CuII Complexes of Isomeric Ligands Derived from 2-Pyridine-carboxaldehyde and m- or p-Xylylenediamine: An Intermolecularly ?-Stacked Dinuclear Species and a Trinuclear Circular Helicate that Encapsulates a Chloride Ion

Abstract

Di- and trinuclear CuII complexes [Cu2L1(2,2′-bipyridine)2Cl2]Cl2·11H2O and [Cu3(L2)3Cl3]Cl3·1.25MeOH·4H2O incorporating the isomeric Schiff base ligands 1,1′-(1,4-phenylene)bis(N-(pyridin-2-ylmethylene)methanamine) (L1) and 1,1′-(1,4-phenylene)bis(N-(pyridin-2-ylmethylene)methanamine) (L2), each incorporating two separated α-diimine coordination domains, have been synthesised and their X-ray crystal structures and variable temperature magnetic properties determined. The X-ray crystal structure of [Cu2L1(2,2′-bipyridine)2Cl2]Cl2·11H2O shows that each CuII centre is bound to two nitrogen atoms from L1, two from a bipyridine ligand, and a chloride anion. Intramolecular π-stacking interactions are present between the central phenyl ring of L1 and both rings of each bipyridine ligand. The structure of [Cu3(L2)3Cl3]Cl3·1.25MeOH·4H2O shows an unusual trinuclear circular helicate arrangement with approximate C3-symmetry. A chloride anion is encapsulated in the structure being bound by six non-classical hydrogen bond interactions. Variable temperature magnetic susceptibility measurements indicated the presence of weak antiferromagnetic behaviour for [Cu2L1(2,2′-bipyridine)2Cl2]Cl2·11H2O and weak ferromagnetic behaviour for [Cu3(L2)3Cl3]Cl3·1.25MeOH·4H2O.