Synthesis and "in Vitro" Trypanocidal Activity Evaluation of Some Organo-iron Compounds

Eight organo-iron ferrocene derivatives and arenocenium salts were prepared and evaluated by "in vitro" assay against one strain of Trypanosoma cruzi (Y). Six of the eight organo-iron compounds assayed, piperazinium diferrocenoate 1, eta(6)-(o-xylene)-eta(5)-(cyclopentadienyl) Iron(II) hexafluorophosphate 3, eta(6)-(mesitylene)-eta(5)-(cyclopentadienyl) iron(II) hexafluorphosphate 5, eta(6)-(durene)-eta(5)-(cyclopentadienyl) iron(II) hexafluorphosphate 6, eta(6)-(rho-chlorotoluene)-eta(5)-(cyclopentadienyl) Iron(II) hexafluorphosphate 7 and eta(6)-(chlorobenzene)-eta(5)-(cyclopentadienyl) iron(II) picrate 8 , were poorly active in the "in vitro" assays. Only two compounds 1,1'-(N-pyperidinocarbonyl) ferrocene 2(IC(50)=2.4 mug/mL) and eta(6)-(o-xylene)-eta(5)(cyclopentadienyl) iron(II) picrate 4 (IC(50)=12.08 mug/mL), were more active. Thus, some of the compounds are promising to be used against Chagas' disease as a prophylactic agents.     

Pentamethylcyclopentadienyl ruthenium(III) vs hexamethylbenzene ruthenium(II) in sulfur-centered reactivity of their thioether-thiolate and allied complexes

The reactivity features of [Cp*Ru(III){eta(3)-tpdt)}] (7) and [(HMB)Ru(II)(eta(3)-tpdt)] (10) {Cp* = eta(5)-C(5)Me(5); HMB = eta(6)-C(6)Me(6); tpdt = 3-thiapentane-1,5-dithiolate, S(CH(2)CH(2)S(-))(2)} are presented, together with selected aspects of their (eta(3)-apdt) analogues 8 and 11 {apdt = 3-azapentane-1,5-dithiolate, HN(CH(2)CH(2)S(-))(2)}. This account will highlight the differences observed in their reactions with metal fragments of compounds of Ru and groups 10 and 11 in various coordination environments and with alkylating agents, including alpha,omega-dibromoalkanes. The mechanistic pathway of the alkylation of 7 will be discussed in some detail.     

Supramolecular metal-organometallic coordination networks based on quinonoid pi-complexes

The use of organometallic pi-complexes in the coordination-directed self-assembly of polymeric structures is a new area with many potential applications. Supramolecular metal-organometallic coordination networks (MOMNs), which are described herein, consist of metal ion or metal cluster nodes connected by bifunctional "organometalloligands" that serve as spacers. The organometalloligand utilized in this work is the stable anionic complex (eta(4)-benzoquinone)Mn(CO)(3)(-) (p-QMTC), which binds through both quinone oxygen atoms to generate MOMNs having both backbone and pendant metal sites. In many cases the MOMNs are obtained as neutral and thermally stable solids, with molecular structures that depend on the geometrical and electronic requirements of the metal nodes, the solvent, and the presence of organic spacers. Redox-active quinone-based organometallic pi-complexes permit the construction of an impressive range of coordination network architectures and hold much promise for the development of functional materials.     

Ligand-bridged oligomeric and supramolecular arrays of the hexanuclear rhenium selenide clusters--exploratory synthesis, structural characterization, and property investigation

Transition metal clusters, by virtue of their well-defined structures and unique properties, present themselves as an attractive class of structural and functional building blocks for molecular and supramolecular construction. Summarized in this Account are highlights of our efforts utilizing face-capped octahedral [Re(6)(mu(3)-Se)(8)](2+) clusters as the fundamental building units to create a wide variety of preprogrammed architectures. These include molecular "Tinkertoys", featuring stereospecific cluster units bridged by multitopic ligands and extended arrays of clusters engineered via hydrogen bonding and secondary metal-ligand coordination.     

