Syntheses,crystal structures and magnetic properties of three new binuclear Ni(II) complexes derived from tripodal tetradentate (N4) ligands

Three new binuclear Ni(II) complexes [{Ni(L_22py)Cl}₂](ClO₄)₂ (1), [{Ni(L_23py)Cl}₂](ClO₄)₂ (2), and [{Ni(L_33py)Cl}₂](ClO₄)₂ (3), {L_22py = N-(2-pyridylmethyl)-N-(2-aminoethyl)-1,2-diaminoethane, L_23py = N-(2-pyridylmethyl)-N-(2-aminoethyl)-1,3-diaminopropane, L_33py = N-(2-pyridylmethyl)-N-(3-aminopropyl)-1,3-diaminopropane} have been synthesized. Single crystal X-ray structure analysis showed that in each complex two distorted octahedral Ni(II) ions are bridged asymmetrically by a pair of chloride anions. Variable temperature magnetic susceptibility measurements of 1 and 3 revealed dominant ferromagnetic exchange interactions.     

One-dimensional and two-dimensional coordination polymers constructed from copper(II) nodes and polycarboxylato spacers: Synthesis,crystal structures and magnetic properties

Four new coordination polymers were obtained by employing polycarboxylato spacers and cationic copper(II) complexes as nodes: ^∞₂[Cu₃(trim)₂(NH₃)₆(H₂O)₃] (1); ^∞₁[Cu(tmen)(dhtp)] (2), ^∞₁[Cu(tmen)(hitp)(H₂O)] (3), ^∞₁[Cu(tmen)(nitp)] (4). (H₃trim = trimesic acid, H₂dhtp = 2,5-dihydroxy-terephthalic acid; H₂hitp = 5-hydroxy-isophthalic acid, H₂nitp = 5-nitro-isophthalic acid; tmen = N,N,N′,N′-tetramethyl-ethylenediamine). The crystal structures of the four compounds have been solved. Compound 1 consists of 2D coordination polymers with heart-shaped meshes, while compounds 2–4 contain infinite zigzag chains. The role of the hydrogen bond interactions in sustaining the supramolecular solid-state architectures in compounds 1 and 3 is discussed. The cryomagnetic investigation of compounds 1, 2, and 4 reveals antiferromagnetic interactions between the copper ions.     

Synthesis, crystal structures and magnetic properties of Cu(II) compounds bridged by the terephthalate ligand and hydrogen bonds

A 3D network [Cu(tmen)(tp)(H₂O)₂]_n (1) (tmen = N,N,N′,N′-tetramethylethylenediamine; tp = terephthalate) and a 2D sheet [Cu(pyrazole)₂(tp)]_n (2), featuring 1D chains interwoven by hydrogen bonds, have been prepared and characterized by means of X-ray analyses and magnetic measurements. For 1, coordinative zigzag chains contain Cu(II) centers capped by the chelate ligand tmen, in which the tetragonal structure is elongated due to Jahn–Teller distortion. Coordinated water molecules are hydrogen-bonded to two free carboxylate oxygens of tp bridges, leading to the observed 3D structure. The use of the non-chelating capping ligand pyrazole produced the covalent-bonded 1D linear compound 2 with hydrogen bonds. A severe octahedral distortion of the Cu(II) center arises from a small bite angle (52.3(1)°) of two carboxylate oxygen atoms of tp, which are in turn hydrogen-bonded to the N–H groups of pyrazole ligands coordinated to Cu(II) atoms in neighboring chains. Magnetic data were fitted with the high-temperature series expansion for the Heisenberg chain spin Hamiltonian H = −J∑_iS_i · S_i + 1 together with consideration of the molecular field approximation (zJ′). Both compounds interestingly exhibit ferromagnetic interactions with g = 2.17, J = 4.08 cm⁻¹, zJ′ = −0.28 cm⁻¹ for 1 and g = 2.09, J = 1.47 cm⁻¹, zJ′ = −0.04 cm⁻¹ for 2. By taking into account structural parameters of distances between Cu atoms, it is reasonably assigned that the ferromagnetic couplings (J > 0) in these systems originate from the hydrogen bonds. The spin density of the d_x²-y² orbital on a Cu(II) atom in a chain is propagated and induced over the d_z² orbital of another Cu(II) atom in an adjacent chain. This orbital orthogonality gives rise to such interactions. The negative zJ′ term suggests that the tp bridges communicate only tiny antiferromagnetic interactions.     

