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 FeIII, VIII, VIV, MnIII and CoIII has been investigated and the following complexes have been prepared as crystalline solids: [FeIII(L1)Cl]1, [FeIIIL1(H2PO4)]2, [FeIII2L12(µ-O)]·H2O 3, [VIIIL2]·1.5H2O 4, [VIVO(H2L)]5, [MnIIIL2]·2H2O 6, [FeIIIL2]·1.5H2O 7, [CoIIIL2]8, [FeIIIL3]·2H2O 9 and [CoIIIL3]·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.