Pyrrophens: Pyrrole-Based Hexadentate Ligands Tailor-Made for Uranyl (UO22+) Coordination and Molecular Recognition
Inorganic chemistry | 28 Jun 2020
JT Mayhugh, JE Niklas, MG Forbes, JD Gorden and AEV Gorden
Derivatives of a novel pyrrole-containing Schiff base ligand system (called “pyrrophen”) are presented which feature substituted phenylene linkers (R1 = R2 = H (H 2 L 1 ); R1 = R2 = CH3 (H 2 L 2 )) and a binding pocket modeled after macrocyclic species. These ligands bind neutral CH3OH in the solid state through pyrrolic hydrogen-bonding. The interaction of the uranyl cation (UO22+) and H 2 L1-2 yields planar hexagonal bipyramdial uranyl complexes, while the Cu2+ and Zn2+ complexes were found to self-assemble as dinuclear helicate complexes (M2L2) with H 2 L 1 under identical conditions. The favorable binding of UO22+ over Zn2+ provides insight into the molecular recognition of uranyl over other metal species. Structural features of these complexes are examined with special attention to features of the UO22+ coordination environment which distinguish them from other related salophen and porphyrinoid complexes.
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