Different supramolecular hydrogen bond structures and significant changes in magnetic properties in dinuclear μ_2-1,1-N_3 copper(II) complexes with very similar tridentate Schiff base blocking ligands

摘要

Three new basal-apical, μ_2-1,1-azide bridged complexes, [CuL~1(N_3)]_2 (1), [CuL~2(N_3)]_2 (2) and [CuL~3(N_3)]_2 (3) with very similar tridentate Schiff base blocking ligands [L~1=N-(3-aminopropyl)salicylaldimine, L~2= 7-amino-4-methyl-5-azahept-3-en-2-one and L~3= 8-amino-4-methyl-5-azaoct-3-en-2-one) have been synthesised and their molecular structures determined by X-ray crystallography. In complex 1, there is no inter-dimer H-bonding. However, complexes 2 and 3 form two different supramolecular structures in which the dinuclear entities are linked by strong H-bonds giving one-dimensional systems. Variable-temperature (300-2 K) magnetic susceptibility measurements and magnetization measurements at 2 K reveal that complexes 1 and 2 have antiferromagnetic coupling while 3 has ferromagnetic coupling which is also confirmed by EPR spectra at 4?00 K. Magnetostructural correlations have been made taking into consideration both the azido bridging ligands and the existence of intermolecular hydrogen bonds in complexes 2 and 3.