Syntheses,crystal structures,and magnetic properties of five new coordination compounds bearing ferrocenedicarboxylate ligands

Five new coordination compounds, {[Mn(L)(CH₃OH)₂] · CH₃OH · H₂O} _n (1), {[Cd(L)(DMF)₂(H₂O)] · H₂O} _n (2), {[Co(L)(CH₃OH)₄] · CH₃OH}₂ (3), {[Cd(L)(phen)(CH₃OH)] · CH₃OH} _n (4), and {[Mn(L)(phen)(H₂O)] · CH₃OH} _n (5) (L = 5-ferrocene-1,3-benzenedicarboxylic acid, phen = 1,10-phenanthroline) were obtained from different metal salts and L with or without 1,10-phen under mild conditions. Complex 1 is a 1-D ladder-like chain composed of 8-membered rings A and 16-membered rings B, which arrange alternately. Complex 2 is an infinite linear chain, further bridged to form a parallel double chain through different hydrogen-bond interactions. Complex 3 is a discrete dinuclear structure, while 4 is a neutral 1-D infinite zigzag coordination chain. Complex 5 is a 1-D linear chain with phen and ferrocene groups of L as pendants hanging on the different sides of the main chain. Variable temperature magnetic susceptibilities of 1 were measured and weak antiferromagnetic exchange interactions between the neighboring Mn(II) ions were found with J = ?0.95 cm^?1.     

Synthesis,structures, and spectroscopic properties of Hg(II) complexes of bidentate NN and tridentate NNO Schiff-base ligands

Reactions of HgX₂ (X?=?Cl, N₃, NO₃) with (E)-2-methoxy-N-(pyridin-2-ylmethylene)aniline (L¹) and (E)-4-methoxy-N-(pyridin-2-ylmethylene)aniline (L²) in ethanol gave two monomers, [HgL¹(Cl)₂] (1) and [HgL²(NO₃)₂(DMSO)] (5), and three coordination polymers, {[HgL¹(N₃)₂]₂·Hg(N₃)₂}_n (2), [HgL²(Cl)₂]_n (3), and [HgL²(NO₃)₂]_n·nCH₃CN (4). Compounds 1–5 were characterized by elemental analysis, IR, NMR spectroscopy, and single-crystal X-ray diffraction. The common feature of monomeric 1 and 5 is the presence of intra- and intermolecular Hg–O bonds. In the absence of these, polymeric structures arise as a result of azide, chloride, and nitrate bridging in 2, 3, and 4, respectively. Fluorescent properties of 1–5 were also investigated.     

Synthesis, crystal structures and magnetic properties of M(II)Cu(II) chains (M = Mn and Co) with sterically hindered alkyl-substituted phenyloxamate bridging ligands

