The structure determination of a binuclear copper(II) complex of aTetra-Schiff base macrocycle

Abstract

The structure of the complex Lcu₂Cl₂,6H₂O (where LH₂ is the tetra-Schiff base macrocycle formed as the condensation product of propane-1,3-diamine and 2-hydroxy-5-methylisophthal- aldehyde in the mole ratio 2: 2) was determined by single-crystal X-ray diffraction methods. The crystals are monoclinic, a 7.720(1), b 17.079(1), c 11.171(1) Å and β 91.50(1)º, with two molecules per unit cell. It has proved difficult to resolve the ambiguity between the three possible space groups (C2, Cm, and C2/m) and the initial model has been refined in each using a full-matrix least-squares method. The space group C2/m seems the most likely and the structure is described in it; R 0.049 for the 1369 independent reflections measured using counter methods. The structure analysis has confirmed the anticipated cyclic structure of the ligand with the two copper atoms held together in a binuclear arrangement by the planar N₄O₂ donor set; the Cu.. .Cu distance is 3.133(1)Å. Each copper atom has a distorted square-pyramidal environment with the apical position of each being occupied by a chlorine atom; the two chlorine atoms are on the opposite sides of the macrocycle. The water molecules are not coordinated, but form an extensive system of hydrogen bonding throughout the crystal with discrete binuclear molecules of the LCu₂Cl₂ complex.