Magnetic property of a triply bridged linear trinuclear nickel complex

A new linear trinuclear nickel(II) complex, Ni₃L₂(OCn)₄] (HL = 2-(3-dimethylamino-propylimino)-methyl]-phenol, OCn = cinnamate), with phenoxo bridge and a novel tridentate bridging mode (in a 2.21 fashion according to Harris notation), of the cinnamate ligand has been synthesized and characterized by IR spectroscopy, UV-Vis spectroscopy, X-ray crystallography and static magnetic measurements. The molecular structure shows that each nickel ion occupies octahedral coordinating geometry. Apart from the phenoxo bridges, the carboxylic group of cinnamic anion shows two types of bridging modes viz. 2.11 and 2.21. The magnetic data indicate that a moderate intramolecular ferromagnetic and a weak intermolecular antiferromagnetic interaction are present in the complex under study. Broken symmetry density functional theory has been used to estimate the sign and magnitude of the coupling constants to understand the magnetic exchange mechanisms of the present system. The relative abilities of different bridging groups to mediate magnetic exchange interactions between paramagnetic nickel centers have been investigated by DFT calculation with variable angles. The results show that a small change in phenoxo-bridging angle has a very strong impact on the magnetic properties.