title: Two EE-azido-bridged nickel(II) layered compounds: vigorous twisted torsion angle Ni-N3-Ni results in ferromagnetic behavior.
abstract: Two coordination polymers, Ni(endi)(N(3))(2) (endi = 1,2-bis(tetrazol-1-yl)ethane) (1) and Ni(4-acpy)(2)(N(3))(2) (4-acpy = 4-acetylpyridine) (2), are obtained by employing a couple of cobalt complex as references. 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 tau value 88.3 degrees and 107.6 degrees for 1 and 89.2 degrees for 2. Different from most EE azide compounds, ferromagnetism is distinctly present, ordering below T(c) = 25 K for 1 and T(c) = 23 K for 2. Fitting of magnetic susceptibility data using the spin Hamiltonian H = -2J SigmaS(1)S(2) 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.
authors: Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, People's Republic of China.
authors: Ru-Yin
authors: RY
authors: Li
authors: Bing-Wu
authors: BW
authors: Wang
authors: Xin-Yi
authors: XY
authors: Wang
authors: Xiu-Teng
authors: XT
authors: Wang
authors: Zhe-Ming
authors: ZM
authors: Wang
authors: Song
authors: S
authors: Gao