Copper(II) and zinc(II) complexes of amide pendant-armed cross-bridged tetraamine ligands

Abstract

Copper(II) and zinc(II) complexes of cross-bridged cyclam and cyclen with primary amide pendant arms (ligands 1 and 2) have been prepared and structurally characterized. The copper complex of cyclam-derived 1 has a Jahn–Teller distorted Cu(II) octahedral coordination geometry with both amide arms coordinated through the carbonyl oxygens. The Cu(II) complex of the cyclen analogue 2 has been found to exist in three slightly different forms. Both zinc complexes also adopt full N 4O 2 coordination from these potentially hexadentate cross-bridged ligands. These structural data confirm the exclusive cis-folded ligand configuration in all four complexes as well as the significantly better fit of ligand 1 towards both Cu(II) and Zn(II) cations when compared to 2. The complexes of 1 provide the first examples of a [2233]/[2233] cross-bridged cyclam conformation, as opposed to the previously observed [2323]/[2323] conformation.