Synthesis and structures of nickel and palladium salicylaldiminato 1,3,5-triaza-7-phosphaadamantane (PTA) complexes

The synthesis of nickel(II) and palladium(II) salicylaldiminato complexes incorporating the water-soluble phosphine 1,3,5-triaza-7-phosphaadamantane(PTA) has been achieved employing two preparative routes. Reaction of the original ethylene polymerization catalyst developed by Grubbs and co-workers (Organometallics 1998, 17, 3149), (salicylaldiminato)Ni(Ph)PPh(3), with PTA using a homogeneous methanol/toluene solvent system resulted in the formation of the PTA analogues in good yields. Alternatively, complexes of this type may be synthesized via a direct approach utilizing (tmeda)M(CH(3))(2) (M = Ni, Pd), the corresponding salicylaldimine, and PTA. Yields by this method were generally near quantitative. The complexes were characterized in solution by (1)H/(13)C/(31)P NMR spectroscopy and in the solid-state by X-ray crystallography. All derivatives exhibited square-planar geometry with the bulky isopropyl groups on the aniline being perpendicular to the plane formed by the metal center and its four ligands. Such orientation of these sterically encumbering groups is responsible for polymer chain growth during olefin polymerization in favor of chain termination via beta-hydride elimination. Polymerization reactions were attempted using the nickel-PTA complexes in a biphasic toluene/water mixture in an effort to initiate ethylene polymerization by trapping the dissociated phosphine ligand in the water layer, thereby eliminating the need for a phosphine scavenger. Unfortunately, because of the strong binding ability of the small, donating phosphine(PTA) as compared to PPh(3), phosphine dissociation did not occur at a temperature where the complexes are thermally stable.     

Structure-related clustering of gene expression fingerprints of thp-1 cells exposed to smaller polycyclic aromatic hydrocarbons

This study was undertaken to test the hypothesis that structurally similar PAHs induce similar gene expression profiles. THP-1 cells were exposed to a series of 12 selected PAHs at 50 µM for 24 hours and gene expressions profiles were analyzed using both unsupervised and supervised methods. Clustering analysis of gene expression profiles revealed that the 12 tested chemicals were grouped into five clusters. Within each cluster, the gene expression profiles are more similar to each other than to the ones outside the cluster. One-methylanthracene and 1-methylfluorene were found to have the most similar profiles; dibenzothiophene and dibenzofuran were found to share common profiles with fluorine. As expression pattern comparisons were expanded, similarity in genomic fingerprint dropped off dramatically. Prediction analysis of microarrays (PAM) based on the clustering pattern generated 49 predictor genes that can be used for sample discrimination. Moreover, a significant analysis of Microarrays (SAM) identified 598 genes being modulated by tested chemicals with a variety of biological processes, such as cell cycle, metabolism, and protein binding and KEGG pathways being significantly (p < 0.05) affected. It is feasible to distinguish structurally different PAHs based on their genomic fingerprints, which are mechanism based.     

“Broken-hearted” carbon bowl via electron shuttle reaction: energetics and electron coupling

Unprecedented one-step C C bond cleavage leading to opening of the buckybowl (π-bowl), that could provide access to carbon-rich structures with previously inaccessible topologies, is reported; highlighting the possibility to implement drastically different synthetic routes to π-bowls in contrast to conventional ones applied for polycyclic aromatic hydrocarbons. Through theoretical modeling, we evaluated the mechanistic pathways feasible for π-bowl planarization and factors that could affect such a transformation including strain and released energies. Through employment of Marcus theory, optical spectroscopy, and crystallographic analysis, we estimated the possibility of charge transfer and electron coupling between “open” corannulene and a strong electron acceptor such as 7,7,8,8-tetracyanoquinodimethane. Alternative to a one-pot solid-state corannulene “unzipping” route, we reported a nine-step solution-based approach for preparation of novel planar “open” corannulene-based derivatives in which electronic structures and photophysical profiles were estimated through the energies and isosurfaces of the frontier natural transition orbitals.

An electron shuttle contributed to breaking corannulene''s heart through a unique one-step reductive C C bond cleavage in the traditionally robust π-bowl. The heartbreak did not stop there as “broken analogs” were developed through a solution-phase route.     

