Zn(II)-selective poly (vinyl chloride) (PVC) membrane electrode based on Schiff base ligand 2-benzoylpyridine semicarbazone as an ionophore

A new poly (vinyl chloride) (PVC) membrane electrode using 2-benzoylpyridine semicarbazone as membrane carrier with dioctylphthalate as plasticizer and sodium tetraphenylborate (NaTBP) as anion excluder has been fabricated and investigated as Zn(II)-selective electrode. Best potential response is observed for the composition PVC 30%, plasticizer 58%, NaTBP 8% and ionophore 4% (w/w). The sensor showed a linear stable response over a concentration range of 1.0 × 10−2–4.56 × 10−6 M with a detection limit of 2.28 × 10−6 M and a response time <10 s. The electrode can be used for at least six months without any divergence in potential.

Sodium tetraphenylborate displays selective bactericidal activity against N. meningitidis and N. gonorrhoeae and is effective at reducing bacterial infection load.

Neisseria meningitidis and Neisseria gonorrhoeae, two highly related species that may have emerged from a common commensal ancestor, constitute major human threats. Vaccines are available to prevent N. meningitidis infection, whereas for N. gonorrhoeae, there are only a limited number of antibiotics available. Unfortunately, some strains of these species are rapidly evolving and capable of escaping human interventions. Thus, it is now urgent to develop new avenues to fight these bacteria. This study reports that a boron-based salt, sodium tetraphenylborate (NaBPh4), displays high bactericidal activity and remarkable specificity against N. meningitidis and N. gonorrhoeae. Other closely related commensal species such as N. lactamica, found in the normal flora of healthy individuals were found to be less affected even at 5-fold higher doses of NaBPh4. This specificity was further observed where much lower sensitivity was found for the more distant Neisseriaceae (such as N. elongata or Kingella oralis) and completely unrelated species. A significant boron uptake by N. meningitidis cells was observed after incubation with 5 μM of NaBPh4, as measured by ICP-MS, suggesting that this drug candidate's target(s) could be located intracellularly or within the cell envelope. Furthermore, mutants with a slightly decreased susceptibility displayed an alteration in genes coding for cell-envelope elements, which reduced their virulence in an animal model of infection. Finally, a single dose of NaBPh4 resulted in a significant reduction in bacterial burden in a mouse model of N. meningitidis bacteremia. Although numerous boron-containing species were previously reported for their complex biological activities, the observation of this narrow selectivity is unprecedented and of potential importance from a therapeutic standpoint.

Recyclable and reusable PdCl2(PPh3)2/PEG-400/H2O system for the hydrophenylation of alkynes with sodium tetraphenylborate

A stable and efficient PdCl2(PPh3)2/PEG-400/H2O catalytic system for the hydrophenylation reaction of alkynes has been developed. In the presence of 3 mol% PdCl2(PPh3)2 and 2 equiv. of HOAc, the hydrophenylation of both terminal and internal alkynes with sodium tetraphenylborate proceeded smoothly in a mixture of PEG-400 and water at room temperature or 50 °C to afford a variety of phenyl-substituted alkenes in moderate to high yields. The isolation of the products was easily performed by extraction with petroleum ether, and the PdCl2(PPh3)2/PEG-400/H2O system could be readily recycled and reused six times without apparent loss of catalytic activity.