Synthesis, crystal structures and magnetic behaviors of two dicyanamide bridged di- and polynuclear complexes of cobalt(II) derived from 2,4,6-tris(2-pyridyl)1,3,5-triazine and imidazole (original) (raw)
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Four new Co(II) containing coordination polymers have been synthesized using an ether bridged tricarboxylic acid ligand, o-cpiaH 3 (5-(2-carboxy-phenoxy)-isophthalic acid). This ligand readily reacts with CoCl 2 ·6H 2 O in the presence of different nitrogen donor ligands such as 1,10-phenanthroline (phen), 4,4′-bipyridyl (bpy), 4,4′azopyridine (apy), and 1,4-bis(4-pyridinylmethyl)piperazine (bpmp) under hydrothermal conditions to afford three 3D and one 2D coordination polymers,
Structure and magnetism of coordination polymers containing dicyanamide and tricyanomethanide
2003
Coordination polymers containing dicyanamide (N(CN) 2 − , dca) or tricyanomethanide (C(CN) − 3 , tcm) bridging ligands are described from the perspective of their structure and magnetism. The binary compounds ␣-M(dca) 2 form an isostructural series (M = Cr, Mn, Fe, Co, Ni, Cu) having a single rutile-like network that involves 1,3,5 -dca bridging. They display quite diverse types of long-range magnetic order viz. canted-spin antiferromagnets (Cr, Mn, Fe), ferromagnets (Co, Ni, Cu). An up-to-date review is given of the diverse range of physical measurements made on the ␣-M(dca) 2 series together with interpretations for the different net exchange coupling and consequent 3D order. The doubly interpenetrating rutile network M(tcm) 2 series generally do not show long-range order except for a few members at very low temperatures. The 'mixed' self-penetrating network compounds M(dca)(tcm) do show long-range order (M = Co, Ni), albeit at lower T c values than for the M(dca) 2 parents. Modification of the M-dca networks is possible by incorporation of coligands into the structures. Ternary species of type M(dca) 2 (L) n , where L is a terminal (e.g. pyridine, MeOH) or a bridging (e.g. pyrazine, 4,4 -bipyridine) coligand, display a diverse range of 1D, 2D and 3D structural types. With a few exceptions, the large number of compounds structurally characterised contain 1,5 -dca bridging and display very weak antiferromagnetic coupling (J < ca. −1 cm −1 ), typical of this bridging mode. Compounds such as Mn(dca) 2 (pyrazine) display a magnetic phase transition at low temperatures. This is also the case in the isostructural 2D layer compounds M(dca) 2 (H 2 O) · phenazine (M = Fe, Ni) which, perhaps not surprisingly, do not have coordinated phenazines but, rather, phenazines intercalated between layers of M(dca) 2 (H 2 O) in which 1,3,5 and 1,5 -dca bridging exists. Anionic networks of types M(dca) − 3 and M(dca) 2− 4 formed by templation around cations of the organic (e.g. Ph 4 E + , R 4 N + ) or inorganic (M(2,2 -bipyridine) 2+ 3 ) types are described.
Inorganic Chemistry, 2009
Structural characterization of the newly synthesized complexes [M II (L 1 OO)(xH 2 O)][ClO 4 ] • 2H 2 O [M) Co, x) 1 (1); M) Cu, x) 0 (2); L 1 OO-) 3-[(2-(pyridin-2-yl)ethyl){2-(pyridin-2-yl)methyl}amino]propionate] reveals that 1 and 2 are 1D chainlike coordination polymers. A tridentate variety of this ligand afforded a discrete tetranuclear complex {[Cu II (L 2 OO)(OClO 3)]} 4 • MeCN (3) [L 2 OO-) 3-[N-methyl-{2-(pyridine-2-yl)ethyl}amino]propionate]. Analysis of the crystal packing diagrams reveals extensive π-π stacking in 1 and C-H • • • O hydrogen bonding interactions in 3, leading to the formation of network structures. For these complexes, absorption spectral properties have been investigated. All three complexes exhibit exchange interaction between the M II ions through a syn-anti bridging carboxylate pathway. Magnetic studies on 1 show spontaneous magnetization below 5 K, which corresponds to the presence of spin-canted antiferromagnetism. At T) 2 K, the values of coercive field (H c) and remnant magnetization (M r) are 200 G and 0.019 µ B , respectively. Analysis of the magnetic data through spin Hamiltonians in the form Ĥ) ∑ i<j n-J ij Ŝ i Ŝ j (J is positive for a ferromagnetic interaction and negative for an antiferromagnetic interaction) leads to the following set of best-fit parameters: J)-2.65(2),-0.66(1), and +12.2(2) cm-1 for 1, 2, and 3, respectively. An attempt has been made to rationalize the observed magnetic behavior.