Molecular Metal Clusters as Catalysts

In earlier analyses [1-8] we have established a correlation between metal clusters and metal surfaces with chemisorbed molecules in the specific contexts of (1) the metal frameworks wherein the metal cluster core structures are fragments of cubic and hexagonal close packed or body centered cubic metal bulk structures; (2) ligand stereochemistry where the geometric features of ligands bound to clusters and to metal surfaces are similar; (3) thermodynamic features where the average bond energies for ligand-metal and metal-metal bonds are comparable, for a specific metal, in the metal cluster and the metal surface regime; and (4) mobility of ligands bonded to metal cluster frameworks and to metal surfaces. Nevertheless, there are sharp distinctions between surfaces and clusters. The average coordination numbers for metal-metal interactions and for metal-ligand interactions are distinctly different for clusters and for surfaces: generally, the former are larger for surfaces and the latter are larger for clusters. Additionally, the surface state is typically differentiated from the cluster state in the degree of coordination saturation—the metal atoms in the surface state are typically less coordinately saturated even for the states in which molecules or molecular fragments are chemisorbed at the surface than those metal atoms at the periphery of a molecular metal cluster. In the crucial chemical issue, metal surfaces are far more reactive than metal clusters. Metal surfaces exhibit a wide range and high level of catalytic activity whereas most metal clusters are catalytically inert, at least under modest reaction conditions, Most reported clusters are relatively stable and nonreactive; they are not the products of sophisticated synthesis procedures designed to generate highly reactive metal clusters. They commonly have been the products of reaction mixtures run at forcing conditions and are thermodynamically controlled, not kinetically controlled, products.     

Molecular Metal Clusters as Catalysts

Abstract

In earlier analyses [1–8] we have established a correlation between metal clusters and metal surfaces with chemisorbed molecules in the specific contexts of (1) the metal frameworks wherein the metal cluster core structures are fragments of cubic and hexagonal close packed or body centered cubic metal bulk structures; (2) ligand stereochemistry where the geometric features of ligands bound to clusters and to metal surfaces are similar; (3) thermodynamic features where the average bond energies for ligand-metal and metal-metal bonds are comparable, for a specific metal, in the metal cluster and the metal surface regime; and (4) mobility of ligands bonded to metal cluster frameworks and to metal surfaces. Nevertheless, there are sharp distinctions between surfaces and clusters. The average coordination numbers for metal-metal interactions and for metal-ligand interactions are distinctly different for clusters and for surfaces: generally, the former are larger for surfaces and the latter are larger for clusters. Additionally, the surface state is typically differentiated from the cluster state in the degree of coordination saturation—the metal atoms in the surface state are typically less coordinately saturated even for the states in which molecules or molecular fragments are chemisorbed at the surface than those metal atoms at the periphery of a molecular metal cluster. In the crucial chemical issue, metal surfaces are far more reactive than metal clusters. Metal surfaces exhibit a wide range and high level of catalytic activity whereas most metal clusters are catalytically inert, at least under modest reaction conditions, Most reported clusters are relatively stable and nonreactive; they are not the products of sophisticated synthesis procedures designed to generate highly reactive metal clusters. They commonly have been the products of reaction mixtures run at forcing conditions and are thermodynamically controlled, not kinetically controlled, products.     

两种季铵盐Gemini表面活性剂的合成及其表征

合成了两种联结基团为含羟基亚甲基链的季铵盐Gemini表面活性剂,即C12-3(OH)-C12·2C1及C12- 4(OH)-C12·2Cl,用红外光谱、核磁共振及元素分析对它们的结构进行了鉴定,并对影响反应的因素进行了讨论,得出了合成C12-3(OH)-C12·2Cl的最佳条件为:n(十二叔胺):n(十二叔胺盐酸盐):n(环氧氯丙烷)=2．0 :1.0:1．0,以正丙醇为溶剂,在回流温度下反应3 h,产率可达94．5％以上;合成C12-4(OH)-C12·2Cl的最佳条件为:n(十二叔胺):n(1,4-二氯-2-丁醇)=2．2:1．0,以正丙醇为溶剂,回流反应24 h,产率可达70％。     

Thermal activation of hydrocarbon C-H bonds by Cp*M(NO) complexes of molybdenum and tungsten

Gentle thermolysis of appropriate CpM(NO)(hydrocarbyl)(2) complexes (Cp = eta(5)-C(5)Me(5)) of molybdenum and tungsten results in loss of hydrocarbon and the transient formation of 16-electron CpM(NO)-containing complexes such as CpM(NO)(alkylidene), CpM(NO)(eta(2)-benzyne), CpM(NO)(eta(2)-acetylene), and CpM(NO)(eta(2)-allene) (M = Mo, W). These intermediates effect the single, double, or triple activation of hydrocarbon C-H bonds intermolecularly, the first step of these activations being the reverse of the transformations by which they were generated. This Account summarizes the various types of C-H activations that have been effected with these nitrosyl complexes and also describes the results of kinetic, mechanistic, and theoretical investigations of these processes.     

