Cerium(IV) Pyrasal Complexes: A pH-Dependent 8- to 10-Coordinate Cerium Chelate Switch.

In this work, five cerium(IV) complexes were synthesized, three of which were structural isomorphs from the same pyrasal ligand with the solid-state result identified by structural analysis dependent on the initial pH of the reaction solution and the temperature at which the reaction is performed. The ligands explored here are pyrasal ligands, which are Schiff-base ligands formed by the condensation of 2,3-diaminopyrazine and a salicylaldehyde derivative. Pyrasal ligands have weaker binding than other salophen-type ligands due to the electron-withdrawing effect of the nitrogen atoms contained within the pyrazine ring.