Interaction of copper(II) with N-substituted bis(2-pyridylmethyl)amine derivatives: New discrete and 1-D polymeric complex systems — The latter displaying ferromagnetic behaviour

Interaction of copper(II) with the N-substituted bis(2-pyridylmethyl)amine derivatives, (R)-N1,N1-bis(pyridine-2-ylmethyl)butane-1,2-diamine (L1) and (R)-2-(bis(pyridin-2-ylmethyl)amino)butan-1-ol (L2), has led to isolation of optically active [Cu(L1)Cl]PF6 (1) and [Cu(L2)Cl]ClO4 (2), respectively. The X-ray structures of (1) and (2) show that the copper is bound to all four heteroatoms of the respective ligands as well as to a chlorine atom in a distorted square pyramidal arrangement in which the three nitrogens of L1 or L2 occupy three positions of each basal plane while the fourth position is occupied by the chloro ligand; apical sites in each case are filled by the amine donor from the NH2-substituted butane arm in L1 or the (protonated) alcohol oxygen of the 2-aminobutane-1-ol substituent in L2. To a first approximation the coordination geometry in 2 is distorted square pyramidal; however, the remaining (axial) site on each copper centre is involved in a long contact (2.96 Å) with a bound chloro ligand from an adjacent complex which connects individual complex units in a zigzag 1-D polymeric chain, so that the coordination geometry could also be seen as pseudo-octahedral. A temperature-dependent magnetic study revealed the presence of ferromagnetic exchange coupling between copper centres in the chain reflecting the orthogonal structure between the chloro-bridged copper(II) ions; in contrast, and as expected, the discrete complex 1 is magnetically dilute.