A Rare phenoxido/acetato/azido bridged trinuclear and an unprecedented phenoxido/azido bridged one-dimensional polynuclear nickel (II) complexes: synthesis, crystal structure and magnetic properties with theoretical investigations on the exchange mechanism

Abstract

The reaction of a tridentate Schiff base ligand HL (2-[(3-dimethylaminopropylimino)-methyl]-phenol) with Ni(II) acetate or perchlorate salts in the presence of azide as coligand has led to two new Ni(II) complexes of formulas [Ni₃L₂(OAc) ₂(μ_1,1-N₃)₂(H₂O) ₂]•2H₂O (1) and [Ni₂L₂(μ_1,1-N₃)(μ_1,3-N₃)]_n (2). Single crystal X-ray structures show that complex 1 is a linear trinuclear Ni (II) compound containing a μ ₂-phenoxido, an end-on (EO) azido and a syn-syn acetato bridge between the terminal and the central Ni (II) ions. Complex 2 can be viewed as a one-dimensional (1D) chain in which the triply bridged (di-μ ₂-phenoxido and EO azido) dimeric Ni₂ units are linked to each other in a zigzag pattern by a single end-to-end (EE) azido bridge. Variable-temperature magnetic susceptibility studies indicate the presence of moderate ferromagnetic exchange coupling in complex 1 with J value of 16.51(6) cm^–1. The magnetic behavior of 2 can be fitted in an alternating ferro- and antiferromagnetic model [J_FM = +34.2(2.8) cm^–1 and J_AF = −21.6(1.1) cm^–1] corresponding to the triple bridged dinuclear core and EE azido bridge respectively. Density Functional Theory (DFT) calculations were performed to corroborate the magnetic results of 1 and 2. The contributions of the different bridges toward magnetic interactions in both compounds have also been calculated.