Increase of Direct C-C Coupling Reaction Yield by Identifying Structural and Electronic Properties of High-Spin Iron Tetra-azamacrocyclic Complexes

Macrocyclic ligands have been explored extensively as scaffolds for transition metal catalysts for oxygen and hydrogen atom transfer reactions. C–C reactions facilitated using earth abundant metals bound to macrocyclic ligands have not been well-understood but could be a green alternative to replacing the current expensive and toxic precious metal systems most commonly used for these processes. Therefore, the yields from direct Suzuki–Miyaura C–C coupling of phenylboronic acid and pyrrole to produce 2-phenylpyrrole facilitated by eight high-spin iron complexes ([Fe3+L1(Cl)2]+, [Fe3+L4(Cl)2]+, [Fe2+L5(Cl)]+, [Fe2+L6(Cl)2], [Fe3+L7(Cl)2]+, [Fe3+L8(Cl)2]+, [Fe2+L9(Cl)]+, and [Fe2+L10(Cl)]+) were compared to identify the effect of structural and electronic properties on catalytic efficiency. Specifically, catalyst complexes were compared to evaluate the effect of five properties on catalyst reaction yields: (1) the coordination requirements of the catalyst, (2) redox half-potential of each complex, (3) topological constraint/rigidity, (4) N atom modification(s) increasing oxidative stability of the complex, and (5) geometric parameters. The need for two labile cis-coordination sites was confirmed based on a 42% decrease in catalytic reaction yield observed when complexes containing pentadentate ligands were used in place of complexes with tetradentate ligands. A strong correlation between iron(III/II) redox potential and catalytic reaction yields was also observed, with [Fe2+L6(Cl)2] providing the highest yield (81%, −405 mV). A Lorentzian fitting of redox potential versus yields predicts that these catalysts can undergo more fine-tuning to further increase yields. Interestingly, the remaining properties explored did not show a direct, strong relationship to catalytic reaction yields. Altogether, these results show that modifications to the ligand scaffold using fundamental concepts of inorganic coordination chemistry can be used to control the catalytic activity of macrocyclic iron complexes by controlling redox chemistry of the iron center. Furthermore, the data provide direction for the design of improved catalysts for this reaction and strategies to understand the impact of a ligand scaffold on catalytic activity of other reactions

Friction and wear behaviour of Mo − W doped carbon-based coating during boundary lubricated sliding

A molybdenum and tungsten doped carbon-based coating (Mo−W−C) was developed in order to provide low friction in boundary lubricated sliding condition at ambient and at high temperature. The Mo−W−C coating showed the lowest friction coefficient among a number of commercially available state-of-the-art DLC coatings at ambient temperature. At elevated temperature (200°C), Mo−W−C coating showed a significant reduction in friction coefficient with sliding distance in contrast to DLC coatings. Raman spectroscopy revealed the importance of combined Mo and W doping for achieving low friction at both ambient and high temperature. The significant decrease in friction and wear rate was attributed to the presence of graphitic carbon debris (from coating) and 'in-situ' formed metal sulphides (WS2 and MoS2, where metals were supplied from coating and sulphur from engine oil) in the transfer layer

New tool coatings for light metal cutting

New carbon based coatings have been developed for cutting light metals such as aluminum. These coatings can be used either directly on the tool or as topcoating combined with another hard base coating. Cutting tests show that the coating gives good performance for materials that tend to stick to the cutting tools, such as aluminum alloys, because of the substantial reduction of appearance of the so-called built up edge (BUE). This results in a longer life time of the tool and smoother surface finish of the cut made in the workpiece material. Especially in dry machining and deep hole drilling this coating performed very well. An overview of the properties and initial cutting results of this coating is presented. This paper also presents the results from recent industrial field tests carried out by a leading European aerospace manufacturer. Cutting forces, BUE formation and surface roughness data are presented to explain the cutting process during dry machining

TiAIN superlattice structured PVD coatings: a new alternative in the machining of aluminium alloys for aerospace and automotive components

A 3 μm thick superlattice structured TiAlN/VN coating has been deposited by the steered cathodic arc/unbalanced magnetron sputtering technique. The coating has been tested in dry high-speed milling of aluminium alloys Al7010-T7651 and AlSi9Cu1 and the performance compared to that of the diamond-like carbon (DLC) coated, TiAlCrYN coated and uncoated tools. In milling the Al7010-T7651 alloy, TiAlN/VN and DLC coated tools showed comparable performance, outperforming TiAlCrYN coated and uncoated tools by a factor of 2.3 and 3.5, respectively. In the case of milling AlSi9Cu1, the DLC coatings failed to produce any lifetime improvement, TiAlCrYN showed 65% longer lifetime thus rendering TiAlN/VN as the best performing coating with 100% longer lifetime compared to that of the uncoated tools. The tests further showed that TiAlN/VN reduces the cutting forces and improves the surface finish. Scanning electron microscopy of the cutting edge carried out after the cutting tests showed that the TiAlN/VN coating significantly reduces metal transfer and built-up edge formation.</p

HPV E6 oncoproteins and nucleic acids in neck lymph node fine needle aspirates and oral samples from patients with oropharyngeal squamous cell carcinoma

Commercial assays measuring HPV E6 viral oncoproteins, E6/E7 mRNA or DNA were used to test neck lymph node fine needle aspirates (FNA) and oropharyngeal samples (saliva and oral swabs) from 59 Canadian patients with oropharyngeal squamous cell carcinomas (OPSCC). Overall agreements of p16 antigen staining of tumors to FNA tested for OncoE6™, Aptima HPV E6/E7 mRNA and cobas HPV DNA were 81.4% (k 0.53), 94.9% (k 0.83) and 91.1% (k 0.73) respectively. Using HPV presence in a subset of 25 tumors as the comparator, overall agreement was 64.0% (k 0.08) with OncoE6™, 88.0% (k 0.65) with Aptima HPV E6/E7 mRNA and 91.7% (k 0.70) with cobas HPV DNA. HPV testing of oropharyngeal samples yielded lower agreements with tumor markers; 23.7–24.0% (k 0.02), 55.9–68.0% (k 0.24–0.37) and 78.9–86.9% (k 0.49–0.58) in the 3 respective tests. HPV 16 was present in 93.7–100% of the samples tested and showed 100% genotype agreement between FNA and tumors. The high rates for HPV E6 oncoproteins and E6/E7 mRNA suggests most patients were experiencing transcriptionally active HPV-related OPSCC. Results from these commercial assays performed on FNA but not oropharyngeal samples showed moderate to very good agreements with p16 and HPV testing of tumors

An Atypical Unfolded Protein Response in Heat Shocked Cells

Contains fulltext : 91546.pdf (publisher's version ) (Open Access