Experimental design and the optimization of a polymer supported palladium complex for use in the Heck reaction

Optimization of the Heck reaction of 4-bromoacetophenone with styrene by a polymer supported, sulfur-containing palladacycle, varying 6 factors at a total of 28 different levels, corresponding to 5760 different possibilities was undertaken. Conversion improved from 34%, with large observable leaching to 88% with no leaching. This was accomplished using a Design of Experiments approach facilitated by the Statistical Design Package, MODDE 7.0^TM.     

A Practical Solution to a Cargo Loading Problem at Bethlehem Steel

The optimum assignment of structural steel shapes to rail cars is an important logistical problem in the steel industry. In this paper, we discuss an application at Bethlehem Steel that not only involves weight and dimensional constraints, but also customer unloading constraints. The formulation is a generalized bin packing problem which is solved by modifying and extending the first fit decreasing algorithm. The solution algorithm, SOLID (for Structural Optimal Loading IDentification), has been used extensively for one of Bethlehem's high tonnage customers providing very good practical (implementable) results that achieve the desired goals. Bethlehem has enhanced this approach for use with other customers.     

Redox and spectroscopic orbitals in Ru(II) and Os(II) phenolate complexes

A detailed spectroscopic and electrochemical study of a series of novel phenolate bound complexes, of general formulas [M(L-L)(2)(box)](PF(6)), where M is Os and Ru, L-L is 2,2-bipyridine or 2,2-biquinoline, and box is 2-(2-hydroxyphenyl)benzoxazole, is presented. The objectives of this study were to probe the origin of the LUMOs and HOMOs in these complexes, to elucidate the impact of metal and counter ligand on the electronic properties of the complex, and to identify the extent of orbital mixing in comparison with considerably more frequently studied quinoid complexes. [M(L-L)(2)(box)](PF(6)) complexes exhibit a rich electronic spectroscopy extending into the near infrared region and good photostability, making them potentially useful as solar sensitizers. Electrochemistry and spectroscopy indicate that the first oxidation is metal based and is associated with the M(II)/(III) redox states. A second oxidative wave, which is irreversible at slow scan rates, is associated with the phenolate ligand. The stabilities of the oxidized complexes are assessed using dynamic electrochemistry and discussed from the perspective of metal and counter ligand (LL) identity and follow the order of increasing stability [Ru(biq)(2)(box)](+) < [Ru(bpy)(2)(box)](+) < [Os(bpy)(2)(box)](+). Electronic and resonance Raman spectroscopy indicate that the lowest energy optical transition for the ruthenium complexes is a phenolate (pi) to L-L (pi) interligand charge-transfer transition (ILCT) suggesting the HOMO is phenolate based whereas electrochemical data suggest that the HOMO is metal based. This unusual lack of correlation between redox and spectroscopically assigned orbitals is discussed in terms of metal-ligand orbital mixing which appears to be most significant in the biquinoline based complex.     

Hybridization and Melting Behavior of Peptide Nucleic Acid (PNA) Oligonucleotide Chimeras Conjugated to Gold Nanoparticles

Peptide nucleic acids (PNA) and PNA–DNA chimeras carrying thiol groups were used for surface functionalization of Au nanoparticles. Conjugation of PNA to citrate‐stabilized Au nanoparticles destabilized the nanoparticles causing them to precipitate. Addition of a tail of glutamic acid to the PNA prevented destabilization of the nanoparticles but resulted in loss of interaction with complementary sequences. Importantly, PNA–DNA chimeras gave stable conjugates with Au nanoparticles. The hybridization and melting properties of complexes formed from chimera–nanoparticle conjugates and oligonucleotide–nanoparticle conjugates are described for the first time. Similar to oligonucleotide–nanoparticle conjugates, conjugates with PNA–DNA chimeras gave sharper and more‐defined melting profiles than those obtained with unmodified oligonucleotides. In addition, mismatch discrimination was found to be more efficient than with unmodified oligonucleotides.     

Synthesis and Reactivity of Metallophosphanes

Abstract

Aspects of the reactivity of metallophosphanes are presented along with the synthesis and structure determinations for new aluminophosphanes.     

