Octahedral Arrangement Research Articles

Syntheses and DFT/GIAO/NMR Study of Polyhedral Selenaboranes: The First Selenahexaborane(5)closo-1-SeB5Cl5

The six-vertex closo-1-SeB5Cl5 (1) and the 12-vertex closo-1-SeB11Cl11 (2) selenaboranes were prepared in low yields from the co-pyrolysis reaction of B2Cl4 with Se2Cl2 at 330 °C. Both compounds are sublimable, colorless solids and were tentatively characterized by 11B NMR and high-resolution mass spectroscopy. DFT/GIAO/NMR calculations support octahedral and icosahedral arrangements for 1 and 2, respectively, as expected due to their closo electron counts. Compound 1 represents the first example of a polyhedral selenaborane with a cluster size smaller than 10 vertices.

(Invited) Synthesis and Characterization of Unprecedented D2h -Symmetrical Trans-1-(S,R,R,S-bis-pyrrolidine)-Tetra-malonate Hexakis Adducts of C60

The unique chemical and physical properties of fullerenes and their derivatives is mainly the result of their unique electron accepting abilities and their high charge transport capabilities in three dimensions. The octahedral arrangement of the addends in hexaadducts of C60 is unique in organic chemistry. However, stereo-chemically controlled functionalization of fullerenes has been scarcely addressed so far. Here we report the synthesis and characterization of unprecedented D2h -symmetrical trans-1-(S,R,R,S-bis-pyrrolidine)-tetra-malonate hexakis adducts of C60, employing the topologically controlled method introduced by Krӓutler et al., followed by a 1,3-dipolar cycloaddition reaction. Figure 1. Synthesis of D2h -symmetrical trans-1-(S,R,R,S-bis-pyrrolidine)-tetra-malonate hexakis adducts of C60. Figure 1

Solvent-rich layered cobalt(II) 1,4-benzenedicarboxylate based on binuclear {Co2(μ-OH2)(RCOO)2} secondary building unit

The reaction of a ditopic ligand, 1,4-benzenedicarboxylic acid (H2bdc) with Co(CH3COO)2·4H2O in solution resulted in a solvent-rich layered coordination polymer with the composition {[Co2(μ2-OH2)(bdc)2(dmf)2(H2O)2]·(dmf)·3(H2O)}n (1) whose crystal structure was determined by single crystal X-ray diffraction. The compound is built on the binuclear {Co2(μ2-OH2)(COO)2} metal clusters, where each Co(II) atom is coordinated by six oxygen atoms in a distorted octahedral arrangement. The crystal lattice of 1 hosts the dmf and water solvent molecules via the OH⋯O hydrogen bonding with coordination network. The easy destruction of the crystals due to the partial solvent loss occurs rapidly in ambient conditions and is confirmed by the TGA data.

Homoleptic Zinc(II) Complexes Based on 4′‐(2‐Thienyl)‐terpyridine: Preparation, Structures, and Properties

The homoleptic complexes ZnII(4′‐(2‐(5‐R‐thienyl))‐terpyridine)2(ClO4)2 [R = hydrogen (1), bromo (2), methyl (3), and methoxy (4)] were prepared. Their structures were determined by single‐crystal X‐ray diffraction analyses, and further characterized by high resolution mass, infrared spectra (IR), and elemental analyses. Single crystal X‐ray diffraction analysis showed that ZnII ions in the complexes are both six‐coordinate with N6 coordination sphere, displaying distorted octahedral arrangements. The absorption and emission spectra of the homoleptic ZnII complexes were investigated and compared to those of the parent complex ZnII(4′‐(2‐thienyl))‐terpyridine)2(ClO4)2. The UV/Vis absorption spectra showed that the complexes all exhibit strong absorption component in UV region, moreover, complex 4 has an absorption component in the visible region. Thus, the photocatalytic activities of the complexes in degradation of organic dyes were investigated under UV and visible irradiation.

