Elongated Octahedral Geometry Research Articles

Slow magnetic relaxation of a {MnIIINaI}n zig-zag chain based single ion magnet

The synthesis using organic Schiff base ligands H2valen, and organic sulfonate ligands Na(4-HBS) in conjunction with Mn(Ac)3⋅2H2O, produces a one-dimensional coordination polymer with the formula {[Mn(valen)Na(4-HBS)2]⋅2CH3OH}n(1) [H2valen=6,6′-((1E,1′E)-(ethane-1,2-diylbis(azaneylylidene))bis(methaneylylidene))bis(2-methoxyphenol); Na(4-HBS)= Sodium 4-hydroxybenzenesulfonate]. Single crystal X-ray diffraction analysis reveals that complex 1 consist of neutral chains with one [Mn(valen)Na]2+ and two 4-HBS−moieties, in which the Mn(III) adopts an elongated octahedral geometry and Na(I) adopts a distorted pentagonal pyramid geometry, respectively. Magnetic investigations indicate the important magnetic anisotropy in the six-coordinated Mn(III) with the zero-field splitting parameter D = -3.2 cm−1. AC measurements suggest that complex 1 displays characteristics of slow magnetic relaxation under a 2000 Oe DC field, indicative of single ion magnet (SIM) behaviour. The effective energy barriers and the pre-exponential factor for complex 1 are determined to be 10.5 cm−1, and 1.36 × 10−7 s, respectively. This research reports not only a rare Mn(III) SIM molecular complex but also provide a potential approach to construct SIM chains.

Synthesis, Crystal Structure, and Optical Properties of a Trinuclear Zinc(II) Complex with Rhodamine B

A heteroleptic homotrinuclear complex, [Zn3(valhydr)2(RhB)2(EtOH)2](ClO4)2 (H2valhydr = 1,2-bis(2-hydroxy-3-methoxybenzylidene)hydrazine, RhB = rhodamine B), was synthesized and structurally characterized by X-ray diffraction on single crystal. In the centrosymmetric complex, the zinc ions are positioned in a linear manner. The external zinc ions are pentacoordinated with a distorted square pyramidal stereochemistry, while the central zinc ion presents an elongated octahedral geometry. Luminescent properties of the complex were investigated in solid state and solution.

Synthesis, structural characterization, and thermal properties of octahedral diperchlorato complexes of copper(II) with the chelating 2-aminomethylpiperidine and 2-aminomethylpyridine ligands

Two distorted octahedral copper(II) coordination compounds; [Cu(AMPp)2(OClO3)2] (1) and [Cu(AMP)2(OClO3)2] (2) (2-aminomethylpiperidine and 2-aminomethylpyridine) have been synthesized on a SP Sephadex C-25 cation exchanger resin for high purity. Their structures have been determined by single-crystal X-ray diffraction, fourier transform infrared spectroscopy, and also thermal analysis. In both structures, the metal center adopts an elongated octahedral geometry in which two chelating amine ligands occupy the square plane in a trans-position, and two perchlorate ligands occupy the axial sites. The thermal stability of both complexes is relatively high. However, the thermal stability of 2 with the aromatic ring was 12 °C higher, due to intermolecular hydrogen bonds, π⋯π, and π⋯O interactions.

Novel 1-D copper(II) coordination polymer based on 2,5-bis(pyridine-2-yl)-1,3,4-thiadiazole as bridging ligand: Synthesis, crystal structure, Hirshfeld surface analysis, spectroscopic characterizations and biological assessment

