Zinc(II) and Nickel(II) Complexes Based on Schiff Base Ligands: Synthesis,Crystal Structure,Luminescent and Magnetic Properties

Three new phenolate oxygen bridged transition metal complexes [Zn₃(HL¹)₃(μ₃‐CH₃O)]·(ClO₄)₂(H₂O)₃ ( 1 ), [Ni₂(HL¹)₂(μ_1,1‐N₃)(o‐vanillin)]·H₂O ( 2 ), [Ni₃(HL²)₂(PhCOO)₂(PhCOOH)₂(EtOH)₂] ( 3 ) have been synthesized by metal ions and potentially multidentate Schiff base ligands (H₂L¹ = 2‐((1‐hydroxy‐2‐methylpropan‐2‐ylimino) methyl)‐6‐methoxyphenol; H₃L² = (E)‐1‐((2‐hydroxy‐3‐methoxy‐benzylidene)amino)ethane‐1,2‐diol). All the three complexes 1 , 2 , and 3 have been characterized by elemental analysis, FT‐IR spectroscopy, and single‐crystal X‐ray diffraction studies. Crystal structures reveal that complex 1 is a trinuclear incomplete cubane‐like zinc cluster whereas complex 2 is a dinuclear nickel complex bridged by azide, and compound 3 is a trinuclear nickel complex. The luminescent property for complex 1 and magnetic behaviors for complexes 2 and 3 have been investigated.     

Synthesis,crystal structure,spectroscopy and magnetism of a trinuclear nickel(II) complex with 3,5-pyrazoledicarboxylic acid as bridge ligands

A new complex of [Ni₃(dcp)₂(H₂O)₁₀] (1) (H₃dcp = 3,5-pyrazoledicarboxylic acid) has been synthesized from H₃dcp and Ni(NO₃)₂·6H₂O by hydrothermal reaction. Complex 1 has the discrete trinuclear structure. Three Ni(II) ions are bridged by two dcp³⁻ ligands, with 10 coordinated water molecules as terminal ligands. The molecules of [Ni₃(dcp)₂(H₂O)₁₀] extend into three-dimensional supramolecular architectures by intermolecular O–H···O hydrogen bonds as well as π-π stacking interactions. Magnetic susceptibility measurement shows that a weak antiferromagnetic interaction is operative between nickel(II) ions and an excellent simulation of the experimental data gives D = 5.27 cm⁻¹, J = −2.19 cm⁻¹ and g = 2.05.     

Pentanuclear Nickel(II) Complex with two Vertex-Shared Triaminoguanidine Fragments and Symmetric Capping Ligand

The pentanuclear nickel(II) complex [Ni₅(saltag^Br)₂(tptz)₄] ( Ni5 ) with the tritopic triaminoguanidine-derived Schiff-base ligand H₅saltag^Br (1,2,3-tris[(5-bromosalicylidene)amino]guanidine) and tptz (2,4,6-tris(2-pyridyl)-1,3,5-triazine) as capping ligands is reported. Ni5 crystallizes in the triclinic space group P1 with the central nickel(II) ion linking two triangular arrangements of nickel(II) ions supported by two tritopic triaminoguanidine ligands. The octahedral coordination of the four peripheral nickel(II) ions is complemented by capping tridentate tptz ligands. By variation of the synthesis also the corresponding trinuclear nickel(II) complex [Ni₃(saltag^Br)(tptz)₃]NO₃ ( Ni3 ) is accessible. Magnetic measurements for Ni3 and Ni5 reveal a singlet ground state with antiferromagnetic coupling between the nickel(II) ions, which in the case of Ni5 can only be simulated assuming a two-J exchange coupled spin topology. For both complexes significant zero-field splitting for the nickel(II) ions is evident from the measured magnetic data, which can be verified by theoretical studies revealing a magnetic anisotropy with strong rhombic distortion due to the presence of the tptz co-ligands in both compounds.     

