Side-bridged cyclam transition metal complexes bearing a phenolic ether or a phenolate pendent arm

Abstract

Side-bridged cyclam transition metal complexes (M = Ni(II), Cu(II) and Zn(II)) bearing a phenolic ether or phenolate pendent arm have been synthesised. For [NiL 1 ] + and [CuL 1 ] + , evidence for a phenoxyl radical was obtained (quasi reversible peak at +0.74 V and +0.48 V respectively), as well as oxidation of OH, due to protonation of the phenolate, at ~+1.24 V. The phenoxyl radical in [Ni(L 1 )] 2+ is harder to oxidise by 0.26 V compared with the corresponding Cu(II) complex. UV-Vis data for [Ni(L 1 )] 2+ suggests that the Ni(II) ion may be 4 or 6 coordinate whereas the Cu(II) ion in [Cu(L 1 )] 2+ is five coordinate. The Ni(II) ion in the crystal structure of [Ni( L 2 )][( ClO4)2] possesses a distorted squareplanar geometry in which the phenolic ether pendent arm is not involved in the coordination sphere. The cyclam ligand in this complex adopts a trans-II configuration.