A new copper (II) mono-dimensional coordination polymer based on 2,5-bis(pyridine-2-yl)-1,3,4-thiadiazole (L) as bridging ligand, noted [CuLCl2]n, has been synthesized by reaction of L with copper salt (CuCl2·2H2O) and characterized by single crystal X-ray diffraction, Hirshfeld surface analysis, as well as UV–Visible, and FTIR techniques. The copper cation lies on an inversion centre and displays elongated octahedral coordination geometry. The equatorial positions are occupied by the N atoms of two ligands, whereas the axial positions are occupied by the chlorine atoms. The 1,3,4-thiadiazole and the pyridyl rings linked to the metal are approximately coplanar, with a maximum deviation from the mean plane of 0.330 (2) Å. The Cu2+ cations form the infinite chains parallel to c-axis and the organic molecules are linked to Cu atoms in zigzag chains building an infinity tape running along [0 0 1] direction. The cohesion of the polymeric complex structure is ensured by C–H⋯Cl weak hydrogen bonds and π–π interactions between pyridyl and thiadiazole rings forming a three-dimensional structure, as established by Hirshfeld surface analysis. This new 1-D copper coordination polymer exhibited elevated antimicrobial activity against several strains of the fungal phytopathogens Verticillium dahliae and Fusarium oxysporum fsp. melonis suggesting its use as a fungicide in crop protection.

One-dimensional coordination polymers constructed from copper(II) ions and chromato bridges: Synthesis, crystal structures and thermal analysis

Three 1D coordination polymers, 1∞[Cu(NH3)4CrO4] (1) and 1∞[CuL(H2O)(CrO4)](H2O)(C2H5OH)0.5 with L = bipy (2) and phen (3), have been assembled using chromate(VI) ions as spacers (μ-ĸO:ĸO’ bridging mode). Their crystal structures have been solved. The copper ions in compound 1, whose structure consists of linear chains, show an elongated octahedral geometry, with four ammonia molecules, forming the equatorial plane, and two oxygen atoms arising from two chromato bridges into the apical positions. The ammonia ligands are involved in intramolecular hydrogen bonds with two chromate oxygen atoms, and intermolecular hydrogen bonds with two chromato oxygen atoms from another chain. The crystal structures of compounds 2 and 3 consist of helicoidal chains and solvent molecules. The copper(II) ions in 2 and 3 are five-coordinated (square-pyramidal geometry), with the apical positions occupied by the oxygen atoms from the chromato bridges. Helicoidal chains with opposite chirality are interconnected by π-π stacking interactions established between the organic ligands, resulting in supramolecular layers. The X-band and Q-band EPR spectra of compounds 1–3 are discussed. The total thermal decomposition of these complexes leads to a mixture of CuCr2O4 and CuO, for 1, and of CuCrO2, CuO and Cr2O3, for 2 and 3.

Crystal structure of catena-poly[[[bis-(3-oxo-1,3-di-phenyl-prop-1-enolato-κ2 O,O')zinc(II)]-μ2-tris-[4-(pyridin-3-yl)phen-yl]amine-κ2 N:N'] tetra-hydro-furan monosolvate

The reaction of bis-(3-oxo-1,3-di-phenyl-prop-1-enolato-κ2 O,O')zinc(II), [Zn(dbm)2], with tris-[4-(pyridin-3-yl)phen-yl]amine (T3PyA) in tetra-hydro-furan (THF) afforded the title crystalline coordination polymer, {[Zn(C15H11O2)2(C33H24N4)]·C4H8O} n . The asymmetric unit contains two independent halves of Zn(dbm)2, one T3PyA and one THF. Each ZnII atom is located on an inversion centre and adopts an elongated octa-hedral coordination geometry, ligated by four O atoms of two dbm ligands in equatorial positions and by two N atoms of pyridine moieties from two different bridging T3PyA ligands in axial positions. The crystal packing shows a one-dimensional polymer chain in which the two pyridyl groups of the T3PyA ligand bridge two independent Zn atoms of Zn(dbm)2. In the crystal, the coordination polymer chains are linked via C-H⋯π inter-actions into a sheet structure parallel to (010). The sheets are cross-linked via further C-H⋯π inter-actions into a three-dimensional network. The solvate THF mol-ecule shows disorder over two sets of atomic sites having occupancies of 0.631 (7) and 0.369 (7).

