title: Triple-bridged ferromagnetic nickel(II) complexes: a combined experimental and theoretical DFT study on stabilization and magnetic coupling.
abstract: Two dinuclear [Ni2L2(o-(NO2)C6H4COO)2(H2O)] (1), [Ni2L2(p-(NO2)C6H4COO)2(H2O)]·0.5CH3OH (2) complexes and one trinuclear [Ni3L2(p-(NO2)C6H4COO)4]·C2H5OH (3) Ni(II) complex have been synthesized using a tridentate Schiff base ligand, 1-[(3-dimethylamino-propylimino)-methyl]-naphthalen-2-ol (HL) along with ortho- and para-nitro benzoate as co-ligands. All these three (1-3) complexes have been characterized by spectral analysis, X-ray crystallography and variable temperature magnetic susceptibility measurements. The structural analyses reveal that complexes 1 and 2 are dinuclear in which two μ2-phenoxido and a water molecule bridge the two Ni(ii) centers to make the complexes face sharing bioctahedra. Complex 3 is a linear triple bridged (phenoxido and carboxylato) trinuclear Ni(II) complex. Variable-temperature magnetic susceptibility studies indicate the presence of ferromagnetic exchange coupling in complexes 1-3 with J values of 25.4, 28.1 and 6.2 cm(-1) respectively. Theoretically obtained J values of 21.4 cm(-1) (for 1), 22.0 cm(-1) (for 2) and 9.3 cm(-1) (for 3) corroborate very well the experimental results. DFT calculation also shows that stronger H-bonding interactions present in the case of carboxylate based coligands stabilise the triple oxido-bridged complexes.
authors.affiliation: Department of Chemistry, University College of Science, University of Calcutta, 92, A.P.C. Road, Kolkata 700 009, India. ghosh_59@yahoo.com.
authors.forename: Rituparna
authors.initials: R
authors.lastname: Biswas
authors.forename: Carmen
authors.initials: C
authors.lastname: Diaz
authors.forename: Antonio
authors.initials: A
authors.lastname: Bauzá
authors.forename: Miquel
authors.initials: M
authors.lastname: Barceló-Oliver
authors.forename: Antonio
authors.initials: A
authors.lastname: Frontera
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Ghosh