Preparation,NMR studies and crystal structure of mononuclear and dinuclear Pd(II) and Pt(II) complexes that contain 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-thiapropyl]benzene

The reaction between 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-thiapropyl]benzene (bddf) and [MCl₂(CH₃CN)₂] (M = Pd(II), Pt(II)) in a 1:1 M/L ratio in CH₂Cl₂ or acetonitrile solution, respectively, gave the complexes trans-[MCl₂(bddf)] (M = Pd(II) (1), Pt(II) (4)), and in a 2:1 M/L ratio led to [M₂Cl₄(bddf)] (M = Pd(II) (2), Pt(II) (5)). Treatment of 1 and 4 with AgBF₄ and NaBPh₄, respectively, gave the compounds [Pd(bddf)](BF₄)₂ (3) and [Pt(bddf)](BPh₄)₂ (6). When complexes 3 and 6 were heated under reflux in a solution of Et₄NBr in CH₂Cl₂/CH₃OH (1:1) for 24 h, analogous complexes to 1 and 4 with bromides instead of chlorides bonded to the metallic centre were obtained. These complexes were characterised by elemental analyses, conductivity measurements, infrared, ¹H, ¹H{¹⁹⁵Pt}, ¹³C{¹H}, ¹⁹⁵Pt{¹H} NMR, HSQC and NOESY spectroscopies. The X-ray crystal structure of the complex [Pd(bddf)](BF₄)₂ · H₂O has been determined. The metal atom is tetracoordinated by the two azine nitrogen atoms of the pyrazole rings and two thioether groups.     

Calculation of Franck-Condon factors including anharmonicity: simulation of the C2H4+X2B3u<--C2H4X1A(g) band in the photoelectron spectrum of ethylene

Our new simple method for calculating accurate Franck-Condon factors including nondiagonal (i.e., mode-mode) anharmonic coupling is used to simulate the C2H4+X2B3u<--C2H4X1A(g) band in the photoelectron spectrum. An improved vibrational basis set truncation algorithm, which permits very efficient computations, is employed. Because the torsional mode is highly anharmonic it is separated from the other modes and treated exactly. All other modes are treated through the second-order perturbation theory. The perturbation-theory corrections are significant and lead to a good agreement with experiment, although the separability assumption for torsion causes the C2D4 results to be not as good as those for C2H4. A variational formulation to overcome this circumstance, and deal with large anharmonicities in general, is suggested.     

Local aromaticity of [n]acenes, [n]phenacenes, and [n]helicenes (n = 1-9)

The local aromaticity of the six-membered rings in three series of benzenoid compounds, namely, the [n]acenes, [n]phenacenes, and [n]helicenes for n = 1-9, has been assessed by means of three probes of local aromaticity based on structural, magnetic, and electron delocalization properties. For [n]acenes our analysis shows that the more reactive inner rings are more aromatic than the outer rings. For [n]phenacenes, all indicators of aromaticity show that the external rings are the most aromatic. From the external to the central ring, the local aromaticity varies in a damped alternate way. The trends for the [n]helicene series are the same as those found for [n]phenacenes. Despite the departure from planarity in [n]helicenes, only a very slight loss of aromaticity is detected in [n]helicenes as compared to the corresponding [n]phenacenes. Finally, because of magnetic couplings between superimposed six-membered rings in the higher members of the [n]helicenes series, we have demonstrated that the NICS indicator of aromaticity artificially increases the local aromaticity of their most external rings.     

Analysis of polyaddition levels in i-Sc3NC80

Using the density functional method, the stabilities of highly hydrogenated and fluorinated [80]fullerenes, both empty and containing the Sc3N molecule, have been calculated. Addition of 44 atoms to i-Sc3NC80 is predicted to be most favorable due to the formation of six octahedrally located benzenoid rings, while addition of up to 52 atoms (consistent with preliminary fluorination data) gives a structure stabilized by the presence of four benzenoid rings. The most stable isomers at this addition level have been determined and the relative stabilities of a number of C80H52, C80F52, and i-Sc3NC80H52 species calculated. The hydrogenation of the i-Sc3NC80 has been computed to be more difficult than the corresponding partner, C80. From the geometrical point of view, the Sc3N molecule is planar in the parent [80]fullerene but is calculated to be pyramidal in some of the hydrogenated/fluorinated derivatives. Moreover, in these it has fixed locations due to orbital interactions arising from deformation of the cage and the presence of localized double bonds.     

Therapeutic monitoring of imipramine and desipramine by micellar liquid chromatography with direct injection and electrochemical detection

A micellar liquid chromatographic (MLC) procedure was developed for the clinical monitoring of imipramine and its active metabolite, desipramine. The determination of these highly hydrophobic substances was carried out after direct injection of the serum samples using a mobile phase composed of 0.15 m SDS--6% (v/v) pentanol buffered at pH 7, pumped at 1.5 mL/min into a C(18) column (250 x 4.6 mm), and electrochemical detection at 650 mV. Using this MLC method, calibration was linear (r > 0.995) and the limits of detection (ng/mL) were 0.34 and 0.24 for imipramine and desipramine, respectively. Repeatabilities and intermediate precision were tested at three different concentrations in the calibration range and a CV (%) below 2.2 was obtained. In this MLC procedure, the serum is determined without treatment, thus allowing repeated serial injections without changes in retention factors, and reducing the time and consumables required to carry out the pretreatment process. The assay method can be applied to the routine determination of serum imipramine and its metabolite in therapeutic drug monitoring.     