Crystal structure of a zigzag CoII coordination polymer: catena-poly[[di-chlorido-bis-(methanol-κO)cobalt(II)]-μ-bis-(pyridin-3-ylmeth-yl)sulfane-κ2N:N'

Reaction of bis-(pyridin-3-ylmeth-yl)sulfane (L) with cobalt(II) chloride in methanol led to the formation of the title coordination polymer, [CoCl2(C12H12N2S)(CH3OH)2] n , in which the CoII cation lies on a crystallographic inversion centre and the S atom of the L ligand lies on a twofold rotation axis. Each CoII ion is coordinated by two pyridine N atoms from two bridging L ligands, two O atoms from methanol mol-ecules and two chloride anions, all inversion-related. The complex unit has an elongated octa-hedral geometry, in which N2O2 donor atoms occupy the equatorial positions and two chloride anions occupy the axial positions. Each L ligand links two CoII ions, forming an infinite zigzag chain propagating along the c-axis direction and further stabilized by O-H⋯Cl hydrogen bonds between the methanol mol-ecules and the chloride anions. Adjacent chains in the structure are connected by inter-molecular C-H⋯Cl hydrogen bonds, resulting in the formation of a three-dimensional supra-molecular architecture.

Synthesis and characterization of a macrocyclic copper complex containing the 14-membered 1,3,5,8,10,12-hexaazacyclotetradecane unit

Abstract In this work, a new macrocyclic copper complex, [Cu(ACE)(SCN)2]; ACE: 1,3,6,10,12,15-hexaazatricyclo[13.3.1.16,10]eicosane, was prepared and characterized by elemental analysis, FT-IR, Raman spectroscopy and single-crystal X-ray diffraction. X-ray analysis of [Cu(ACE)(SCN)2] reveals an elongated octahedral geometry around the copper atom in a centrosymmetric CuN6 environment.

Crystal structure of bis-[2,5-bis-(pyridin-2-yl)-1,3,4-thia-diazole-κ(2) N (2),N (3)]bis-(thio-cyanato-κS)copper(II).

The mononuclear title complex, [Cu(SCN)2(C12H8N4S)2], was obtained by the reaction of 2,5-bis-(pyridin-2-yl)-1,3,4-thia-diazole and potassium thio-cyanate with copper(II) chloride dihydrate. The copper cation lies on an inversion centre and displays an elongated octa-hedral coordination geometry. The equatorial positions are occupied by the N atoms of two 2,5-bis-(pyridin-2-yl)-1,3,4-thia-diazole ligands, whereas the axial positions are occupied by the S atoms of two thio-cyanate anions. The thia-diazole and the pyridyl rings linked to the metal are approximately coplanar, with a maximum deviation from the mean plane of 0.190 (2) Å. The cohesion of the crystal structure is ensured by weak C-H⋯N hydrogen bonds and π-π inter-actions between parallel pyridyl rings of neighbouring mol-ecules [centroid-to-centroid distance = 3.663 (2) Å], leading to a three-dimensional network.

A novel two-dimensional cadmium(II) complex: poly[diaquatris(μ4-cyclohexane-1,4-dicarboxylato)bis[2-(pyridin-4-yl)-1H-benzimidazole]tricadmium(II).

The title compound, [Cd3(C8H10O4)3(C12H9N3)2(H2O)2]n or [Cd3(chdc)3(4-PyBIm)2(H2O)2]n, was synthesized hydrothermally from the reaction of Cd(CH3COO)2·2H2O with 2-(pyridin-4-yl)-1H-benzimidazole (4-PyBIm) and cyclohexane-1,4-dicarboxylic acid (1,4-chdcH2). The asymmetric unit consists of one and a half Cd(II) cations, one 4-PyBIm ligand, one and a half 1,4-chdc(2-) ligands and one coordinated water molecule. The central Cd(II) cation, located on an inversion centre, is coordinated by six carboxylate O atoms from six 1,4-chdc(2-) ligands to complete an elongated octahedral coordination geometry. The two terminal rotationally symmetric Cd(II) cations each exhibits a distorted pentagonal-bipyramidal geometry, coordinated by one N atom from 4-PyBIm, five O atoms from three 1,4-chdc(2-) ligands and one O atom from an aqua ligand. The 1,4-chdc(2-) ligands possess two conformations, i.e. e,e-trans-chdc(2-) and e,a-cis-chdc(2-). The cis-1,4-chdc(2-) ligands bridge the Cd(II) cations to form a trinuclear {Cd3}-based chain along the b axis, while the trans-1,4-chdc(2-) ligands further link adjacent one-dimensional chains to construct an interesting two-dimensional network.

