First-row transition-metal complexes of mixed ‘pendant-arm’ derivatives of 1,4,7-triazacyclononane containing phenolate and carboxylate functional groups

Abstract

Three mixed pendant-arm azamacrocyclic ligands of the 1,4,7-triazacyclononane backbone containing one N-bound phenolate and one or two N-bound carboxylate functionalities have been synthesized, namely 4-(3-tert-butyl-2-hydroxybenzyl)-1,4,7-triazacyclononane-1-acetate(2–), [L¹]^2–, 7-(3-tert-butyl-2-hydroxybenzyl)-1,4,7-triazacyclononane-1,4-diacetate(3–), [L²]^3–, and 7-(2-hydroxybenzyl)-1,4,7-triazacyclononane-1,4-diacetate(3–), [L³]^3–. Their co-ordination chemistry with Fe^III, V^III, V^IV, Mn^III and Co^III has been investigated and the following complexes have been prepared as crystalline solids: [Fe^III(L¹)Cl]1, [Fe^IIIL¹(H₂PO₄)]2, [Fe^III₂L¹₂(µ-O)]·H₂O 3, [V^IIIL²]·1.5H₂O 4, [V^IVO(H²L)]5, [Mn^IIIL²]·2H₂O 6, [Fe^IIIL²]·1.5H₂O 7, [Co^IIIL²]8, [Fe^IIIL³]·2H₂O 9 and [Co^IIIL³]·3H₂O 10. Electronic spectra, magnetic properties and the electrochemistry of the new complexes are reported. The crystal structures 3, 4, 7 and 10 have been determined by X-ray crystallography.