Double Azido Bridges Research Articles

Structural and magnetic behavior of mono- and dinuclear nickel (II) complexes of N, N′-bis-(3,5-dipiperidin-1-yl-[2,4,6]triazin-1-yl)-pyridin-2-ylmethyl-ethane-1,2-diamine

Reaction of nickel (II) perchlorate with the ligand N, N′-bis-(3,5-dipiperidin-1-yl-[2,4,6]triazin-1-yl)-pyridin-2-ylmethyl-ethane-1,2-diamine yields an octahedral Ni(II) high-spin complex 1 ([C 40H 56N 14Ni(H 2O)(CH 3OH)](ClO 4) 2(CH 3OH) 2) with moderate zero-field splitting (ZFS) axial distortion parameter D/ k B = 5.37 K. The ligand contributes a N4 donor set; the remaining two coordinating positions are occupied by coordinating solvents molecules. Exchange of the coordinating solvents molecules in complex 1 to thiocyanate moieties leads to formation of complex 2 ([C 40H 56N 14Ni(NCS) 2](CHCl) 3) with an extended parameter D/ k B = 8.80 K. The analysis of the structural and magnetic properties of complexes 1 and 2 led to the design of dinuclear complex 3 ([C 40H 56N 14NiN 3] 2(ClO 4) 2(CH 3OH) 2), where two azido groups were utilized as bridging ligands. The double azido bridges in complex 3 cross each other to form a rarely observed non-coplanar (N 3) 2 structure. The magnetic behavior of complex 3 reveals ferromagnetic coupling interactions characterized by J/ k B = 23.25 K, D 1/ k B = 7.90 K, D 2/ k B = 0.54 K.

Four [Cd(L) 2(N 3) 2] n 1D systems with different azide bridging sequences: Synthesis, spectral and structural characterization

Four new cadmium(II) complexes: [Cd(4-Etpy) 2(N 3) 2] n ( 1) (4-Etpy = 4-ethylpyridine), [Cd(3-acpy) 2(N 3) 2] n ( 2) (3-acpy = 3-acetylpyridine), [Cd(4-OHMepy) 2(N 3) 2] n ( 3), (4-OHMepy = 4-hydroxymethylpyridine) and [Cd(3-OHMepy) 2(N 3) 2] n ( 4), (3-OHMepy = 3-hydroxymethylpyridine), are synthesized and structurally characterized. The IR spectra of the complexes are measured and discussed. The single crystal X-ray diffraction revealed that all of these four complexes exhibit 1D [Cd 2(N 3) 2] n chains, six-coordinate cadmium centers and trans arrangement of the two pyridines. In the structure of 1, the azide groups in the double bridges are alternately in the μ-1,3 and μ-1,1 modes between neighboring cadmium atoms, whereas in 2 the chain is formed only from double μ-1,1 azide bridges. In the structure of 3, the double azido bridges show the unprecedented –Cd-(μ-1,1-N 3) 2–Cd-(μ-1,1-N 3) 2–Cd-(μ-1,1-N 3) 2–Cd-(μ-1,3-N 3) 2–Cd– sequence. In the structure of 4, each pair of cadmium centers is simultaneously bridged by two different azides: μ-1,1 and μ-1,3 bridges. In the chain of polyhedra these μ-1,1 and μ-1,3 azido bridges are trans to each other. In all of the four complexes the μ-1,1 azides are asymmetric whereas the μ-1,3 azido ligands are more symmetric, and the azides of both types are almost linear within the experimental error.