A series of neutral oxamato‐bridged heterobimetallic chains of general formula [MCu(L^x)₂(S)₂] ? p S ? q H₂O [p=0–1, q=0–2.5; L¹=N‐2,6‐dimethylphenyloxamate, S=DMF with M=Mn ( 1 a ) and Co ( 1 b ); L²=N‐2,6‐diethylphenyloxamate, S=DMF with M=Mn ( 2 a ) and Co ( 2 b ) or S=DMSO with M=Mn ( 2 c ) and Co ( 2 d ); L³=N‐2,6‐diisopropylphenyloxamate, S=DMF with M=Mn ( 3 a ) and Co ( 3 b ) or S=DMSO with M=Mn ( 3 c ) and Co ( 3 d )] were prepared by treating the corresponding anionic oxamatocopper(II) complexes [Cu(L^x)₂]^2? (x=1–3) with M²⁺ cations (M=Mn and Co) in DMF or DMSO as the solvent. The single‐crystal X‐ray structures of 2 a and 3 a reveal the occurrence of well‐isolated, zigzag, oxamato‐bridged manganese(II)–copper(II) chains. The intrachain Cu ??? Mn distances across the oxamato bridge are 5.3761(7) and 5.4002(17) Å for 2 a and 3 a , respectively, whereas the shortest interchain Mn ??? Mn distances are 9.4475(16) and 8.1649(14) Å for 2 a and 3 a , respectively. All of these M^IICu^II chains (M=Mn and Co) exhibit 1D ferrimagnetic behaviour with moderately strong intrachain antiferromagnetic coupling between the square‐planar Cu^II and octahedral high‐spin M^II ions across the oxamato bridge [?J=31.4–35.2 and 33.4–44.8 cm^?1, respectively; H =∑_i?J S _M,i( S _Cu,i+ S _Cu,i?1)]. Only the Co^IICu^II chains show slow magnetic relaxation effects characteristic of single‐chain magnets (SCMs). Analysis of the magnetic relaxation dynamics of 3 d shows a thermally activated mechanism (Arrhenius law dependence) with values of the pre‐exponential factor (τ₀=2.6×10^?9 s) and activation energy (E_a=7.7 cm^?1) that are typical of SCMs. In contrast, two relaxation regimes are observed for 2 d in different temperature regions (τ₀=3.2×10^?10 s and E_a=24.7 cm^?1 for T<4.5 K and τ₀=3.2×10^?14 s and E_a=37.5 cm^?1 for T>4.5 K).     

Syntheses,structures, and magnetic properties of two 1-D dicyanamide manganese(III) complexes with Schiff-base ligands

Two new 1-D manganese(III) Schiff-base complexes bridged by dicyanamide (dca), [Mn(III)(5-Brsalen)(dca)] ? CH₃OH (1) and [Mn(III)(3,5-Brsalen)(dca)] · CH₃OH · CH₃CN (2) (5-Brsalen = N,N′-ethylenebis(5-bromo salicylaldiminato) dianion; 3,5-Brsalen = N,N′-ethylenebis(3,5-dibromosalicylal diminato) dianion), have been synthesized and characterized. X-ray diffraction analyses reveal that the two complexes have 1-D chain structures constructed by μ _1,5-dca bridge. Magnetic susceptibility measurements exhibit weak antiferromagnetic exchange coupling in the complexes.     

Syntheses,crystal structures and magnetic properties of a new thienyl-substituted nitronyl nitroxide and its copper(II) complex

A new building block for molecule-based magnetic materials???thiophene-substituted nitronyl nitroxide, NIT2-thp, [1, NIT2-thp?=?4,4,5,5-tetramethyl-2-(thiophenal-2-yl)imidazoline-1-oxyl-3-oxide] and its copper(II) complex [Cu(hfac)₂]₃(NIT2-thp)₂ (2) (hfac?=?hexafluoroacetylacetonate) have been synthesized and characterized structurally and magnetically. For 1, dimers were formed and arranged through intermolecular interactions, the shortest contact between nitroxide groups is 4.115?Å among adjacent dimers. In 2 two types of copper interaction with 1 give three colinear Cu(II) ions linked by two μ???1,4 bridging nitroxide ligands. The central metal ion is in a distorted octahedron, axially coordinated by two nitroxide oxygen atoms, while the two external metal ions are in distorted square-pyramidal environments with the nitroxide oxygen atom coordinated in the basal plane. Magnetic susceptibility data for 1 and 2 have been measured in the range 3–300?K. There are antiferromagnetic interactions (J?=??3.89?cm^?1) between the dimers of 1 and also ferromagnetic interactions in 2. The magnetic properties of 1 and 2 are discussed in connection with their crystal structures.     

Synthesis,crystal structure,and magnetic properties of a new Fe(II) complex with reduced radical ligands

A new Fe(II) complex, [Fe(HIM2Py)₂(N(CN)₂)₂]?·?2H₂O (HIM2py?=?1-hydroxyl-2(2′-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1?H-imidazole), has been synthesized and characterized. The X-ray analysis reveals that HIM2py ligands are coordinated to iron as an unusual six-membered bidentate chelate with κ²N(py), O(HIM) mode. The variable-temperature magnetic susceptibility suggests that weak antiferromagnetic interactions exist in the complex.     

