Crystal Structure of a New Allotropic Form of trans-Pd(Creat)2Cl2·2H2O

Pd(creat)₂Cl₂·2H₂O crystallizes in space group P&1macr; with a= 7.257(2), b= 8.159(2), c= 14.640(2) Å, f =73.97(2), g =77.0(1), u =72.22(2)°, Z=2, and represents a new allotropic form of this compound. Pd atoms have planar fourfold coordination of N and Cl atoms in trans configuration. Creatinine moieties are coordinated to the Pd atoms via endocyclic N atoms and their essential planarity causes significant delocalization of electron density. The structure is stabilized by a system of weak hydrogen bonds involving interstitial water molecules and creatinine amino-groups.     

A New Preparation of Mo2(CO)8(μ-PPh2)2 and W2(CO)8(μ-PPh2)2 by a Phosphorus-Carbon Bond Cleavage Reaction. Crystal Structure of a New Polymorph of Mo2(CO)8(μ-PPh2)2

A new synthesis of Mo₂(CO)₈(-PPh₂)₂ and W₂(CO)₈(-PPh₂)₂ by the reaction of molybdenum and tungsten hexacarbonyls with a tetraazamacrocyclic ligand containing —CH₂PPh₂ side chains, comprising cleavage of the phosphorus-methylene bond has been performed. The complexes have been investigated by magnetic and spectroscopic measurements and by single-crystal structure analyses. The structural characterization of a new polymorph of Mo₂(CO)₈(-PPh₂)₂ has been described.     

Synthesis of a new complex Chromium (Ⅲ) 2-mercaptonicotinate

Chromium is an essential trace element for mammals[1-3].Diabetes is a chronic disease with major health consequence.Studies show that the occurrence of diabetes have great thing to do with the chromium deficient。Almost 40 years after the first report of glucose tolerance factor(GTF) [4] no conclusive evidence for an isolable ,biologically active form of chromium exited。Three materials have been proposed to be the biologically active form of chromium:“glucose tolerance factor”,chromium Pi…     

Theoretical investigation of rotationally inelastic collisions of CH2(ã) with helium

Rotationally inelastic collisions of the CH(2) molecule in its a?(1)A(1) electronic state have been investigated. We have determined a potential energy surface (PES) for the interaction of rigid CH(2)(a?), frozen at its equilibrium geometry, with a helium atom, using a coupled-cluster method that includes all single and double excitations, as well as perturbative contributions of connected triple excitations [RSSCD(T)]. The PES is quite anisotropic, due to lack of electron density in the unoccupied CH(2) non-bonding orbital perpendicular to the molecular plane. Quantum scattering calculations have been carried out to compute state-to-state rotational energy transfer and elastic depolarization cross sections at collision energies up to 2400 cm(-1). These cross sections were thermally averaged to derive room-temperature rate constants. The total removal and elastic depolarization rate constants for the ortho k(a) = 1 levels agree well with recent experimental measurements by Hall, Sears, and their co-workers. We observe a strong even-odd alternation in the magnitude of the total rate constants which we attribute to the asymmetry splitting of the k(a) = 1 levels.     

Synthesis and Crystal Structure of a Novel (2:2) Macrocyclic Thiocarbohydrazone

Thiocarbohydrazoneshavebeentestedasantindcrobialandantitumouragentsandwidelyusedinanalyticalchemistry'-'.Ontheotherhand,thechemistryofmacrocycliccompoundshasattTactedcontinuousinterestformanyyears.Thiocarbohydrazide,HZN'N'HC(S)NHN'Hz,anditsSchiffbasecomplexesconstitUteintersstingligandsystemsbecauseoftheavailbilityofseveralpotentialdonorsites,inwhichthioketo-thioenoltautomerismispossible.Significantly,theyareabletoformbothmono-andbinuclearcomplexesbydifferentmethods3-6.Withtheaimofdesign…     

Computational studies of bacterial resistance to β-lactam antibiotics: mechanism of covalent inhibition of the penicillin-binding protein 2a (PBP2a)

β-Lactam resistance of methicillin-resistant Staphylococcus aureus (MRSA), a pathogenic bacterium that causes staph infections, represents a serious threat to public health. This arises primarily due to the inability of β-lactam antibiotics to inhibit the transpeptidase activity of penicillin-binding protein 2a (PBP2a). Effective inhibition of PBP2a to prevent the bacterial cell wall biosynthesis is of great importance for the treatment of a variety of clinically challenging infectious diseases caused by MRSA. To gain fundamental insights into the mode of covalent inhibition of the enzyme, we have carried out computational studies of the acylation reactions between small β-lactam molecules (methicilin and nitrocefin) and PBP2a using the B3LYP/6-31G* and ONIOM(B3LYP/6-31G*:AMBER) hybrid quantum mechanical/molecular mechanical methods. Our calculations show that the acylation involves two transition states and that methicilin and nitrocefin undergo acylation in slightly different manners. The acylation of nitrocefin is more facile, which is attributed to the larger release of ring strain and the larger resonance stabilization gained upon ring opening. We suggest that, in addition to the nonbonded interactions between the ligand and the protein, these quantum chemical factors, which are associated with efficiency of the acylation step, should be taken into account and carefully controlled in designing novel β-lactam inhibitors of PBP2a.     

