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

摘要

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 [Ni _3L _2(OAc) _2(μ _(1,1)- N _3) _2(H _2O) _2]·2H _2O (1) and [Ni _2L _2(μ _(1,1)-N _3) (μ _(1,3)-N _3)] 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 Ni _2 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.