Neutral and Cationic Bis-Chelate Monoorganosilicon(IV) Complexes of 1-Hydroxy-2-pyridinone

A series of spirocyclic monoorganosilicon compounds of the form RSi(OPO)2Cl (R = phenyl (1), p-tolyl (2), benzyl (3), Me (4), tBu (5), thexyl (6); OPO = 1-oxo-2-pyridinone) was synthesized and characterized by 1H, 13C, and 29Si NMR spectroscopy, X-ray crystallography, and elemental analysis. In the solid state, complexes 1–3 are neutral and possess cis-OPO ligands in an octahedral arrangement and complexes 4–6 are cationic and possess effectively trans-OPO ligands in nearly ideal square-pyramidal geometries along the Berry pseudorotation coordinate. In 4–6, chloride dissociation is attributed to the additive effect of multiple intermolecular C–H···Cl interactions in their crystals. In DMSO-d6 solution, compounds 1–6 form cationic hexacoordinate DMSO adducts with trans-OPO ligands, all of which undergo dynamic isomerization with energy barriers of ∼18–19 kcal/mol. Compounds with better leaving groups, (p-tolyl)Si(OPO)2X (X = I (7), X = triflate (8)), exhibit solution NMR spectra identical with those of 2, ...

Structural variety of mono- and binuclear transition metal complexes of 3-[(2-hydroxy-benzylidene)-hydrazono]-1-(2-hydroxyphenyl)-butan-1-one: Synthesis, spectral, thermal, molecular modeling, antimicrobial and antitumor studies

A new polydentate Schiff base ligand and its metal complexes were synthesized and characterized by elemental analyses, IR, 1H NMR, electronic, ESR and mass spectra, conductivity and magnetic susceptibility measurements as well as thermal analyses. The free ligand was synthesized by condensation of o-acetoacetylphenol with salicylaldehyde hydrazone. The analytical and spectroscopic tools showed that the obtained complexes are mono- and binuclear complexes, which can be generally formulated as: [(L)M2X2(H2O)m]·nZ; M = Cr, Fe, Ni or Cu, X = OAc or NO3, m = 5 or nil and n = 3, 1.5 or 0.5 and Z = EtOH or H2O, [(H2L)2M(X)m].nH2O; M = Mn, Zn, or Cd, X = EtOH, H2O or nil, m = 2 or nil and n = 3.5 or 0, [(HL)2Co2]·0.5H2O and [(H2L)2UO2(H2O)]. The metal complexes displayed octahedral, tetrahedral and square-planar geometrical arrangements, while uranium complex displayed seven-coordinate. Kinetic parameters (Ea, A, ΔH, ΔS and ΔG) of the thermal decomposition stages have been evaluated using Coats–Redfern equations. The molecular structural parameters of the ligand and its metal complexes have been calculated and correlated with the experimental data such as IR. The antimicrobial activity of the ligand and its complexes was screened against some kinds of bacteria and fungi. The antitumor activity of the ligand and its Ni(II) and Cu(II) complexes was investigated against HepG2 cell line.

Rehydroxylation in smectites and other clay minerals observed in-situ with a modified thermogravimetric system

Dehydroxylation-rehydroxylation experiments were performed on various dioctahedral aluminous 2:1 layer clay minerals using the precise thermogravimetry (TG) system equipped with a continuous N2 gas flow enriched with H2O vapor of controlled concentration. The setup and rehydroxylation conditions applied are specifically sensitive to study in-situ rehydroxylation of smectites with various octahedral compositions and vacancy, saturated with counterions in various sizes and valences. Under the conditions applied, the pyrophyllite structure does not rehydroxylate, illite shows a minor ability to rehydroxylate, and smectites present an entire range of potential rehydroxylation, from remaining in the completely dehydroxylated state to an almost complete rebuild of the octahedral sheet.The mass gained during single- or multi-isotherm rehydroxylation matches the mass lost during the subsequent (secondary) dehydroxylation. In smectites, the Al-pyrophyllite-like arrangement is preferentially rehydroxylated, but at higher degrees of rehydroxylation, OH groups in other octahedral arrangements are also rebuilt. Among the temperatures tested, smectites and illite rehydroxylate most intensively during isothermal heating at 400°C (H2O content=0.28molH2O/m3), which is the onset temperature of dehydroxylation of their rehydroxylated forms. The smectites capability to rehydroxylate comes from an interplay of the counterions' size, the tetrahedral substitution in the 2:1 layers, and the negative charge generated in the former-octahedral sheet that controls the ability of cations to move from the surface of the tetrahedral sheet or from the octahedral sheet back to the interlayer.The conventional (time)1/4 power law and the logarithmic kinetic models of rehydroxylation produced good fits of the experimental data. Calculation of activation energies (Ea) for the rehydroxylation reaction produced values from 30kJ/mol to 173kJ/mol, highly dependent on the interlayer cation, 2:1 layer structure, and the experimental protocol. The kinetic models developed for rehydroxylation at temperature near ambient remain valid for the experiments up to 400°C. At 500°C the mechanism of rehydroxylation is influenced by other factors.

