ABSTRACT
New monodimensional Co(II)/azido systems with unusual topological ferrimagnetic response have been characterised.
ABSTRACT
A new polynuclear azido-bridged Co(II) compound with formula [Co(2)(N(3))(4)(HMTA)(H(2)O)](n) (1) (HMTA = hexamethylenetetramine) has been structurally and magnetically characterized. The compound 1 crystallizes in the monoclinic system C2/m space group, and consist of a complex three-dimensional system in which end-to-end and end-on azido bridging ligands between the Co(II) atoms coexist. The HMTA ligand is also linking three different Co(II) atoms. The network analysis shows for 1 a three- and six-connected network topology not previously reported. The magnetic properties of 1 are also reported, and it was found that the magnetic interactions define another new three- and four-connected net assigned as a (6.8(2))(6(4).10(2))-tfo net. In the high temperature region the chi(M) versus T plot can be fitted by using the Curie-Weiss law, and the best fit theta value is -26.6 K. For 1 magnetic ordering and spontaneous magnetization is achieved below T(c) = 15.6 K.
ABSTRACT
The syntheses, structural characterization, and magnetic behaviour of three new 3D manganese(II) complexes with the empirical formulae [Mn(N3)2(5-Brpym)]n (1), [Mn(N3)2(Mepyz)]n (2) and [Mn(N3)2(2-acpy)]n (3), (5-Brpym=5-bromopyrimidine, Mepyz=methylpyrazine, 2-acpy=2-acetylpyridine), are reported. In 1, each manganese atom is linked to the four nearest neighbours by only end-to-end azido bridges, forming square layers. These layers are further connected to 3D networks by the N,N'-bridging ligand. In 2, Mn2(micro(1,1)-N3)2 subunits are connected to the four nearest neighbours by end-to-end azido bridges to form a 3D Mn-azido-sublattice. The Mn2(micro(1,1)-N3)2 subunits are further linked by pairs of N,N'-bridging Mepyz ligands to form 1D ribbons extended along the c-axis of the unit cell. The Mepyz pairs show pi-pi-interactions. In 3, the only end-to-end azido bridges form a diamondoid-like 3D Mn-azido-sublattice. The magnetic properties of 1-3 are reported. At high temperatures, the plots of chiM or chiMTvs.T for can be fitted as a homogeneous 2D system with J=-5.4 cm(-1), g=2.05. Also, at high temperatures the plots of chiM or chiMTvs.T for compound can be fitted with the simple cubic expansion series with J=-1.6 cm(-1), g=2.04. Compound 1 shows spontaneous magnetization below Tc=45 K, which corresponds to the presence of spin-canted antiferromagnetism, whereas 2 and 3 do not show spontaneous magnetization up to 2 K.
ABSTRACT
The syntheses, structural characterization, and magnetic behavior of five new 2D manganese(II) complexes with empirical formulas [Mn(N(3))(2)(2,6-DiMepyz)(H(2)O)](n)() (1), [Mn(N(3))(2)(Etpyz)(H(2)O)](n)() (2), [Mn(N(3))(2)(H(2)O)(2)](n)()(2,3-DiMepyz)(n)() (3), [Mn(N(3))(2)(Clpyz)(2)](n)() (4), and [Mn(N(3))(2)(Ipyz)(2)](n)() (5) (pyz = pyrazine (1,4-diazine)) are reported. 1 crystallizes in the monoclinic system, space group P2(1)/c, with unit cell parameters a = 7.513(4) A, b = 17.438(7) A, c = 8.404(4) A, beta = 94.53(4) degrees , and Z = 4. 2 crystallizes in the triclinic system, space group P, with unit cell parameters a = 7.386(2) A, b = 8.434(2) A, c = 9.442(3) A, alpha = 71.82(2) degrees , beta = 72.08(2) degrees , gamma = 88.54(2) degrees , and Z = 2. 3 crystallizes in the monoclinic system, space group C2/c, with unit cell parameters a = 20.438(7) A, b = 7.711(2) A, c = 7.457(2) A, beta = 93.76(3) degrees , and Z = 4. 4 crystallizes in the orthorhombic system, space group Pbca, with unit cell parameters a = 8.600(2) A, b = 13.440(4) A, c = 24.083(7) A, and Z = 8. 5 crystallizes in the orthorhombic system, space group Pbca, with unit cell parameters a = 8.521(2) A, b = 13.787(3) A, c = 26.237(5) A, and Z = 8. The compounds 1-5 have only azido bridging ligands. In 1-3 each manganese atom is linked to the four nearest neighbors by only end-to-end azido bridges, forming square layers. 4 and 5 show alternating end-to-end and end-on azido bridges between manganese atoms. The magnetic properties of 1-5 are reported. At high temperatures the plots of chi(M) or chi(M)T vs T for the 1-3 compounds can be fitted as homogeneous 2D systems with J = -4.9, -4.4, and -3.9 cm(-)(1) for 1-3, respectively. For 1, 3, and 5 magnetic ordering and spontaneous magnetizations is achieved below T(c) = 35, 29, and 22 K, respectively, whereas 2 and 4 do not show spontaneous magnetization up to 2 K.