Trends in structure-toxicity relationships for carbonyl-containing alpha,beta-unsaturated compounds

Using toxicity data for 30 aliphatic polarized alpha,beta-unsaturated derivatives of esters, aldehydes, and ketones, a series of six structure-toxicity relationships were evaluated. The structure feature of all assessed compounds, an acetylenic or olefinic moiety conjugated to a carbonyl group, is inherently electrophilic and conveys the capacity to exhibit enhanced toxicity. However, the toxic potency of alpha,beta-unsaturated carbonyl compounds is dependent on the specific molecular structure with several trends being observed. Specific observations include: (1) between homologues, the acetylenic-substituted derivative was more toxic than the corresponding olefinic-substituted one, respectively; (2) between olefinic-homologues, terminal vinyl-substituted derivative was more toxic than the internal vinylene-substituted one; (3) within alpha,beta-unsaturated ketones, methyl substitution on the vinyl carbon atoms reduces toxicity with methyl-substitution on the carbon atom farthest from the carbonyl group exhibiting the greater inhibition; (4) between alpha,beta-unsaturated carbonyl compounds with the carbon-carbon double bond on the end of the molecule (vinyl ketones) and those with carbon-oxygen double bonds on the end of the molecule (aldehydes), the ketones are more toxic than the aldehydes; (5) between homologues of alpha,beta-unsaturated esters, those with additional unsaturated moieties (allyl, propargyl, or vinyl groups) were more toxic than homologues having relevant unsaturated moieties (propyl or ethyl groups); (6) between alpha,beta-unsaturated carbonyl compounds with different shaped alkyl-groups (i.e. different degrees of branching), homologues with straight-chain hydrocarbon moieties were more toxic than those with branched groups.     

Laminar flow of non-Newtonian liquid films inside a vertical pipe

Summary Equations describing the laminar, gravitationally accelerated flow of power-law liquid films flowing inside of a vertical pipe have been studied mathematically. The flow depends on the values of the flow behavior index, the initial film thickness, the magnitude of the initial uniform velocity, and the distance traveled by the fluid along the vertical wall. Values for the film thickness, boundary-layer thickness as well as entrance length are obtained numerically. The numerical solutions show the magnitude of deviations from the flow of Newtonian fluids that can be expected with power-law fluid characteristics.

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Zusammenfassung Es werden die Gleichungen, welche eine laminare schwerkraftbeschleunigte Filmströmung von Ostwald-deWaele-Flüssigkeiten längs der Innenseite eines senkrechten Rohrs beschreiben, mathematisch analysiert. Die Strömung hängt vom Fließindex, der anfänglichen Filmdicke, der Größe der gleichförmigen Anfangsgeschwindigkeit und der Laufstrecke ab. Die Werte von Filmdicke und Eintrittslänge werden numerisch bestimmt. Diese Lösungen zeigen die Größenordnung der Abweichungen von der Strömung newtonscher Flüssigkeiten, die bei Ostwald-deWaele-Flüssigkeiten erwartet werden können.

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G Dimensionless parameter, (3U ₀) ⁿ m/(gh ₀ ⁿ⁺¹ ) - g Gravitational acceleration, ft/sec² - h Liquid film thickness, ft;h ₀ initial value; - k Fluid consistency index, lb _f ^sec nft^–2 - m k/, lb _f lb _m ^-1 sec ⁿ ft - n Flow behavior index, dimensionless - R Radius of the considered curved surface, ft - r Radial distance in cylindrical coordinates, ft - U ₀ Initial velocity, ft/sec - U _s Free stream velocity, ft/sec - V _r Velocity component inr-direction in cylindrical coordinates, ft/sec - V _z Velocity component inz-direction in cylindrical coordinates, ft/sec - z Coordinate axis, distance from original in direction of flow, ft; , dimensionless - z ^* Entrance length, ft; , dimensionless - Boundary-layer thickness, ft; ; ^* = at end of entrance region; - Defined by Eq. [8], dimensionless; ^* = when - Dimensionless parameter, (R –r)/ - Fluid density, lb _m /ft³ - _rz Shear stress inz-direction on surface normal tor, lb _f /ft² With 4 figures and 1 table     