Determination of ageing time of spirits in oak barrels using a headspace–mass spectrometry (HS-MS) electronic nose system and multivariate calibration

The aromatic composition of sugar cane spirits and, in general, of alcoholic beverages, is mainly influenced by the ageing process in wood barrels. There are several factors that affect the quality of the final aged product, but the time of the storage in the barrel is perhaps the most important one. Ageing time must therefore be controlled in order to detect counterfeits; however, this parameter is very difficult to control and, at present, there is no analytical method available to determine it. We propose a quantitative method for determining the ageing time of sugar cane spirits in oak barrels by using an electronic nose based on coupling directly a headspace sampler to a mass spectrometer (HS-MS), and multivariate calibration. The method developed is simple and provides, in 5 min, the ageing time of spirits with an accuracy of about 1 month.     

Catalytic Reduction of Oximes to Hydroxylamines: Current Methods,Challenges and Opportunities

Catalytic reduction of oximes represents a direct efficient approach to synthesize valuable hydroxylamine derivatives. However this transformation presents significant challenges: oximes are hard to reduce and, if reactive, reductive cleavage of the weak N−O bond often leads to primary amine side products. The first suitable systems involved the use of platinum-based heterogeneous catalysts with hydrogen as reductant and stoichiometric amounts of a strong Brønsted acid. More recently metal-free and transition-metal-based homogeneous catalysts have been developed, which display the highest turnovers (up to 4000). In the asymmetric variants, the E/Z-geometry of the oxime double bond affects significantly the stereoselectivity, sometimes requiring extra synthetic efforts in substrate preparation. This minireview provides an overview of the advances and limitations in catalytic oxime to hydroxylamine reduction. Emphasis is put on highlighting and comparing the practical aspects of the existing methods, such as their reaction conditions and substrate scope. Additionally, future directions for improving this young research area are suggested.     

Low n-6/n-3 Gestation and Lactation Diets Influence Early Performance,Muscle and Adipose Polyunsaturated Fatty Acid Content and Deposition,and Relative Abundance of Proteins in Suckling Piglets

Elevated omega-6 (n-6) and omega-3 (n-3) polyunsaturated fatty acids (PUFAs) ratios in swine diets can potentially impose a higher risk of inflammatory and metabolic diseases in swine. A low ratio between the two omega PUFAs has beneficial effects on sows’ and piglets’ production performance and immunity status. At present, there are few studies on how sow nutrition directly affects the protein and fat deposition in suckling piglets. Two groups of sows were fed diets with high or low n-6/n-3 polyunsaturated ratios of 13:1 (SOY) and 4:1 (LIN), respectively, during gestation and lactation. Longissimus dorsi muscle and adipose tissue from newborn piglets, nourished only with sow’s milk, were subjected to fatty acid profiling by gas chromatography–mass spectrometry (GC-MS) and to proteomics assays based on nano-liquid chromatography coupled to high-resolution tandem mass spectrometry (nLC-HRMS). Fatty acid profiles on both muscle and adipose tissues resembled the magnitude of the differences between fatty acid across diets. Proteomic analysis revealed overabundance of 4 muscle and 11 adipose tissue proteins in SOY compared to LIN in both piglet tissues. The detected overabundance of haptoglobin, an acute-phase protein, and the stimulation of protein-coding genes and proteins related to the innate immune response and acute inflammatory response could be associated with the pro-inflammatory role of n-6 PUFAs.     

Supercritical fluid extraction of atrazine and its metabolites from soil

Soxhlet (methanol) and SFE extraction with carbon dioxide in the presence of modifiers at different temperatures (100–200°C) for the extraction of atrazine and its main metabolites from a soil sample were compared. The most effective extraction conditions for both atrazine and its metabolites (i.e. deethylatrazine and deisopropylatrazine) were Co₂ modified with 20% molar methanol-trifluoroacetic acid (MeOH-TFA) (TFA 0.65M in MeOH) at 100°C, leading to an extraction efficiency comparable with that of Soxhlet extraction with MeOH for atrazine and ca. 20% higher for its main metabolites. The relative standard deviation (RSD) of SFE was lower than that obtained by Soxhlet extraction, probably because of less interference in the cGC-NPD determination. All the other modifiers evaluated (acetone, triethylamine, and methanol) were less effective than MeOH-TFA for the extraction of atrazine and its metabolites from a soil sample, even at high molar concentrations (20%) and use of higher extraction temperatures (200°C). These results indicate the importance of matrix effects and the need of the selection of an appropriate modifier in order to obtain quantitative extractions by SFE.