Synthesis, structure, and stability in acid of copper(II) and zinc(II) complexes of cross-bridged tetraazamacrocycles

New copper(II) and zinc(II) complexes of cross-bridged tetraazamacrocyclic ligands derived from 1,4,8,11-tetraazacyclotetradecane (cyclam), 1,4,7,10-tetraazacyclotridecane([13]aneN4), and 1,4,7,10-tetraazacyclododecane (cyclen) have been synthesized. The X-ray crystal structures of the two cyclen-derived complexes have been determined and show both metal ions to be in distorted octahedral environments with the ligand in a cis-folded conformation. The bridged-ligand complexes are remarkably stable kinetically under harsh acidic conditions, as seen from their dissociation reactions. The electrochemical and spectroscopic properties of the Cu2+ complexes have also been investigated. (C) 2003 Elsevier Science B.V. All rights reserved.