Six-fold oxygen-coordinated triplet (S = 1) palladium(II) moieties templated by tris(bipyridine)ruthenium(II) ions

Tris(bipyridine)ruthenium(II) is used as a templating agent to insert palladium(II) into three-dimensional oxalate-based networks. The templated-assembly of [Ru(bpy)(3)][Pd(2)(ox)(3)] (Pd(2)) and [Ru(bpy)(3)][PdMn(ox)(3)] (PdMn) is described. The latter compound is structurally characterized by powder X-ray diffraction and X-ray absorption spectroscopy. These techniques reveal an unusual 6-fold oxygen environment around the Pd(II) atoms with two short (2.02 Angstrom) and four long (2.17 Angstrom) Pd-O distances. As stated by magnetometry, this environment is associated with a triplet ground state (S = 1) of the palladium(II) ion: when the temperature is decreased, the chiMT product shows a monotonous decrease from 5.54 cm(3) K mol(-1) at 300 K, a value which is slightly lower than the one expected for independent paramagnetic Pd(II) (S = 1, g = 2) and Mn(II) (S = 5/2, g = 2) ions. This thermal variation is due to antiferromagnetic exchange interactions between the two spin bearers. Nevertheless, no long-range magnetic order is detected down to 2 K. These results are confirmed by an analysis of the [MII(C(2)O(4))(3)](4-) (M = Ni, Pd, Pt) complex and of a [Pd(II){mu-(C(2)O(4))Mn(II)(OH(2))(4)}(3)](2+) tetranuclear model using density functional theory.     

FTIR spectroscopy in medical mycology: applications to the differentiation and typing of <Emphasis Type="Italic">Candida</Emphasis>

The incidence of fungal infections, in particular candidiasis and aspergillosis, has considerably increased during the last three decades. This is mainly due to advances in medical treatments and technologies. In high risk patients (e.g. in haematology or intensive care), the prognosis of invasive candidiasis is relatively poor. Therefore, a rapid and correct identification of the infectious agent is important for an efficient and prompt therapy. Most clinical laboratories rely on conventional identification methods that are based on morphological, physiological and nutritional characteristics. However, these have their limitations because they are time-consuming and not always very accurate. Moreover, molecular methods may be required to determine the genetic relationship between the infectious strains, for instance in Candida outbreaks. In addition, the latter methods require time, expensive consumables and highly trained staff to be performed adequately. In this study, we have applied the FTIR spectroscopic approach to different situations encountered in routine mycological diagnosis. We show the potentials of this phenotypic approach, used in parallel with routine identification methods, for the differentiation of 3 frequently encountered Candida species (C. albicans, C. glabrata and C. krusei) by using both suspensions and microcolonies. This approach, developed for an early discrimination, may help in the initial choice of antifungal treatment. Furthermore, we demonstrate the feasibility of the method for intraspecies comparison (typing) of 3 Candida species (C. albicans, C. glabrata and C. parapsilosis), particularly when an outbreak is suspected.     

Bounds for modular L-functions in the level aspect

Let f be a primitive (holomorphic or Maaß) cusp form of level q and non-trivial nebentypus. Then for the associated L-function satisfies , where the implied constant depends polynomially on s and the Archimedean parameters of f (weight or Laplacian eigenvalue).     

Hydrogen Storage: Modeling and Analytical Results

We present a thermomechanical model describing hydrogen storage by use of metal hydrides. The problem is considered as a phase transition phenomenon. The model is recovered by continuum mechanics laws, using a generalization of the principle of virtual power accounting for microscopic movements related to the phase transition. The resulting nonlinear PDE system is investigated from the point of view of existence, uniqueness, and regularity of solutions.     

Reaction rates as a function of scale within ionic liquids: microscale in droplet microreactors versus macroscale reactions in the case of the Grieco three-component condensation reaction

Task-specific ionic liquids (TSILs) and more specifically binary task-specific ionic liquids (BTSILs), a unique subclass, have been shown to be excellent supports for solution-phase chemistry. The negligible volatility of ionic liquids enables their use as stable droplet microreactors in atmospheric environments without oil protection or confinement. These droplets can be moved, merged and mixed by electrowetting on a chip. Solution-phase synthesis can be performed on these open digital microfluidic labs-on-a-chip as illustrated by a study of the Grieco three-component reaction in [tmba][NTf(2)]-droplet (tmba=N-trimethyl-N-butylammonium NTf(2)=bis(trifluoromethylsulfonyl)imide) microreactors. A detailed study of matrices and scale effects on conversion and kinetic rates of this three-component condensation is presented in this paper. Reactions have been shown to be slower in droplets than in batches in the absence of additional mixing. Also, a significant influence of the ionic-liquid matrix has been observed. Finally, an increase of droplet's temperature resulted in a kinetics enhancement so as to reach macroscale reaction rates, probably because of a much better mixing of reaction's components involving a Marangoni's effect.     