Novel Copper(I) Clusters with 2‐(Diphenylphosphanyl)anilide Ligands. Synthesis and Crystal Structures of [Cu6X2(NHR)4] (X = Cl, Br, I; R = C6H4‐2‐PPh2)

Treatment of copper(I) halides CuX (X = Cl, Br, I) with lithium 2‐(diphenylphosphanyl)anilide [Li(HL)] in THF led to the formation of hexanuclear copper(I) complexes [Cu6X2(HL)4] [X = Cl (1), Br (2), I (3)]. In compounds 1–3, the copper atoms are in a distorted octahedral arrangement and the amide ligands adopt a μ3‐κP,κ2N bridging mode. Additionally there are two μ2‐bridging halide ligands. Each of the [Cu6X2(HL)4] clusters comprises two copper atoms, which are surrounded by two amide nitrogen atoms in an almost linear coordination [Cu–N: 186.2(3)–188.0(3) pm] and four copper atoms, which are connected to an amide N atom, a P atom, and a halogen atom in a distorted trigonal planar fashion [Cu–N: 199.6(3)–202.3(3) pm)].

The influence of local distortion on the electrical properties of the (1-x)(K0.5Na0.5)NbO3-x(Ba0.8C0.2)TiO3 system

In this work, the composition of (1-x)(K0.5Na0.5)NbO3-x(Ba0.8Ca0.2)TiO3 and the so-called (1-x)KNN-xBCT were successfully synthesised using a combination of solid-state reaction and co-precipitation oxalate methods. Phase identification and crystal structure determination were carried out by means of XRD pattern analysis. Local distortion due to the dopant was studied by XANES at the Nb L3-edge, XANES at the Ti K-edge, and EXAFS at the Ti K-edge. Electrical characterisation of dielectric properties and conductivity were investigated to elucidate the changes in local distortion. XRD analysis at room temperature concluded that while x=0 has an orthorhombic structure, x=0.1 and x=0.2 have as tetragonal structure. Furthermore, EXAFS analysis using Artemis revealed the oxygen octahedral distortion and distance of TiNb′ to its surroundings. Conductivity measurements at various temperatures showed that at room temperature, all samples behave as positive charge carriers, and when the temperature is increased, the charge carriers become negative. The temperatures at which charge carrier alteration increases with increasing BCT content are: 150°C for KNN, 180°C for 0.9KNN-0.1BCT and 220°C for 0.8KNN-0.2BCT. The characterisation of dielectric properties exhibited two Curie temperatures at 220°C and 420°C for KNN, while for KNN-BCT, the peaks shift to lower temperature and become broader, which is a typical relaxor characteristic and was thought to be related to the distortion of oxygen octahedral arrangement surrounding the B sites in the ABO3 structure.

