Ruthenium(II) carbonyl complexes of dehydroacetic acid thiosemicarbazone: Synthesis, structure, light emission and biological activity

The reaction of [RuHCl(CO)(B)(EPh₃)₂] (where E = As, B = AsPh₃; E = P, B = PPh₃, py, pip, or mor) and dehydroacetic acid thiosemicarbazone (abbreviated as H₂dhatsc where H₂ stands for the two dissociable protons) in benzene under reflux afford a series of new ruthenium(II) carbonyl complexes containing dehydroacetic acid thiosemicarbazone of general formula [Ru(dhatsc)(CO)(B)(EPh₃)] (where E = As, B = AsPh₃; E = P, B = PPh₃, py, pip or mor; dhatsc = dibasic tridentate dehydroacetic acid thiosemicarbazone). All the complexes have been characterized by elemental analyses, FT-IR, UV-Vis, and ¹H NMR spectral methods. The thiosemicarbazone of dehydroacetic acid behaves as dianionic tridentate O, N, S donor and coordinates to ruthenium via phenolic oxygen of dehydroacetic acid, the imine nitrogen of thiosemicarbazone and thiol sulfur. In chloroform solution, all the complexes exhibit metal-to-ligand charge transfer transitions (MLCT). The crystal structure of one of the complexes [Ru(dhatsc)(CO)(PPh₃)₂] (1) has been determined by single crystal X-ray diffraction which reveals the presence of a distorted octahedral geometry in the complexes. All the complexes exhibit an irreversible oxidation (Ru^III/Ru^II) in the range 0.76-0.89 V and an irreversible reduction (Ru^II/Ru^I) in the range −0.87 to −0.97 V. Further, the free ligand and its ruthenium complexes have been screened for their antibacterial and antifungal activities. The complexes show better activity in inhibiting the growth of bacteria Staphylococcus aureus and Escherichia coli and fungus Candida albicans and Aspergillus niger. These results made it desirable to delineate a comparison between free ligand and its ruthenium complexes.     

Analysis of trifluoroacetic acid and other short-chain perfluorinated acids (C2-C4) in precipitation by liquid chromatography-tandem mass spectrometry: comparison to patterns of long-chain perfluorinated acids (C5-C18)

This paper provides analytical chemical information on selected new molecular entities (NMEs) which are drugs that have recently been approved by the FDA. These are the antiretroviral drugs, atazanavir, indinavir and emtricitabine, the antibacterial gemifloxacin, rosuvastatine which is a cholesterol-lowing drug, the anti-cancer drug gefitinib and aprepitant for neurological disorders. Electrospray ionisation-quadrupole ion trap mass spectrometry (ESI-MSⁿ) was employed to generate tandem mass spectrometric (MS²) data of the drugs studied and structural assignments of product ions were supported by quadrupole time-of-flight mass spectrometry (QToF-MS/MS). These fragmentation studies were then utilised in the development and validation of a specific and sensitive liquid chromatographic method (LC–ESI-MS²) to identify and determine these drugs at therapeutic concentration levels in serum after a single protein precipitation procedure with acetonitrile. In addition, this method was compared to the application of gas liquid chromatography-flame ionisation detection (GLC-FID) and differential pulse polarography (DPP) for the analysis of these NMEs in serum.     

Lanthanum(III) and uranyl(VI) diglycolamide complexes: synthetic precursors and structural studies involving nitrate complexation

The synthesis and structural characterization of lanthanum(III) and uranyl(VI) complexes coordinated by tridentate diglycolamide (DGA) ligands O(CH2C(O)NR2)2[R=i-Pr (L1), i-Bu (L2)] are described. Reaction of L with UO2Cl2(H2O) n forms the uranyl(VI) cis-dichloride adducts UO2Cl2L [L=L1 (1a), L2 (1b)], while reaction of excess L with the corresponding metal nitrate hydrate produces [LaL3][La(NO3)6] [L=L1 (2a), L2 (2b)] for lanthanum and UO2(NO3)2L [L=L1 (3a), L2 (3b)] for uranium. Compounds 2b and 3a have been structurally characterized. The solid-state structure of the cation of 2b shows a triple-stranded helical arrangement of three tridentate DGA ligands with approximate D3 point-group symmetry, while the counteranion consists of six bidentate nitrate ligands coordinated around a second La center. The solid-state structure of 3a shows a tridentate DGA ligand coordinated along the equatorial plane perpendicular to the OUO unit as well as two nitrate ligands, one bidentate and oriented in the equatorial plane and the other monodentate and oriented parallel to the uranyl unit with the oxygen donor atom situated above the mean equatorial plane. Ambient-temperature NMR spectra for 3a and 3b indicated an averaged chemical environment of high symmetry consistent with fluxional nitrate hapticity, while spectroscopic data obtained at -30 degrees C revealed lower symmetry consistent with the slow-exchange limit for this process.     

