Heterocyclic thionates as a new class of bridging ligands in oxo-centered triangular cyclopentadienylchromium(III) complexes

The interactions of the benzothiazolate complex, CpCr(CO)(2)(SCSN(C(6)H(4))) (2), and the tetrazole thiolate complex, CpCr(CO)(3)(eta(1)-SCN(4)Ph) (3), with controlled amounts of Me(3)OBF(4) and (MeO)(2)SO(2), respectively, produced the corresponding mu(3)-oxo trinuclear thionate-bridged complexes, [Cp(3)Cr(3)(mu(2)-OH)(mu(3)-O)(mu(2)-eta(2)-SCSN(C(6)H(4)))(2)](5)BF(4) (45%) and [Cp(3)Cr(3)(mu(2)-OH)(mu(3)-O)(mu(2)-eta(2)-SCN(4)Ph)(2)](9)(MeOSO(3)) (53%), together with their respective free dimethylated thiolate ligands, [MeSCSNMe(C(6)H(4))](4)BF(4) and (Me(2)SCN(4)Ph)(8)MeOSO(3). The reaction of 3 with Me(3)OBF(4) resulted in the isolation of a binuclear complex, [Cp(2)Cr(2)(mu-OH)(mu-eta(2)-SCN(4)Ph)(2)](7)BF(4) (43%), and (8)BF(4) (27%). The reaction of the thiopyridine complex, CpCr(CO)(2)(SPy) (4), with I(2) also produced a similar mu(3)-oxo complex 10 (31%), together with CpCrI(2)(THF) (11) and the disulfide (SPy)(2). Similar reactions with 2 and 3 and I(2) yielded species 5 and 7, together with 11 and disulfides derived from their respective ligands. Cyclic voltammograms recorded in solutions of 5 and 9 indicated that the compounds could be reduced and oxidized at very similar potentials. An EPR spectrum characteristic of a compound with axial symmetry was obtained for 9 at 7 K. Single-crystal X-ray diffraction analyses confirmed that species 7 is dinuclear, whereas 5 and 9 are structural trinuclear analogues, each containing a mu(3)-oxo central core.     

Gas-phase ligand loss and ligand substitution reactions of platinum(II) complexes of tridentate nitrogen donor ligands

The source of protons associated with the ligand loss channel of HX((n - 1)+) from [Pt(II)(dien)X](n+) (X = Cl, Br and I for n = 1 and X = NC(5)H(5) for n = 2) in the gas phase was investigated by deuterium-labelling studies. The results of these studies indicate that these protons originate from both the amino groups and the carbon backbone of the dien ligand. In some instances (e.g. X = Br and I), the protons lost from the carbon backbone can be even more abundant than the protons lost from the amino groups. The gas-phase substitution reactions of coordinatively saturated [Pt(II)(L(3))L(a)](2+) complexes (L(3) = tpy or dien) were also examined using ion-molecule reactions. The outcome of the ion-molecule reactions depends on both the ancillary ligand (L(3)) as well as the leaving group (L(a)). [Pt(II)(tpy)L(a)](2+) complexes undergo substitution reactions, with a faster rate when L(a) is a good leaving group, while the [Pt(II)(dien)L(a)](2+) complex undergoes a proton transfer reaction.     

Designing copper(II) ternary complexes to generate radical cations of peptides in the gas phase: role of the auxiliary ligand

A series of ternary copper(II) complexes of the type [Cu(II)(L)(M)](2+), where M represents the hexapeptides GGGFLR, YGGFLR and WGGFLR and L a set of 12 nitrogen donor ligands have been evaluated for their ability to form cationic peptide radicals, M(+)*, in the gas phase. Although the fragmentation chemistry of these ions is complex, two main conclusions emerge: (i) Complexes containing a tri- or tetra-dentate ligand were found to be more effective at producing the peptide radical because in these instances competitive loss of the ligand from the complex is inhibited; (ii) The ligands ought not possess any acidic protons in order to prevent competitive loss of the protonated peptide, [M + H](+). There is significant interaction of the N-terminal aromatic residues in YGGFLR and WGGLFR with the copper(ii) ion in several of the complexes as revealed by the formation of [Cu(I)(L)(p-quinomethide)](+) and [Cu(I)(L)(3-methyleneindoline)](+) fragment ions. Following its dissociation from the ternary complex, CID of the YGGFLR(+)* radical cation shows a dependence on the ligand in the complex from which it was formed. This 'memory effect' most likely reflects differences in the coordinated peptide structure induced by the ligand in the precursor complex which are maintained following dissociation.     

