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(μ1,1-N3)2(H2O)2]·2H2O (1) and [Ni2L2(μ1,1-N3)­(μ1,3-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 [JFM = +34.2(2.8) cm–1 and JAF = −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.