Metallation of Isatin (2,3-Indolinedione). X-Ray Structure and Solution Behavior of Bis(Isatinato)Mercury(II)

The first X-ray structure of an isatin (2,3-indolinedione, isaH) metal complex, bis(isatinato)memury(II) (C(16)H(8)N(2)O(4)Hg) (1), was determined. (1) was obtained from the reaction of isaH with mercury(II) acetate in methanol. Analogously, treatment of sodium saccharinate and mercury(II) acetate in methanol yielded Hg(saccharinato)(2) (*)0.5CH(3)OH (3). (1) crystallizes in the monoclinic system, space group P2(1)/ a with a = 7.299(1) A, b = 8.192(1) A, c = 11.601(1) A , beta = 105.82(1) degrees , V = 667.4 A(3), Z = 2, D(calc) = 2.452 g cm(-3), MoKalpha radiation(lambda = 0.71073 A), mu = 115.5 cm(-1), F(000) = 460, 21(1) degrees C. The structure was refined on the basis of 2023 observed reflections to R= 0.044. The two deprotonated, non coplanar isa ligands are trans to each other in a head to tail orientation and bound to the Hg through the nitrogen in a linear N-Hg-N arrangement. The Hg atom is at the center of symmetry of the complex and displaced by 0.62 A from the two planes of the isa ligands (tau Hg-N1-C2-O2= -16 degrees ). The Hg-N bond length is 2.015 A. Nopi-aryl-memury(ll)-pi-aryl stacking interaction was observed either in the solid state or in the solution state. The IR, electronic, and (1)H and (13)CNMR spectral data of (1) and (3) suggest binding of the memury to the heterocyclic nitrogen, in agreement with the crystal structure determination of (1).     

Regiospecific Analysis of Mono- and Diglycerides in Glycerolysis Products by GC × GC-TOF-MS

Comprehensive bidimensional gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOF-MS) was used for the characterization of regiospecific mono- and diglycerides (MG-DG) content in the glycerolysis products derived from five different lipids included lard (LA), sun flower seed oil (SF), corn oil (CO), butter (BU), and palm oil (PA). The combination of fast and high temperature non-orthogonal column set namely DB17ht (6 m × 0.10 mm × 0.10 μm) as the primary column and SLB-5 ms (60 cm × 0.10 mm × 0.10 μm) as the secondary column was applied in this work. System configuration involved high oven ramp temperature to obtain precise mass spectral identification and highest effluent’s resolution. 3-Monopalmitoyl-sn-glycerol (MG 3-C16) was the highest concentration in LA, BU and PA while monostearoyl-sn-glycerol (MG C18) in CO and 1,3-dilinoleol-rac-glycerol (DG C18:2c) in SF. Principal component analysis accounted 82% of variance using combination of PC1 and PC2. The presence of monostearoyl-sn-glycerol (MG C18), 3-Monopalmitoyl-sn-glycerol (MG 3-C16), 1,3-dilinoleol-rac-glycerol (DG C18:2c), 1,3-dipalmitoyl-glycerol (DG 1,3-C16), and 1,3-dielaidin (DG C18:1t) caused differentiation of the samples tested.     

