Pyrrophens: Pyrrole-Based Hexadentate Ligands Tailor-Made for Uranyl (UO) Coordination and Molecular Recognition.

Derivatives of a novel pyrrole-containing Schiff base ligand system (called "pyrrophen") are presented which feature substituted phenylene linkers (R = R = H (); R = R = CH ()) and a binding pocket modeled after macrocyclic species. These ligands bind neutral CHOH in the solid state through pyrrolic hydrogen-bonding. The interaction of the uranyl cation (UO) and yields planar hexagonal bipyramdial uranyl complexes, while the Cu and Zn complexes were found to self-assemble as dinuclear helicate complexes (ML) with under identical conditions. The favorable binding of UO over Zn 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 UO coordination environment which distinguish them from other related salophen and porphyrinoid complexes.