A linear trinuclear cobalt(II) complex with 4-(2-pyridine)-1,2,4-triazole: synthesis,structure and characterization

The linear trinuclear cobalt(II) complex [Co₃(pytrz)₆(H₂O)₆](NO₃)₆ (1) with pytrz = 4-(2-pyridine)-1,2,4-triazole has been prepared and characterized. It crystallizes in the rhombohedral R-3 space group with Z = 3, a = 13.955(2), b = 13.955(2), c = 28.942(9) Å, γ = 120°, V = 4881.2(18) ų. The structure of 1 comprises the cation [Co₃(pytrz)₆(H₂O)₆]⁶⁺, in which linear trinuclear Co(II) units are bridged by six L ligands and have six aqua molecules as terminal ligands. The six free nitrates link the terminal aqua ligands through N–H ··· O hydrogen bonds with C₃ symmetry. 1 was characterized by FT-IR, electronic spectra and magnetic measurements. The variable-temperature magnetic measurements reveal weak anti-ferromagnetic interactions in 1.     

Synthesis and Characterization of Two Trinuclear Nickel(II) Complexes

Two novel trinuclear nickel(II) complexes have been synthesized and characterized by X‐ray single crystal diffraction. Compound [Ni₃(ashz)₃(py)₂(DMF)₂]·(DMF)₂ ( 1 ) crystallizes in the monoclinic, space group C2/c, with a = 22.114(2), b = 10.509(9), c = 19.485(2) Å, β = 114.443(1)°, Z = 4; compound [Ni₃(acshz)₃(py)₂(DMF)₂]·(DMF)₂ ( 2 ) crystallizes in the monoclinic space group P2₁/n with a = 20.0620(2), b = 9.7017(6), c = 25.0533(2) Å, β = 97.0610(2)°, Z = 4, where ashz and acshz are deprotonated N‐acetylsalicylhydrazide (H₃ashz) and N‐acetyl‐5‐chlorosalicylhydrazide (H₃acshz), respectively. The crystal structure analysis of 1 and 2 showed that three Ni²⁺ ions in a linear arrangement are bridged by two ligands ((ashz)^3? or (acshz)^3?) to form a neutral nuclear with two four‐coordinate square‐planar nickel ions linked by a six‐coordinate octahedral central nickel ion.     

Synthesis, Crystal and Molecular Structures, and Properties of Optically Active Copper(II) Complexes with 3-N,N-Dimethylaminocaran-4-one-oxime

Copper(II) complexes with 3-N,N-dimethylaminocaran-4-one-oxime (HL) were synthesized and characterized by X-ray diffraction analysis, photoelectronic, IR, and EPR spectroscopy, magnetic susceptibility, and thermal analysis methods, and their optical activities were studied. The [Cu₂(HL)₂Cl₄] complex is a dimer with weak exchange interactions between unpaired electrons of the Cu(II) ions. The [Cu₃L₃(OH)Cl]Cl · 8H₂O structure is composed of triangular trinuclear complex cations, outer-sphere Cl^–anions, and water molecules. The exchange parameter Jfor the trinuclear exchange cluster is –190 cm^–1. The title complexes are optically active in the visible range of the spectrum.     

Spin Interactions and Magnetic Anisotropy in a Triangular Nickel(II) Complex with Triaminoguanidine Ligand Framework

