N‘-dimethyl-2-tetradecylpropane-1,3-diamide (2), or N,N,N‘N‘-tetramethylpropane-1,3-diamide (6), are poorly organized complexation. Molecular mechanics analyses show unfavorable enthalpic entropic terms eliminated by use novel bicyclic found in 3,9-diaza-3,9-dimethylbicyclo[4.4.0]decane-2,10-dione (7). Diamide 7 was prepared, X-ray crystal structure complex [Eu(7)2(NO3)3] exhibits same chelate conformation predicted molecular model. A hydrophobic derivative, 3,9-diaza-3,9-dioctylbicyclo[4.4.0]decane-2,10-dione (8), solvent extraction studies reveal preorganized 8 gives dramatic enhancement affinity, exhibiting Eu3+ distribution coefficients orders magnitude larger than ligand, 1.