Synthesis, Structure, and Magnetic Properties of Two New Ferromagnetic/Antiferromagnetic One-Dimensional Nickel(II) Complexes. Magnetostructural Correlations

Abstract

Two new one-dimensional nickel(II) complexes were synthesized and characterized: [Ni(N,N-dimethylethylenediamine)(N3)2] (1) and [Ni(2-aminoethylpyridine)(N3)2] (2). The crystal structures of 1 and 2 were solved. Complex 1 crystallizes in the monoclinic system, space group P2(1)/n with a = 10.569(2) A, b = 7.331(4) A, c = 12.9072(8) A, beta = 111.324(10) degrees, and Z = 4. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c with a = 12.299(5) A, b = 14.307(2) A, c = 12.604(3), beta = 106.72(2) degrees, and Z = 4. The two complexes are similar and may be described as one-dimensional systems with double-azido-bridged ligands in end-to-end and end-on coordination alternatively. The end-on moiety is almost identical for 1 and 2, but the end-to-end moiety is different in each structure: for 1 this part is almost planar but for 2 is nonplanar. In both cases the Ni atoms are situated in similar distorted octahedral environments. The magnetic properties of the two compounds were studied by susceptibility measurements vs temperature. The chi M vs T plots for 1 and 2 show a global antiferromagnetic behavior with a maximum near room temperature for 1 and at very low temperature for 2. J values for 1 and 2 were deduced from the spin Hamiltonian -sigma(J1SiSi+1 + J2Si+1Si+2). The computational method was based on the numerical solution for finite systems of increasing size. J values for 1 were J1 = -187 cm-1 and J2 = +77 cm-1 and for 2 J1 = -28 cm-1 and J2 = +73 cm-1. The positive values correspond to end-on azido ligands and the negative values to end-to-end azido ligands. Since the geometries of the [Ni(N3)]2 moieties involving the end-on azido ligands are almost the same in the two structures, the ferromagnetic coupling is nearly identical in the two compounds, while the significantly different antiferromagnetic couplings reflect the near planarity of the end-to-end Ni2(N3)2 fragment in 1 and its twisted geometry in 2.

Coexistence of Spin Canting and Metamagnetism in a One-Dimensional Mn(II) Compound Bridged by Alternating Double End-to-End and Double End-On Azido Ligands and the Analog Co(II) Compound

“…Toggling EO and EE modes along a 1D polymeric structure is rare, but not unprecedented (see Table S1). Indeed, quite similar azido-bridged structures have been described using other ancillary ligands and a variety of transition metals: Schiff bases and Mn(II) [22,23] pyridine derivatives and Mn(II) [24,25], Co(II), Ni(II) [14] or Zn(II) [21] amine/pyridine derivatives and Ni(II) [11,26,27], among others. The nearest structurally related compound is certainly [Mn(N 3 ) 2 (2,2 -bipyridine)], which crystallizes in space group P-1, with unit-cell parameters quite close to those of [Mn(N 3 ) 2 (dmbpy)] [13,28] and in fact is even isostructural with the Fe(II) and Co(II) analogues [29].…”

“…In [Mn(N 3 ) 2 (dmbpy)], the N-N bond lengths are symmetrical in the EE azido ligands but are asymmetric in the EO ligands. The bite angle exhibited by the dmbpy ligand (72.26 (11) • ) is the largest distortion in the geometry of the cis-octahedral coordination sphere. The four-membered Mn 2 (EO-N 3 ) 2 ring is planar as a result of the inversion center.…”

“…In the bridging mode, dinuclear compounds can be formed, like in M(azide) 2 M species [10], as depicted in Figure 1, but also polynuclear compounds, including polymeric linear or zig-zag species of formula •••(azide) 2 M(azide) 2 M(azide) 2 •••. Mixed species with both terminal (non-bridging) and bridging azide are known in the literature [8,[11][12][13][14], but are not so common.…”

“…In the bridging mode, dinuclear compounds can be formed, like in M(azide)2M species [10], as depicted in Figure 1, but also polynuclear compounds, including polymeric linear or zig-zag species of formula •••(azide)2M(azide)2M(azide)2 •••. Mixed species with both terminal (non-bridging) and bridging azide are known in the literature [8,[11][12][13][14], but are not so common. In earlier reports from our laboratories, we have given attention to metal-azide compounds as bridging ligands for dinuclear compounds, or higher aggregates up to 2D networks [15][16][17][18] and we have found both ferromagnetic and antiferromagnetic cases.…”

catena-Poly[[chlorodipyridinemanganese(II)]-μ3-6-oxo-1,6-dihydropyridine-2-carboxylato]

“…Bridging carboxylates, which are a common feature of these complexes, are interesting ligands, both because of their ability to assume a large range of coordination modes and because of their biological relevance (Christou et al, 1989;Wieghardt, 1989;Rardin et al, 1991;Akhriff et al, 1999). Low-dimensional extended structures (one-dimensional, chain-like) have attracted particular interest due to their speci®c structural features and unusual non-linear optical and magnetic properties (Chen et al, 1993;Cox et al, 1998;Monfort et al, 2000;Matouzenko et al, 2003). 2-Pyridone derivatives have been extensively studied since they cause base mispairing and enzymatic reactions related to bifunctional catalysis (Beak et al, 1976), and show excellent pharmacodynamic properties, justifying the view that this is a very promising new class of totally synthetic antibacterial agents (Li et al, 2000).…”