Selection Rules for Helicate Ligand Component Self-Assembly: Steric, pH, Charge, and Solvent Effects

The reaction between 1,10-phenanthroline-2,9-dicarboxaldehyde, copper(I), and certain primary
amines was found to give quantitatively a dicopper double-helicate product (two of which were
crystallographically characterized) by imine self-assembly around CuI templates. The parameters of this
reaction were investigated, and important roles were found to be played by (i) the steric bulk of the amine,
(ii) the charge of the amine, (iii) the solvent used, and (iv) the pH of the solution. Water was found to allow
the broadest range of structures to form, and ligand-component exchange reactions (involving the substitution
of an aromatic for an aliphatic amine) were demonstrated to proceed readily in this solvent.