Synthesis,characterization and structures of copper(II) complexes with amide-based ligands: Unusual formation of a linear trimer and a zig-zag chain and their contrast magnetic behaviour

The present work illustrates the versatile coordination modes of the amide-based ligands towards copper(II) ion. The reaction of the deprotonated form of the ligand, [L¹]²⁻ with CuCl₂ affords a linear trinuclear complex, [Cu₃(L¹)₂(Cl)₂(H₂O)] (1) which has been characterized thoroughly including single crystal structure analysis. The structure of 1 shows that one of the arm of the flexible ligand flips to coordinate second copper(II) centre, resulting in the formation of a trinuclear complex. On the other hand, ligand H₂L² in its deprotonated form reacts with Cu(II) ion to give complex 2 with general formula, [Cu(L²)]_n (2). The crystal structure of the complex 2 shows that each copper is square-pyramidal with 5th coordination coming from the O-atom of the amide group from a neighbouring complex. This results in the generation of an one-dimensional zig-zag chain. The variable temperature magnetic measurements of the complexes, 1 and 2 show that while Cu ions in the former are antiferromagnetically coupled (J = −110.34 cm⁻¹), a weak ferromagnetic interaction (J = +3.08 cm⁻¹) exists in the later. A rationale, based on the orbital overlap from the copper ions and associated ligands, is provided for the observed magnetic coupling between the copper ions.     

Comparison of crystal structures and magnetic properties of two Co(II) complexes containing different dicarboxylic acid ligands

Two novel cobalt(II) complexes, [Co(μ-succinato)(H₂O)₂(pyridine)₂]_n1 and {[Co₂(μ-H₂O)(μ-glutarato)₂(pyridine)₂]·pyridine}_n2 have been synthesized by a wet chemistry method. In complex 1, the Co(II) ions are linked through succinate ligands to created one-dimensional polymeric chain along the b-axis. Complex 2 consists of a polymeric chain of dinuclear Co(II) moieties in which two cobalt(II) ions are linked through a bridging water and two bridging carboxylate groups from two glutarate ligands. The glutarate ligands in complex 2 display two coordination modes, interbinuclear bridging and intrabinuclear bridging. All the bond angles of the alkyl chain in complex 2 are between 115.7° and 118.5°, supporting the gauche conformation. Free pyridine molecules were found in the cavities between the chains. Two strong intramolecular hydrogen bonds are observed between the coordinated water and the uncoordinated carboxylate oxygen atom in both complexes. Complex 2 is further stabilized by π–π stacking of pyridine molecules. Complex 1 is a paramagnet (C = 3.50(1) cm³ K mol and θ = −5.0(5) K) and complex 2 exhibits a broad maximum at 4 K due to weak coupling within the dimeric unit.     

Synthesis, spectral properties, crystal structures and antimicrobial effects of copper(II) pyridinecarboxylate adducts with chelating ligands

The reaction of an ethanolic solution of copper(II) pyridinecarboxylates CuX₂·nH₂O (where X is nicotinate (nic) (n=0) or isonicotinate (isonic) (n=4)) with ethylenediamine (en) in a molar ratio of 1:2 lead to the isolation of solid tetragonally distorted octahedral complexes of the type [Cu(en)₂(H₂O)₂]X₂·nH₂O (n=1 for nic; n=0 for isonic). The analogous reaction of CuX₂·nH₂O with diethylenetriamine (dien) in a molar ratio of 1:1 leads to the formation of square-pyramidal pentacoordinated complexes of the type [CuX(dien)(H₂O)]X. On the other hand, the reaction of equimolar quantities of copper(II) nitrate and dien with nicotinate anions (equimolar quantities of pyridinecarboxylic acid and NaOH) in ethanolic solutions gives a solid monomeric complex [Cu(nic)(NO₃)dien)(H₂O)]·H₂O in which the coordination polyhedron around the Cu(II) atom is a (4+1+1) distorted tetragonal bipyramid. Based on the molecular structure the electronic and IR spectra are discussed. Moreover, the results of the quantitative determination of antimicrobial activity of the isonic complexes [Cu(isonic)₂(H₂O)₄], [Cu(en)₂(H₂O)₂](isonic)₂, [Cu(isonic)(dien)(H₂O)](isonic), as well as isonicotinic acid, ethylenediamine and diethylenetriamine alone are discussed.     

