Inorganic Chemistry

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Although silicon nanoparticles dispersed in liquids are used in various applications ranging from bio-labeling to hydrogen production, their reactivities with their solvents and their catalytic properties remain still unexplored. Here, we discovered that, because of their surface structures and mechanical strain, silicon nanoparticles react strongly with their solvents and may act as catalysts for the dehydrogenation, at room temperature, of secondary alcohols (e.g. isopropanol) into ketones and hydrogen. This catalytic reaction was monitored by gas chromatography, pH measurements, mass spectroscopy and solid-state NMR. This discovery provides new understanding of the role played by silicon nanoparticles, and nanosilicon in general, in their reactivity in solvents in general as well as being candidates in catalysis.

Ruthenium compounds of general formula Cp′RuX(PR 2 R′) 2 (Cp′ ) η 5 -C 5 H 5 (Cp), η 5 -C 9 H 7 (Ind), are examined as catalysts for the aldehyde olefination starting from diazo compounds, phosphanes, and aldehydes. Cp*RuCl(PPh 3 ) 2 is highly active for the olefination of several aldehydes, displaying a very high E-selectivity, as well as for ketone olefination (with benzoic acid as cocatalyst). The reaction's mechanism is substantiated by the isolation of a catalytic active reaction species, namely, a mixed carbene/phosphane ruthenium complex, Cp*RuCl(dCHCO 2 Et)(PPh 3 ) (8). Spectroscopic studies reveal that the latter compound reacts with PPh 3 to produce the phosphorus ylide Ph 3 PdCHCO 2 -Et, which further reacts with the aldehyde to produce the olefin.

A new allelochemical (1), m.p. 282-284 ºC, m.f. C31H36O19, [M] + 712 (FABMS), has been isolated from methanolic extract of the seeds of Adenanthera pavonina Linn. alongwith two known compounds 2',4',7-trihydroxy isoflavone and isovitexin. The structure of a new compound was characterized as 3,5,7,3',4'-pentahydroxy flavone-3'-O-α-L-rhamnopyranosyl-(1→4)-O-α-L-arabinopyranosyl-(1→3)-O-β-D-xylopyranoside, by various colour reactions, spectral analysis and chemical degradations.

In the present study, we have used neem (Azadirachta indica) leaf powder as a non-conventional biosorbent for the removal of Cd(II) from aqueous solutions. Batch experiments were conducted to identify equilibrium time, equilibrium adsorbent dosage and equilibrium metal concentration. The data were analyzed by applying Freundlich, Langmuir and Temkin isotherm models. The kinetics of adsorption was studied from the data obtained through pseudo-first-order and pseudo-second-order equations. The adsorption data best fitted for Freundlich isotherm and the process obeyed pseudo-second-order. The adsorption of Cd(II) was rapid initially and reached the peak at 180 min of agitation (96.9 %). The adsorbent dose indicated instantaneous adsorption (92.8 %) at 0.4 g and reached equilibrium at 1.6 g (97.4 %). The adsorption was rapid initially (99.6 %) at Cd(II) concentration of 60 mg L -1 and decreased (96.2 %) at 200 mg L -1 . It was revealed that neem leaf powder has effective potential for the removal of Cd(II) from aqueous solution.

Oxidative dehydrogenation of ethane to ethylene was investigated at temperatures below 500 °C over Cr-O and Cr-V-O oxide catalysts prepared by the complexation method. The catalysts were characterized by XRD, H 2 TPR, and XPS techniques. The Cr-O catalyst was more active than Cr-V-O mixed oxide in the selective oxidation of ethane using O 2 or CO 2 as the oxidant. Cr-O showed activity at temperatures as low as 250 °C. TPR results showing easier reduction of Cr-O at much lower temperatures than Cr-V-O support a correlation between the reducibility and the activity of the catalysts in this reaction. XPS results indicating the reduction of chromium and vanadium species from Cr 6+ to Cr 3+ and from V 5+ to V 4+ (and V 3+ ) support a redox mechanism for this oxidative dehydrogenation reaction. Over Cr-O catalyst, total conversion and ethylene selectivity values of 0.11 and 0.91 were obtained, respectively, at 250 °C for an O 2 /C 2 H 6 feed ratio of about 0.33 and at a space time of 0.24 g s/cm 3 . With this catalyst, the ethane conversion increased to 0.3, and the ethylene selectivity decreased to about 0.75 when the temperature was increased to 400 °C. For both catalysts, higher selectivity values, i.e., above 0.95, were observed when CO 2 was used as a mild oxidant instead of O 2 .

Two-dimensional materials are crystalline materials consist of a single layer of atoms and sometimes referred to as single layer materials. Electrocatalytic energy conversion using renewable power sources is one of the most promising ways for energy storage and energy utilization in the new century. Over the past years, a great number of two-dimensional (2D) materials have been explored for various electrocatalytic reactions, such as the hydrogen evolution reaction, Carbon (IV) oxide (CO 2 ) reduction reaction and Oxygen (O 2 ) reduction reaction. This research provides an overview on the synthesis techniques of materials including bottom up approaches such as chemical vapor deposition (CVD) and physical vapor deposition (PVD) and top-down approaches like mechanical exfoliation, chemical exfoliation. Then, the characterization techniques of the two-dimensional (2D) materials such as Raman spectroscopy, X-ray diffraction, temperature-dependent resistivity and magnetic susceptibility and scanning tunneling microscopy (STM) are reviewed. Finally, potential applications of two-dimensional (2D) materials and conclusion, challenges and future work are discussed.