Oxidative halogenation of Sn(II)heteroaryl alkenolates: Formation of unusual trans-dihalo Sn(IV) complexes

A series of novel tin(IV)-heteroaryl alkenolates of the general formula [Sn(DMOTFP)2X2] (3–6, X=F, Cl, Br, I) were prepared by direct oxidative halogenation of the corresponding tin(II) derivative [SnII(DMOTFP)2] (2) and by cleavage of the carbon-tin bonds in diphenyltin dichloride [Ph2SnCl2] by (4,5-dimethyloxazolyl)-1,1,1-trifluoropropen-2-ol, (H-DMOTFP, 1) with a subsequent halide exchange reaction. The molecular structures elucidated in solution (multi-nuclear NMR spectroscopy) and by single crystal X-ray diffraction confirmed the sixfold coordination of the tin(IV) center with a distorted octahedral arrangement of ligands. An unusual centrosymmetric octahedral trans-dihalo configuration was found for the compounds [SnIV(DMOTFP)2X2] (X=Cl, Br, I), while the compound [Sn(DMOTFP)2F2] adopted a cis-dihalide configuration.

Synthesis and Cytotoxic Activity of 6-Hydroxy-4- Methyl-5,7-(Bis-Phenylazo) Coumarin with Divalent Transition Metal Ions

Background/Objectives: One of the severe disease intimidating human health and continues to be a main health problem worldwide is cancer. Hence, discovering new compounds with powerful anticancer activity is of extreme important. The main objective of this paper is the synthesize 6-hydroxy-4-methyl-5,7-(bis-phenylazo) coumarin and its complexes and evaluate the cytotoxic activity of the ligand and complexes against breast cancer cells. Methods/Statistical Analysis: A novel compounds of 6-hydroxy-4-methyl-5,7-(bis-phenylazo) coumarin have been synthesized by 6-hydroxy-4-methylcoumarin. The complexation of nickel (II), copper (II) and cobalt (II) using this ligand gave salt type complexes with the formula of M(C22H15O3N4) the compounds were characterized by microelemental analysis, infra-red, nuclear magnetic resonance spectroscopic techniques and molar conductivity. Cytotoxic activity for the ligand and the complexes were evaluated against breast cancer cells by using MTT assay and the absorbance at 570 nm was measured by ELISA reader. Findings: The CHN analysis of the compounds are in good agreement with the calculated values and the spectroscopic analysis of the complexes indicated that the ligand coordinated to the metal centres as polydentate ligand in bisazocoumarin and form a distorted octahedral arrangement around nickel (II), copper (II) and cobalt (II) centres. The molar conductivity of the divalent metal ions complexes was small which directly supports the fact that all of the investigated complexes are non ionic. The overall results of cells MCF7 breast cancer revealed of cell proliferation was much more highly inhibited by the ligand and complexes Cu, Co and Ni with cell viability 5.21%, 17.36%, 46.20% and 74.43%, respectively at a concentration of 30 mg/ml compared to untreated control cells and IC50 values of the ligands and complexes of Cu, Co and Ni were 1.87, 1.87, 30 and >30 g/ml, respectively. Improvements: Lastly, some suggestions were presented to use these compounds in vivo should be assessed to obtain worthy anticancer drugs.

Preparation and Characterization of Bi-metallic and Tri-metallic Metal Organic Frameworks Based on Trimesic Acid and Co(II), Ni(II), and Cu(II) Ions

Trimesic acid-M1(II):M2(II) (M1,2(II)=M(II)=Co(II), Ni(II) and Cu(II)) bi-metallic or tri-metallic organic frameworks (MOFs) were synthesized by the reaction of trimesic acid (H3BTC) ligand with the corresponding MCl2nH2O aqueous solutions. Here, bi- and tri-metallic MOF preparations were demonstrated by using H3BTC as an organic linker, with dual metal ion mixtures at different mole ratios such as Co(II):Ni(II), Ni(II):Cu(II), and Cu(II):Co(II) as metal ion sources in the synthesis of bi-metallic MOFs, and the triple metal ion mixture of Co(II):Ni(II):Cu(II) as the metal ion source in the synthesis of tri-metallic MOFs. The bi- or tri-metallic MOFs were characterized via the Brunauer–Emmett–Teller method, thermogravimetric analyzer (TGA), and magnetic susceptibility measurements with the Gouy method, FT-IR spectroscopy, and electronic spectral studies. The results revealed that the H3BTC MOFs have octahedral and distorted octahedral arrangement around the metal ions, and the d–d transition was not observed in the complex. It was further found that all the prepared MOFs contain water molecules confirmed by Fourier transform infrared (FT-IR) and TGA analyses. The FT-IR spectra of the MOF complexes were characterized by the appearance of a broad band in the region of 3454–3300 cm−1 due to the ν(-OH) of the coordinated water; therefore, the location of the two water molecules was assumed to be inside the complex structure. Remarkably, the synthesized bi-metallic MOFs had unique and distinct colors depending on the amounts of metal ions used in the feed, implying that these bi-metallic MOFs with tunable M1(II) and M2(II) ratios offer great potential in the design of color-coded materials for use as sensors.