Two new heterodinuclear Schiff base complexes: Synthesis, crystal structure and thermal studies

Two new heterodinuclear Schiff base complexes, [Hg(L)NiCl2(DMF)2] 1, and [Zn(L)NiCl2(DMF)2] 2, where H2L=N,N′-bis(salicylidene)-1,3-diaminopropane and DMF=dimethylformamide have been synthesized and characterized using elemental analysis, IR spectroscopy, thermal analysis and X-ray diffraction. Structural studies on 1 and 2 reveal the presence of a heterodinuclear [NiIIHgII] unit and [ZnIINiII] in which the central metal ions are connected to each other by two phenolate oxygen bridges. For complex 1 the Ni(II) ion adopts an elongated octahedral geometry (NiN2O4) while the Hg(II) ion assumes a distorted tetrahedral arrangement (HgO2Cl2) whereas for complex 2 the Zn(II) ion adopts an elongated octahedral geometry (ZnN2O4) while the Ni(II) ion assumes a distorted tetrahedral arrangement (NiO2Cl2). There are intermolecular CH···ClM interactions among the dinuclear complexes which are interconnected for 1 and 2. These intermolecular interactions result in the formation of a three dimensional structure for 1 and one dimensional zig-zag chains for 2.

Solvent-Induced Reversible Crystal-to-Amorphous Transformation Properties of Cobalt(II) 4-Aminomethylpyridine-Sulfate with Chromotropism

The crystalline CoII coordination compound with empirical formula [Co(Hampy)2(H2O)4](SO4)2(H2O)3 (1); ampy = 4-aminomethylpyridine was obtained. The structure contains a mononuclear [Co(Hampy)2(H2O)4]4+ cation unit, two sulfate ions, and three lattice water molecules. The Co2+ cation shows an elongated octahedral geometry comprised of four oxygen atoms from water molecules at equatorial positions and two nitrogen atoms from Hampy ligands which are protonated at NH2. Each mononuclear cation unit is assembled by intermolecular hydrogen bonding and π–π stacking interactions by the coordinated and lattice water molecules, amino group, and sulfate anions to form a 3D supramolecular network. Investigations of the dynamic structural behaviour demonstrate that the title compound exhibits a solvent-induced reversible crystal-to-amorphous transformation with chromotropism when exposed to water and methanol vapour. This indicates that the dehydrated amorphous form, [Co(Hampy)2(SO4)2] 1A, may be utilised as an indicator for humidity and methanol vapour.

Synthesis, characterization, and crystal structure of a 2-D metal diphosphonate: Cu3(H2O)2[HO3PCH2N(CH3)CH2PO3]2 · 2H2O

Hydrothermal reaction of N-methyl-iminobis(methylenephosphonic acid), CH3N(CH2PO3H2)2, (H4L) with copper(II) acetate afforded a new layered Cu(II) amino diphosphonate, Cu3(H2O)2(HL)2 · 2H2O (1). Compound 1 was studied by IR spectroscopy, TGA/DTA data, and X-ray diffraction (XRD) techniques. The XRD patterns are the same for the hydrated and the dehydrated complexes. A single-crystal X-ray crystallographic determination reveals copper in two different coordination environments. Cu1 has a distorted elongated tetragonal octahedral geometry, whereas Cu2 has a square-pyramidal distorted geometry. The HL trianion is a pentadentate ligand with a deprotonated nitrogen atom and two oxygen atoms of each phosphonate binding to copper. Hydrogen bonds between lattice water molecules in interlayer spaces and the non-coordinated phosphonate oxygen atoms as well as water ligands leads to a 3-D supramolecular network structure.

Bis{1,2-bis[2-(1H-imidazol-1-yl)ethoxy]ethane-κ2N3,N3′}dichloridocadmium(II) monohydrate

The asymmetric unit of the title compound, [CdCl2(C12H18N4O2)2]·H2O, contains one water mol­ecule and two halves of a [CdCl2(BIEE)2] complex mol­ecule {BIEE is 1,2-bis­[2-(1H-imidazol-1-yl)eth­oxy]ethane}, with the CdII atoms lying on inversion centres. Each metal atom displays an elongated octa­hedral coordination geometry provided by two trans-arranged chloride anions and four N atoms from two BIEE ligands. Weak O—H⋯Cl hydrogen-bond inter­actions contribute to the stability of the crystal packing.

