Uranyl salophens : synthesis and use as ditopic receptors

Abstract

Uranyl salophens are ditopic receptors that can simultaneously bind both the anion and cation of the salt at the same time. The anion is bound to the seventh coordination site of the uranium atom in the uranyl moiety and the cation binds to the aromatic re-system of the salophen moiety through cation‧‧‧π and C-H‧‧‧π interactions. The uranyl salophens offer a great potential for further functionalization, which makes them ideal building blocks for the purposes of supramolecular chemistry and molecular recognition. As an introduction to the subject, the review of the literature gives both a brief account of the history and recent advances in the uranyl salophen chemistry as well as a description of their synthesis and use as receptors and catalysts. In the experimental part, altogether 12 novel uranyl-salophen complexes and some of their starting compounds were prepared and characterized by 1H and 13C NMR, mass spectrometry and elemental analysis. The complexation behavior of the prepared uranyl salophens was studied both in the solution and in the solid state. In the solution the binding constants for phenyl methoxy uranyl salophens towards various quaternary ammonium chlorides were determined by NMR titrations. In the solid state, the structures of 12 new solvent complexes and 13 new complexes with other guest molecules (R4NX, DABCO or Cs2CO3) and 3 novel dimer arrangements were determined by single crystal X-ray crystallography.