Spectroscopic, DFT, magnetic and biological activity evaluation of Pd(II), Pt(II) and Ru(III) complexes of Nitazoxanide

[M(NTZ)Cl2] (M=Pd(II) (1), Pt(II) (2) and NTZ=Nitazoxanide) and [Ru(NTZ)Cl3(OH2)] (3) complexes have been synthesized and characterized by elemental analysis, thermogravimetric analysis, IR, 1HNMR, conductance and magnetic measurements. NTZ is coordinated to the metal ions as a bidentate ligand via the N-atom of the thiazole ring and amide CO. The susceptibility of Staphylococcus aureus and Escherichia coli towards NTZ and its complexes has been evaluated. The calculated electronic structures and the related electronic transitions have been obtained at TD-DFT/B3LYP/LANL2DZ level of theory. Upon the chelation, the value of the natural charge of Ru(III) ion (+0.182e) was found to be lower than those of Pd(II) and Pt(II) ions (∼+0.398e) in their complexes, which reflects the higher complexation ability of NTZ towards the high oxidation state and low-d-orbital population metal ion. Complex 3 is existing in a low-spin octahedral arrangement. The DC magnetic measurements in terms of Weiss constant revealed the presence of the intermolecular interactions among the spin carriers. The low stability of 1–3inDMSO and the rate of the releasing of NTZ was the factor which reproduces the order of the toxicity (NTZ>2>3>1) against the tested microbes.

Coordination behavior of new bis(tridentate ONO, ONS and ONN) donor hydrazones towards some transition metal ions: Synthesis, spectral, thermal, antimicrobial and antitumor studies

Three new hydrazone ligands, H2L1, H2L2 and H4L3, were prepared by condensation of 4,6-bis(1-hydrazonoethyl)benzene-1,3-diol with furan-2-carboxaldehyde, thiophene-2-carboxaldehyde and 1H-pyrrole-2-carboxaldehyde, respectively. The ligands reacted with copper(II), nickel(II), cobalt(II), zinc(II), cadmium(II) and dioxouranium(VI) ions to yield binuclear complexes formulated as [(L)M2(OAc)2(H2O)n(EtOH)m]·xH2O·yEtOH where L = L1 or L2; M = Cu, Ni, Co, Zn or Cd; n = nil, 1 or 4; m, x and y = nil or 1, [(H2L2)Cd2(OAc)4(H2O)2]·EtOH, [(L)(UO2)2(OAc)2(H2O)2Y2]·nH2O where L = L1 or L2; Y = nil or H2O; n = 2.5 or 7, [(L3)M2(H2O)6]·nH2O where M = Cu or Zn; n = 1 or 6, [(L3)(UO2)2(H2O)4]·2.5H2O and dimeric complexes; [(L1)2Ni2]·3H2O and [(H2L3)2M2]·nH2O where M = Ni or Co; n = 1.5 or 3. The ligands and their metal complexes were characterized by elemental analyses, IR, 1H and 13C NMR, electronic, ESR and mass spectra, conductivity, magnetic susceptibility measurements and powder XRD as well as thermal analysis. The coordinating sites are phenolic oxygens, azomethine nitrogens and the hetero O/N/S atoms. Octahedral, tetrahedral and square planar geometrical arrangements are proposed for metal complexes whilst the uranium ion is hepta- or octa-coordinated. The kinetics of the thermal decomposition for some metal complexes were studied and their thermodynamic parameters were calculated using Coats-Redfern method. The antimicrobial activity of the ligands and their complexes was screened. The antitumor activity of the ligands and their complexes was tested on Ehrlich Ascites Carcinoma. Copper(II) complexes showed promising IC50 values, which are comparable to that of cisplatin.

