One‑, Two‑, and Three-Dimensional Heterospin Complexes Consisting of 4‑(<i>N</i>-<i>tert</i>-Butyloxylamino)pyridine (4NOpy), Dicyanamide Ion (DCA), and 3d Metal Ions: Crystal Structures and Magnetic Properties of [M^II(4NOpy)_<i>x</i>(DCA)_<i>y</i>(CH₃CN)_<i>z</i>]_<i>n</i> (M = Mn, Co, Ni, Cu, Zn)

Solutions of 3d metal ion salts, M­(NO₃)₂, 4-(<i>N</i>-<i>tert</i>-butyloxylamino)­pyridine (<b>4NOpy</b>), and dicyanamide (DCA) in CH₃CN were mixed to afford single crystals of the polymeric complexes [M^II(<b>4NOpy</b>)_<i>x</i>(DCA)_<i>y</i>(CH₃CN)_{<i><b>z</b></i>}]_<i>n</i> (M^II = Mn (<b>1</b>), Co (<b>2</b>), Ni (<b>3</b>), Cu (<b>4a</b> and <b>4b</b>), Zn (<b>5</b>)). X-ray crystallography revealed that the crystal structures are a three-dimensional (3-D) network for <b>1</b>, 2-D networks for <b>2</b>, <b>3</b>, <b>4a</b>, and <b>5</b>, and a 1-D chain for <b>4b</b>. Crystals of <b>2</b>, <b>3</b>, <b>4a</b>, and <b>5</b> contained CH₃CN molecules as crystal solvents, which were readily desorbed in the ambient atmosphere. After desorption of the CH₃CN molecules, the crystal structures of <b>2</b> and <b>3</b> were confirmed to be slightly shrunk without destruction of the crystal lattice. Crystals of <b>2</b>, <b>3</b>, <b>4a</b>, and <b>5</b> after desorption of crystal solvents were used for investigations of the magnetic properties. Complex <b>1</b> showed antiferromagnetic interactions to form a ferrimagnetic chain and exhibited the magnetic behavior of a 2-D (or 3-D) spin-canted antiferromagnet with <i>T</i>_N = 12 K. Complex <b>2</b> containing anisotropic Co^II ions also showed the behavior of a 1-D (or 2-D) spin-canted antiferromagnet with <i>T</i>_N = 6 K. In <b>3</b>, <b>4a</b>, and <b>4b</b>, the aminoxyl of <b>4NOpy</b> ferromagnetically interacted with the metal ion with coupling constants of <i>J</i>_M–NO/<i>k</i>_B = 45, 45, and 43 K, respectively. In <b>5</b>, the magnetic couplings between the aminoxyls in <b>4NOpy</b> through the diamagnetic Zn^II ion were weakly antiferromagntic (<i>J</i>_NO–NO = −1.2 K). DCA might be a weak antiferromagnetic connector for the metal chains

Preparations, Crystal Structures, and Magnetic Properties of <i>N</i>,<i>N</i>-Dipyridylaminoxyl as a New Magnetic Coupler and Its One-Dimensional Cobalt(II) Chains

<i>N</i>,<i>N</i>-Dipyridilaminoxyl, <b>NOpy</b>_<b>2</b>, having a stable aminoxyl, was prepared as a new magnetic coupler for heterospin systems. Solutions of <b>NOpy</b>_<b>2</b> were mixed with those of bis­{1,1,1,5,5,5, hexafluoro-4-(phenylimino)-2-pentanonate}­cobalt derivatives, Co­(hfpip-X)₂, at a 1:1 ratio to afford the polymeric cobalt­(II) complexes, [Co­(hfpip-X)₂(<b>NOpy</b>_<b>2</b>)]_<i>n</i>; X = H (<b>1</b>), F (<b>2</b>), F₃ (<b>3</b>), F₅ (<b>4</b>), Cl (<b>5</b>), Cl₃ (<b>6</b>), Br (<b>7</b>), and I (<b>8</b>) as single crystals. In all complexes, the local structures of the cobalt-complex units were compressed octahedra and the pyridine ligands in <b>NOpy</b>_<b>2</b> units coordinated to the cobalt ions in trans configuration to form linear chains for <b>1</b>–<b>4</b> and in cis configuration to form helical chains for <b>5</b>–<b>8</b>. In the chains, the aminoxyl in <b>NOpy</b>_<b>2</b> ferromagnetically interacted with the cobalt ions to produce the ferromagnetic chains with <i>J</i>_intra/<i>k</i>_B = 9–14 K. In the magnetic susceptibility experiments of aligned sample of <b>6</b>, the magnetic easy axis was determined to be the <i>a</i>* axis, which was the direction perpendicular to the <i>b</i> axis of the chain axis. The resulting chains, all except <b>4</b>, interacted antiferromagnetically among each other, and especially in <b>1</b>, <b>5</b>, <b>7</b>, and <b>8</b>, the magnetic behaviors characteristic to canted two-dimensional (2D) antiferromagnets with <i>T</i>_c = 5.6, 4.0, 4.0, and 6.2 K, respectively, were observed. All complexes showed slow magnetic relaxations affected by the interchain antiferromagnetic interaction. The effective activation barriers, Δ_eff/<i>k</i>_B, for the reorientation of the magnetism for all complexes except <b>4</b> were estimated to be 25–39 K in the presence of a direct current (dc) field