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

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 μ₂-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-μ₂-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.