Thermal decomposition of 1-methyl-1-(4-methyl-1-naphthyl)ethyl hydroperoxide under gas chromatography-mass spectroscopy (GC–MS)
conditions gives 2-((4-methyl-1-naphthyl)oxy)propene as the main product (50.5%), without any detectable traces of the isomeric
2-((5-methyl-1-naphthyl)oxy)propene. This finding excludes the rearrangement pathway of 1-methyl-1-(1-naphthyl)ethyl hydroperoxides
to the corresponding 2-(1-naphthyloxy)propenes, which involves formation of a naphthofuran derivative as an intermediate and
transfer of the isopropenyloxy group to the 8 position. This result, as well as our previous density functional theory (DFT)
calculations, points to the rearrangement pathway involving an oxirane-type intermediate as the most plausible pathway to
2-(1-naphthyloxy)propenes. This rearrangement is responsible for the unusual inhibition effects of 1-methyl-1-(1-naphthyl)ethyl
hydroperoxide on the liquid-phase oxidation of isopropylarenes with oxygen. 相似文献
Two photosensitizing systems: (1) tetrakis(4-hydroxyphenyl)porphyrin (p-THPP) encapsulated in sterically stabilized liposomes (SSL) and (2) p-THPP functionalized by covalent attachment of poly(ethylene glycol) (p-THPP–PEG2000) were studied in vitro. The dark and photo cytotoxicity of these systems were evaluated on two cell lines: HCT 116, a human colorectal carcinoma cell line, and DU 145, a prostate cancer cell line and compared with these determined for free p-THPP. It was demonstrated that both encapsulation in liposomes as well as attachment of PEG chain result in pronounced reduction of the dark cytotoxicity of the parent porphyrin. The liposomal formulation showed higher than p-THPP–PEG2000 photocytotoxicity towards both cell lines used in the studies. 相似文献
A variety of new coordination compounds with transition-metal salts and the ligand trimethyl[1,2,4]triazolo[1,5-a]pyrimidine (abbreviated as tmtp) is described, together with several of their 3D crystal structures and spectroscopic and magnetic properties. The compounds were selected based on the coordination ability of the counterion, halide, nitrate, sulfate, thiocyanate and perchlorate. The formed coordination compounds and their coordination numbers were found to be strongly dependent on both the cation and the used counter-anion. The several compounds studied have the following structural formulae: [CuCl2(tmtp)2], [CuBr2(tmtp)2], [ZnBr2(tmtp)2], [Cu(NO3)2(tmtp)2], [CuSO4(tmtp)2]2(H2O)(MeOH), [Cu(H2O)(NCS)2(tmtp)2], [Zn(NCS)2(tmtp)2], [Cd(NCS)2(tmtp)2] and [M(H2O)2(tmtp)4](BF4)2, in which M = Co, Ni, Zn.The new coordination compounds have been further characterized by NMR, (far-)IR and LF spectra, as well as by C, H, N element analyses, and EPR spectra for the Cu(II) compounds. The coordination around the metal varies from 4 (Zn, Cu), via 5 (Cu) to 6 (for Co, Cu and Cd). The anions usually complete the coordination sphere; only the Co and Zn compounds with the tetrafluoridoborate anions have no coordinated anions, but water ligands complete the octahedral coordination sphere. In the 5-coordinated [Cu(H2O)(NCS)2(tmtp)2] water completes the square pyramid geometry. 相似文献
Molecular diagnostics of infectious diseases, in particular, nucleic-acid-based methods, are the fastest growing field in
clinical laboratory diagnostics. These applications are stepwise replacing or complementing culture-based, biochemical, and
immunological assays in microbiology laboratories. The first-generation nucleic acid assays were monoparametric such as conventional
tests, determining only a single parameter. Improvements and new approaches in technology now open the possibility for the
development of multiparameter assays using microarrays, multiplex nucleic acid amplification techniques, or mass spectrometry,
while the introduction of closed-tube systems has resulted in rapid microbial diagnostics with a subsequently reduced contamination
risk. Whereas the first assays were focused on the detection and identification of microbial pathogens, these new technologies
paved the way for the parallel determination of multiple antibiotic resistance determinants or to perform microbial epidemiology
and surveillance on a genetic level. 相似文献
Under UV light irradiation on a gaseous mixture of Fe(CO)5 and Co(CO)3NO, both the crystalline deposits with sizes of 5 and 18 μm and the spherical particles with a mean diameter of 0.3 μm were produced. From FT-IR spectra and SEM–EDS analysis, it was suggested that the chemical structure of the crystalline deposits was the one of Fe2(CO)9 being modified by involving Fe(CO)Co bond. By decreasing a partial pressure of Fe(CO)5 to 0.5 Torr in the gaseous mixture, only the spherical aerosol particles could be produced. Chemical composition of the particles was rich in Co species. From the disappearance of bridging CO band in the FT-IR spectra of the particles and the appearance of CO bands coordinated to a metal atom, Fe atom in Fe(CO)4 was suggested to be coordinated by the O atom in bridging CO bond in Co(CO)Co structure and/or in α-diketone structure which was formed from two CO groups in dicobalt species. Chemical compositions of the crystalline deposits and the spherical particles were influenced differently by the application of a magnetic field. Atomic ratio of Fe to Co atom decreased in the crystalline deposits whereas it increased in the spherical particles with increasing magnetic field up to 5 T. Linearly aggregated particles (i.e., particle wires) as long as 30 μm were produced on the front side of a glass plate placed at the bottom of the irradiation cell. 相似文献
