The first dicopper(II) complex of a new bis(1,5,9-triazacyclododecane) ligand: synthesis, crystal structure and magnetic coupling of the complex

A new binucleating macrocylic polyamine ligand based on 1,5,9-triazacyclododecane ([12]aneN(3)), 2,6-bis(1,5,9-triazacyclododecan-9-ylmethyl) benzoate (L), has been synthesized from a selectively Boc protected [12]aneN(3) precursor and 2,6-bis(bromomethyl) benzoate. L can form a stable binuclear comdex with Cu(II) in aqueous solution and the complex has been characterized by X-ray crystallography. The intramolecular binuclear Cu(II) centers are bridged by a mu-carboxyl group on L and separated by 5.947 Angstrom. Both of the Cu(II) centers are coordinated by three amine nitrogens of [12]aneN(3) subunit and one oxygen of the carboxyl group, as well as one azide anion, and each Cu(II) center is in a distorted square-pyramid environment. To our knowledge, this is the first binuclear Cu(II) complex formed with a bis([12]aneN(3)) ligand. Variable temperature magnetic susceptibility studies indicate that there exists intramolecular antiferromagnetic coupling (- 2J= 71.4 cm (-1)) between the two unpaired electrons of the two Cu(II) ions in complex I. (C) 2000 Elsevier Science S.A. All rights reserved.