Syntheses, structures and magnetic properties of five iron(II) coordination polymers with flexible bis(imidazole) and bis(triazole) ligands

Five iron(II) coordination polymers, {[Fe(bte)₂(NCS)₂][Fe(bte)(H₂O)₂(NCS)₂]}_n (1), [Fe(bime)(NCS)₂]_n (2), [Fe(bime)(dca)₂]_n (3), [Fe(bime)₂(N₃)₂]_n (4) and [Fe(btb)₂(NCS)₂]_n (5), were synthesized using the flexible ligands 1,2-bis(1,2,4-triazol-1-yl)ethane (bte), 1,2-bis(imidazol-1-yl)ethane (bime) and 1,4-bis(1,2,4-triazol-1-yl)butane (btb), together with NCS⁻, dicyanamide (dca) and N₃⁻. The compound 1 contains two kinds of motifs (double chain and single chain) and forms a three-dimensional hydrogen bonded network; 2 and 3 contain one-dimensional triple chains; and 4 and 5 form two-dimensional (4, 4) networks. The coordination anions (NCS⁻, dca and N₃⁻) and the structural characteristics of the ligands (bte, bime and btb) play an important role in the assembly of the topologies. Magnetic studies reveal that 1-5 remain in the high-spin state over the whole temperature range 2-300 K and no detectable spin-crossover is observed.     

Two Cd(II) complexes derived from mercapto-triazole ligands: syntheses,crystal structures,and luminescent properties

Two cadmium complexes, {[Cd(a-ptt)(ptt)]·H₂O} _n (1) and [Cd(a-Hmtt)₂(SO₄)H₂O]·CH₃OH (2), have been prepared based on 4-amino-3-(4-pyridine)-5-mercapto-1,2,4-triazole (a-Hptt) and 4-amino-3-methyl-5-mercapto-1,2,4-triazole (a-Hmtt), respectively. In 1, amino-triazole ligand a-Hptt can partly be deaminated and transformed into 3-(4-pyridine)-5-mercapto-triazole (Hptt) under hydrothermal conditions. X-ray diffraction analysis reveals that 1 exhibits an unusual 2-D lampshade-type layer structure in which the amino ligand a-ptt and the deamination ligand ptt display exo-tridentate bridging and bidentate bridging, respectively. Complex 2 is mononuclear and further assembled into a 3-D supramolecular architecture via non-covalent interactions. Complexes 1 and 2 were characterized by elemental analyses, IR, and thermogravimetric analyses. Furthermore, solid-state luminescent properties of 1 and 2 have also been investigated.     

Synthesis and crystal structures of three novel coordination polymers constructed from Ag(I) thiocyanate and nitrogen donor ligands

Three supramolecular coordination polymers (SCPs) [(AgSCN)₂L] {L = 4,4′-bipyridine (bpy) (1), trans-1,2-bis(4-pyridyl)ethylene (tbpe) (2) and phenazine (phenz) (3)} have been synthesized and structurally characterized by single-crystal X-ray diffraction. Synthesis was affected in H₂O/acetonitrile/NH₃ media at room temperature. The bpy, tbpe and phenz bipodal ligands adopt different conformations which would affect the skeleton of the (AgSCN)_n building blocks that allow the interconnection of the (AgSCN)_n fragments and propagation of the network structure in three dimensions. Supramolecular interactions such as hydrogen-bonding, argentophilic interaction and π–π stacking play an important role in the assembly of these coordination polymers.     