The effect of the bite angle on regioselectivity in the rhodium-catalyzed hydroformylation reaction was studied with a series of bidentate diphosphines based on xanthene-like backbones as ligands. The bite angles of these ligands are fine-tuned by subtle alterations of the backbone of the ligands. When the bridge (X) in the 10-position of xanthene is varied, the bite angle as calculated from molecular mechanics increases stepwise from 102 to 131", whereas the changes in steric bulk and electronic effects are virtually absent for the following ligands: bis(2-(diphenylphosphino)phenyl) ether (DPEphos, 11, X = H, H; 4,6-bis(diphen-y1phosphino)-10,lO-dimethylphenoxasilin (Sixantphos, 2), X = Si(CH&; 2,8-dimethyl-4,6bis(dipheny1phosphino)phenoxathiin (Thixantphos, 3), X = S; 9,9-dimethyl-4,6-bis(diphen-y1phosphino)xanthene (Xantphos, 4), X = C(CH&; 4,6-bis(diphenylphosphino)dibenzofuran (DBFphos, 51, X = bond. In the hydroformylation of l-octene the regioselectivity increased regularly with increasing bite angle: a t 40 "C up to 98.3% n-aldehyde was obtained with Xantphos, without isomerization or hydrogenation of l-octene. DBFphos does not form chelates, and consequently no increased selectivity was observed. The selectivity of the catalyst was almost unaffected by raising of the temperature to 80 "C, resulting in a higher turnover frequency (to0 with a constant selectivity: 97.7% n-aldehyde, 0.5% isomerization, and a tof value of 800 mol (mol of Rh)-l h-l. Xantphos induces the highest selectivity for the formation of the linear aldehyde reported for diphosphines in the hydroformylation of l-alkenes until now. The complexes (diphosphine)Rh(H)(CO)(PPh3) and (diphosphinel-Rh(H)(CO)z were prepared and identified with lH, 31P, and 13C NMR. The enhanced selectivity t o the linear aldehyde was also observed for styrene (70% n-aldehyde with xantphos compared to 11% with triphenylphosphine). An X-ray crystal structure of the Xantphos ligand is presented (orthorhombic, space group P b n m , with a = 8.7678(8) A, b = 18.967(1) A, c = 19.181(1) A, V = 3189.8(4) Hi3, and 2 = 4).

Suitability of TBP for recovery of uranium(VI) from dilute HNO 3 using LEM extraction is investigated. TBP co-extracts significant amount of HNO 3 along with U(VI). Beyond a critical time, extraction of U(VI) ceases due to attainment of critical acid level when the strip phase is unable to break TBP-U(VI) complex. The observed critical time is in good agreement with that estimated from rate of acid extraction. Optimal conditions at which the relative extraction of HNO 3 is minimal with respect to U(VI) is arrived at. The extraction efficiency of TBP is compared with other ligands viz., TiAP, TEHP, TOPO, TOA and D2EHPA.

The response surface methodology is used to obtain optimal rate and extent of extraction of low concentration U(VI) (B100 mg/L) by liquid emulsion membrane technique. Three different ligands viz. Tri-n-octyl phosphine oxide (TOPO), Tri-n-octyl amine (TOA) and Di-(2-ethylhexyl)phosphoric acid (D2EHPA), are used. 2 3 factorial design is applied to generate second order regression equation for studying the effect of concentration of ligand, surfactant and feed acidity. The regression model is in good agreement with the experimental data for all ligands. The rate of extraction of U(VI) by LEM is found to be in the order TOA [ TOPO [ D2EHPA.

A novel, periodic polarity-switching technique is developed for the electrolytic production of sodium hypochlorite from aqueous sodium chloride. The technique employs a flow-through cell having two identical platinum electrodes. Polarities of these electrodes are periodically swapped. The main purpose of this step is to prevent the growth of platinum oxide film and thereby retain high initial activity of the electrodes throughout the operation. The performance of this mode of operation is evaluated using the cumulative productivity and current efficiency of the cell as indicators. Typical ranges of parameters used are as follows: concentration of Cl -ions, 0.1-0.5 M; switching frequency, 0.01-1 Hz; and current density, 100-700 A m -2 . The productivity of the switching mode is 5-6 times higher and its current efficiency is 15%-20% higher than that of the DC mode. The switching frequency has a strong influence on both the cumulative production rate and the average current efficiency and an optimal switching frequency exists under the given operating conditions. At high frequencies, the major side reaction is oxidation of the adsorbed hydrogen. As the concentration of NaCl increases, the optimal switching frequency decreases, and both the cumulative productivity and the average current efficiency increase. At the optimal frequency, the current efficiency of the switching mode varies from 60% to 95% as the concentration of NaCl is varied from 0.1 M to 0.5 M. The higher rate of circulation of the electrolyte improves the cell performance. The main cause for the loss in the current efficiency at high conversions of Cl -ions is the reduction of the hypochlorite ions at the cathode, which occurs under diffusion limiting conditions.