Dinuclear, tetranuclear and one-dimensional pyrazine-based copper(ii) complexes: preparation, X-ray structure and magnetic properties

The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula [Cu(2)(tppz)(H(2)O)(2)(CF(3)SO(3))(4)] (1), [Cu(tppz)(CrO(4))](n) x 3nH(2)O (2) and [Cu(4)(tppz)(4)(H(2)O)(4)(MoO(4))(2)](CF(3)SO(3))(4) x 7 H(2)O (3) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine] are reported. Complex 1 is a dinuclear species where tppz adopts a bis-tridentate bridging mode with an intramolecular copper-copper separation of 6.5221(6) A. Each copper(II) ion in 1 has an elongated octahedral geometry with three tppz nitrogen atoms and a water molecule in the equatorial positions and two triflate oxygen atoms occupying the axial sites. Complex 2 is a uniform copper(II) chain where the copper atoms are bridged by two oxygen atoms of the chromate group (mu(1,2)-CrO(4)), the value of the intrachain metal-metal separation being 4.2614(5) A. Each copper(II) ion in 2 exhibits a somewhat distorted square pyramidal geometry with three nitrogen atoms from a tridentate tppz ligand and a chromate oxygen atom in the basal plane and an oxygen atom of a symmetry-related chromate group in the apical position. Complex 3 is a cyclic tetranuclear compound where peripheral [Cu(tppz)(H(2)O)](2+) units are connected through two molybdate groups, each one adopting the mu(1,1,2)-MoO(4) bridging mode. Regular alternating five [Cu(1) and Cu(4)] and six [Cu(2) and Cu(3)] coordinated copper(II) ions occur in 3 with distorted square pyramidal CuN(3)O(2) and elongated octahedral CuN(3)O(3) surroundings, respectively. The four copper atoms in 3 have in common the presence of a molybdate-oxygen and three tppz-nitrogen atoms in the basal [Cu(1) and Cu(4)]/equatorial [Cu(2) and Cu(3)] planes and a water molecule in the apical [Cu(1) and Cu(4)]/one axial [Cu(2) and Cu(3)] positions whereas the remaining axial position is occupied by a molybdate-oxygen [Cu(2) and Cu(3)]. The shorter intramolecular copper-copper separation is 3.371(1) A [Cu(2)...Cu(3)], the other ones varying in the range 5.537(1)-6.301(1) A. The investigation of the magnetic properties of 1-3 in the temperature range 1.9-295 K has shown the occurrence of intermediate antiferro- [J = -48.0(1) cm(-1) with H = -JS(1) x S(2) (1)], weak ferro- [J = +0.28(1) cm(-1) with H = -JSigma(i)S(i) x S(i+I) (2)] and coexistence of weak ferro- and antiferromagnetic interactions [J(1) = +2.38(2) cm(-1), J(2) = +0.56(2) cm(-1) and J(3) = -1.53(2) cm(-1) with H = -J(1) (S(2) x S(3)) + J(2) (S(1) x S(3) + S(2) x S(4)) + J(3) (S(1) x S(2) + S(3) x S(4)) (3)] between the copper(II) ions across bis-tridentate tppz (1), mu(1,2)-CrO(4) (2), di-mu(1,1)-MoO(4) and mu(1,2)-MoO(4) (3) bridges. The values of the magnetic interactions are analyzed in terms of simple orbital symmetry considerations and compared with those reported for parent systems.

Catena-Poly[[[diaquacopper(II)]-bis[μ2-1,3-bis(1,2,4-triazol-1-yl)propane]] dinitrate monohydrate

The title CuII coordination polymer, {[Cu(C7H10N6)2(H2O)2](NO3)2·H2O}n, was obtained by the reaction of equimolar Cu(NO3)2·4H2O and 1,3-bis­(1,2,4-triazol-1-yl)propane (btp) in a water–methanol solvent. The CuII atom is located on a centre of inversion and has an elongated octa­hedral coordination geometry formed by four N atoms from four symmetry-related btp ligands and two coordinated water mol­ecules. Adjacent CuII atoms are connected by btp ligands, generating a double-stranded chain. The nitrate anion is disordered over two positions in a 0.828 (7):0.172 (2) ratio.

