Two EE-Azido-Bridged Nickel(II) Layered Compounds: Vigorous Twisted Torsion Angle Ni—N3—Ni Results in Ferromagnetic Behavior.

Two coordination polymers, Ni(endi)(N3)2 (endi = 1,2-bis(tetrazol-1-yl)ethane) (1) and Ni(4-acpy)2(N3)2 (4-acpy = 4-acetylpyridine) (2), are obtained by employing a couple of cobalt complex as referances. Both compounds have similar 2D (4,4) EE azide-nickel layer structures, but different interlayer separations. Their EE azide bridges are vigorously twisted, with the torsion angle τ value 88.3° and 107.6° for 1 and 89.2 for 2. Different from most EE azide compounds, ferromagnetism is distinctly present, ordering below Tc = 25 K for 1 and Tc = 23 K for 2. Fitting of magnetic susceptibility data using the spin Hamiltonian H = —2JΣS1S2 gives the ferromagnetic intralayer coupling J = 14.70(6) cm-1 for 1 and 14.32(0) cm-1 for 2, respectively. The magnetostructural correlations of 1 have been calculated using the density function theory based method. The computational results are consistent with the trend of the experimental data. One possible mechanism was proposed to explain the emergence of ferromagnetism based on the theoretical studies, and the ferromagnet construction approach was also proposed accordingly. [ABSTRACT FROM AUTHOR]