A New Class of Remote N‐Heterocyclic Carbenes with Exceptionally Strong σ‐Donor Properties: Introducing Benzo[c]quinolin‐6‐ylidene

We make the case for benzo[c]quinolin‐6‐ylidene ( 1 ) as a strongly electron‐donating carbene ligand. The facile synthesis of 6‐trifluoromethanesulfonylbenzo[c]quinolizinium trifluoromethanesulfonate ( 2 ) gives straightforward access to a useful precursor for oxidative addition to low‐valent metals, to yield the desired carbene complexes. This concept has been achieved in the case of [Mn(benzo[c]quinolin‐6‐ylidene)(CO)₅]⁺ ( 15 ) and [Pd(benzo[c]quinolin‐6‐ylidene)(PPh₃)₂(L)]²⁺ L=THF ( 21 ), OTf ( 22 ) or pyridine ( 23 ). Attempts to coordinate to nickel result in coupling products from two carbene precursor fragments. The CO IR‐stretching‐frequency data for the manganese compound suggests benzo[c]quinolin‐6‐ylidene is at least as strong a donor as any heteroatom‐stabilised carbene ligand reported.     

Match statistics for sequence-based alleles in profiles from forensic PCR-mps kits

The first autosomal sequence-based allele (aka SNP-STR haplotype) frequency database for forensic massively parallel sequencing (MPS) has been published, thereby removing one of the remaining barriers to implementing MPS in casework. The database was developed using a specific set of flank trim sites. If different trim sites or different kits with different primers are used for casework, then SNP-STR haplotypes may be detected that do not have frequencies in the database. We describe a procedure to address calculation of match probabilities when casework samples are generated using an MPS kit with different trim sites than those present in the relevant population frequency database. The procedure provides a framework for comparison of any MPS kit or database combination while also accommodating comparison of MPS and CE profiles.     

Oxidative Addition to Palladium(0) Diphosphine Complexes: Observations of Mechanistic Complexity with Iodobenzene as Reactant

Using a combination of electrochemical and NMR techniques, the oxidative addition of PhX to three closely related bis‐diphosphine P₂Pd⁰ complexes, where the steric bulk of just one substituent was varied, has been analysed quantitatively. For the complex derived from MetBu₂P, a rapid reaction ensued with PhI following an associative mechanism, and data was also obtained by cyclic voltammetry for PhOTs, PhBr and PhCl, revealing distinct relative reactivities from the related (PCx₃)₂Pd complex (Cx=cyclohexyl) previously studied. The corresponding EttBu₂P complex reacted more slowly with PhI and was studied by NMR spectroscopy. The reaction course indicated a mixture of pathways, with contribution from a component that was [PhI] independent. For the CxtBu₂P complex, reaction was again monitored by NMR spectroscopy, and was even slower. At high PhI concentrations reaction was predominantly linear in [PhI], but at lower concentrations the [PhI] independent pathway was again observed, and an accelerating influence of the reaction product was observed over the concentration range. The NMR spectra of the EttBu₂P and CxtBu₂P complexes conducted in C₆D₆ shows some line broadening that was augmented on addition of PhI. NMR experiments carried out in parallel show that there is rapid ligand exchange between free phosphine and the Pd₂Pd complex and also a slow ligand crossover between different P₂Pd complexes. DFT calculations were carried out to further test the feasibility of C₆D₆ involvement in the oxidative addition process, and located Van der Waals complexes for association of the P₂Pd⁰ complexes with either PhI or benzene. PhI or solvent‐assisted pathways for ligand loss are both lower in energy than direct ligand dissociation. Taken all together, these results provide a consistent explanation for the surprising complexity of an apparently simple reaction step. The clear dividing line between reactions that give a di‐ or monophosphine palladium complex after oxidative addition clarifies the participation of the ligand in coupling catalysis.     

The synthesis and evaluation of unsymmetrical dimeric X-ray contrast agents

Novel dimeric iodinated contrast agents with low osmolality have been prepared and evaluated with the aim of improving the already good safety profile of such agents. The aim of low osmolality was achieved, and the viscosity of these dimeric agents was also found to be beneficially lower than current dimeric agents in clinical use.     

A data-driven,high-throughput methodology to determine tissue-specific differentially methylated regions able to discriminate body fluids

Tissue-specific differentially methylated regions (tDMRs) are regions of the genome with methylation patterns that modulate gene expression in those tissue types. The detection of tDMRs in forensic evidence can permit the identification of body fluids at trace levels. In this report, we have performed a bioinformatic analysis of an existing array dataset to determine if new tDMRs could be identified for use in body fluid identification from forensic evidence. Once these sites were identified, primers were designed and bisulfite modification was performed. The relative methylation level for each body fluid at a given locus was then determined using qPCR with high-resolution melt analysis (HRM). After screening 127 tDMR's in multiple body fluids, we were able to identify four new markers able to discriminate blood (2 markers), vaginal epithelia (1 marker) and buccal cells (1 marker). One marker for each target body fluid was also tested with pyrosequencing showing results consistent with those obtained by HRM. This work successfully demonstrates the ability of in silico analysis to develop a novel set of tDMRs capable of being differentiated by real time PCR/HRM. The method can rapidly determine the body fluids left at crime scenes, assisting the triers of fact in forensic casework.     

Surface state study of ion implanted GaAs (Se) from photoreflectance

The surfaces of single crystal (100) GaAs specimens ion implanted with Se (fluence to 5 × 10¹⁴ cm^?2) were studied by photoreflectance (PR). It is found that the PR concentration correlation for the ion-implanted crystals follow the Franz-Keldysh relationship. This establishes the electronic structural mechanistic basis of the PR surface phenomenon. The technique also offers a convenient, non-destructive means of studying dopant concentration levels at surfaces of crystalline ion implanted semiconductors.     

The selective aerobic oxidation of methylaromatics to benzaldehydes using a unique combination of two heterogeneous catalysts

A unique combination of a supported cobalt complex and the first example of supported NHPI in acetic acid gives a surprisingly stable heterogeneous catalytic system for the selective aerobic oxidation of methylaromatics to benzaldehydes at atmospheric pressure.