Recently, researchers have proven the therapeutic properties of copper nanoparticles as a common product of nanotechnology science. Due to the excellent antioxidant potential of copper nanoparticles, it seems that they can be used for the treatment of infectious diseases and cutaneous wounds. Also, Allium eriophyllum Boiss leaf is used in Kurdish traditional medicine, as one of the popular medicines of the Iranian traditional medicines, for increasing the trend of wound healing. So, we decided to synthesize the copper nanoparticles containing A. eriophyllum leaf aqueous extract, and analyze their potentials in removing bacteria and fungi and healing of cutaneous wounds. After synthesizing the copper nanoparticles, they were characterized with common techniques of organic chemistry, i.e. UV–Vis, Fourier transform‐infrared, X‐ray diffraction, field emission‐scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM). For investigating the antimicrobial properties ...

An adiabatic calorimeter was used to measure the enthalpy of solution of 1-octyl-3-methylimidazolium tetrafluoroborate (0.0035 mol‚kg -1 to 0.02 mol‚kg -1 ) in water and in aqueous sodium fluoride of different ionic strengths (0.1 mol‚kg -1 to 0.43 mol‚kg -1 ) at nominal temperatures of 298 K, 306 K, and 313 K. Two additional measurements of the enthalpy of solution of 1-butyl-3-methylimidazolium tetrafluoroborate (0.013 mol‚kg -1 ) in water at 298 K are also reported. The present results lead to the standard-state changes of enthalpy and heat capacity for the solution process. The contribution of a methylene group to the enthalpy of solution of these ionic liquids was determined from the measurements and is shown to be in agreement with the value obtained from other classes of organic compounds. The enthalpy of solution increment for the methylene group is used to calculate the enthalpy of solution of the series of 1-alkyl-3-methylimidazolium tetrafluoroborates. Calculated standard-state heat capacity values for the aqueous solution process and the aqueous solute are also given. Potential micelle formation of 1-octyl-3methylimidazolium tetrafluoroborate in water was examined.

Graphene nanoflakes (GNF) with lateral dimensions of ca. 30 nm and edge-terminated with carboxylic acid functionalities have been characterised and the influence of acidic functionalities on the [Fe(CN) 6 ] 3À/4À redox couple studied using cyclic voltammetry and spectroelectrochemical methods. The presence of the COOH-terminated GNF in solution as well as immobilised onto an electrode surface was found to inhibit the redox reaction, supporting the conclusion that GNF promote instability of [Fe(CN) 6 ] 3À/4À in solution. The redox reaction was also much less influenced by the presence of GNF in D 2 O, highlighting the role played by readily available protons in destabilising the [Fe(CN) 6 ] 3À/4À redox couple. In the presence of GNF in solution, an additional, very intense cyanide stretch IR band was observed that was attributed to the formation of a new, non-soluble species. When D 2 O was used as the solvent, the IR spectrum showed no evidence of a new cyano species.

A two stage model of the physicochemical processes at the electrolysis of pure water is proposed. The presence of nascent hydrogen in the catholyte and nascent oxygen in the anolyte during the first stage explains the antioxidant properties of the catholyte and the strong biocidal action of the anolyte. In the second stage the nascent hydrogen and oxygen are combined into hydrogen and oxygen molecules, respectively. The comparison between their average energies with the average energy of the control sample of water shows an increase in the average energy of the catholyte and decrease in the average energy of the anolyte. This indicates that some changes in the structure of the activated water have occurred. Keywords: Electrochemically activated water (ECAW), catholyte, anolyte, nascent hydrogen, nascent oxygen, energetic spectrum, energy of hydrogen bonds.

An efficient and general method has been developed for synthesis of 1-and 5-substituted 1H-tetrazoles from nitriles and amines using magnetite nanoparticles immobilized Salen Cu(II) as an efficient and recyclable catalyst. The structural and magnetic properties of functionalized magnetic silica are identified by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) instruments. NMR, FT-IR, elemental analysis and XRD were also used for identification of these structures. Nanocatalyst can be easily recovered by a magnetic field and reused for subsequent reactions for at least 7 times with less deterioration in catalytic activity.

The salts [RuII(L–L)3](CF3SO3)2 (L–L = bpy or phen) have been prepared in high yields via reactions of [RuII(DMF)6](CF3SO3)2 (DMF = N,N′-dimethylformamide), generated in situ by reduction of [RuIII(DMF)6]-(CF3SO3)3, with an excess of bpy or phen at room temperature in DMF solutions.

A novel heterogenized organometallic catalyst was synthesized by coordinating palladium with polyvinyl alcohol-functionalized Fe 3 O 4 @SiO 2 nanospheres. This novel catalyst was characterized using Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscope, field emission scanning electron microscope, dynamic light scattering, UVvis spectroscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray analysis, thermogravimetric analysis and inductively coupled plasma analysis. The prepared palladium nanoparticles supported on polyvinyl alcohol functionalized Fe 3 O 4 @SiO 2 nanoparticles were successfully applied as a magnetically recyclable catalyst in Heck and Sonogashira coupling reactions in water. They showed remarkable activity toward aryl halides (I, Br, Cl) using very low palladium loading in excellent yields and demonstrated high TONs (mmol of product per mmol of catalyst). Also, the catalyst could be magnetically separated and reused seven times without any appreciable loss of catalytic activity.