Syntheses and crystal structures of a series of new divalent metal phosphonates with imino-bis(methylphosphonic acid)

Hydrothermal reactions of divalent transition metal salts with imino-bis(methylphosphonic acid), NH(CH₂PO₃H₂)₂ (H₄L) afforded three new metal phosphonates, namely, Cu[NH(CH₂PO₃H)₂] 1, {Co[NH₂(CH₂PO₃H)(CH₂PO₃)](H₂O)₂}·H₂O 2 and Mn[NH₂(CH₂PO₃H)(CH₂PO₃)](H₂O) 3. When HO₂C(CH₂)₃N(CH₂PO₃H₂)₂ was used as the phosphonate ligand and 4,4′-bipy as the second metal linker, {Cu₄[NH(CH₂PO₃)₂]₂(4,4′-bipy)(H₂O)₄}·9H₂O 4 with a pillared layered architecture was obtained. The NH(CH₂PO₃)₂ anion resulted from the cleavage of the HO₂C(CH₂)₃-group during the reaction. Although compounds 1-3 have a same M/L ratio (1:1), they exhibit totally different structures.Compound 1 has a linear chain structure, in which each pair of square-pyramidal coordinated copper(II) ions are bridged by two phosphonate oxygen atoms to form a Cu₂O₂ dimeric unit, and such dimeric units are further interconnected via phosphonate groups to form a [010] chain. Compound 2 has a layered architecture built from CoO₆ octahedra bridged by phosphonate ligands. In compound 3, the interconnection of the manganese(II) ions by bridging imino-diphosphonate ligands leads to a 3D network. Compound 4 has a pillar-layered structure, the layers composed of Cu(II) ions bridged by aminodiphosphonate ligands are interconnected by 4,4′-bipy ligands to form channels along c-axis. Several factors that affect the structures of the metal phosphonates formed have also been discussed. Compounds 2 and 3 show predominant antiferromagnetic interactions between magnetic centers.     

Syntheses, characterization, X-ray crystal structures and emission properties of five oxovanadium(V) complexes with pyridyl/pyrimidyl-pyrazole derived ditopic ligands

Four oxovanadium(V) complexes of heterocycle based ditopic ligands PyPzOAP (N-[amino(pyridin-2-yl)methylidene]-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazonic acid), PyPzOAPz (N-[amino(pyrazin-2-yl)methylidene]-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazonic acid), PymPzOAP (N-[amino(pyridin-2-yl)methylidene]-1-(4,6-dimethylpyrimidin-2-yl)-5-methyl-1H-pyrazole-3-carbohydrazonic acid) and PyPzCAP (5-methyl-1-(pyridin-2-yl)-N′-[1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazide) and a binuclear (di-μ-oxo) oxovanadium(V) complex of the ligand PymPzCAP (1-(4,6-dimethylpyrimidin-2-yl)-5-methyl-N′-[1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazide) have been investigated. The ligands act as uninegative NNO tridentates donors for the VO₂⁺ ion exhibiting their monotopicity. The ligands show varying emission properties due to the presence of fluophoric groups like 1-(2-pyridyl)pyrazole or 1-(2-pyrimidyl)pyrazole. The vanadium(V) complexes show fluorescence quenching with respect to the used ligands to a varying extent. The complexes were characterized by UV-Vis, IR, cyclic voltammetry and X-ray crystallography.     

Two-dimensional layer architecture assembled by Keggin polyoxotungstate, Cu(II)-EDTA complex and sodium linker: Synthesis, crystal structures, and magnetic properties

Reaction of Keggin polyoxotungstate with copper(II)-EDTA (EDTA=ethylenediamine tetraacetate) complex under mild conditions led to the formation of hybrid inorganic-organic compounds Na₄(OH)[(Cu₂EDTA)PW₁₂O₄₀]·17H₂O (1) and Na₄[(Cu₂EDTA)SiW₁₂O₄₀]·19H₂O (2). The single-crystal X-ray diffraction analyses reveal their two structural features: (1) one-dimensional chain structure consisting of Keggin polyoxotungstate and copper(II)-EDTA complex; (2) Two-dimensional layer architecture assembled by the one-dimensional chain structure and sodium linker. The results of magnetic measurements in the temperature range 300-2 K indicated the existence of ferromagnetic exchange interactions between the Cu^II ions for both compounds. In addition, TGA analysis, IR spectra, and electrochemical properties were also investigated to well characterize these two compounds.