The trinuclear nickel(II) complex [Ni₃(saltag^tBu)(bpy)₃(H₂O)₃]Cl (H₅saltag^tBu = 1,2,3-tris[(5-tert-butylsalicylidene)amino]guanidine) was synthesized and characterized by experimental as well as theoretical methods. The complex salt crystallizes with three molecules of dimethylformamide (dmf) and water as [Ni₃(saltag^tBu)(bpy)₃(H₂O)₃]Cl · 3dmf · 3H₂O ( 1 ) in the trigonal space group P3 , with the complex located on a threefold rotation axis, which is consistent with the molecular C₃ symmetry of the complex cation. Magnetic measurements reveal an antiferromagnetic coupling (J = –35.9 cm^–1) between the nickel(II) ions leading to a diamagnetic ground state for the trinuclear complex cation. Theoretical investigations based on broken-symmetry DFT confirm the antiferromagnetic exchange within the complex cation of 1 . Additional single-ion CASSCF ab initio studies reveal that magnetic anisotropy is present in the system. The experimental and theoretical results for 1 are compared with those of a structurally similar nickel(II) complex that is based on the bromo-substituted derivative of the triaminoguanidine ligand. The differences in their magnetic properties can be attributed to the stronger elongation of the pseudo-octahedral coordination sphere at the nickel(II) centers in case of 1 . The analysis of the magnetic properties of 1 clearly shows that for such exchange coupled systems reliable parameters for the magnetic anisotropy cannot be extracted from experimental data alone.     

Crystal Structures,Magnetic Properties and Catecholase‐Like Activities of μ‐Alkoxo‐μ‐Carboxylato Double Bridged Dinuclear and Tetranuclear Copper(II) Complexes

One μ‐alkoxo‐μ‐carboxylato bridged dinuclear copper(II) complex, [Cu₂(L¹)(μ‐C₆H₅CO₂)] ( 1 )(H₃L¹ = 1,3‐bis(salicylideneamino)‐2‐propanol)), and two μ‐alkoxo‐μ‐dicarboxylato doubly‐bridged tetranuclear copper(II) complexes, [Cu₄(L¹)₂(μ‐C₈H₁₀O₄)(DMF)₂]·H₂O ( 2 ) and [Cu₄(L²)₂(μ‐C₅H₆O₄]·2H₂O·2CH₃CN ( 3 ) (H₃L² = 1,3‐bis(5‐bromo‐salicylideneamino)‐2‐propanol)) have been prepared and characterized. The single crystal X‐ray analysis shows that the structure of complex 1 is dimeric with two adjacent copper(II) atoms bridged by μ‐alkoxo‐μ‐carboxylato ligands where the Cu···Cu distances and Cu‐O(alkoxo)‐Cu angles are 3.5 11 Å and 132.8°, respectively. Complexes 2 and 3 consist of a μ‐alkoxo‐μ‐dicarboxylato doubly‐bridged tetranuclear Cu(II) complex with mean Cu‐Cu distances and Cu‐O‐Cu angles of 3.092 Å and 104.2° for 2 and 3.486 Å and 129.9° for 3 , respectively. Magnetic measurements reveal that 1 is strong antiferromagnetically coupled with 2J =‐210 cm^?1 while 2 and 3 exhibit ferromagnetic coupling with 2J = 126 cm^?1 and 82 cm^?1 (averaged), respectively. The 2J values of 1–3 are correlated to dihedral angles and the Cu‐O‐Cu angles. Dependence of the pH at 25 °C on the reaction rate of oxidation of 3,5‐di‐tert‐butylcatechol (3,5‐DTBC) to the corresponding quinone (3,5‐DTBQ) catalyzed by 1–3 was studied. Complexes 1–3 exhibit catecholase‐like active at above pH 8 and 25 °C for oxidation of 3,5‐di‐tert‐butylcatechol.     