Rational Design of a Uranyl Metal–Organic Framework for the Capture and Colorimetric Detection of Organic Dyes

A new uranyl containing metal–organic framework, RPL-1 : [(UO₂)₂(C₂₈H₁₈O₈)] ^. H₂O (RPL for Radiochemical Processing Laboratory), was prepared, structurally characterized, and the solid-state photoluminescence properties explored. Single crystal X-ray diffraction data reveals the structure of RPL - 1 consists of two crystallographically unique three dimensional, interpenetrating nets with a 4,3-connected tbo topology. Each net contains large pores with an average width of 22.8 Å and is formed from monomeric, hexagonal bipyramidal uranyl nodes that are linked via 1,2,4,5-tetrakis(4-carboxyphenyl)benzene (TCPB) ligands. The thermal and photophysical properties of RPL-1 were investigated using thermogravimetric analysis and absorbance, fluorescence, and lifetime spectroscopies. The material displays excellent thermal stability and temperature dependent uranyl and TCPB luminescence. The framework is stable in aqueous media and due to the large void space (constituting 76 % of the unit cell by volume) can sequester organic dyes, the uptake of which induces a visible change to the color of the material.     

Molecular Design Principles for Near‐Infrared Absorbing and Emitting Indolizine Dyes

Desirable components for dye‐sensitzed solar cell (DSC) sensitizers and fluorescent imaging dyes include strong donating building blocks coupled with well‐balanced acceptor functionalities for absorption beyond the visible range. We have evaluated the effects of increasing acceptor strengths and incorporation of dye morphology controlling groups on molar absorptivity and absorption breadth with indolizine donor‐based dyes. Indolizine‐based D –A and D –π–A sensitizers incorporating bis‐rhodanine, tricyanofuran (TCF), and cyanoacrylic acid functionalities were analyzed for performance in DSC devices. The TCF derivatives were also evaluated as near‐infrared (NIR)‐emissive materials with the AH25 emissions extending past 1000 nm.     

Generalized formulation of the interactions between soft spheres

The goal of this paper is to identify the most general formulation that consistently links the different degrees of freedom in a contact between spherical soft particles. These contact laws have two parts: a set of “generalized contact velocities” that characterize the relative motion of the two particles, and a set of “generalized contact forces” that characterize the interparticle forces. One well known constraint on contact models is that the contact velocities must be objective. This requirement fixes the number of linearly independent contact velocities. We also present a previously unnoticed (in this context) constraint, namely, that the velocities and forces must be related in such a way that the stiffness matrix is symmetric. This constraint also places restrictions on the coupling between the contact forces. Within our generalized contact model, we discuss the expression for rolling velocity that need to be used in the calculation of rolling resistance, and the risk or producing perpetual mobile when other expressions of rolling velocity are using instead.     

Development of a trace gas stable isotope capture system in a mobile laboratory for temporal and spatial sampling of field and laboratory experiments

We describe the development of a novel mobile field laboratory, purposely designed for the automated capture and subsequent stable isotopic analyses of multiple gas samples. The multiple capture system is integrated into a mobile laboratory that is fully capable of measuring the concentration of carbon dioxide, methane and nitrous oxide trace gases in a flow-through system connected to a gas chromatograph fitted with both electron capture and flame ionisation detectors. The capture of gases is achieved by routing samples through a series of 135 mL gas flasks that are sealed by micro-solenoid valves triggered by a timing system. Trace gas light stable isotope ratio mass spectrometry can then be carried out on gas samples collected by the system (NERC (15)N Stable Isotope Facility). The excitingly unique potential of the system to the ecological research field is that it will allow the collection of cyclical data for three different trace gases both in real-time and in situ. We present data arising from the validation of this mobile system as well as a preliminary experimental assessment of this technique. This technique was used to measure delta(13)C in CO(2) and CH(4) in soil gases released from waterlogged cores and delta(13)C-CH(4) values were significantly depleted in wet cores compared with dry ones (p < 0.001).     

A convergent synthesis of a novel non-peptidyl growth hormone secretagogue, L-692,429

A practical, convergent synthesis of L-692,429 (1) from three key intermediates - the 3- aminobenzlactam 2, the β-lactam 3 and the biphenyltetrazole 4 is described. The mechanism of the coupling reaction in which 3 is used as a β-aminoacid equivalent is also presented.