A trinuclear copper(II) complex with 2,5-pyridine-dicarboxylato bridges – [Cu3(2,5-pydc)2(Me5dien)2(H2O)2(BF4)2]·H2O: Synthesis, crystal structure and magnetic properties

A trinuclear copper(II) complex, [Cu 3 (2,5-pydc) 2 (Me 5 dien) 2 (BF 4 ) 2 (H 2 O) 2 ] · H 2 O 1 , has been constructed from 2,5-pyridine-dicarboxylato bridges (2,5-pydc 2− ) and N , N , N ′, N ″, N ″-pentamethyl-diethylenetriamine (Me 5 dien) acting as a blocking ligand. The copper ions, within the centrosymmetric trinuclear cations, are connected by two 2,5-pydc 2− bridges, with an intramolecular Cu···Cu separation of 8.432 A. The central copper ion exhibits an elongated octahedral geometry, with semicoordinated ( BF 4 - ) ions, while the terminal ones are pentacoordinated (distorted square-pyramidal geometry). The cryomagnetic investigation of 1 reveals an antiferromagnetic coupling of the copper(II) ions ( J = −5.9 cm −1 , H = − J S Cu1 S Cu2 − J S Cu2 S Cu1a ).

Metal-Organic Frameworks Constructed from 2,4,6-Tris(4-pyridyl)-1,3,5-triazine

Five new metal-organic frameworks based on 2,4,6-tris(4-pyridyl)-1,3,5-triazine (tpt) ligand have been hydrothermally synthesized. Reaction of tpt and AgNO 3 in an acidic solution at 180 degrees C yields {[Ag(Htpt)(NO3)]NO(3).4H2O}n (1).Ag(I) is trigonally coordinated by two pyridyl nitrogen and one nitrato oxygen to form a 1D zigzag chain. Reaction of tpt with CuSO4 affords {[Cu2(tpt)2(SO4)2(H2O)2].4H2O}n (2). Copper(II) is bonded to two pyridyl nitrogen, two sulfato oxygen, and two water oxygen atoms to form an elongated octahedral geometry. Each H2O ligand bridges two copper(II), whereas sulfate bridges copper(II) via micro-1,3 and micro-1,1 fashions. The copper(II)-sulfate-H2O2D layers are linked by bidentate tpt to form a 3D polymeric structure. Reaction of Cu(SO4)2, tpt, and 1,2,4,5-benzenetetracarboxylic acid (H4btec) in the presence of piperidine gives [Cu(tpt)(H2btec)1/2]n (3). Copper(I) is located in a trigonal-pyramidal coordination environment and coordinated by three pyridyl nitrogen of tpt in a plane, whereas a carboxylate oxygen is coordinated to the copper(I) axially. The tpt-Cu forms a layer, and the layers are linked through H 2btec2- to form a 2D double-layered coordination polymer. Replacing CuSO4 with ZnI2 in the synthesis gives {[Zn(tpt)(btec)1/2].H2O}n (4). Zinc(II) is in a distorted tetrahedral geometry and linked through bidentate tpt and exotetradentate btec4- to form a 2D coordination grid. Reaction of tpt with CuCN leads to the assembly of a 3D metal-organic framework [Cu3(CN)3(tpt)]n (5). Copper(I) is trigonally coordinated by one pyridyl nitrogen and two cyanides to form an intriguing honeycomb architecture. Luminescence study shows that 1, 3, 4, and 5 have blue fluorescence, which can be assigned to be ligand-centered emissions. Thermal analysis shows that all of these complexes are quite stable, and especially for 4, the framework is stable up to 430 degrees C.

