Zinc and cadmium complexes of an 18-membered N4O2 oxaaza-Schiff base macrocycle and the corresponding reduced form†

Abstract

The metal templated (Cd and Zn) cyclocondensation of 2,6-pyridinedicarbaldehyde and 1,5-bis(2-aminophenoxy)-3-azapentane is reported together with the crystal structures of two mononuclear cadmium macrocyclic Schiff base complexes, [CdL¹(NO₃)₂] 1 and [CdL¹(H₂O)₂][ClO₄]₂ 2 and a dinuclear, µ-hydroxy-bridged zinc macrocyclic Schiff base complex [Zn₂L¹₂(OH)][ClO₄]₃·CH₃CN 3·CH₃CN. The corresponding reduced macrocycle, L², has been synthesised by using the Mn^II-templated cyclocondensation of 2,6-pyridinedicarbaldehyde and 1,5-bis(2-aminophenoxy)-3-azapentane in methanol followed by an in situ reductive demetallation of the Schiff base macrocyclic manganese(II) complex using excess sodium borohydride. The crystal structures of the free macrocycle L², [CdL²(NO₃)₂] 4 and [CdL²(CH₃CN)₂][ClO₄]₂ 5 are reported.