Anion directed template synthesis of Cu(II) complexes of a N,N,O donor mono-condensed Schiff base ligand: a molecular scaffold forming highly ordered H-bonded rectangular grids

Abstract

Anion directed, template syntheses of two dinuclear copper (II) complexes of mono-condensed Schiff base ligand Hdipn (4-[(3-aminopentylimino)-methyl]-benzene-1,3-diol) involving 2,4-dihydroxybenzaldehyde and 1,3-diaminopentane were realized in the presence of bridging azide and acetate anions. Both complexes, [Cu₂(dipn) ₂(N₃)₂] (1) and [Cu₂(dipn) ₂(OAc) ₂] (2) have been characterized by X-ray crystallography. The two mononuclear units are joined together by basal–apical, double end-on azido bridges in complex 1 and by basal–apical, double mono-atomic acetate oxygen-bridges in 2. Both complexes form rectangular grid-like supramolecular structures via H-bonds connecting the azide or acetate anion and the p-hydroxy group of 2,4-dihydroxybenzaldehyde. Variable-temperature (300–2 K) magnetic susceptibility measurements reveal that complex 1 has antiferromagnetic coupling (J = −2.10 cm⁻¹) through the azide bridge while 2 has intra-dimer ferromagnetic coupling through the acetate bridge and inter-dimer antiferromagnetic coupling through H-bonds (J = 2.85 cm⁻¹, J′ = −1.08 cm⁻¹).