A triad [FeFe] hydrogenase system for light-driven hydrogen evolution

A novel molecular triad [FeFe]-H(2)ase 1, and its model complexes 2 and 3 have been successfully constructed. The multistep PET and long-lived Fe(i)Fe(0) species were found to be responsible for the better performance of triad 1 than that of 2 with 3 for light-driven H(2) evolution.     

A mesogenic triphenylene-perylene-triphenylene triad

A straightforward synthesis of triphenylene-perylene-triphenylene triad structures has been achieved by using versatile triphenylene intermediates bearing a single oxyalkyl amine side chain. Among these, PBITP(10) showed a stable columnar mesophase implying favorably matched core-core separations in the structure. Importantly, the triad can be used as a vehicle for doping columnar triphenylene matrices with functional but incompatible perylene units and a mixture of hexahexyloxytriphenylene matrix doped with 0.1% PBITP(10) is homogeneous and liquid crystalline.     

A new redox-fluorescence switch based on a triad with tetrathiafulvalene and anthracene units

The fluorescence of a triad with TTF and anthracence units can be reversibly modulated by sequential oxidation and reduction. Thus, a new redox fluorescence switch can be established on the basis of this new triad. [structure: see text]     

A triad of rhenium-mediated transformations

The title transformations are oxygen atom transfer, twin isomerization and regiospecific imine oxidation.Bispyridyldiazole ligands have furnished new oxygen atom transfer reagents of coordination type Re^VOCl₃(NN) which undergo a slower transfer to PPh₃ than the corresponding azole reagents. The rate of twin isomerization (linkage and geometrical) of meridional azole complexes of coordination type Re^III(OPnP)Cl₃(NN) to facial Re^III(PnPO)Cl₃(NN) decreases rapidly asn increases in the interval 1–4 (PnP is Ph₂P(CH₂)_nPPh₂). An α-diimine chelate of type Re^V(NPh)Cl₃(NN) is shown to undergo facile oxidation to the corresponding iminoamide complex Re_VI(NPh)Cl₃(NN) upon treating with dilute nitric acid. The reaction proceeds via regiospecific nucleophilic addition of waterto the more polarized imine function. Dedicated to Professor C N R Rao on his 70th birthday     

A two-step valence tautomeric transition in a dinuclear cobalt complex

A dinuclear cobalt complex with cobalt centers bridged by a bis(dioxolene) ligand exhibits a rare two-step valence tautomeric transition.     

The minicellirradiator: A new system for a new market

Since the commissioning of the first industrial Gamma Irradiator design, designers and operators of irradiation systems have been attempting to meet the specific production requirements and challenges presented to them. This objective has resulted in many different versions of irradiators currently in service today, all of which had original charters and many of which still perform very well within even the new requirements of this industry.

Continuing changes in the marketplace have, however, placed pressures on existing designs due to a combination of changing dose requirements for sterlization, increased economic pressures from the specific industry served for both time and location and the increasing variety of product types requiring processing. Additionally, certain market areas which could never economically support a typical gamma processing facility have either not been serviced, or have forced potential gamma users to transport product long distances to one of these existing facilities.

The MiniCell^TM removes many of the traditional barriers previously accepted in the radiation processing industry for building a processing facility in a location. Its reduced size and cost have allowed many potential users to consider in-house processing and its ability to be quickly assembled allow it to meet market needs in a much more timely fashion than the previous designs.

The MiniCell system can cost effectively meet many of the current market needs of reducing total cost of processing and also be flexible enough to process product in a wide range of industries effectively.     

Gas phase ionization of 1,3-propanedial tautomeric forms: A theoretical study

Two stable 1,3-propanedial tautomers and three their anions have been studied theoretically at MP2 and DFT levels of theory. The energies, structural parameters, ionization potentials, and vibration frequencies have been calculated at the two theoretical levels in order to compare the accuracy of the methods used. The ionization potential of the end form of 1,3-propanedial enol form was estimated to be 752 kJ mol^?1; the first and second potentials of the diketo form of 1,3-propanedial are 661 and 1239 kJ mol^?1, respectively.     

