Fiona H. Fry

Zinc(II) complexes of xylyl bridged bis(1,4,7-triazacyclononane) derivatives

Abstract The xylyl bridged bis(tacn) ligands, T2-o-X (1,2-bis(1,4,7-triazacyclonon-1-ylmethyl)benzene) and T2-p-X (1,4-bis(1,4,7-triazacyclonon-1-ylmethyl)benzene) have yielded one mononuclear, [Zn(T2-o-X)](ClO4)2 (1), and one dinuclear complex [Zn2(T2-p-X)(H2O)4(DMF)2][ZnCl4]2 (2). A single-crystal X-ray structure determination of 1 has established that T2-o-X ligand sandwiches a single zinc(II) centre, which adopts a distorted octahedral geometry. A structural analysis of 2 confirmed the formation of a binuclear [Zn2(T2-p-X)(H2O)4(DMF)2]4+ complex in which each zinc centre binds to one of the macrocyclic compartments of the T2-p-X ligand and the remaining zinc coordination sites are occupied by water and DMF ligands. The coordination of DMF highlights the ability of carbonyl groups in amide molecules to bind to zinc(II), a feature of zinc enzymes that catalyse the hydrolysis of amide bonds in proteins (peptidases). A synthetic procedure has been developed which enables single pendant carboxymethyl groups to be attached to T2-o-X and T2-m-X. These bis(tetradentate) ligands form dinuclear zinc(II) complexes [Zn2(T2-o-X Ac2)(H2O)4](ClO4)2·2H2O (3) and [Zn2(T2-m-X Ac2)(H2O)4](ClO4)2·2H2O (4), whose structure has been probed by spectroscopic methods.

Binuclear copper complexes of bis(1,4,7-triazacyclonon-1-yl) ligandsincorporating acetate pendant arms

Two new bis(pentadentate) compounds, n1,2-bis[4,7-bis(carboxymethyl)-1,4,7-triazacyclonon-1-yl]ethane n(L n 1 n) and n1,4-bis[4,7-bis(carboxymethyl)-1,4,7-triazacyclonon-1-yl]butane n(L n 2 n), have been prepared by functionalisation of the ncorresponding alkyl-bridged bis(macrocycles) with acetate pendant arms. nTheir binuclear copper(II) complexes have been prepared and ncharacterised by X-ray crystallography. Both n[Cu n 2 nL n 1 n]·5H n 2 nO and n[Cu n 2 nL n 2 n]·2H n 2 nO are centrosymmetric nabout the alkyl bridge with the pentadentate compartments hosting the ncopper(II) centres oriented away from one another. Each nCu n II n exhibits distorted square-pyramidal geometry with an nN n 2 nO n 2 n basal plane and an apical N atom.