两个N-己酰基水杨酰肼合镍(Ⅱ)配合物的合成、结构及抗菌活性的研究

The two trinuclear nickel（Ⅱ） complexes, Ni3（C13H15N2O3）2（C5H5N）4 （1） and Ni3（C13H15N2O3）2（C5H5N）2- （C3H7NO）2 （2）, were prepared by the reaction of Ni（OAc）2·4H2O with N-hexanoylsalicylhydrazide. The crystal structures of complexes were determined by X-ray diffraction analysis. Complex 1 takes triclinic symmetry with space group P-1 and cell dimensions of a=0.92377（2） nm, b= 1.08786（6） nm, c= 1.29391（3） nm, α=76.395（4）°, β=78.418（3）°, γ=67.378（4）°, V= 1.15772（7） nm^3, Z= 1,μ= 12.63 cm^-1. Complex 2 belongs to triclinic system and P2（1） space group and the crystallographic data： a= 1.4889（2） nm, b= 1.0389（1） nm, c= 1.4994（2） nm, β= 96.174（4）°, V=2.3058（5） nm^3, Z=2,μ= 12.70 cm^-1. The structures of the two molecules are similar. The three nickel atoms in each molecule of the two title complexes arrange in a strictly linear structure. The central nickel atom of the molecule adopts octahedral configuration, while the two nickel atoms on the two sides adopt square-planar configuration in each molecule. But the central nickel atoms of the two complexes have different axial ligands, which cause a slight difference in the bond distances of the octahedron. The antibacterial activity of compound 1 against seven common bacteria was investigated.     

The Crystal and Molecular Structures of Pb(II) Complexes with Furan-2-Carboxylate and Furan-3-Carboxylate Ligands

The crystals of Pb(II) 2-furancarboxylate (title compound I) contain tetrameric structural units Pb₄(2-FCA)₈(H₂O₂) in which four Pb(II) ions are bridged by carboxylate oxygen atoms forming a circular moiety. In addition, pairs of Pb(II) ions are bridged by carboxylate oxygen atoms inside this moiety. The molecular pattern observed in Pb(II) 3-furancarboxylate (title compound II) is polymeric. It consists of Pb(3-FCA)₂(H₂O) structural units bridged by carboxylate oxygen atoms donated by the furan-3-carboxylate (3-FCA) ligands which are bidentate, using both their carboxylate oxygen atoms for chelation. The coordination around Pb(II) ions is eightfold and ninefold including, apart from carboxylate oxygen atoms, a water oxygen atom and oxygen atoms donated by the furan rings of the ligand molecules. Hydrogen bonds with the water molecule as the donor operate between adjacent ligand molecules. The stereochemical activity of the lone 6s ² electron pair on the Pb(II) is observed in title compound II.     

Cyano-bridged Heterotrinuclear Molybdenum(IV)-Nickel(II) Complexes: Synthesis,Crystal Structure and Magnetic Properties

Two novel cyano-bridged heterotrinuclear molybdenum(IV)-nickel(II) complexes ([Ni(en)₂(H₂O)]_2-[Mo(CN)₈]·2H₂O, 1, and [NiL(H₂O)]₂[Mo(CN)₈]·4H₂O, 2), where en=1,2-diaminoethane and L= 1,3,6,9, 11,14-hexaazacyclo[12,2,1,1^6,9]octodecanne were synthesized and characterized. The crystal structure of 1 was determined. The structure consists of trinuclear units, space group C2/c, with unit cell dimensions a=17.178(9), b=11.032(5), c=17.629(8) Å, α=108.484(8)°. The temperature dependence of the magnetic susceptibilities for 1 and 2 was analyzed by means of a Hamiltonian expression leading to J=-0.87cm^-1, ZJ'=0.65cm^-1, D=0.02cm^-1, g _Ni=2.45 for complex 1, and J=-0.87cm^-1, ZJ'=0.56cm^-1, D=0.02cm^-1, g, _Ni=2.45 for complex 2.     

Magnetic Exchange Interactions in Dinuclear Copper(II) and Nickel(II) Complexes with μ‐Oxalato Bridges. The Structure of μ‐Oxalato(O,O′, O″, O‴)‐bis{[1, 8‐di(2‐pyridyl)‐3, 6‐dithiaoctane‐N,N′, S,S′]nickel(II)} Dinitrate Dihydrate