In this study, dendrimer‐encapsulated Cu(Π) nanoparticles immobilized on superparamagnetic Fe3O4@SiO2 nanoparticles were prepared via a multistep‐synthesis. Then, the synthesized composite was fully characterized by various techniques such as fourier transform infrared (FT‐IR) spectroscopy, X‐ray diffraction (XRD), dynamic light scattering (DLS), UV‐vis spectroscopy, energy dispersive X‐ray analysis (EDX), thermogravimetric analysis (TGA) and vibration sample magnetometer (VSM). From the information gained byFE‐SEM and TEM studies it can be inferred that the particles are mostly spherical in shape and have an average size of 50 nm. Also, the amount of Cu is determined to be 0.51 mmol/g in the catalyst by inductively coupled plasma (ICP) analyzer. This magnetic nano‐compound has been successfully applied as a highly efficient, magnetically recoverable and stable catalyst for N‐arylation of nitrogen heterocycles with aryl halides (I, Br) and arylboronic acids without using external li...

We reported the synthesis and characterization of butylene linked bis-benzimidazole based N-heterocyclic carbene (NHC) precursors and their PEPPSI-type bimetallic Pd-complexes, and we implemented its activities in the direct C5-arylation of 2-acetylfuran and 1-methylpyrrole-2-carboxaldehyde with various aryl bromides. The catalytic activities of the synthesized palladium-complexes were found to be very high. These complexes were fully characterized by different techniques such as 1 H NMR, 13 C NMR, FT-IR spectroscopy and elemental analysis.

In this study, a series of benzimidazolium salts were synthesized as unsymmetrical N‐heterocyclic carbene (NHC) precursors. Benzimidazolium salts were used for synthesis of the PEPPSI (pyridine enhanced precatalyst preparation stabilization and initiation)‐themed, six new Pd‐complexes with the general formula [PdX2(NHC)(pyridine)]. The structures of all compounds were characterized by various spectroscopic techniques such as 1H NMR, 13C NMR and FT‐IR. The more detailed structural characterization of four of the complexes was determined by single‐crystal X‐ray diffraction study. The catalytic activities of all Pd‐complexes were evaluated in the direct arylation of the 2‐acetylfuran and 2‐acetylthiophene with aryl bromides in the presence of 1 mol% catalyst loading.

Six benzimidazolium salts, having two nitrogen atoms substituted by various alkyl groups, have been synthesized in high yields. The benzimidazolium salts readily converted into the corresponding PEPPSI‐type palladium–NHC complexes (PEPPSI = pyridine‐enhanced precatalyst preparation, stabilization, and initiation). The structures of all compounds have been characterized by 1H NMR, 13C NMR, and IR spectroscopy, as well as elemental analysis techniques, which support the proposed structures. The molecular structure of one complex has been determined by single‐crystal X‐ray diffraction. The catalytic activity of the PEPPSI‐type palladium–NHC complexes has been evaluated with respect to the direct C5‐arylation of 2‐substituted thiophene derivatives with various aryl halides. This arylation occurs efficiently and selectively at the C5‐position of 2‐substituted thiophene derivatives.

Novel palladium-1,3-dialkylperhydrobenzimidazolin-2-ylidene (2a-c) and palladium-1,3-dialkylimidazolin-2-ylidene complexes (4a,b) have been prepared and characterized by C, H, N analysis, 1 H-NMR and 13 C-NMR. Styrene or phenylboronic acid reacts with aryl halide derivatives in the presence of catalytic amounts of the new palladium-carbene complexes, PdCl 2 (1,3dialkylperhydrobenzimidazolin-2-ylidene) or PdCl 2 (1,3-dialkylimidazolin-2-ylidene) to give the corresponding C-C coupling products in good yields.

In the past decade, metal-free approaches for C-C bond formation have attracted a great deal of attention due to their ease of use and low cost. This report represents a novel and metal-free synthesis of 3,3'-bisimidazopyridinylmethanes via intermolecular oxidative C(sp(2))-H bond functionalization of imidazo[1,2-a]pyridines with dimethyl sulfoxide as the carbon synthon (CH2) using H2O2 as a mild oxidant under air. A library of 3,3'-bis(2-arylimidazo[1,2-a]pyridin-3-yl)methanes has been achieved in good to excellent yields. The present methodology has been successfully applied to imidazo[2,1-b]thiazoles and imidazo[2,1-b]benzothiazoles. Furthermore, the current approach was also extended for the synthesis of unsymmetrical 3,3'-bisimidazopyridinylmethanes under optimized reaction conditions. A mechanistic pathway is proposed on the basis of experiments with radical scavengers and DMSO-d6 and ESI-MS observations.

A phenyliodine(III) diacetate (PIDA)-mediated, highly efficient and tandem approach for the synthesis of aryldiazenylisoxazolo(isothiazolo)arenes from simple 2-amino-N'-arylbenzohydrazides has been developed. The reaction proceeds via formation of (E)-(2-aminoaryl)(aryldiazenyl)methanone as the key intermediate, followed by intramolecular oxidative O-N/S-N bond formation in one pot at room temperature. The quiet different reactivity of the substrate is due to the formation of a diazo intermediate which encounters a nucleophilic attack by carbonyl oxygen on the electrophilic amine to produce isoxazole products, as compared to the previous reportsa,b,4 in which an N-acylnitrenium ion intermediate is intramolecularly trapped by an amine group.