Two new 1-D dicyanamide bridged polymeric complexes [Mn(μ1,5-dca)2(salicyh)2]n and {Ni(μ1,5-dca)(TTA)}n (dca=dicyanamide, ; salicyh=salicylic hydrazide; TTA=triethylenetetramine): Synthesis, structures and magnetic studies
Inorganica Chimica Acta, 2005
Yap, et al.. Two new 1-D dicyanamide bridged polymeric complexes [Mn(µ1,5-dca)2(salicyh)2]n and [Ni(µ1,5dca)(TTA)](ClO4)n (dca = dicyanamide, ; salicyh = salicylic hydrazide; TTA = triethylenetetramine): Synthesis, structures and magnetic studies. Inorganica Chimica Acta, Elsevier, 2005, vol. 358, n15, p.
Inorganica Chimica Acta, 2006
Synthesis, spectroscopic and magnetic properties, and X-ray crystal structures of two copper(II) polymers Cu(2-qic)Br (2-qic = quinoline-2-carboxylate) (1) and Cu(2-pic)Br (2-pic = pyridine-2-carboxylate) (2) are described. These compounds are isostructural with Cu(2-qic)Cl and Cu(2-pic)Cl, respectively, the X-ray crystal structures of which were reported recently. Both complexes are polynuclear copper(II) compounds (1D and 2D, respectively) based on syn-anti carboxylate bridges and additionally on linear monobromo-(in 1) and dibromo-bridging (in 2) motifs. The magnetic properties were investigated in the temperature range 1.8-300 K. They reveal the occurrence of strong antiferromagnetic coupling (J 1 = À102.5 cm À1 ) through the single bromo-bridge in 1, which is much stronger than that transmitted by the single chloro-bridge (J = À57.0 cm À1 ). Very weak ferromagnetic interaction through the syn-anti carboxylate bridge J 2 is expected as it was observed in isomorphous Cu(2-qic)Cl (J = 0.37 cm À1 ). For 2 a weak ferromagnetic couplings through the syn-anti carboxylate (zJ 0 = 1.35 cm À1 ) and dibromo-bridges (J = 8.31 cm À1 ) were found. The experimental results indicate that the observed ferromagnetic exchange through dibromo-bridge is weaker than that in the chloride analog (J = 15.0 cm À1 ). The magnitude of magnetic interactions is discussed on the basis of structural data of compounds 1 and 2 and their halide analogues.
Polyhedron, 2001
Anionic metal tris-dicyanamide complexes of type (Ph 4 As)[M(dca) 3 ], where M = Co(II) and Ni(II) have been synthesised and characterised by X-ray crystallography, powder diffraction and detailed magnetic measurements. The anions form extended sheets with (4,4) connectivity and octahedral geometry about individual d-block ions. The cations lie in between the sheets and display cation-cation interactions of the p···p and 'multiple phenyl embrace' types. The nickel(II) complex, (Ph 4 As)[Ni(dca) 3 ], displays long-range magnetic order, with an ordering temperature of 20.1 K. (Ph 4 As)[Co(dca) 3 ], in contrast, did not show long-range order, but did show unusual field dependence of the magnetic moments at temperatures below 20 K. The syntheses also yield a second, needle-shaped product, (Ph 4 As) 2 [M 2 (dca) 6 (H 2 O)]·H 2 O·xCH 3 OH, which could be separated. They are isostructural and contain ladder-like 1D polymers which are cross-linked by hydrogen bonding into sheets; these sheets are separated by layers of cations. The cation layers again show multiple phenyl embraces and other supramolecular interactions. Magnetic studies on these hydrate-methanolate species show that they do not display long range order but, rather, very weak coupling.