Conformational and tautomeric preferences in 3‐aminoacrylaldehyde: A theoretical study

The conformational study of 3‐aminoacrylaldehyde were performed at various theoretical levels and the equilibrium conformations were determined. Furthermore, to have more reliable energies, the total energies of all forms recomputed at G2MP2 and CBS‐QB3. Theoretical calculations clearly show that the intramolecular hydrogen bond (IHB) is the origin of conformational preference and the resultant IHB order at HF/6‐311++G(d,p), MP2/6‐311++G(d,p), and CBS‐QB3 levels is different from the order which obtained from the B3LYP/6‐311++G(d,p), G2MP2, the geometrical parameters, AIM, and NBO analyses. Furthermore, our theoretical results reveal that the ketoamine (KA) tautomeric group is more stable than the enolimine (EI) and ketoimine (KI) ones. The IHB and tautomeric process could not rationalize the irregular stability of KA group with respect the others. But the population analyses of the possible conformations by NBO predict that the π‐electron delocalization, especially unusual π → π charge transfer, is the origin of tautomeric preference. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

A new tautomeric zwitterion form of 2-acylamino-4H-1,3,4-oxadiazino[5,6-b]quinoxalines in solution

The reaction of 2-acyiamino-8-chloro-4-methyl-4H-1,3,4-oxadiazino[5,6-b]quinoxalines 2a-d with methyl iodide/base gave the 8-chloro-4,10-dimethyl-4H-1,3,4-oxadiazino[5,6-b]quinoxalin-10-ium-2-acylamidates 4a-d , respectively. Comparison of the nmr spectral data between compounds 2a-d and 4a-d in deuteriodimethyl sulfoxide or in deuteriotrifluoroacetic acid established that compounds 2a-d existed as the zwitterionic tautomers 2′a-d in solution.     

A new anatase-type phase in the system Mg-Ta-O-N

Magnesium doped tantalum oxynitrides were prepared by ammonolysis of amorphous mixed oxides. An orange colored anatase-type phase with the composition Mg_0.05Ta_0.95O_1.15N_0.85 was found. It is metastable and undergoes a phase transformation to a baddeleyite-type phase between 900 and 1000 °C. X-ray diffraction measurements indicate spacegroup I4₁/amd with lattice parameters and . A possible anion ordering was examined by theoretical methods and neutron diffraction experiments. In addition, anosovite-type (Ti₃O₅) phases Mg_xTa_3−xO_3xN_5−3x; 0?x?0.3 were obtained. The electronic spectra of all phases were investigated by UV/vis spectroscopy.     

Solvation of the tautomeric forms of 2-oxopyrimidine in carbon tetrachloride solution: A Monte Carlo simulation

Solvation of both tautomeric forms of 2-oxopyrimidine by carbon tetrachloride has been investigated using the Monte Carlo method for a cluster consisting of 50 molecules at T=300 K. The results indicate that, in oposition to hydration, this solvation shifts the tautomeric equilibrium a little towards the lactim form, in agreement with experiment. The structure of the solvation shell in both tautomers closely resembles that of the pure solvent. Local minima of the interaction energy between n = 1, 2, 3, 4, 6 and 8 CCl₄ molecules and 2-oxopyrimidine have been examined. The results shed some light on the nature of the poor solubility of purines and pyrimidines in carbon tetrachloride.     

A doubly 2,6-pyridylene-bridged porphyrin-perylene-porphyrin triad

A doubly 2,6-pyridylene-bridged porphyrin-perylene-porphyrin triad was synthesized via Suzuki-Miyaura cross coupling reaction, which captures a tetrakis(3-pyridyl)porphyrin guest in a 2 : 1 manner to form a supramolecular complex that undergoes photo-induced electron transfer.     

The 1,3-benzotellurazole : A new heterocyclic system

We describe the synthesis of a new heterocyclic system : the 1,3-benzotellurazole, and some of its substituted derivatives.     

Synthesis of the stereogenic triad of the halicyclamine A core

We describe herein our progress toward the synthesis of halicyclamine A, which possesses very interesting biological activities and has never been synthesized. For this purpose, we proposed a stereoselective Diels-Alder reaction as a key step for the establishment of the stereogenic triad of the bis(piperidinyl) core of this molecule. A series of NMR studies was then conducted to establish the correct stereochemical assignment subsequent to the Diels-Alder reaction.     

Benzimidazole-based anion receptors: tautomeric switching and selectivity

Tautomeric switching is observed in a series of benzimidazole-based anion receptors upon addition of basic anions. An N-methylbenzimidazole based receptor selectively interacts with dihydrogen phosphate over a variety of other putative anionic guests via a combination of donated and accepted hydrogen bonds.     

A simple NMR method for determination of the position of the tautomeric equilibrium in diarylformazanes

Conclusions Analysis of the shielding of the¹³C nuclei in 1,3-diphenyl-5-arylformazanes permits evaluation of the position of the tautomeric equilibrium in the red formazanes. In the case of the electron-withdrawing p-NO₂ substituent, the substituted ring is attached to the NHN=hydrazone fragment. An opposite effect is found for electron-donor substituents. In the case of ortho substituents, the shift of the tautomeric equilibrium is largely determined by steric factors.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 691–694, March, 1987.