Functionalized propiolamidine derivatives were prepared in good to excellent yields under very mild conditions via a copper‐catalyzed multicomponent reaction (MCR) of readily available terminal alkynes, acid chlorides and carbodiimides with the assistance of triethylamine. The mechanism of this MCR is postulated.

Three new trinuclear hetero-metallic complexes [(CuL)2Zn(NCS)2] (), [(CuL(R))2Zn(NCS)(μ1,1-NCS)] () and [(CuL(R))2Cd(μ1,3-NCS)2] () have been synthesized using [CuL] and [CuL(R)] as "metalloligands" (where H2L = N,N'-bis(salicylidene)-1,3-propanediamine and H2L(R) = N,N'-bis(2-hydroxybenzyl)-1,3-propanediamine). All three complexes are characterized by elemental analysis, spectroscopic methods and single crystal XRD. Complex is an angular trinuclear species, in which two terminal four-coordinate square planar "metalloligands" [CuL] are coordinated to a central Zn(ii) through double phenoxido bridges along with two mutually cis nitrogen atoms of terminal isothiocyanate ions as is usually found in such complexes. In contrast, in complex , the two terminal "metalloligands" [CuL(R)] are square pyramidal, as one of the SCN(-) ions makes an unusual μ1,1-NCS bridge between copper centers while the other one coordinates to Zn(ii) through a N atom in a u...

Three new trinuclear heterometallic Ni II -Mn II complexes have been synthesized using [NiL] metalloligand where H2L = N,N′-bis(salicylidene)-1,3-propanediamine. The complexes [(NiL)4Mn2(OCn)4(CH3OH)4]•2CH3OH (1), [(NiL)4Mn2(OPh)4(CH3OH)2]•H2O (2) and [(NiL)4Mn(OSal)2(CH3OH)2] (3) (where OCn = cinnamate, OPh = phenylacetate, OSal= salicylate) have been structurally characterized. In all three complexes, in addition to the double phenoxido bridge, the two terminal Ni II atoms are linked to the central Mn II by means of syn-syn bridging carboxylate, giving rise to a linear structure. Complexes 1 and 2 with Ni-O-Mn angle of 97.24 and 96.43° respectively exhibit ferromagnetic interactions ( JNi-Mn = +1.38 and +0.50 cm -1 respectively) whereas 3 is antiferromagnetic (JNi-Mn= -0.24 cm -1 ) having Ni-O-Mn angle of 98.51°. DFT calculations indicate that there is a clear magneto-structural correlation between Ni-O-Mn angle and JNi-Mn values which is in agreement with the experimental results.

Three new supramolecular assemblies of co-crystallized metal complexes and aliphatic dicarboxylic acids, {[Cu(pic) picolinic acid, H 2 mal = malonic acid and H 2 succ = succinic acid} have been synthesized and characterized by X-ray single-crystal structure determination. The crystal packings of the complexes reveal that supramolecular associations of the monomeric complex units lead to the formation of layers through hydrogen bonding. In all the complexes, the dicarboxylic acid units connect the 2-D layers to act as pillars. The interaction between water molecules and the dicarboxylic acid plays an important role in the overall supramolecular assembly.

The complex cis-[RuCl(DMSO)(phen) 2 ]BPh 4 , where DMSO is dimethylsulfoxide and phen is 1,10-phenanthroline, crystallizes in the monoclinic space group P2 1 /c with a ϭ 19.505(4), b ϭ 10.045(2), c ϭ 21.199(4) A ˚, β ϭ 90.137(4)°, V ϭ 4153(2) A ˚3, Z ϭ 4, D calc ϭ 1.430 g cm Ϫ3 . The ruthenium coordination geometry is that of a slightly distorted octahedron with a cis-RuN 4 ClS arrangement of the ligand donor atoms. The RuϪCl dis-Ruthenium complexes having sulfoxide, chloro and N-donor ligands are of recent interest for their antimetastatic (antitumor) properties [1], as precursors for the synthesis of heteroleptic polypyridyl complexes and for their DMSO-and chloro-ligand substitution with retention of the absolute configuration [2, 3], as catalysts for alkene epoxidation or for the diastereoselective preparation of Ru-bis(diimine) sulfoxide complexes . Of main interest in this regard, so far, has been the compound cis-[RuCl(2,2'bipy) 2 (DMSO)] ϩ [3, 4, 6Ϫ10]. The value of this complex arises from its ability to react with suitable bidentate ligands particularly those that could act as DNA intercalators in connection with the photophysical properties of ruthenium(II) polypyridyl complexes . We report here on the structure of the related prototypical complex cis-[chloro(dimethylsulfoxide)bis(1,10-phenanthroline)ruthenium(II)] ϩ as the tetraphenylborate salt, [RuCl(DMSO)(1,10phen) 2 ][BPh 4 ] (1).