Crystal of Tetrakis(1-ethyl-1H-imidazole)diisothiocyanatocopper(II) bis(1-ethyl-1H-imidazole)diisothiocyanatocopper(II)

A new complex [Cu(NCS)4 (N-Eim)4] [Cu(NCS)2 (N-Eim)2] (where N-Eim = N-ethylimidazole) has been synthesized and structurally characterized by single-crystal X-ray diffraction. The compound crystallizes in the Triclinic space group P−1 with the parameters: a = 8.7707(18) A, b = 10.712(2) A, c = 13.511(3) A, α = 104.73(3)°, β = 104.84(3)°, γ = 102.52(3)°, V = 1131.54(3) A3, with Z = 1 formula units. In the structure, the copper atoms all assume an elongated octahedral geometry with two distinct coordination environments; one is coordinated by four N-ethyl-imidazole ligands and two axial SCN groups, and another by two SCN groups and two N-ethyl-imidazole ligands. The two units form one infinite 1D zigzag chain along the [1 0 1] plane by two thiocyanate ligands from the [Cu(NCS)4 (N-Eim)4] units. The title compound, tetrakis(1-ethyl-1H-imidazole)diisothio cyanatocopper(II) bis(1-ethyl-1H-imidazole)diisothiocyanatocopper(II) has been synthesized and structurally characterized by single-crystal X-ray diffraction. In the structure, the copper atoms all assume an elongated octahedral geometry with two distinct coordination environments. The two units form one infinite 1D zigzag chain along the [1 0 1] plane by two thiocyanate ligands from the [Cu(NCS)4 (N-Eim) 4] units.

Synthesis, crystal structures and magnetic properties of tricyanomethanide-containing copper(II) complexes

The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula [Cu(pyim)(tcm)(2)](n) (1), [Cu(bpy)(tcm)(2)](n) (2), [Cu(4)(bpz)(4)(tcm)(8)] (3), {[Cu(terpy)(tcm)].tcm}(n) (4) and {[Cu(2)(tppz)(tcm)(4)].3/2H(2)O}(n) (5) [pyim = 2-(2-pyridyl)imidazole, tcm = tricyanomethanide, bpy = 2,2'-bipyridine, bpz = 2,2'-bipyrazine, terpy = 2,2':6',2''-terpyridine and tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine] are reported. Complexes, 1, 2 and 4 are uniform copper(II) chains with single- (1 and 4) and double-(2) micro-1,5-tcm bridges with values of the intrachain copper-copper separation of 7.489(1) (1), 7.520(1) and 7.758(1) (2) and 7.469(1) A (4). Each copper atom in 1, 2 and 4 is five-coordinate with bidentate pyim (1)/bpy (2) and tridentate terpy (4) ligands and nitrile-nitrogen atoms from bridging (1,2 and 4) and terminal (1) tcm groups building a distorted square pyramidal surrounding. The structure of 3 is made up of neutral centrosymmetric rectangles of (2,2'-bipyrazine)copper(II) units at the corners, the edges being built by single- and double-micro-1,5-tcm bridges with copper-copper separations of 7.969(1) and 7.270(1) A, respectively. Five- and six-coordinated copper atoms with distorted square pyramidal and elongated octahedral environments occur in . Compound 5 is a neutral copper(II) chain with regular alternating bis-tridentate tppz and double micro-1,5-tcm bridges, the intrachain copper-copper distances being 6.549(7) and 7.668(1) A, respectively. The two crystallographically independent copper atoms in 5 have an elongated octahedral geometry with three tppz nitrogen atoms and a nitrile-nitrogen atom from a bridging tcm group in the equatorial positions, and two nitrile nitrogen atoms from a terminal and a bridging tcm ligand occupying the axial sites. The investigation of the magnetic properies of 1-5 in the temperature range 1.9-295 K has shown the occurrence of weak ferro- [J = +0.11(1) cm(-1) (2)] and antiferromagnetic interactions [J = -0.093(1) (1), -0.083(1) (4), -0.04(1) and 1.21(1) cm(-1) (3)] across the micro-1,5-tcm bridges and intermediate antiferromagnetic coupling [-J = 37.4(1) cm(-1) (5)] through bis-tridentate tppz. The values of the magnetic interactions are analyzed through simple orbital symmetry considerations and compared with those previously reported for related systems.