Self-assembly snapshots of a 2 × 2 copper(I) grid

Self-assembled 2 × 2 grids have been characterised as high-fidelity species produced when the correct stoichiometric ratios are met, but rarely are the individual steps leading to and from their formation characterised. Here, we present such a study using equilibrium-restricted factor analysis to model a set of UV–vis spectra starting from a bis-bidentate ligand to the assembly of a 2 × 2 grid complex upon titration with 1 equiv. of [Cu(MeCN)₄](PF₆) and to disassembly upon further titration. Intermediate species [CuL₂]⁺, [Cu₂L₃]²⁺, [Cu₃L₂]³⁺ and [Cu₂L]²⁺ are evidenced along the assembly and disassembly pathways. Complementary ¹H NMR titrations are consistent with the rich set of complexes and equilibria involved. Given the nature of the assembly process, the assembly is entropy driven and likely enthalpy driven as well. The disassembly process is both enthalpy and entropy driven according to the standard free energy values derived from the modelling of the spectrophotometric titration data.     

Formation of a Dimer with a Double Hydroxo Bridge in Nitric Acid Solutions of the Nitrosotetranitrohydroxo Complex of Ruthenium(II). Crystal Structure of K2[RuNO(NO2)3(μ-OH)]2

Fine yellowish orange crystals of the binuclear complex K₂[RuNO(NO₂)₃(-OH)]₂ were obtained by the reaction of K₂[RuNO(NO₂)₄OH] with a stoichiometric amount of 0.8 M nitric acid at room temperature. The compound was investigated by IR spectroscopy, X-ray phase analysis (DRON-3M, CuK radiation), and X-ray diffraction analysis (Nonius CAD-4, MoK radiation, graphite monochromator, scan mode, 1406 reflections). The crystals are poorly soluble in water and practically insoluble in ethanol and acetone; the compound is stable when stored in air. Crystal data for H₂K₂N₈O₁₆Ru₂ are: a = 8.596(2), b = 10.111(1), c = 9.537(1) , = 104.42(1)°, V = 802.8(2) ³, space group , Z = 2, _calc = 2.691 g/cm³. The structure is built of [RuNO(NO₂)₃(- complex anions and K⁺ cations.     

Synthesis and reactions of ν2-(2-formylphenyl)tetracarbonylmanganese(I) complexes; cyclopentaanulation of a diterpenoid

Reaction of tetracarbonylmangenese(I) complexes derived from a diterpenoid aryl aldehyde or aryl methyl ketone with acetylene or ethylene leads to cyclopentaannulation to give 1H-inden-1-ols or 1H-indan-ols, respectively.     

Blue electroluminescence of a novel Zn~(2+)–β-diketone complex with a carbazole moiety

In this letter, a novel zinc complex of Zn(ECTFBD)2 was synthesized by an environment-friendly grinding technique in high yield. Its structure was confirmed by1H NMR, MS and EA. HECTFBD is 1-(9-ethyl-9Hcarbazol-3-yl)-4,4,4-trifluorobutane-1,3-dione. Zn(ECTFBD)2-based light-emitting devices were fabricated. The architecture of the devices was ITO/PEDOT(40 nm)/100 wt% PVK: 40 wt% OXD-7: x wt% Zn(ECTFBD)2(85 nm)/CsF(1.5 nm)/Al(100 nm), where x = 1, 5, and 10(relative to the mass of PVK and OXD-7). The three devices displayed blue emissions with peaks at 450, 458, and 460 nm, respectively. A maximum luminous efficiency of 0.86 cd/A and a luminance of 228 cd/m2were achieved by the 1 wt% doped device. So, we demonstrated further that Zn2+–b-diketone complexes can be effectively severed as a class of new electroluminescent materials. In addition, the thermal stability of Zn(ECTFBD)2 was tested and the UV–vis and photoluminescent behaviors of Zn(ECTFBD)2 in CH2 Cl2 were investigated.     