TiCl4—C60Cln催化体系引发异丁烯正离子聚合

研究了碳笼烯非质子酸经体系引发异丁烯正离子聚合的反应规律,并与ＴｉＣｌ４正离子催体系进行了比较。ＧＰＣ的测试结果表明,ＴｉＣｌ４－Ｃ６０Ｃｌｎ催化体系中可能存在２种活性中心：（１）体系中的微量水与ＴｉＣｌ４配位形成的质子引发体系;（２）（ＴｉＣｌ５）－（Ｃ６０Ｃｌｎ－１）＾＋离子引对引发活性中心。     

Size effect of endohedral cluster on fullerene cage: preparation and structural studies of Y3N@C78-C2

A new metallofullerene Y(3)N@C(78)-C(2) was synthesized and characterized. It was shown that Y(3)N@C(78) has an unconventional C(78)-C(2) cage with two pairs of fused pentagons closely bonded with two yttrium atoms. DFT calculations showed that the size of the ionic radii of the metals forming the caged cluster plays an important role in the non-isolated-pentagon-rule-feature of the C(78) cage.     

C₇₄ endohedral metallofullerenes violating the isolated pentagon rule: a density functional theory study

Precise studies on M(2)@C(74) (M = Sc, La) series by means of DFT methods have disclosed that certain non-IPR isomers are more stable than the IPR structure. M(2)@C(2)(13295)-C(74) and M(2)@C(2)(13333)-C(74), both of which have two pentagon adjacencies (PA), present excellent thermodynamic stability with very small energy differences. Statistical mechanics calculations on the M(2)@C(74) series reveal that M(2)@C(2)(13295)-C(74) and M(2)@C(2)(13333)-C(74) are quite favoured by entropy effects below 3000 K. Sc(2)@C(74) and La(2)@C(74) series are found to have similar electronic transfer but different electronic structures due to the distinct properties of scandium and lanthanum elements according to Natural Bond Orbital (NBO) analysis in conjunction with orbital interaction diagrams. Investigations of bonding energies reflect quite different influences of the two types of metal atoms to C(74) metallo-fullerenes. Further examinations on C(74) metallo-fullerenes uncover significant stabilization effects of metal atoms acting on PA fragments. Geometrical structures of certain non-IPR cages (from C(72) to C(76)), which exhibit splendid stabilities when encapsulating metallo-clusters, are found to be related by Stone-Wales transformation and C(2) addition. Furthermore, IR spectra and (13)C NMR spectra of M(2)@C(2)(13295)-C(74) and M(2)@C(2)(13333)-C(74) have been simulated to assist further experimental characterization.     

A copper–cyclen coordination complex associated with a polyoxometalate anion: Synthesis,crystal structure and electrochemistry of [Cu(cyclen)(MeCN)][W6O19]

The reaction between Cu(NO₃)₂·3H₂O and a tetra-aza macrocycle, more specifically, cyclen in 1:1 MeCN–MeOH solvent mixture forms a Cu²⁺–cyclen coordination complex in situ, that has been reacted with an isopolyanion [W₆O₁₉]^2? in a slow diffusion technique, resulting in the isolation of an ion-pair solid [Cu(cyclen)(MeCN)][W₆O₁₉] (1). Single crystal structural investigation on 1 shows a square pyramidal geometry around the metal centre (copper ion) with an axially bound MeCN solvent molecule. The title compound 1 is the first crystallographically characterized ion-pair compound, in which a transition metal coordination complex of a tetra-aza-crown ether (cyclen) has been associated with a polyoxometalate cluster anion. This communication deals with synthesis, spectroscopic, structural and electrochemical analyses of compound 1.     

Characterization of amorphous carbon films deposited by surface wave plasma CVD

Many dangling bonds in hydrogenated amorphous carbon (a-C:H) films are usually generated by bombardments of high-energy ion precursors in typical chemical vapor deposition (CVD). To generate low dangling bonds, a-C:H films should be deposited from low-energy radical species. Surface wave plasma (SWP) generates low-energy and high-density radicals. We prepare a-C:H films using SWP and investigate the relationship between the plasma characteristics and structures of a-C:H films. The microwave of the TM01 mode was introduced through the dielectric window and SWP generate under the dielectric window. An Ar and C₂H₂ plasma mixture mainly consists of neutral radical species, and the electron temperature is as low as 1 eV. Electron density significantly decreases with increasing distance from the dielectric window. The a-C:H films are prepared from these hydrocarbon and carbon low-energy radicals as main precursors. The sp² bonded network cluster size in a-C:H films increase with electron density in SWP. This structure change is the influence of the termination structure of clusters changing to CH from CH₃ and CH₂.     