Four trinuclear Cu(II) complexes, [(CuL 1 ) 3 (l 3 -OH)](NO 3 ) 2 (1), [(CuL 2 ) 3 (l 3 -OH)](I) 2 AEH 2 O (2), [(CuL 3 ) 3 (l 3 -OH)](I) 2 (3) and [(CuL 1 ) 3 (l 3 -OH)][Cu I I 3 ] (4), where HL 1 (8-amino-4-methyl-5-azaoct-3-en-2-one), HL 2 [7-amino-4-methyl-5-azaoct-3-en-2-one] and HL 3 [7-amino-4-methyl-5-azahept-3-en-2-one] are the three tridentate Schiff bases, have been synthesized and structurally characterized by X-ray crystallography. All four complexes contain a partial cubane core, [(CuL) 3 (l 3 -OH)] 2+ in which the three [CuL] subunits are interconnected through two types of oxygen bridges afforded by the oxygen atoms of the ligands and the central OH À group. The copper(II) ions are in a distorted square-pyramidal environment. The equatorial plane consists of the bridging oxygen of the central OH À group together with three atoms (N, N, O) from the Schiff base. The oxygen atom of the Schiff base also coordinates to the axial position of Cu(II) of another subunit to form the cyclic trimer. Magnetic susceptibilities have been determined for these complexes over the temperature range of 2-300 K. The isotropic

The synthesis of two new sodium perchlorate adducts (1:2 and 1:3) with copper(II) ''ligand-complexes'' is reported. One adduct is trinuclear [(CuL 1 ) 2 NaClO 4 ] (1) and the other is tetranuclear [(CuL 2 ) 3 Na]-ClO 4 ÁEtOH (2). The ligands are the tetradentate di-Schiff base of 1,3-propanediamines and salicylaldehyde (H 2 L 1 ) or 2-hydroxyacetophenone (H 2 L 2 ). Both complexes have been characterized by X-ray single crystal structure analyses. In both structures, the sodium cation has a six-coordinate distorted octahedral environment being bonded to four oxygen atoms from two Schiff-base complexes in addition to a chelated perchlorate anion in 1 and to six oxygen atoms from three Schiff-base complexes in 2. We have carried out a DFT theoretical study (RI-B97-D/def2-SVP level of theory) to compute and compare the formation energies of 1:2 and 1:3 adducts. The DFT study reveals that the latter is more stabilized than the former. The X-ray crystal structure of 1 shows that the packing of the trinuclear unit is controlled by unconventional C-HÁÁÁO H-bonds and Cu 2+ -p non-covalent interactions. These interactions explain the formation of 1 which is a priori disfavored with respect to 2.

A new tetranuclear complex, [Cu 4 L 4 ](ClO 4 ) 4 Á2H 2 O (1), has been synthesized from the self-assembly of copper(II) perchlorate and the tridentate Schiff base ligand (2E,3E)-3-(2-aminopropylimino) butan-2-one oxime (HL). Single-crystal X-ray diffraction studies reveal that complex 1 consists of a Cu 4 (NO) 4 core where the four copper(II) centers having square pyramidal environment are arranged in a distorted tetrahedral geometry. They are linked together by a rare bridging mode (l 3 -g 1 ,g 2 ,g 1 ) of oximato ligands. Analysis of magnetic susceptibility data indicates moderate antiferromagnetic (J 1 = À48 cm À1 , J 2 = À40 cm À1 and J 3 = À52 cm À1 ) exchange interaction through r-superexchange pathways (in-plane bridging) of the oxime group. Theoretical calculations based on DFT technique have been used to obtain the energy states of different spin configurations and estimate the coupling constants and to understand the exact magnetic exchange pathways.

Three Cu(II)-azido complexes of formula [Cu 2 L 2 (N 3 ) 2 ] (1), [Cu 2 L 2 (N 3 ) 2 ]ÁH 2 O (2) and [CuL(N 3 )] n (3) have been synthesized using the same tridentate Schiff base ligand HL (2-[(3-methylaminopropylimino)methyl]-phenol), the condensation product of N-methyl-1,3-propanediamine and salicyldehyde). Compounds 1 and 2 are basal-apical l-1,1 double azido bridged dimers. The dimeric structure of 1 is centrosymmetric but that of 2 is non-centrommetric. Compound 3 is a l-1,1 single azido bridged 1D chain. The three complexes interconvert in solution and can be obtained in pure form by carefully controlling the synthetic conditions. Compound 2 undergoes an irreversible transformation to 1 upon dehydration in the solid state. The magnetic properties of compounds 1 and 2 show the presence of weak antiferromagnetic exchange interactions mediated by the double 1,1-N 3 azido bridges (J = À2.59(4) and À0.10(1) cmÀ 1 , respectively). The single 1,1-N 3 bridge in compound 3 mediates a negligible exchange interaction.