A copper(II) and two nickel(II) dinuclear oxalato‐bridged compounds of formulae [{Cu(bpdto)}₂(μ‐ox)](ClO₄)₂ ( 1 ), [{Ni(bpdto)]₂(μ‐ox)](ClO₄)₂( 2 ), and [{Ni(bpdto)}₂(μ‐ox)](NO₃)₂·2H₂O ( 3 ), where bpdto = 1, 8‐bis(2‐pyridyl)‐3, 6‐dithiaoctane and ox = oxalate = C₂O₄^2— anion, have been synthesized and characterized. The crystal structure of 3 was determined by single‐crystal X‐ray analysis. It is a dinuclear complex with i symmetry in which the oxalate ligand is coordinated in bis(didentate) fashion to the inversion centre‐related nickel atoms. The distorted octahedral environment of each nickel atom is completed by two sulphur atoms in the equatorial plane and by two pyridyl nitrogen atoms in axial positions. Magnetic susceptibility measurements over the range 5 — 299K, show antiferromagnetic interactions that are weak in 1 (J = —12.8 cm^—1) and strong in 2 and 3 (J = —37.8 and —40.9 cm^—1, respectively), which in the case of 3 is in keeping with the observed structural parameters.     

Synthesis and Physicochemical Study of Iron(II), Cobalt(II), Nickel(II), and Copper(II) Complexes with 4-(2-Pyridyl)-1,2,4-Triazole

New complexes of iron(II), cobalt(II), and nickel(II) with 4-(2-pyridyl)-1,2,4-triazole (PyTrz), [Fe₃(PyTrz)₈(H₂O)₄]A₆ (A = NO₃ ^-, ClO₄ ^-, Br^-) and [M₃(PyTrz)₈(H₂O)₄](NO₃)₆ (M = Co, Ni), were synthesized and studied by X-ray diffraction, magnetochemical method, and electronic and IR spectroscopy. The complex [Fe₃(PyTrz)₈(H₂O)₄](NO₃)₆) was also studied by adiabatic calorimetry. The Fe(II), Co(II), and Ni(II) nitrate complexes were shown to be isostructural to the previously synthesized linear trinuclear [Cu₃(PyTrz)₈H₂O)₄](NO₃)₆ complex. In all compounds, antiferromagnetic exchange interactions between M²⁺ ions were detected. The complex [Fe₃(PyTrz)₈(H₂O)₄](NO₃)₆ undergoes the ¹ A ₁ ⁵ T ₂ spin transition.     

Structure and magnetism of a linear trimanganese (III,II, III) complex based on benzoate and Schiff-base ligands

Reaction of [Mn₃O(PhCO₂)₆(py)₂(H₂O)] with a tridentate Schiff-base 2-salicylideneaminoethanol (H₂sae) affords a trinuclear manganese complex [Mn₃(PhCO₂)₄(sae)₂] (1). X-ray structural analysis of 1 reveals that three manganese ions are linear with each pair bridged by two benzoate groups and one μ-alkoxo oxygen of the sae^2? ligand. The central manganese has an octahedral {Mn^IIO₆} configuration and the terminal ones are five-coordinate {Mn^IIINO₄} with a Jahn-Teller elongation axis. The trinuclear complex shows small antiferromagnetic exchange J coupling. The magnetic susceptibility data in the temperature range 2–300 K give the best fitting parameters with J?=??8.44 cm^–1, g?=?2.02, zJ ′?=??0.34 cm^–1, and R ²?=?0.99942. The magnetization versus external magnetic field measurements at 2 K proved that the ground state is S?=?3/2.     

Binuclear Copper(II) Complexes with Robsori-Type Ligands. Synthesis,characterization, crystal structure,and magnetic properties

Three binuclear copper(II) complexes, [Cu₂(μ-L)(μ-N₃)](ClO₄)2′ 1-5 EtOH (1), [Cu₂(μ-L)(μ-MeO)(ClO₄)]-ClO₄ - EtOH ( 2 ) and [Cu₂(μ-L)(μ-C₃H₃N₂)](ClO₄)₂ · 2H₂O, ( 3 ) where L is the pentadentale bridging ligand derived from 5-(tert-butyl)-2-hydroxybenzene-1, 3-dicarbaldehyde bis(benzoylhydrazone) ( HL ) were synthesized and characterized. The crystal-structure determination of complex 2 provided the following crystal data: monoclinic, space group P2₁}/a, a = 11.412(2), b = 24.509(4), c = 14.833(4) Å, β = 104.41(2)°, K = 4018(3) ų, Z = 4. The structure shows that the Cu^II ions are bridged by the endogenous phenolato O-atom and by an exogenous bridge CH₃O^?. The analysis of variable-temperature magnetic susceptibility data (4-300 K.) indicates that there is an antiferromagnetic interaction between the Cu^II ions in these complexes with an exchange parameter (2J) of ?119.1 cm^?1 for complex 1 and ?361.8 cm^?1 for complex 3 . The effect of some exogenous bridging ligands on magnetic coupling for this type of complex is suggested.     

