Double template effect in [4+4] Schiff base macrocycle formation: an ESI-MS study

The mechanism of self-assembly of a polynuclear complex of a [4 + 4] Schiff base iminomethylenediphenolate macrocycle [BaCu4(4 + 4)]2+ via a non-macrocyclic dialdehyde intermediate has been followed using ESI-MS of the reaction solutions. Both assembly of the intermediate and Schiffbase condensation with diamine give rise to single products; formation of the intermediate metallacycle is fast but Schiffbase condensation ismuch slower. Both intermediate complex andmacrocyclic product have been structurally characterised.