Sensing of sulfur dioxide by base metal thiolates: structures and properties of molecular NiN2S2/SO2 adducts

The cis-dithiolate N2S2Ni complex bismercaptoethanediazacycloheptanenickel(II), (bme-dach)Ni or Ni-1', takes up two equivalents of sulfur dioxide in which thiolate-sulfur to SO2-sulfur interactions are well-defined by X-ray crystallography. Ni-1' x 2SO2, C9H18N2NiO4S4, yields monoclinic crystals belonging to the P2(1)/c space group: a = 10.308(4) angstroms, b = 13.334(5) angstroms, c = 10.842(4) angstroms, alpha = 90 degrees, beta = 91.963(6) degrees, gamma = 90 degrees, and Z = 4. Further characterization by nu(SO) IR spectroscopy, thermal gravimetric analysis, electronic spectroscopy, and visual color changes upon reversible SO2 adduct formation establish Ni-1' and the analogous bismercaptoethanediazacyclooctane derivative, (bme-daco)Ni, Ni-1, to be viable candidates for technical development as chemical sensors of this noxious gas. Visual SO2 detection limits of Ni-1 and Ni-1' are established at 25 and 100 ppm, respectively. Both the Ni-1' x 2SO2 adduct and the Ni-1' reactant are air stable. In addition, the stability of Ni-1' x SO2 to vacuum and removal of SO2 by heating make Ni-1' a possible storage/controlled release complex for SO2 gas.     

Carbon dioxide/epoxide coupling reactions utilizing Lewis base adducts of zinc halides as catalysts. Cyclic carbonate versus polycarbonate production

The reactions of zinc halides with 2,6-di-methoxypyridine or 3-trifluoromethylpyridine in dichloromethane have led to the formation of quite different complexes. Specifically, reactions involving pyridine containing electron donating methoxy substitutents have provided salts of the type [Zn(2,6-dimethoxypyridine)4][Zn2X6], as revealed by elemental analysis and X-ray crystallography. On the other hand, simple bis-pyridine adducts of zinc halides were isolated from the reactions involving the pyridine ligand with electron withdrawing substituents and characterized by X-ray crystallography, for example, Zn(3-trifluoromethylpyridine)2Br2. These zinc complexes were shown to be catalytically active for the coupling of carbon dioxide and epoxides to provide high molecular weight polycarbonates and cyclic carbonates, with the order of reactivity being Cl > or = Br > I, and 2,6-di-methoxypyridine > 3-trifluoromethylpyridine. Polycarbonate production from carbon dioxide and cyclohexene oxide was shown to be first-order in both metal precursor complex and cyclohexene oxide, as monitored by in situ infrared spectroscopy at 80 degrees C and 55 bar pressure. For reactions carried out in CO2 swollen epoxide solutions in the absence of added quantities of pyridine, the copolymer produced contained significant polyether linkages. Alternatively, reactions performed in the presence of excess pyridine or in hydrocarbon solvent, although slower in rate, afforded completely alternating copolymers. For comparative purposes, zinc chloride was a very effective homopolymerization catalyst for polyethers. Additionally, zinc chloride afforded copolymers with 60% carbonate linkages in the presence of high carbon dioxide pressures. In the case of cyclohexene oxide, the copolymer back-biting reaction led exclusively to the production of the trans cyclic carbonate as shown by infrared spectroscopy in v(C=O) region and X-ray crystallography. The unique feature of these catalyst systems is their simplicity.     

Structure of chlorohydroxonitrosyl(terpyridine)ruthenium(II) hexafluorophosphate

The title complex has the NO grouptrans to the hydroxyl ligand and the chloride ion in the plane of the tripyridyl ligand. The Ru−O and Ru−N(O) distances are 1.939(5) ? and 1.764(6) ?, respectively; the Ru−N−O bond angle is 171.7(6)⁰. These values are consistent with previously reported shortening of Ru−O distances whentrans to a linear NO ligand. The space group of the structure isP2₁/c, witha=9.7213(9) ?,b=13.9318(11) ?,c=14.523(4) ?, and β=105.820(13)⁰.