Schiff base pyrazolone complexes of iron (III): synthesis, characterization, antimicrobial and antioxidant activity

A series of novel Schiff base tetradentate ligands and its iron (III) coordination compounds were synthesized, characterized and evaluated for antibacterial and antioxidant activity. All the synthesized ligands and complexes were characterized by spectroscopic and crystallographic techniques. Electronic spectra, Mossbauer spectra, magnetic moment and conductance study evidence the fact of octahedral arrangement around iron (III). The in vitro antimicrobial Schiff base complexes bear polar and nonpolar properties together; this makes them suitable for permeation to the cells and tissues, it enhances the activity against the bacteria. The antioxidant properties were measured with DPPH (2,2’-diphenyl-2-picrylhydrazyl). These properties were due to the unique feature of ligands such as highest lipophilicity, lowest electron withdrawing power and highest polarisability.

A Capped Octahedral MHC6 Compound of a Platinum Group Metal.

A MHC6 complex of a platinum group metal with a capped octahedral arrangement of donor atoms around the metal center has been characterized. This osmium compound OsH{κ(2) -C,C-(PhBIm-C6 H4 )}3 , which reacts with HBF4 to afford the 14 e(-) species [Os{κ(2) -C,C-(PhBIm-C6 H4 )}(Ph2 BIm)2 ]BF4 stabilized by two agostic interactions, has been obtained by reaction of OsH6 (PiPr3 )2 with N,N'-diphenylbenzimidazolium chloride ([Ph2 BImH]Cl) in the presence of NEt3 . Its formation takes place through the C,C,C-pincer compound OsH2 {κ(3) -C,C,C-(C6 H4 -BIm-C6 H4 )}(PiPr3 )2 , the dihydrogen derivative OsCl{κ(2) -C,C-(PhBIm-C6 H4 )}(η(2) -H2 )(PiPr3 )2 , and the five-coordinate osmium(II) species OsCl{κ(2) -C,C-(PhBIm-C6 H4 )}(PiPr3 )2 .

Photorelease and Cellular Delivery of Mitocurcumin from Its Cytotoxic Cobalt(III) Complex in Visible Light.

Ternary cobalt(III) complexes of curcumin (Hcur) and mitocurcumin [Hmitocur, a dicationic bis(triphenylphosphonium) derivative of curcumin] having a tetradentate phenolate-based ligand (H2L), namely, [Co(cur)(L)] (1) and [Co(mitocur)(L)]Cl2 (2), were prepared and structurally characterized, and their photoinduced cytotoxicity was studied. The diamagnetic cobalt(III) complexes show an irreversible Co(III)-Co(II) redox response and a quasireversible curcuminoid-based reduction near -1.45 and -1.74 V SCE, respectively, in DMF/0.1 M [(n)Bu4N](ClO4). The complexes exhibit a curcumin/mitocurcumin-based absorption band near 420 nm. Complex 1 was structurally characterized by X-ray crystallography. The structure contains the metal in a CoN2O4 distorted octahedral coordination arrangement with curcumin binding to the metal in its enolic form. Binding to cobalt(III) increases the hydrolytic stability of curcumin. Complex 2, having a dicationic curcuminoid, shows significant cellular uptake and photoinduced cytotoxicity compared to its curcumin analogue 1. The dicationic cobalt(III) complex 2 has significantly better cellular uptake and bioactivity than the neutral species 1. Complex 2 with mitochondrial localization releases the mitocurcumin dye upon exposure to visible light (400-700 nm) in human breast cancer MCF-7 cells through photoreduction of cobalt(III) to cobalt(II). Complex 2 displays a remarkable photodynamic therapy (PDT) effect, giving an IC50 value of ∼3.9 μM in visible light (400-700 nm) in MCF-7 cells while being much less toxic in the dark (>50 μM). The released mitocurcumin acts as a phototoxin, generating intracellular reactive oxygen species (ROSs). The overall process leads to light-controlled delivery of a curcuminoid (mitocur) into the tumor cells while the dye alone suffers from hydrolytic instability and poor bioavailability.