Preparation and Identification of a New [Cr2(NTA)2(μ-OH2)]·2H2O Complex

[Cr₂(NTA)₂(μ-OH₂)]·2H₂O is prepared by heating nitrilotriacetic acid (H₃NTA) with an aqueous suspension of freshly precipitated Cr₂O₃·nH₂O. Elemental analysis, IR spectra, UV/vis spectra, X-ray diffraction, thermogravimetric analysis, mass spectra and magnetic susceptibility measurements suggest the existence of a Cr-Cr bond. One of the three water molecules acts as a bridging ligand (μ-H₂O) while the other two are waters of crystallization.     

Synthesis of the solvento species [Ru2(CO)5(solvent){μ- (RO)2PN(Et)P(OR)2}2]2+ and its potential as a source for a wide range of dinuclear derivatives of ruthenium

Treatment of [Ru₂(μ-CO)(CO)₄{μ-(RO)₂PN(Et)P(OR)₂}₂] (R = Me or Prⁱ), electron-rich derivatives of [Ru₂(CO)₉], with a twice molar amount of a silver(I) salt in aprotic, weakly co-ordinating solvents such as acetone, acetonitrile or benzonitrile leads to the formation of the solvento species [Ru₂(CO)₅(solvent)- {μ-(RO)₂PN(Et)P(OR)₂}₂]²⁺. The structure of the benzonitrile derivative, [Ru₂(CO)₅(PhCN){μ-(PrⁱO)₂PN(Et)P(OPr_i)₂}₂](SbF₆)₂, has been established by X-ray crystallography. The acetone molecule in [Ru₂(CO)₅(acetone){μ- (RO)₂PN(Et)P(OR)₂}₂]²⁺ is readily replaced by various nucleophiles to afford products of the type [Ru₂(CO)₅L{μ-(RO)₂PN(Et)P(OR)₂}₂]²⁺, where L is a neutral ligand such as CO, Me₂C₆H₃NC, PhCN, C₅H₅N, H₂O, Me₂S or SC₄H₈, [Ru₂Y(CO)₅{μ-(RO)₂PN(Et)P(OR)₂}₂]²⁺, where Y⁻ is an anionic ligand such as Cl⁻, Br⁻, I⁻, CN⁻, SCN⁻, MeCO₂⁻, CF₃CO₂⁻ or [Ru₂(μ-Y)(CO)₄{μ-(RO)₂- PN(Et)P(OR)₂}₂]⁺ where Y⁻ is an anionic ligand such as Cl⁻, Br⁻, I⁻, SPh⁻, S₂CNEt₂⁻, MeCO₂⁻ or CF₃CO₂⁻.     

Is there a homolytic substitution chemistry (SH2) of sulfones?

[reaction: see text] A series of 2-alkylsulfonyl-2'-biphenyl radicals, in which the alkyl group is primary, secondary, or tertiary, were generated and the products of their reactions investigated. Dibenzothiophene S,S-dioxide was not identified among the products, which arose mainly from intramolecular hydrogen abstraction from the alkyl group or addition to the solvent, benzene. On this basis, it is concluded that homolytic substitution at sulfonyl sulfur, if possible at all, is too slow to take precedence over a number of competing decomposition pathways. Previous literature results suggesting the possibility of intramolecular homolytic substitution at sulfonyl sulfur may be explained by alternative processes.     

Efficient Synthesis of a New Series of Piperidine Ring-Modified Analogs of (±)-threo-Methyl Phenyl(piperidin-2-yl)acetate

A series of novel piperidine ring modified analogs of (±)-threo-methyl phenyl(piperidin-2-yl)acetate was synthesized by direct alkylation and reductive amination procedure, using sodium borohydride over molecular sieves. The chemical structures of these compounds were established based on mass spectra, ¹H NMR spectra, and CHN elemental analysis data. Several significant modifications in the literature methodologies were made to make the reaction more efficient, and good yields were generally obtained.     

Synthesis of a dehydroabietyl derivative bearing a 2-(2'-hydroxyphenyl)benzimidazole unit and its selective Cu²+ chemosensing

A dehydroabietyl derivative 2 bearing a 2-(2'-hydroxyphenyl)benzimidazole unit was synthesized and its sensing behaviors toward metal ions were investigated by UV-Vis and fluorescence spectroscopy methods. In THF solution, compound 2 exhibited excellent selectivity for CuII over miscellaneous other metal ions including CrII, MnII, CoII, NiII, ZnII, CdII, AlIII, MgII, PbII, HgII, NaI, LiI and KI evidenced through the quenching of the fluorescence of the benzimidazole fragment. The reaction between 2 and Cu2+ was found to be stoichiometric with the formation of a 1:1 complex.     

