Synthesis and co-ordination of 1,4,7,10-tetraazacyclododecanes disubstituted with imidazole and pyrazole

Abstract

The potentially hexadentate ligands 1,7-bis(1-methylimidazol-2-ylmethyl)-(L¹), 1,7-dimethyl-4,10-bis(1-methylimidazol-2-ylmethyl)-(L²) and 1,7-dimethyl-4,10-bis(pyrazol-3-ylmethyl)-1,4,7,10-tetraazacyclododecane (L³) have been synthesized and their basicity constants determined by potentiometry at 25 °C in 0.15 mol dm^–3 NaClO₄. Nickel(II) and zinc(II) complexes with the three compounds have been prepared and characterized. The structures of [NiL¹][BPh₄]₂ and [NiL²][ClO₄]₂·0.5H₂O have been determined by single-crystal X-ray analyses. In both complex cations the metal ion is co-ordinated by the six nitrogen donor atoms of the ligand.