Versatile coordination modes of bis[5-(2-pyridine-2-yl)-1,2,4-triazole-3-yl]alkanes in Cu(ii) complexes (original) (raw)
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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.
Inorganic Chemistry, 2010
Two mixed bridged one-dimensional (1D) polynuclear complexes, [Cu 3 L 2 (μ 1,1 -N 3 ) 2 (μ-Cl)Cl] n (1) and {[Cu 3 L 2 (μ-Cl) 3 Cl] 3 0.46CH 3 OH} n (2), have been synthesized using the tridentate reduced Schiff-base ligand HL (2-[(2dimethylamino-ethylamino)-methyl]-phenol). The complexes have been characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. In both complexes the basic trinuclear angular units are joined together by weak chloro bridges to form a 1D chain. The trinuclear structure of 1 is composed of two terminal square planar [Cu(L)(μ 1,1 -N 3 )] units connected by a central Cu(II) atom through bridging nitrogen atoms of end-on azido ligands and the phenoxo oxygen atom of the tridentate ligand. These four coordinating atoms along with a chloride ion form a distorted trigonal bipyramidal geometry around the central Cu(II). The structure of 2 is similar; the only difference being a Cl bridge replacing the μ 1,1 -N 3 bridge in the trinuclear unit. The magnetic properties of both trinuclear complexes can be very well reproduced with a simple linear symmetrical trimer model (H = -JS i S iþ1 ) with only one intracluster exchange coupling (J) including a weak intertrimer interaction (j) reproduced with the molecular field approximation. This model provides very satisfactory fits for both complexes in the whole temperature range with the following parameters: g = 2.136(3), J = -93.9(3) cm -1 and zj = -0.90(3) cm -1 (z = 2) for 1 and g = 2.073(7), J = -44.9(4) cm -1 and zJ 0 = -1.26(6) cm -1 (z = 2) for 2.
Three copper-azido complexes [Cu 4 (N 3 ) 8 (L 1 ) 2 (MeOH) 2 ] n (1), [Cu 4 (N 3 ) 8 (L 1 ) 2 ] (2), and [Cu 5 (N 3 ) 10 (L 1 ) 2 ] n (3) [L 1 is the imine resulting from the condensation of pyridine-2-carboxaldehyde with 2-(2-pyridyl)ethylamine] have been synthesized using lower molar equivalents of the Schiff base ligand with Cu(NO 3 ) 2 ·3H 2 O and an excess of NaN 3 . Single crystal X-ray structures show that the basic unit of the complexes 1 and 2 contains Cu II 4 building blocks; however, they have distinct basic and overall structures due to a small change in the bridging mode of the peripheral pair of copper atoms in the linear tetranuclear structures. Interestingly, these changes are the result of changing the solvent system (MeOH/H 2 O to EtOH/H 2 O) used for the synthesis, without changing the proportions of the components (metal to ligand ratio 2:1). Using even lower proportions of the ligand, another unique complex was isolated with Cu II 5 building units, forming a two-dimensional complex (3). Magnetic susceptibility measurements over a wide range of temperature exhibit the presence of both antiferromagnetic (very weak) and ferromagnetic exchanges within the tetranuclear unit structures. Density functional theory calculations (using B3LYP functional, and two different basis sets) have been performed on the complexes 1 and 2 to provide a qualitative theoretical interpretation of their overall magnetic behavior.
Inorganic chemistry, 2006
Reactions of two hydrated cupric salts (CuCl(2).2H(2)O and Cu(ClO(4))(2).6H(2)O) with three azopyridyl ligands, viz. 2-[(arylamino)phenylazo]pyridine [aryl = phenyl (HL(1a)), p-tolyl (HL(1b)), and 2-thiomethyl phenyl (HL(1c))], 2-[2-(pyridylamino)phenylazo]pyridine (HL(2)), and 2-[3-(pyridylamino)phenylazo]pyridine (HL(3)), afford the mononuclear [CuClL(1)] (1), dinuclear [Cu(2)X(2)L(2)(2)](n)()(+) (X = Cl, H(2)O, ClO(4); n = 0, 1; 2, 3), and polynuclear [CuClL(3)](n)() (4) complexes, respectively, in high yields. Representative X-ray structures of these complexes 1-4 are reported. X-ray structure analysis of 4 reveals an infinite 1D zigzag chain that adopts a saw-tooth-like structure. Variable-temperature cryomagnetic measurements (2-300 K) on the complexes 2-4 have revealed weak magnetic interactions between the copper centers with J values -1.04, 9.88, and -1.31 cm(-1), respectively. Positive ion ESI mass spectra of the soluble complexes 1-3 are studied which provide the evidence...