Synthesis, crystal structure and magnetic property of one-dimensional heterometallic cyanide-bridged complex: {[Cu(hmpH)2Cu(hmp)(hmpH)Co(μ-CN)4(CN)2]·2H2O}n

A novel one-dimensional (1D) coordination polymer, {[Cu(hmpH)2Cu(hmp)(hmpH)Co(μ-CN)4(CN)2]·2H2O}n (1) (hmpH=2-pyridinemethanol), was synthesized and characterized by elemental analysis, spectral (FT-IR, Raman and EPR) methods, thermal analysis, single crystal X-ray diffraction and magnetic measurement techniques. In 1, the Co(III) ions are six coordinated with six cyanide-carbon atoms in a octahedral arrangement. The Cu1 and Cu2 ions are coordinated with two cyanide-nitrogen atom, two nitrogen and two oxygen atoms from chelating two hmpH and hmpH/hmp ligands, respectively. The hmpH ligand in the complex has behaved as both anionic ligand (with its hydroxyl group being deprotonated) and as neutral form with the preserved OH group. The hydrogen bonding interactions between the crystal water molecules and hydroxyl group of hmpH ligands extends structure to the two dimensional (2D) supramolecular structure. The 2D layers were extended into 3D supramolecular networks by π⋯π and C–H⋯π interactions between pyridine rings of hmpH ligands. Variable temperature magnetic susceptibility measurement recorded in the 10–300K range showed the presence of a very small antiferromagnetic within chains through CN bridges. Thermal stability and decomposition reactions of the complex take place in the temperature range 30–950°C in a dry air atmosphere.

Syntheses, Crystal Structures, and Magnetic Properties of Two Mononuclear Nickel‐Nitronyl Nitroxide Radical Compounds

AbstractTwo nickel(II) complexes were synthesized and structurally as well as magnetically characterized by using two positional isomeric nitronyl nitroxide radical ligands and H3cda as co‐ligand: [Ni(NIToPy)(cda)]H2O·CH3OH (1) and [Ni(IM4Py)2(cda)H2O] (2) [NIToPy = 2‐(3′‐pyridinyl)‐4,4,5,5‐tetramethyl‐4,5‐dihydro‐1H‐imidazolyl‐1‐oxyl‐3‐oxide; IM4Py = 2‐(4′‐pyridinyl)‐4,4,5,5‐tetramethylimidazoline‐l‐oxyl; H3cda = 4‐hydroxypyridine‐2,6‐dicarboxylic acid]. Single‐crystal structures analyses show that both complexes have similar mononuclear structures, in which the central NiII ions are hexacoordinated with a distorted octahedral arrangement. The magnetic properties of 1 and 2 were studied, and antiferromagnetic interactions between NiII ion and radicals are observed.

Crystal structure of bis-(2-methyl-1H-imidazol-3-ium) di-hydroxidobis(oxalato-κ(2) O (1),O (2))stannate(IV) monohydrate.

In the structure of the hydrated title salt, (C4H7N2)2[Sn(C2O4)2(OH)2]·H2O, the asymmetric unit comprises one stannate(IV) dianion, two organic cations and one water mol-ecule of crystallization. The [Sn(C2O4)2(OH)2](2-) dianion consists of an Sn(IV) atom chelated by two oxalate anions and coordinated by two OH(-) ligands in a cis octa-hedral arrangement. Neighbouring anions are connected through O-H⋯O hydrogen bonds between hydroxide groups and non-coordinating oxalate O atoms into layers expanding parallel to (100). In addition, cations and anions are linked through N-H⋯O hydrogen bonds, and the water mol-ecule bridges two anions with two O-H⋯O hydrogen bonds and is also the acceptor of an N-H⋯O hydrogen bond with one of the cations. Weak C-H⋯O hydrogen bonds are also observed. The intricate hydrogen bonding leads to the formation of a three-dimensional network.