Ir(PCy3)2(H)2(H2B-NMe2)]+ as a latent source of aminoborane: probing the role of metal in the dehydrocoupling of H3B⋅NMe2H and retrodimerisation of [H2BNMe2]2

The Ir^III fragment {Ir(PCy₃)₂(H)₂}⁺ has been used to probe the role of the metal centre in the catalytic dehydrocoupling of H₃B?NMe₂H ( A ) to ultimately give dimeric aminoborane [H₂BNMe₂]₂ ( D ). Addition of A to [Ir(PCy₃)₂(H)₂(H₂)₂][BAr^F₄] ( 1 ; Ar^F=(C₆H₃(CF₃)₂), gives the amine‐borane complex [Ir(PCy₃)₂(H)₂(H₃B?NMe₂H)][BAr^F₄] ( 2 a ), which slowly dehydrogenates to afford the aminoborane complex [Ir(PCy₃)₂(H)₂(H₂B? NMe₂)][BAr^F₄] ( 3 ). DFT calculations have been used to probe the mechanism of dehydrogenation and show a pathway featuring sequential BH activation/H₂ loss/NH activation. Addition of D to 1 results in retrodimerisation of D to afford 3 . DFT calculations indicate that this involves metal trapping of the monomer–dimer equilibrium, 2 H₂BNMe₂ ? [H₂BNMe₂]₂. Ruthenium and rhodium analogues also promote this reaction. Addition of MeCN to 3 affords [Ir(PCy₃)₂(H)₂(NCMe)₂][BAr^F₄] ( 6 ) liberating H₂B? NMe₂ ( B ), which then dimerises to give D . This is shown to be a second‐order process. It also allows on‐ and off‐metal coupling processes to be probed. Addition of MeCN to 3 followed by A gives D with no amine‐borane intermediates observed. Addition of A to 3 results in the formation of significant amounts of oligomeric H₃B?NMe₂BH₂?NMe₂H ( C ), which ultimately was converted to D . These results indicate that the metal is involved in both the dehydrogenation of A , to give B , and the oligomerisation reaction to afford C . A mechanism is suggested for this latter process. The reactivity of oligomer C with the Ir complexes is also reported. Addition of excess C to 1 promotes its transformation into D , with 3 observed as the final organometallic product, suggesting a B? N bond cleavage mechanism. Complex 6 does not react with C , but in combination with B oligomer C is consumed to eventually give D , suggesting an additional role for free aminoborane in the formation of D from C .     

Nature of the binding of a c(2×2)-CO overlayer on Ag(001) and surface mediated intermolecular coupling

We present a first-principles study of the nature of the binding of a c(2×2)-CO overlayer on Ag(001) and of the origin of CO-CO interactions upon adsorption. Electronic structural changes induced by molecular adsorption provide an interpretation for earlier X-ray photoemission valence band spectra of CO/Ag(001). Our results establish that CO chemisorbs on clean Ag(001) and follows the Blyholder model of donation and back-donation between CO and metal orbitals. We analyze the origin of the dispersion of the C-O stretch mode and attest that it is caused by the metal-CO coupling. Specifically, the coupling of CO to Ag, although the weakest of those between it and transition and other noble metals, greatly enhances the intermolecular force constants. We also find that the response of the charge density around CO is much stronger and of longer range when the molecule stretches than when it rigidly vibrates against the surface. This difference explains why the C-O stretch mode disperses while the Ag-CO stretch mode does not.     

Structure of a new binuclear complex of tungsten [W2S4Cl2(dppe)2]·2CH3CN

Journal of Structural Chemistry - In the reaction of (Et4N)2[W2S4Cl4] with 1,2-bis(diphenylphosphino)ethane in acetonitrile a new binuclear complex of tungsten(V) [W2S4Cl2(dppe)2]·2CH3CN is...     

Preparation And Characterization of a New Blend of Poly(2-hydroxyethyl methacrylate) And Poly(ethylene glycol)

Poly(2-hydroxyethylmethacrylate)(PHEMA)isahydroge1widelyusedinthefieldsofcontactlenses,atificialcorneasandsofttissuesubstitutes.However,theuseofPHEMAhydrogelisrestrictedduetoitsinsufficientlypermeablecharacterandlimitedwaterintake.Therefore,modificationsofthePHEMAhydrogelp1ayakeyroleinitspracticalaPplications'.Poly(ethyleneglycol)(PEG)isanonionicwatersolublematerialthathascomplexsolubilityproperties'.Meanwhile,PEGisnontoxic.Water-swellable,water-insolublehydrogelsmaybemadefromPEGbym…