Physical insights from a penetration depth model of optically pumped NMR

A model of optically pumped NMR (OPNMR) behavior in GaAs that connects the photon energy dependence of the OPNMR signal intensity for (69)Ga with different polarizations of light has been developed. Inputs to this model include experimental conditions--external magnetic field (B(0)), temperature (T), and optical pumping parameters (tau(L), laser helicity)--as well as parameters that arise from sample-specific characteristics--electron spin lifetime (T(1e)), electron lifetime (tau(e)), electron-nuclear correlation time (tau(c)), and sample thickness (z). These various inputs affect the profile of the OPNMR signal intensity as a function of photon energy (E) in a predictable manner. Therefore, the profile can serve as a composite fingerprint by which individual parameters can be inferred when not known. Characteristics of the profile include the photon energy for maximum OPNMR signal intensity and the intensity ratio between sigma(+) and sigma(-) light.     

Optically pumped nuclear magnetic resonance of semiconductors

Optically pumped NMR (OPNMR) of direct gap and indirect gap semiconductors has been an area of active research interest, motivated by both basic science and technological perspectives. Proposals to enhance and to spatially localize nuclear polarization have stimulated interest in this area. Recent progress in OPNMR has focused on exploring the experimental parameter space in order to elucidate details of the underlying photophysics of optical pumping phenomena. The focus of this review is on recent studies of bulk samples of GaAs and InP, namely, the photon energy dependence, the magnetic field dependence, and the phase dependence of OPNMR resonances. Models for the development of nuclear polarization are discussed.     

Target‐Induced and Equipment‐Free DNA Amplification with a Simple Paper Device

We report on a paper device capable of carrying out target‐induced rolling circle amplification (RCA) to produce massive DNA amplicons that can be easily visualized. Interestingly, we observed that RCA was more proficient on paper than in solution, which we attribute to a significantly higher localized concentration of immobilized DNA. Furthermore, we have successfully engineered a fully functional paper device for sensitive DNA or microRNA detection via printing of all RCA‐enabling molecules within a polymeric sugar film formed from pullulan, which was integrated with the paper device. This encapsulation not only stabilizes the entrapped reagents at room temperature but also enables colorimetric bioassays with minimal steps.     

On the Automorphism Group of a Smooth Schubert Variety

Let G be a simple algebraic group of adjoint type over the field \(\mathbb {C}\) of complex numbers. Let B be a Borel subgroup of G containing a maximal torus T of G. Let w be an element of the Weyl group W and let X(w) be the Schubert variety in G/B corresponding to w. Let α ₀ denote the highest root of G with respect to T and B. Let P be the stabiliser of X(w) in G. In this paper, we prove that if G is simply laced and X(w) is smooth, then the connected component of the automorphism group of X(w) containing the identity automorphism equals P if and only if w ^?1(α ₀) is a negative root (see Theorem 4.2). We prove a partial result in the non simply laced case (see Theorem 6.6).     

Copolymerization of 2,3,4,5,6‐Pentafluorostyrene and Methacrylic Acid by Nitroxide‐Mediated Polymerization: The Importance of Reactivity Ratios

Amphiphilic block copolymers of 2,3,4,5,6‐pentafluorostyrene (PFS) and methacrylic acid (MAA) are synthesized via nitroxide‐mediated polymerization (NMP). It is established that to obtain a controlled copolymerization a minimum of 40 mol% of PFS is required, which is significantly greater than other copolymerization systems such as using 4.5–8 mol% styrene or 1 mol% of 9‐(4‐vinylbenzyl)‐9H‐carbazole to control the copolymerization of methacrylates. It is surmised that this lack of control is due to the reactivity ratios that favor the addition of MAA rather than PFS (r_PFS = 0.14, r_MAA = 6.97). However this reactivity ratio pair suggests that a one‐shot delayed injection approach can be utilized to synthesize almost pure block copolymers in one pot. Therefore, poly(PFS)‐b‐(PFS‐ran‐MAA) block copolymers are synthesized by a one‐shot delayed addition of MAA. While the concentration of irreversibly terminated chains is evident these results suggest a promising route to the synthesis of fluorinated amphiphilic block copolymers by NMP.

     

Insight into the nonlinear absorbance of two related series of two-photon absorbing chromophores

A comprehensive photophysical study of the linear and nonlinear absorption properties has been carried out on two series of two-photon absorbing dyes to gain insight into how structure-property relationships influence observed nonlinear absorption. The materials studied consist of an electron accepting benzothiazole group connected to an electron donating diphenylamine via a fluorene bridging group. Two series differ from each other by the addition of one phenyl group and for each series one-arm (dipolar, AF240 and AF270), two-arm (quadrupolar, AF287 and AF295), and three-arm (octupolar, AF350 and AF380) versions were studied. Overall the AF240 series exhibits higher intrinsic two-photon absorption (TPA) cross-sections than the AF270 series as well as enhanced nanosecond nonlinear absorption, with an increase with number of branches. The enhanced nanosecond nonlinearity is understood by taking into account the contribution from the singlet and triplet excited states and was verified by a two-photon assisted excited-state absorption model that satisfactorily predicts the nonlinear absorption of the chromophores.