The synthesis and stereochemistry of some pyrido[3,4-d]carbazole derivatives

Pyrido[3,4-d]carbazole derivatives have been synthesised from N-acetyl-5-oxodecahydro-isoquinoline by the Fischer indole synthesis, and their stereochemistry established by ¹H-NMR spectroscopy. In contrast to experience with simpler systems, cyclisation in acetic acid gave only the alternative pyrido[3,4-a]-carbazole, and the desired pyrido[3,4-d]carbazole formation occurred only in the presence of sodium acetate.     

Continuous production of succinic acid by a fumarate-reducing bacterium immobilized in a hollow-fiber bioreactor

Enterococcus faecalis RKY1, a fumarate-reducing bacterium, was immobilized in an asymmetric hollow-fiber bioreactor (HFBR) for the continuous production of succinic acid. The cells were inoculated into the shell side of the HFBR, which was operated in transverse mode. Since the pH values in the HFBR declined during continuous operation to about 5.7, it was necessary to change the feed pH from 7.0 to 8.0 after 24 h of operation in order to enhance production of succinic acid. During continuous operation with a medium containing fumarate and glycerol, the productivity of succinate was 3.0–10.9 g/(L·h) with an initial concentration of 30 g/L of fumarate, 4.9–14.9 g/(L·h) with 50 g/L of fumarate, and 7.2–17.1 g/(L·h) with 80 g/L of fumarate for dilution rates between 0.1 and 0.4 h⁻¹. The maximum productivity of succinate obtained by the HFBR (17.1 g of succinate /[L·h]) was 1.7 times higher than that of the batch bioconversions (9.9 g of succinate /[L·h]) with 80 g/L of fumarate. Furthermore, the long-term stability of the HFBR was demonstrated with a continuously efficient production of succinate for more than 15 d (360 h).     

Stereoselective synthesis of the nonproteinogenic amino acid (2S,3R)-3-amino-2-hydroxydecanoic acid from (4S,5S)-4-formyl-5-vinyl-2-oxazolidinone

(4S,5S)-4-Formyl-5-vinyl-2-oxazolidinone (4b), which is readily obtained via a zinc-silver-mediated reductive elimination of alpha-d-lyxofuranosyl phenyl sulfone (3b), is successfully converted to the naturally occurring, nonproteinogenic amino acid (2S,3R)-3-amino-2-hydroxydecanoic acid (2). Also in this study, a facile "oxazolidinone rearrangement" reaction is uncovered during the attempted formation of the (methylthio)thiocarbonate derivative of the oxazolidinone alcohol 7.     

Chemical Bonding of Fullerene and Fluorinated Fullerene on Bare and Hydrogenated Diamond

We investigate the interface between a C₆₀ fullerite film, C₆₀F₃₆, and diamond (100) by using core‐level photoemission spectroscopy, cyclic voltammetry (CV), and high‐resolution electron energy loss spectroscopy (HREELS). We show that C₆₀ can be covalently bonded to reconstructed C(100)‐2×1 and that the bonded interface is sufficiently robust to exhibit characteristic C₆₀ redox peaks in solution. The bare diamond surface can be passivated against oxidation and hydrogenation by covalently bound C₆₀. However, C₆₀F₃₆ is not as stable as C₆₀ and desorbs below 300 °C (the latter species being stable up to 500 °C on the diamond surface). Neither C₆₀ fullerite nor C₆₀F₃₆ form reactive interfaces on the hydrogenated surface—they both desorb below 300 °C. The surface transfer doping process of hydrogenated diamond by C₆₀F₃₆ is the most evident one among all the adsorbate systems studied (with a coverage‐dependent band bending induced by C₆₀F₃₆)_.     

Aminophosphine complex as a catalyst precursor in Suzuki coupling reactions

A palladium complex with an aminophosphine ligand has been prepared and investigated as a catalyst precursor in Suzuki coupling reactions in toluene. Nanoparticles composed of elemental palladium have been isolated from the reaction media and analyzed using transmission electroscopic microscope (TEM), which shows the essential catalysts palladium nanoparticles to have a size of ca. 3.0 nm. dedicate to the 60th birthday of Prof. Dr. Yuan Kou     

Effects of Oxygen (O2) Plasma Treatment in Promoting the Germination and Growth of Chili

In general, seed germination is improved by low-pressure plasma treatment using precursors such as air, nitrogen, O_2, and argon, etc. For the first time, low-pressure O₂ plasma was used to treat chili seeds in this study. When compared to untreated and vacuum-treated seeds, O₂ plasma treatment using the discharge power of 80 W for 60 s significantly improves chili seed germination and growth. The effect of vacuum on the germination and growth of chili seeds was also studied and shown to be negligible. The physical and chemical changes induced by O₂ plasma treatment were investigated to understand the plasma treatment to germination improvement. Combinatory etching and chemical modification aided imbibition and increased germination percentage in this O₂ plasma treatment on chili seeds. The success of this method has the potential to be scaled up to solve food security issues with seeds that would otherwise struggle to germinate.