Oxime-based tridentate Schiff base ligands 3-[2-(diethylamino)ethylimino]butan-2-one oxime (HL 1 ) and 3-[3-(dimethylamino)propylimino]butan-2-one oxime (HL 2 ) produced the dinuclear complex [Ni 2 L 1 2 ](ClO 4 ) 2 (1) and trinuclear complex [Ni 3 (HL 2 ) 3 (μ 3 -O)](ClO 4 ) 4 •CH 3 CN (2), respectively, upon reaction with Ni(ClO 4 ) 2 •6H 2 O. However, in a slightly alkaline medium, both of the ligands underwent hydrolysis and resulted in tetranuclear complexes [{Ni(deen)(H 2 O)} 2 (μ 3 -OH) 2 {Ni 2 (moda) 4 }](ClO 4 ) 2 •2CH 3 CN (3) and [{Ni(dmpn)(CH 3 CN) 2 } 2 (μ 3 -OH) 2 {Ni 2 (moda) 4 }](ClO 4 ) 2 •CH 3 CN ( ), where deen = 2-(diethylamino)ethylamine, dmpn = 3-(dimethylamino)-1-propylamine, and modaH = diacetyl monoxime. All four complexes have been structurally characterized. Complex 1 is a centrosymmetric dimer where the square planar nickel(II) atoms are joined solely by the oximato bridges. In complex 2, three square planar nickel atoms form a triangular core through a central oxido (μ 3 -O) and peripheral oximato bridges. Tetranuclear complexes 3 and 4 consist of four distorted octahedral nickel(II) ions held together in a rhombic chair arrangement by two central μ 3 -OH and four peripheral oximato bridges. Magnetic susceptibility measurements indicated that dinuclear 1 and trinuclear 2 exhibited diamagnetic behavior, while tetranuclear complexes 3 and 4 were found to have dominant antiferromagnetic intramolecular coupling with concomitant ferromagnetic interactions. Despite its singlet ground state, both 3 and 4 serve as useful examples of Kahn's model for competing spin interactions. High-frequency EPR studies were also attempted, but no signal was detected, likely due to the large energy gap between the ground and first excited state. Complexes 3 and 4 exhibited excellent catecholase-like activity in the aerial oxidation of 3,5-di-tert-butylcatechol to the corresponding o-quinone, whereas 1 and 2 did not show such catalytic activity. Kinetic data analyses of this oxidation reaction in acetonitrile revealed that the catalytic activity of 3 (k cat = 278.4 h -1 ) was slightly lower than that of 4 (k cat = 300.0 h -1 ). X-band EPR spectroscopy indicated that the reaction proceeded through the formation of iminoxyl-type radicals.

Two new Mn(III) complexes of formulas [MnL 1 (N 3 )(OMe)] 2 (1) and [MnL 2 (N 3 ) 2 ] n (2) have been synthesized by using two tridentate NNO-donor Schiff base ligands HL 1 {(2-[(3-methylaminoethylimino)-methyl]-phenol)} and HL 2 {(2-[1-(2-dimethylaminoethylimino)methyl]phenol)}, respectively. Substitution of the H atom on the secondary amine group of the N-methyldiamine fragment of the Schiff base by a methyl group leads to a drastic structural change from a methoxido-bridged dimer (1) to a single μ 1,3azido-bridged 1D helical polymer (2). Both complexes were characterized by single-crystal X-ray structural analyses and variable-temperature magnetic susceptibility measurements. The magnetic properties of compound 1 show the presence of weak ferromagnetic exchange interactions mediated by double methoxido bridges (J = 0.95 cm -1 ). Compound 2 shows the existence of a weak antiferromangetic coupling along the chain (J = -8.5 cm -1 ) through the single μ 1,3 -N 3 bridge with a spin canting that leads to a long-range antiferromagnetic order at T c ≈ 9.3 K and a canting leading to a weak ferromagnetic long-range order at T c ≈ 8.5 K. It also exibits metamagnetic behavior at low temperatures with a critical field of ca.1.2 T due to the weak antiferromagnetic interchain interactions that appear in the canted ordered phase.

Two mixed bridged one-dimensional (1D) polynuclear complexes, [Cu 3 L 2 (μ 1,1 -N 3 ) 2 (μ-Cl)Cl] n (1) and {[Cu 3 L 2 (μ-Cl) 3 Cl] 3 0.46CH 3 OH} n (2), have been synthesized using the tridentate reduced Schiff-base ligand HL (2-[(2dimethylamino-ethylamino)-methyl]-phenol). The complexes have been characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. In both complexes the basic trinuclear angular units are joined together by weak chloro bridges to form a 1D chain. The trinuclear structure of 1 is composed of two terminal square planar [Cu(L)(μ 1,1 -N 3 )] units connected by a central Cu(II) atom through bridging nitrogen atoms of end-on azido ligands and the phenoxo oxygen atom of the tridentate ligand. These four coordinating atoms along with a chloride ion form a distorted trigonal bipyramidal geometry around the central Cu(II). The structure of 2 is similar; the only difference being a Cl bridge replacing the μ 1,1 -N 3 bridge in the trinuclear unit. The magnetic properties of both trinuclear complexes can be very well reproduced with a simple linear symmetrical trimer model (H = -JS i S iþ1 ) with only one intracluster exchange coupling (J) including a weak intertrimer interaction (j) reproduced with the molecular field approximation. This model provides very satisfactory fits for both complexes in the whole temperature range with the following parameters: g = 2.136(3), J = -93.9(3) cm -1 and zj = -0.90(3) cm -1 (z = 2) for 1 and g = 2.073(7), J = -44.9(4) cm -1 and zJ 0 = -1.26(6) cm -1 (z = 2) for 2.