Synthesis, Characterization and Stability Constants of Polynuclear Metal Complexes
Transition Metal Chemistry, 2000
Unsymmetric tridentate ligands, 4-methyl-2,6-di(4-methyliminomethyl)phenol (HL 1 ), 4-(t-butyl)-2,6-di(4-methylphenyliminomethyl)phenol (HL 2 ), 2,6-di(4-bromophenyliminomethyl)-4-methylphenol (HL 3 ), 2,6-di(4-bromophenyliminomethyl)-4-(t-butyl)phenol (HL 4 ), 2,6-di(4-hydroxyphenyliminomethyl)-4-methylphenol (HL 5 ) and 4-(tbutyl)-2,6-di(4-hydroxyphenyliminomethyl)phenol (HL 6 ), and their binuclear Cu II , Co II and Ni II complexes were synthesized and characterized by elemental analysis, FT-IR, u.v.-vis spectrometry magnetic moments, 1 H( 13 C)n.m.r. and mass spectral data. Also, the electrical conductivities of the complexes have been measured using 10 )3 M solutions in MeCN. The complexes are weak electrolytes. In the electronic spectra of the complexes of the HL 1 -HL 6 ligands, the 480-410 nm band has been determined as the charge-transfer band. While the HL 5 and HL 6 ligands have five potential donor atoms, other ligands have only three. Protonation constants of the ligands have been studied in dioxan-water mixtures. In addition, the antimicrobial properties of the ligands and their metal complexes have been studied: Bacillus megaterium, Micrococcus luteus, Corynebavterium xenosis, Enterococcus faecalis, bacteria and Saccoramyces cerevisia, yeast. The keto-enol tautomeric equilibria of the ligands have been investigated in polar and non-polar solvents.
Journal of the American Chemical Society, 1988
The preparation, crystal structures and magnetic properties of two copper(II) complexes with di-2-pyridylamine (dpa) as end-cap ligand and azide (1) and cyanate (2) as bridging groups, [Cu(dpa)(N 3 ) 2 ] n (1) and [Cu 2 (dpa) 2 (NCO) 4 ] (2), are reported. Compound 1 consists of uniform chains of copper(II) ions bridged by single l-1,1-azido groups whereas that of compound 2 is made up of centrosymmetric dicopper(II) units with double l-1,1-N-cyanate bridges, the other two cyanate groups acting as terminal ligands. The copper atoms in 1 and 2 are five-coordinated with two nitrogen atoms of a bidentate dpa ligand (1 and 2), one nitrogen atom from a terminally bound azide (1)/cyanate (2) and two other nitrogens from two azide (1)/cyanate (2) bridges building intermediate square pyramidal/trigonal bipyramidal (1) and distorted square pyramidal (2) surroundings. The values of the copper-copper separation through the double end-on azido (1) and cyanato (2) bridges are 3.8556(4) and 3.5154(5) Å , respectively. Variable-temperature magnetic susceptibility measurements show the occurrence of weak magnetic interactions in both complexes being antiferromagnetic in 1 [J = À4.60 cm À1 , the Hamiltonian is defined aŝ H ¼ ÀJ P iŜ i ÁŜ iþ1 ] and ferromagnetic in 2 [J = +3.14 cm À1 withĤ ¼ ÀJŜ 1 ÁŜ 2 ]. The magnitude and nature of these magnetic interactions are discussed in the light of the respectives structures and they are compared with those reported for related systems.
European Journal of Inorganic Chemistry, 1999
The ditopic ligand 3 has been synthesized. In its crystallography. Magnetic studies of complex 1 indicate a very weak antiferromagnetic coupling between the deprotonated form, it reacts with copper(II) ions to form a tetranuclear complex 1 of the [2 × 2] Cu II 4 grid type, the phenoxo-bridged Cu II ions. structure of which has been confirmed by X-ray Self-assembly of suitably designed ligands with tran-occurs through a super-exchange mechanism, with the hydroxo bridge acting as the primary pathway for ex-sition-metal ions allows the creation of inorganic architectures with well-defined structures in a spontaneous but di-change. [8] Most hydroxo-bridged copper(II) complexes are pentacoordinated and typically exhibit square-pyramidal or rected manner. [1] One of the aims of supramolecular chemistry is the formation of assemblies that may possess inter-trigonal-bipyramidal geometries. Here, we report the synthesis, structural details, and magnetic properties of 1, esting physical properties. Previously, we have reported the self-assembly of metal [LCu] 4 (CF 3 SO 3) 4 , a tetrametallic copper(II) complex of the [2 ϫ 2] grid type, where the copper atoms adopt a distorted complexes of rack-[2] and grid-type [3] geometries, where the metal ions are bridged by pyrimidine rings. The metallic bipyramidal geometry and are bridged by the phenolate oxygen atom of the ionized form L Ϫ of ligand 3. Recently, centers in these arrays are located at appropriate distances (6.16Ϫ6.50 Å) such as to allow electronic interaction, which an Mn 2ϩ complex of the [2 ϫ 2] grid type with a ligand similar to 3, but where the metal centers are bridged by is manifested in the physical properties of the complexes such as redox potentials, [2,3] optical, [4] and magnetic [5] fea-non-conjugated alkoxide-type oxygen atoms, has been reported. [9] tures. In order to enhance the coupling between the metalion centers compared to that provided by a pyrimidine group, and to obtain inorganic architectures exhibiting new properties, we have explored the use of ligands that introduce oxygen bridges between the coordination binding sites. Oxo-bridged binuclear copper(II) complexes have been extensively studied as a result of the magnetic properties arising from ferromagnetic or antiferromagnetic spin-coupling between the copper ions, [6] which depend strongly on the geometry of the CuϪOϪCu bridge (CuϪCu distances and bridge angles). While a linear correlation of the magnetic exchange parameter J with bridge angle Φ is wellestablished for dihydroxo-bridged copper(II) complexes with square-pyramidal d x 2 Ϫy 2 electronic ground states, this might not be the case for monohydroxo-bridged complexes with a different electronic ground state (i.e. trigonal-bipyramidal, d z 2). [7] The antiferromagnetic coupling observed for most monohydroxo-bridged complexes is larger than that found for di-µ-hydroxocopper(II) complexes and normally