Impact of Reaction Conditions on the Structures of Nickel(II) Complexes Based on 3‐(4‐Carboxyphenyl)propionic Acid

Two new nickel(II) complexes, [Ni(4, 4′‐bpy)(H₂O)₄]_n · n(cpp) · 0.5nH₂O ( 1 ) and [Ni(cpp)(4, 4′‐bpy)(H₂O)₂]_n ( 2 ) [4, 4′‐bpy = 4, 4′‐bipyridine, H₂cpp = 3‐(4‐carboxyphenyl)propionic acid] were synthesized and characterized by single‐crystal X‐ray diffraction, elemental analysis, IR spectroscopy, and thermal analysis. In complex 1 , Ni^II ions are bridged by 4, 4′‐bpy into 1D chains, and cpp ligands are not involved in the coordination, whereas in complex 2 , cpp ligands adopt a bis(monodentate) mode and link Ni^II ions into 2D (4, 4) grids with the help of 4, 4′‐bpy ligands. Triple interpenetration occurs, which results in the formation of a complicated 3D network. The difference in the structures of the two complexes can be attributed to the different reaction temperatures and bases.     

A novel cadmium(II) coordination polymer with a four‐connected (4,4)‐net based on a trinuclear cadmium(II) node

In the title cadmium(II) coordination polymer, poly[tri‐μ₄‐adipato‐bis(2‐phenyl‐1H‐1,3,7,8‐tetraazacyclopenta[l]phenanthrene‐κ²N⁷,N⁸)tricadmium(II)], [Cd₃(C₆H₈O₄)₃(C₁₉H₁₂N₄)₂]_n, one of the Cd atoms is in a distorted pentagonal bipyramidal coordination environment, surrounded by five O atoms from three adipate (adip) ligands and two N atoms from one 2‐phenyl‐1H‐1,3,7,8‐tetraazacyclopenta[l]phenanthrene (L) ligand. A second Cd atom occupies an inversion center and is coordinated by six O atoms from six adip ligands in a distorted octahedral geometry. The carboxylate ends of the adip ligands link Cd^II atoms to form unique trinuclear Cd^II clusters, which are further bridged by the adip linkers to produce a two‐dimensional layer structure. Topologically, each trinuclear Cd^II cluster is connected to four others through six adip ligands, thus resulting in a unique two‐dimensional four‐connected framework of (4,4)‐topology. This work may help the development of the coordination chemistry of 1,10‐phenanthroline derivatives.     

Synthesis,crystal structures and physical properties of two terephthalate-bridged copper(II) and nickel(II) complexes

Two ₂-terephthalate (tp) bridged complexes, [Cu₂(tp)(pren)₄](ClO₄)₂ (pren = 1,3-diaminopropane) (1) and [Ni₂(tp)(pren)₄(Him)₂](ClO₄)₂ (Him = imidazole) (2), have been synthesized and characterized by X-ray single-crystal structural analysis. In the discrete dinuclear [Cu₂(tp)(pren)₄]²⁺ cation of complex (1), each Cu^II atom has a square-pyramidal geometry, being coordinated by four nitrogen atoms (avg. 2.031 Å) from two pren ligands at the basal plane and one oxygen atom [2.259(3) Å] from a bis-monodentate tp group at the axial position. In the discrete dinuclear [Ni₂(tp)(pren)₄(Him)₂]²⁺ cation of complex (2), each Ni^II center is coordinated by five nitrogen atoms [Ni—N 2.069(3)–2.109(2) Å] from one Him group and two pren groups, and completed by one oxygen atom [Ni—O 2.138(3) Å] from a bis-monodentate tp group to furnish a distorted octahedron. Magnetic susceptibility studies show that the pair of metal atoms, although being separated by >11.5 Å, exhibit weak intramolecular antiferromagnetic interactions in complexes (1) (g = 2.07 and J = –3.4 cm^–1) and (2) (g = 2.10 and J = –0.7 cm^–1). The electrochemical behaviors of the complexes have also been studied by cyclic voltammogram processes.     

