Lanthanide(III) Complexes of Two Novel N 3 O 4 -donor Macrocycles Derived from 3,6-Dioxa-1,8-Octanediamine

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Two novel N3O4 macrocycles, L1 and L2, have been synthesised, and their complexation potential towards Ln(III) ions has been investigated. Direct cyclocondensation between 2,6-bis(2-formylphenoxymethyl)pyridine and 3,6-dioxa-1,8-octanediamine yields the macrocycle L1 as the main product. The diamine macrocycle L2 is formed by reaction of the diamine and dicarbonyl precursors followed by an in situ reduction with NaBH4. Series of Ln(III) complexes have been obtained for both ligands, by direct synthesis between L1 or L2 and different Ln(III) hydrated nitrates or perchlorates; however, attempts to synthesise the corresponding Ln(III) complexes with L1 following a template method have been unsuccessful. All complexes obtained with L1 give a [2 : 1, Ln : L1] stoichiometry. The reduction of the diiminic bonds increases the flexibility of the macrocycle and leads to a change in the stoichiometry; all complexes obtained with L2 show a [3 : 1, Ln : L2] relation.