Preparation of a Novel Nano-scale Lead (II) Zig-Zag Metal–Organic Coordination Polymer with Ultrasonic Assistance: Synthesis,Crystal Structure,Thermal Properties,and NBO Analysis of [Pb(μ-2-pinh)N<Subscript>3</Subscript> H<Subscript>2</Subscript>O]<Subscript>n</Subscript>

A novel nano-cauliflower-shaped lead(II) metal–organic coordination polymer, [Pb(μ-2-pinh)N₃ H₂O]_n (1), was synthesized using an ultrasonic method. The nanostructure was characterized by scanning electron microscopy (SEM), X-ray powder diffraction, IR spectroscopy, elemental analysis, and thermal analysis. The compound was structurally characterized by single-crystal X-ray diffraction. The coordination compound takes the form of a zig-zag one-dimensional polymer in solid state. The coordination number of the lead(II) ions is six (PbN₄O₂) with three nitrogen atoms and one oxygen atom from two linker organic ligands, as well as one oxygen from coordinated water and one nitrogen atom from terminal coordinated azide anion. It has a stereo-chemically active lone electron pair, and the coordination sphere is hemidirected. The zig-zag 1D chains interact with neighbouring chains through weak interactions, creating a 3D supramolecular metal–organic framework. Lead oxide nanoparticles were obtained by thermolysis of the new nano coordination compound at 180 °C with oleic acid as a surfactant. The morphology and size were further studied using SEM. Natural bond orbital analyses demonstrate the electronic properties of the lead centre and other atoms.     

Catalytic ethylene dimerization and oligomerization: recent developments with nickel complexes containing P,N-chelating ligands

Catalytic ethylene oligomerization represents a topic of considerable current academic and industrial interest, in particular for the production of linear alpha-olefins in the C4-C10 range, whose demand is growing fast. Identifying and fine-tuning the parameters that influence the activity and selectivity of metal catalysts constitute major challenges at the interface between ligand design, coordination/organometallic chemistry, and homogeneous catalysis. In this Account, we show how comparative studies aiming at modulating the coordinating properties of functional ligands for a metal, such as nickel, which is used in industrial processes, lead to beneficial effects in catalytic ethylene oligomerization.     

Zeolite beta catalysts for n-C7 hydroisomerization

Zeolite β with Si/2Al ratios of 60, 100, and 200 were synthesized using tetraethlammonium hydroxide (TEAOH) as the structure-directing agent (SDA) in the absence of alkali metal cations. Pt, Pd and Pt-Pd catalysts supported on the zeolite β samples were studied in n-heptane (n-C7) hydroisomerization. The Pt/β catalysts showed a higher catalytic activity than the Pd/β catalysts. For the Pt/β with a Si/2Al ratio of 100, its n-C7 conversion and selectivity of C7 isomers were observed to be 87.06% and 75.48% respectively at 250^°C. The activity of n-C7 conversion was stable for at least 82 h. However, the selectivity of C7 isomers was gradually decreased with the reaction time. Experimental data also showed that the addition of Pd to catalyst Pt/β enhanced the n-C7 conversion, but lowered the selectivity of C7 isomers. Pd catalyst was also observed to minimize the formation of aromatics in comparison with Pt catalyst.     

A Review of the Pharmacological Activities and Recent Synthetic Advances of γ-Butyrolactones

γ-Butyrolactone, a five-membered lactone moiety, is one of the privileged structures of diverse natural products and biologically active small molecules. Because of their broad spectrum of biological and pharmacological activities, synthetic methods for γ-butyrolactones have received significant attention from synthetic and medicinal chemists for decades. Recently, new developments and improvements in traditional methods have been reported by considering synthetic efficiency, feasibility, and green chemistry. In this review, the pharmacological activities of natural and synthetic γ-butyrolactones are described, including their structures and bioassay methods. Mainly, we summarize recent advances, occurring during the past decade, in the construction of γ-butyrolactone classified based on the bond formation in γ-butyrolactone between (i) C5-O1 bond, (ii) C4-C5 and C2-O1 bonds, (iii) C3-C4 and C2-O1 bonds, (iv) C3-C4 and C5-O1 bonds, (v) C2-C3 and C2-O1 bonds, (vi) C3-C4 bond, and (vii) C2-O1 bond. In addition, the application to the total synthesis of natural products bearing γ-butyrolactone scaffolds is described.