Crystal Growth & Design, 2004
The crystal structures of M(dca) 2 (Mepyz) 2 ‚H 2 O, M ) Co (1), Ni (2), dca ) dicyanamide, N(CN) 2 -, and Mepyz ) methylpyrazine; [Mn(dca) 2 (Mepyz) 2 ][Mn(dca) 2 (Mepyz)] 2 ‚2MeCN (3); and Mn 2 (dca) 3 (NO 3 )(Mepyz) 2 (4) are reported. Compounds 1 and 2 are isomorphous and consist of two-dimensional (2D) (4,4) sheets, with bridging µ 1,5dca ligands and trans-disposed monodentate Mepyz ligands. Compounds 3 and 4 were obtained as an intimate mixture from the same reaction mixture. Compound 3 contains both one-dimensional (1D) chains, in which Mn atoms are bridged by double µ 1,5 -dca bridges and the Mepyz ligands are trans and monodentate, and 2D (4,4) sheets, in which similar 1D chains are connected by bridging Mepyz ligands. The structure of 4 contains two interpenetrating 4,6-connected three-dimensional networks, with bridging µ 1,5 -dca anions, bridging Mepyz ligands, and chelating NO 3anions. Only very weak coupling and no long-range magnetic ordering intrinsic to these materials were observed for 1 or 2, although traces of the ferromagnets R-Co(dca) 2 and R-Ni(dca) 2 were observable in very small applied fields, with ordering temperatures at 9 and 21 K, respectively.
Dalton Transactions, 2009
Five new complexes were obtained from solution or hydrothermal reactions of M(OAc) 2 (M = Mn, Cu and Cd) or CuCl 2 with 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (abpt) and NaN 3 or 1,3,5-benzenetricarboxylic acid (btcH 3 ) in different molar ratios. Structural analysis reveals that Cd(abpt) units in [Cd(abpt)(m 1,1 -N 3 ) 2 ] n (1) are bridged by double m 1,1 end-on (EO) azides into 1D zigzag coordination chains. Similar structural motifs, i.e. the chelation of abpt to the metal center and the double bridges of EO azides, are found in [Mn 4 (abpt) 4 (m 1,1 -N 3 ) 8 (H 2 O) 2 ] (2). The terminal aqua molecules and the monodentate N 3 groups lead to the formation of a tetranuclear complex rather than a polymeric compound. The abpt underwent deamination in the presence of copper ions during the process of coordination and became 3,5-bis(pyridin-2-yl)-1,2,4-triazolate (bpt-H) in 3-5. [Cu 4 (bpt-H) 4 (N 3 ) 4 ]·4.5H 2 O (3) is a neutral tetranuclear grid-like complex, in which the azides act as monodentate ligands. A similar [Cu 4 (bpt-H) 4 ] 4+ grid-like unit was found in [Cu 4 (bpt-H) 4 (m-btcH)Cl 2 ]·2H 2 O (4) and a pair of symmetry-related copper atoms are bridged by the m-btcH 2 coligand in a butterfly-shaped structure. In [Cu 2 (bpt-H)(m 6 -btc)(H 2 O)] n (5), the tetranuclear {Cu 4 (m-bpt-H) 2 (m 3 -carboxylate) 2 } 4+ units are bridged by m 6 -btc 3ligands in a 2D step-like layer structure. Temperature-dependent magnetic susceptibility measurements reveal that the double m 1,1 -N 3 bridges in 2 transmit the ferromagnetic interactions between Mn 2+ centers (J 1 = J 2 = +3.09(4) cm -1 , g Mn(II) = 2.02(1)), and the m-(bpt-H)bridges transmit moderate antiferromagnetic interactions in both 3 (J = -12.78(13) cm -1 ) and 4 (J 1 = -14.96(11) cm -1 ). In 4 the antiferromagnetic coupling via the m-btcH 2bridge was found as the second coupling pathway (J 2 = -9.48(7) cm -1 ). The coexistence of ferromagnetic and antiferromagnetic coupling between four Cu 2+ centers occurs in 5 (J 1 = -0.88(3) cm -1 and J 2 = +5.01(2) cm -1 ). The magneto-structural relationship for tetranuclear copper pyrazolate/triazolate compounds has been discussed. † Electronic supplementary information (ESI) available: : XRPD data for 2-5; : 2D hydrogen-bonded layer in 2; : crystal structure of 3; : crystal structure of 4; : coordination layer in 5; : bond lengths and angles of 1-5. CCDC reference numbers 741068-741072. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/b914702k ligand in the field of magnetic materials since the mid 1980s. 3 Besides five N-donor coordination sites, abpt contains three potentially conjugated aromatic rings and is likely to chelate two metal ions in the shortest M-N-N-M bridge. It is expected that an antiferromagnetic coupling would occur via the 1,2,4triazolate-N,N¢ bridge as the magnetic d(x 2 -y 2 ) orbitals for the metal ions are coplanar and overlap with the s orbitals of the coplanar bridging 1,2,4-triazole fragments. 4-6 So far, many abpt-containing metal complexes have been synthesized, 7 most of which are mono-or di-nuclear complexes. 3a,3d,8 Noteworthy cases are the widely studied spin-crossover [Fe(abpt) 2 (X) 2 ] (where X = SCN -, SeCNor N(CN) 2 -, TCNQ -) and [Fe(abpt) 2 (tcpd)] (tcpd = C[C(CN) 2 ] 3 2-). 9 In the previous study we have reported an interesting tetranuclear nickel-abpt complex [Ni 4 (abpt) 2 (abpt-H)(N 3 ) 5 (OAc) 2 ]·5H 2 O, in which an overall ferromagnetic coupling between Ni 2+ centers was found through the slightly dominative ferromagnetic interaction via the (m 1,1 -N 3 ) 2 (m-OAc) and (m 1,1 -N 3 )(m 1,1 -NH abpt-H )(m-OAc) bridges versus the antiferromagnetic interaction via the abpt Ni-N-N-Ni bridges. 8c Here we report the reactivity of this multi-dentate ligand and utilized it for new magnetic metal-organic materials.
Crystal Growth & Design, 2006
1,2,4,5-Benzenetetracarboxylic acid (H 4 btec) and a combination of N-donor coligands, such as 4-aminopyridine (4apy), pyrazine (pyz), 2,4,6-tris(2-pyridyl)-1,3,5-triazine (tptz), and 4,4′-bipyridine (4,4′-bipy) with transition metal ions Co(II) and Cu(II), give rise to five coordination complexes namely, [{Co(H 2 . All these complexes form supramolecular frameworks through ligand-based hydrogen bonding interactions. They have been characterized by a combination of analytical, spectroscopic, and crystallographic methods. These highly crystalline complexes have been obtained under different pH conditions at room temperature and the btec binding mode differs in these five complexes. Complex 1 is a one-dimensional (1D) layered solid consisting of alternating neutral metal-organic coordination polymeric chains, [Co(H 2 btec)(H 2 O) 4 ] n , and amines whereas the molecular structure of 2 is made up of alternating layers of anionic [Cu(btec)(4apy) 2 ] 2n coordination polymers and 4-apy cations (4-Hapy). In both 1 and 2, btec links the metal centers. Complex 3 is composed of zigzag 1D copper chains, and complex 4 is a mononuclear cobalt complex. In both 3 and 4, btec binds as a monodentate ligand. In the crystal structure of 5, btec 4is present unbound in the lattice and linked to 1D chains of [Co(4,4′-bipy)(H 2 O) 4 ] 2+ through strong hydrogen bonding interactions. The magnetic properties of the polymers were investigated in the temperature range 300-2 K. The values for the spin coupling constant J were estimated to be -0.60, -0.50, -0.79, and -5.72 cm -1 for 1-3 and 5, respectively, indicative of antiferromagnetic interactions.