Dimorphic Modification of the Trinuclear Nickel(II) Complex [Ni3(NCS)6(pdz)6]: Synthesis,Crystal Structure,Thermal, Magnetic and Spectroscopic Properties

Reaction of nickel(II) thiocyanate and pyridazine (pdz) as organic spacer ligand leads to the formation of the ligand‐rich 1:2 (1:2 = metal to ligand ratio) trinuclear nickel(II) complex of composition [Ni₃(NCS)₆(pdz)₆]. Depending on the reaction solvent, different polymorphic modifications are obtained: Reaction in acetonitrile leads to the formation of the new modification 1I and reaction in ethanol leads to the formation of modification 1II reported recently. In their crystal structures discrete [Ni₃(NCS)₆(pdz)₆] units are found, in which each of the Ni²⁺ cations exhibits a NiN₆ distorted octahedral arrangement. The central Ni²⁺ cation is coordinated by four bridging pdz ligands and two thiocyanato anions in trans positions. Both thiocyanato anions exhibit the end‐on bridging mode. The peripheral Ni²⁺ cations are bridged by one thiocyanato anion and by two pdz ligands with the central Ni²⁺ cation. Further they are coordinated by two terminal N‐bonded thiocyanato anions and one terminal N‐bonded pdz ligand. The structure of 1I was determined by X‐ray single crystal structure investigation and emphasized by infrared spectroscopy. Magnetic measurements revealed a quasi Curie behavior with net ferromagnetic interactions for 1I and net antiferromagnetic interactions for 1II . Solvent‐mediated conversion experiments clearly show that modification 1I represents the thermodynamic most stable form at room temperature and that modification 1II is metastable. On thermal decomposition, both modification transform quantitatively in a new ligand‐deficient intermediate. Elemental analysis revealed a 3:4 compound of composition [Ni₃(NCS)₆(pdz)₄]. A structure model supported by IR spectroscopic investigations was assumed, in which three coordination modes of the thiocyanato anion exist, resulting in a 2D polymeric network.     

Two tetranuclear Ni(II) complexes from substituted imidazole dicarboxylates: syntheses,structures, thermal and magnetic properties

Two tetranuclear nickel(II) complexes, [Ni₄ (p-BrPhHIDC)₄(py)₄(H₂O)₄]·CH₃OH (p-BrPhH₃IDC = 2-(p-bromophenyl)-1H-imidazole-4,5-dicarboxylic acid) (1) and [Ni₄(p-ClPhHIDC)₄ (CH₃CN)₄(H₂O)₄]·4H₂O (p-ClPhH₃IDC = 2-(p-chlorophenyl)-1H-imidazole-4,5-dicarboxylic acid, py = pyridine) (2), have been solvothermally synthesised and structurally characterised. Both compounds consist of similar tetranuclear Ni(II) cores, in which the imidazole dicarboxylate ligands adopt the similar coordination mode. The thermal properties of 1 and 2 have been investigated. Also, it is discovered that there exists antiferromagnetic coupling between the Ni(II) ions in 1 and 2; the best fittings to the experimental magnetic susceptibilities gave J = ? 9.89 cm^? 1 and g = 2.18 for 1, and J = ? 10.54 cm^? 1 and g = 2.14 for 2.