Four tetrathiafulvalene (TTF)‐annulated porphyrins 1 – 4 were synthesized and characterized. All contain a tetraphenylporphyrin (TPP) core onto which four, two, or one TTF subunits were annulated. Absorption and fluorescence spectroscopic studies together with electrochemical investigations reveal that interactions between the porphyrin system and the annulated TTF units take place in solution. The annulation of one or more TTF units to the porphyrin core has a profound effect on the reduction potentials associated with this latter framework, with positive shifts in the range of 0.105 to 0.355 V and 0.200 to 0.370 V for the first and second reduction potential, respectively, compared to the corresponding processes in the model compound TPP, 18 . The redox potentials for the first oxidation of the TTF units are considerably shifted in 4 (ΔEox1=+0.285 V) and 2 (ΔEox1=?0.140 V), whereas for 1 and 3 these potentials remain within the region expected for a normal TTF unit. Considerable changes in the second oxidation potential associated with the TTF subunits were seen for 2 (ΔEox1=?0.085) and 3 (ΔEox1=?0.175). The emission spectra of 1 – 4 revealed that the porphyrin fluorescence is almost quenched in the neutral state of the TTF‐annulated porphyrins, a finding that is consistent with substantial electron transfer taking place from the TTF subunits to the porphyrin core. Oxidation of the TTF unit(s) (TTF→TTF.+) present in 1 – 4 leads to the emission intensity being restored. 相似文献
C′mon 1,2‐dione : A new diastereo‐ and enantioselective Lewis base catalyzed domino Michael/aldol reaction converts α,β‐unsaturated aldehydes and 1,2‐diones into chiral bicyclo[3.2.1]octane‐6‐carbaldehydes. The products are produced in good to excellent enantioselectivities (90–98 % ee) and can be transformed into bicyclic diols and triols. Additionally, a retro‐aldol cyclization provides access to valuable tetrahydrochromenones (see scheme).
Novel 2‐(1‐substituted‐1H‐1,2,3‐triazol‐4‐yl)pyridine (pytl) ligands have been prepared by “click chemistry” and used in the preparation of heteroleptic complexes of Ru and Ir with bipyridine (bpy) and phenylpyridine (ppy) ligands, respectively, resulting in [Ru(bpy)2(pytl‐R)]Cl2 and [Ir(ppy)2(pytl‐R)]Cl (R=methyl, adamantane (ada), β‐cyclodextrin (βCD)). The two diastereoisomers of the Ir complex with the appended β‐cyclodextrin, [Ir(ppy)2(pytl‐βCD)]Cl, were separated. The [Ru(bpy)2(pytl‐R)]Cl2 (R=Me, ada or βCD) complexes have lower lifetimes and quantum yields than other polypyridine complexes. In contrast, the cyclometalated Ir complexes display rather long lifetimes and very high emission quantum yields. The emission quantum yield and lifetime (Φ=0.23, τ=1000 ns) of [Ir(ppy)2(pytl‐ada)]Cl are surprisingly enhanced in [Ir(ppy)2(pytl‐βCD)]Cl (Φ=0.54, τ=2800 ns). This behavior is unprecedented for a metal complex and is most likely due to its increased rigidity and protection from water molecules as well as from dioxygen quenching, because of the hydrophobic cavity of the βCD covalently attached to pytl. The emissive excited state is localized on these cyclometalating ligands, as underlined by the shift to the blue (450 nm) upon substitution with two electron‐withdrawing fluorine substituents on the phenyl unit. The significant differences between the quantum yields of the two separate diastereoisomers of [Ir(ppy)2(pytl‐βCD)]Cl (0.49 vs. 0.70) are attributed to different interactions of the chiral cyclodextrin substituent with the Δ and Λ isomers of the metal complex. 相似文献
An efficient voltammetric method was developed for the determination of maleic acid at a silver amalgam paste electrode (AgA‐PE) in Britton–Robinson buffer pH 2.0. The experimental parameters, such as pH of Britton–Robinson buffer, type of the supporting electrolyte and activation of the electrode surface were optimized. Under the optimal conditions, a linear response was observed over the 2×10?6–1×10?4 mol L?1 maleic acid concentration range, determination limit being 5×10?7 mol L?1. A highly stable response, with a relative standard deviation (RSD) of 1.6% for 45 repetitive measurements of 1×10?4 mol L?1 maleic acid showed that there was no apparent surface passivation indicating the suitability of the method. The method was successfully applied for direct determination of maleic acid in drinking and river water. 相似文献
A silicon field‐effect transistor is operated as a logic circuit by electrically addressing the ground and excited electronic states of an embedded single dopant atom. Experimental results—complemented by analytical and computational calculations—are presented. First, we show how a complete set of binary logic gates can be realized on the same hardware. Then, we show that these gates can be operated in parallel on the very same dopant up to the logic level of a full adder. To use the device not as a switch but as a full logic circuit, we make essential use of the excited electronic states of the dopant and of the ability to shift their energy by gating. The experimental ability to use two channels to measure the current flowing through the device and the conductance (dI/dV) allows for a robust reading of the output of the logic operations. 相似文献
