Binuclear and trinuclear complexes of exoO2-cyclam

Abstract

Complexes of the ligand 2,3-dioxo-1,4,8,11-tetraaza-cyclotetradecane (exoO₂-cyclam) have been prepared of formula [M¹{M²(exoO₂-cyclam)}₂][BPh₄]₂ where M¹M² = CoCo (3), ZnZn (4), MnCu (5), FeCu (6), CoCu (7), NiCu (8), ZnCu (9), and [(bipy)₂Ru{Cu(exoO₂-cyclam)}][NO₃]₂ (10). Complex 10 crystallised in the space group C2/c and shows Jahn–Teller distorted Cu(II) with axial nitrate ligands. The {Cu(exoO₂-cyclam)} moiety chelates to the Ru with Ru–O distances of 2.082(5) Å. Complexes 5–10 show a Cu(II)/Cu(III) redox process and additional metal-centred (6, 8, 10) processes and ligand-centred (10) processes. The electrochemical and UV-Vis spectroelectrochemical study of 10 suggested two closely-spaced oxidations based on the Cu and Ru centres which suggests that substituted derivatives of 10 will be of interest for enhanced charge separation in dye-sensitised solar cells. Magnetic susceptibility measurements revealed dominant antiferromagnetic coupling within the trinuclear species 3, 5–8. Complex 10 showed Curie–Weiss behaviour with weak intermolecular interactions.