A rare ferromagnetically coupled asymmetric doubly azido bridged copper(II) dimer with an N, N, O donor Schiff base

A new end-to-end (EE) doubly azido bridged dinuclear complex [Cu 2L 2(μ 1,3-N 3) 2] ( 1) [where L = ( E)-4-(2-(dimethylamino)ethylimino)-1,1,1-trifluoropentan-2-one)] has been synthesized and characterized by elemental and spectroscopic techniques. Single crystal X-ray diffraction analysis reveals that the dimeric complex possesses a center of inversion. Each copper atom in 1 is in a distorted square pyramidal geometry with a CuN 4O chromophore as revealed from the τ value, 0.19. The four basal positions are occupied by two imine N and one keto O atom of the Schiff base and one N atom from the azide anion. Another N atom from a coordinated azide occupies the apical position. Temperature dependent magnetic susceptibility of 1 was fitted using the Bleaney–Bowers expression which led to the parameters J = 13.6 cm −1 and R = 3.4 × 10 −5. It indicates a ferromagnetic interaction through the double azido bridges connecting the individual copper Schiff base units.

High-dimensional azido-bridged cadmium(ii) polymeric complexes with bis(bidentate) diazine ligands

Five new Cd(II)-azido polymeric complexes with bis(bidentate) diazine Schiff bases as auxiliary bridging ligands have been synthesized and crystallographically characterized. The differences in side constituents of the coligands lead to different diazine-bridged binuclear units and hence to three different types of polymeric networks, all being 3-connected nets. In complex 1, [Cd2(L1)2(N3)4]n (L1 = 1,4-bis(2-pyridyl)-2,3-diaza-1,3-butadiene), a single diazine ligand links two metal ions into a centrosymmetric binuclear unit, and each unit is connected with four neighbors via double azido bridges in the end-on (EO) mode, yielding 2-D layers with the (6,3) net topology. Complex 2, [Cd2(L2)2(N3)2]n(ClO4)n·nH2O (L2 = 1,4-bis(2-pyridyl)-1-amino-4-methyl-2,3-diaza-1,3-butadiene), shows a layer structure with the (6,3) net topology, but the binuclear unit contains two diazine bridges and the neighboring units are interlinked via single azido bridges in the end-to-end (EE) mode. The remaining three complexes, [Cd2(L)2(N3)4]n (L = 1,4-bis(2-pyridyl)-1-amino-2,3-diaza-1,3-butadiene for 3, 1-(2-pyridyl)-4-(2-pyrazinyl)-4-amino-1-methyl-2,3-diaza-1,3-butadiene for 4, and 2,5-bis(2-pyridyl)-3,4-diaza-2,4-hexadiene for 5), are isostructural and form the 3-D (10,3)-b net with three different connectors around each node (the cadmium ion): adjacent cadmium ions are alternately bridged by double EO azido bridges and mixed EO azido-diazine double bridges to produce a chain, and each chain is connected to four neighboring chains by single EE azido bridges to generate the 3D framework.

Topological ferrimagnetic behavior of two new [Mn(L)2(N3)2]n chains with the new AF/AF/F alternating sequence (L = 3-methylpyridine or 3,4-dimethylpyridine).

The reaction of manganese(II) and pyridine derivatives such as 3-methylpyridine (3-Mepy) and 3,4-dimethylpyridine (3,4-Dmepy) led to the new one-dimensional systems trans-[Mn(3-Mepy)2(N3)2]n (1) and trans-[Mn(3,4-Dmepy)2(N3)2]n (2). Compound 1 crystallizes in the monoclinic system, space group P2(1)/n, a = 11.201(3) A, b = 14.499(4) A, c = 14.308(4) A, Z = 6, and compound 2 crystallizes in the triclinic system, space group P1, a = 11.502(4) A, b = 14.246(5) A, c = 16.200(8) A, Z = 6. The two compounds show the same general one-dimensional arrangement of double azido bridges between neighboring manganese atoms with the unprecedented -Mn-(mu(1,3)-N3)2-Mn-(mu(1,3)-N3)2-Mn-(mu(1,1)-N3)2-Mn- sequence. Susceptibility and magnetization measurements reveal a ferrimagnetic-like behavior derived from the topology of the chain. A model of the Heisenberg chain, comprising classical spins coupled through alternating exchange interactions J1J1J2... is proposed to describe the magnetic behavior.