Silver versus gold catalysis in tandem reactions of carbonyl functions onto alkynes: a versatile access to furoquinoline and pyranoquinoline cores

An efficient and versatile tandem process of acetalization and cycloisomerization reactions has been developed for the reactions of 1-alkynyl-2-carbonylquinoline substrates. The reaction occurs thanks to Au(I) and Ag(I) catalysis. Silver(I) catalysis has been extensively studied (11 different silver species) on a broad range of quinoline derivatives (variation of alkyne substituent, of carbonyl function and of nucleophiles), leading to a variety of furoquinoline and pyranoquinoline moieties. An insight is given for the presumed mechanism along with DFT-B3 LYP/6-31G** calculations to address the 6-endo and 5-exo regioselectivities observed.     

Preventive doping control analysis: liquid and gas chromatography time-of-flight mass spectrometry for detection of designer steroids

A new combined doping control screening method for the analysis of anabolic steroids in human urine using liquid chromatography/electrospray ionization orthogonal acceleration time-of-flight mass spectrometry (LCoaTOFMS) and gas chromatography/electron ionization orthogonal acceleration time-of-flight mass spectrometry (GCoaTOFMS) has been developed in order to acquire accurate full scan MS data to be used to detect designer steroids. The developed method allowed the detection of representative prohibited substances, in addition to steroids, at concentrations of 10 ng/mL for anabolic agents and metabolites, 30 ng/mL for corticosteroids, 500 ng/mL for stimulants and beta-blockers, 250 ng/mL for diuretics, and 200 ng/mL for narcotics. Sample preparation was based on liquid-liquid extraction of hydrolyzed human urine, and the final extract was analyzed as trimethylsilylated derivatives in GCoaTOFMS and underivatized in LCoaTOFMS in positive ion mode. The sensitivity, mass accuracy, advantages and limitations of the developed method are presented.     

DNA cleavage by new oxovanadium(IV) complexes of N-salicylidene alpha-amino acids and phenanthroline bases in the photodynamic therapy window

Oxovanadium(IV) complexes [VO(salmet)(B)] (1-3) and [VO(saltrp)(B)] (4-6), where salmet and saltrp are N-salicylidene-l-methionate and N-salicylidene-l-tryptophanate, respectively, and B is a N,N-donor heterocyclic base (viz. 1,10-phenanthroline (phen, 1, 4), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq, 2, 5), and dipyrido[3,2-a:2',3'-c]phenazine (dppz, 3, 6)) are prepared and characterized and their DNA binding and photoinduced DNA cleavage activity studied. Complexes 1, 2, and 4 are structurally characterized by single-crystal X-ray crystallography. The molecular structure shows the presence of a vanadyl group in the VO3N3 coordination geometry. The dianionic alpha-amino acid Schiff base acts as a tridentate O,N,O-donor ligand in a meridional binding mode. The N,N-donor heterocyclic base displays a chelating mode of bonding with a N-donor site trans to the oxo group. The complexes show a d-d band in the range of 680-710 nm in DMF with a shoulder near 840 nm. They exhibit an irreversible oxidative cyclic voltammetric response near 0.8 V assignable to the V(V)/V(IV) couple and a quasi-reversible V(IV)/V(III) redox couple near -1.1 V vs SCE in DMF-0.1 M TBAP. The complexes show good binding propensity to calf thymus DNA giving binding constant values in the range from 5.2 x 10(4) to 7.2 x 10(5) M(-1). The binding site size, thermal melting, and viscosity data suggest DNA surface and/or groove binding nature of the complexes. The complexes show poor "chemical nuclease" activity in the dark in the presence of 3-mercaptopropionic acid or hydrogen peroxide. The dpq and dppz complexes show efficient DNA cleavage activity on irradiation with UV-A light of 365 nm via a mechanistic pathway involving formation of singlet oxygen as the reactive species. They also show significant DNA cleavage activity on photoexcitation in red light (>750 nm) by (1)O2 species. Observation of red-light-induced cleavage of DNA is unprecedented in the vanadium chemistry. The DNA cleavage activity is metal promoted as the ligands or vanadyl sulfate alone are cleavage inactive on photoirradiation at these wavelengths.     

Isolation and identification of inulooligosaccharides resulting from inulin hydrolysis

In this study, inulooligosaccharides (F_n-type inulin) resulting from the endo-inulinase hydrolysis of globe artichoke inulin were purified and characterized. The aim was to produce F_n oligomer standards with the intention of identifying them in the complex inulin chromatogram. Inulin was extracted from globe artichoke and presented a high average degree of polymerization (DP) of about 80 as determined by high-performance anion exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD). This inulin was hydrolyzed by a commercial endo-inulinase yielding a product with a very high F_n/GF_n molecule ratio, thus limiting the interference of GF_n during the purification process. High-performance size exclusion chromatography was used to individually isolate and collect each retention peak corresponding to a specific oligomer. The purity of these fractions was checked by HPAEC-PAD and showed that relatively pure molecules were produced. Electrospray ionization mass spectrometry allowed the molecular weight determination of these purified oligomers and ascertained their DP as F₂, F₃ and F₄. These F_2-4 standards were used with glucose, fructose, sucrose and GF_2-4 (commercially available) to spike commercial oligofructose products in order to determine the elution profile in the HPAEC-PAD chromatogram.