A multifunctional porous metal organic framework based on mixed-valence hexa-nuclear [Mn III 2 Mn II 4 O 2 (pyz) 2 (C 6 H 5 CH 2 COO) 10 ] (pyz = pyrazine) units has been synthesized. The complex has been characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction analysis, and variable-temperature magnetic measurements. The structural analysis reveals that the bidentate pyz molecules connect each [Mn 6 ] unit to its four [Mn 6 ] neighbors through the peripheral Mn(II) centers, giving rise to a threedimensional (3D) distorted diamond-like porous framework. Variable-temperature (2-300 K) magnetic susceptibility measurements show the presence of dominant antiferromagnetic interactions within the discrete [Mn 6 ] cluster that have been fitted with a model containing three exchange constants developed for the complex (J 1 = -8.6 cm -1 , J 2 = -3.9 cm -1 , and J 3 = -100.0 cm -1 ). Using 3,5-di-tert-butyl catechol (3,5-DTBC) as the substrate, catecholase activity of the complex has been studied; the turn over number is determined to be of 2547 h -1 in acetonitrile. This porous compound shows remarkable selectivity for adsorption of CO 2 over N 2 that may be correlated with the effect of window flexibility of the pore to the corresponding adsorbate molecules.

A new linear trinuclear nickel(II) complex, [Ni 3 (salme) 2 (OCn) 4 ] (Hsalme = 2-[(3-methylamino-propylimino)-methyl]-phenol, OCn = cinnamate), showing weak ferromagnetic coupling (J = 1.8(1) cm À1 ) through phenoxo and a novel tridentate bridging mode (1j 2 OO 0 :2jO 0 ) of the cinnamate ligand has been synthesized and structurally characterized by X-ray crystallography.

Four new cadmium(II) complexes [Cd 2 (bz) 4 (H 2 O) 4 (μ 2 -hmt)] 3 Hbz 3 H 2 O (1), [Cd 3 (bz) with hexamine (hmt) and monocarboxylate ions, benzoate (bz), phenylacetate (pa), or acetate (ac) have been synthesized and characterized structurally. Structure determinations reveal that 1 is dinuclear, 2 is trinuclear, 3 is a one-dimensional (1D) infinite chain, and 4 is a two-dimensional (2D) polymer with fused hexagonal rings consisting of Cd II and hmt. All the Cd II atoms in the four complexes (except one Cd II in 2) possess sevencoordinate pentagonal bipyramidal geometry with the various chelating bidentate carboxylate groups in equatorial sites. One of the Cd II ions in 2, a complex that contains two monodentate carboxylates is in a distorted octahedral environment. The bridging mode of hmt is μ 2 -in complexes 1-3 but is μ 3 -in complex 4. In all complexes, there are significant numbers of H-bonds, C-H/π, and π-π interactions which play crucial roles in forming the supramolecular networks. The importance of the noncovalent interactions in terms of energies and geometries has been analyzed using high level ab initio calculations. The effect of the cadmium coordinated to hmt on the energetic features of the C-H/π interaction is analyzed. Finally, the interplay between C-H/π and π-π interactions observed in the crystal structure of 3 is also studied.

Lantern-type Ru 2 (OAc) 4 Cl reacts with pySH with complete substitution of the acetate ligands and oxidation to give a bioctahedral dimer [Ru 2 (l-pyS) 3 (pyS) 2 ](CF 3 SO 3 ) (1), (Ru±Ru 2.693 A) ± the ®rst Ru(III) complex of 2-mercaptopyridine. One-electron oxidation and reduction states of the dimer are also electrochemically accessible. The similarity in the behaviour of 2-mercaptopyridine and dithiocarbamates as ligands to Ru(III) is also addressed.

Characterization and modeling of the molecular-level behavior of simple hydrocarbon gases, such as methane, in the presence of both nonporous and nano-porous mineral matrices allows for predictive understanding of important processes in engineered and natural systems. In this study, changes in local electromagnetic environments of the carbon atoms in methane under conditions of high pressure (up to 130 bar) and moderate temperature (up to 346 K) were observed with 13C magic-angle spinning (MAS) NMR spectroscopy while the methane gas was mixed with two model solid substrates: a fumed non-porous, 12 nm particle size silica and a mesoporous silica with 200 nm particle size and 4 nm average pore diameter. Examination of the interactions between methane and the silica systems over temperatures and pressures that include the supercritical regime was allowed by a novel high pressure MAS sample containment system, which provided high resolution spectra collected under in situ conditions. Fo...

Reported are the synthesis, spectral and structural characteristics of new quinoxaline-related regioisomeric ligands L1-L4 (1,x,11,11-tetramethyl-1,2,3,4-tetrahydro-1,4-methanophenazine, x = 7, 8, 9 and 6, respectively) and their mononuclear Au(III) complexes (1-4). Fusion of the camphor moiety to the quinoxaline core made two N-atoms of quinoxaline nonequivalent while the introduction of a methylsubstituent at positions 6-9 enabled a tuning of coordination properties of L1-L4. Gold(III) complexes 1-4 and ligands L1-L4 have been studied in detailed by 1D and 2D NMR and the structures of 1-4 have been determined by X-ray crystallography. The results of these analyses revealed a regiospecific coordination of Au(III) to the sterically less hindered N-5 atom (spatially close to the non-substituted bridgehead carbon) of L1-L3, and to N-10 (spatially close to the methyl-substituted bridgehead carbon) of L4. The results of DFT calculations shed light on disparate coordination modes of L1-L4 toward the AuCl 3 fragment and explain formation of single coordination products in high yield.