Carbon Monoxide Bonding With BeO and BeCO3: Surprisingly High CO Stretching Frequency of OCBeCO3

The complexes OCBeCO₃ and COBeCO₃ have been isolated in a low‐temperature neon matrix. The more stable isomer OCBeCO₃ has a very high C? O stretching mode of 2263 cm^?1, which is blue‐shifted by 122 cm^?1 with respect to free CO and 79 cm^?1 higher than in OCBeO. Bonding analysis of the complexes shows that OCBeO has a stronger OC? BeY bond than OCBeCO₃ because it encounters stronger π backdonation. The isomers COBeCO₃ and COBeO exhibit red‐shifted C? O stretching modes with respect to free CO. The inverse change of C? O stretching frequency in OC? BeY and CO? BeY is explained with the reversed polarization of the σ and π bonds in CO.     

Gas‐Phase Affinity Scales for Typical Ionic Liquid Moieties Determined by using Cooks’ Kinetic Method

Gas‐phase affinity studies based on cations and anions commonly present in ionic liquid structures, give quantitative information about the magnitude of the interactions holding the two species together when ILs are formed. They also provide clues on how these interactions depend on the nature of the cationic and anionic moieties. In the present work, mass spectrometric experiments, performed using electrospray ionization quadrupole ion‐trap and Fourier transform ion cyclotron resonance mass spectrometry, were used to obtain two affinity scales by Cooks’ kinetic method: one scale for the various cations for the bis(trifluoromethylsulfonyl)imide anion, [NTf₂]^?, and another for the different anions for the 1‐butyl‐3‐methylimidazolium cation, [C₄mim]⁺. The obtained results are compared with previously reported data and discussed in terms of the structural characteristics of the different cationic and anionic species.     

Sequential Determination of 13 Elements in Complex Matrices by Stripping Voltammetry with Mixed Complexing Electrolytes

This paper presents the determination of 13 elements in a simultaneous and sequential analysis using solochrome violet (SVRS), chloranilic acid (CA), diethylenetriaminepentaacetic acid (DTPA), dimethylglyoxime (DMG), and oxine as complexing electrolytes. The Methods were applied to determine Al³⁺, Fe³⁺, Mo⁶⁺, Zn²⁺, Cd²⁺, Pb²⁺, Cu²⁺, Ni²⁺, Co²⁺, Tl⁺, U⁶⁺, V⁵⁺, and Cr⁶⁺ in fertilizers, plant materials, and foodstuffs. The Method was found to be selective and accurate (82.13–119.03 %) for elemental analysis in complex matrices that were previously submitted to a total oxidative digestion step (calcination and wet digestion). Mutual interferences of the elements were systematically investigated. The Sequential Method could be useful for the routine quality control of foodstuffs and fertilizer formulations regarding mineral nutrients or contaminants.     

A standard protocol for obtaining fish chromosomes under post-mortem conditions

In order to improve cytogenetical analyses on fish, especially focusing on delicate and rare species, we have adopted a new in vitro methodology using dead animals. The results obtained from 24 neotropical freshwater and marine fish species demonstrate that chromosomes can be obtained under post-mortem conditions. Significantly, the samples analyzed provided reliable cytogenetical data in nearly all cases. Other advantages of this new methodology are also discussed.     

Intrinsic gas-phase reactivity of ionized 6-(oxomethylene)cyclohexa-2,4-dienone: evidence pointing to its neutral alpha-oxoketene counterpart as a proper precursor of various benzopyran-4-ones and analogues

Despite its unique structure and potential use as an important building block in organic synthesis, the title alpha-oxoketene 1 has been formed mostly under very special conditions as a short-lived species. The reactivity of 1 is, therefore, nearly unexplored. In great contrast, it seemed that its ionized gaseous form 1*+ is stable and easily accessible. In this study, we used multiple-stage pentaquadrupole mass spectrometry to probe the formation of gaseous 1*+ and explore its stability and intrinsic reactivity. With water and methanol, gaseous 1*+ was found to react similarly to solvated 1, which indicates that there is a close parallel between their reactivities. Gaseous 1*+ was also found to react promptly via polar [3 + 2] cycloadditons with various dienophiles including alkenes, alkynes, isocyanates, ketones and esters, thus forming a series of benzopyran-4-ones (flavones, 4-chromanones, 4-chromenones, benzo[1,3]dioxin-4-ones, and analogues) that are common structural units in many natural products. The present availability of 1 at room temperature and the gas-phase findings reported herein for gaseous 1*+ indicate that solvated 1 should undergo many [4 + 2] cycloadditions and functions as a versatile precursor of a variety of biologically active molecules.     

Identification of the sex pheromone of Phyllophaga cuyabana (Coleoptera: Melolonthidae)

Phenol 1 and p-cresol 2 were identified as sex pheromone components released by females Phyllophaga cuyabana. The compounds are produced in a ratio of 1:1, as detected by the analysis of pheromone gland extract. In field experiments, the capture of males in traps baited with the synthetic blend were significantly higher than in control traps.     

Adulteration of diesel/biodiesel blends by vegetable oil as determined by Fourier transform (FT) near infrared spectrometry and FT-Raman spectroscopy

In this work it has been shown that the routine ASTM methods (ASTM 4052, ASTM D 445, ASTM D 4737, ASTM D 93, and ASTM D 86) recommended by the ANP (the Brazilian National Agency for Petroleum, Natural Gas and Biofuels) to determine the quality of diesel/biodiesel blends are not suitable to prevent the adulteration of B2 or B5 blends with vegetable oils. Considering the previous and actual problems with fuel adulterations in Brazil, we have investigated the application of vibrational spectroscopy (Fourier transform (FT) near infrared spectrometry and FT-Raman) to identify adulterations of B2 and B5 blends with vegetable oils. Partial least square regression (PLS), principal component regression (PCR), and artificial neural network (ANN) calibration models were designed and their relative performances were evaluated by external validation using the F-test. The PCR, PLS, and ANN calibration models based on the Fourier transform (FT) near infrared spectrometry and FT-Raman spectroscopy were designed using 120 samples. Other 62 samples were used in the validation and external validation, for a total of 182 samples. The results have shown that among the designed calibration models, the ANN/FT-Raman presented the best accuracy (0.028%, w/w) for samples used in the external validation.     

Rhenium and technetium tricarbonyl complexes anchored by pyrazole-based tripods: novel lead structures for the design of myocardial imaging agents

This report describes the synthesis and biological evaluation of cationic (99m)Tc-tricarbonyl complexes anchored by ether-containing tris(pyrazolyl)methane or bis(pyrazolyl)ethanamine ligands to be applied in the design of radiopharmaceuticals for myocardial imaging: fac-[(99m)Tc(CO)(3){RC(pz)(3)}](+) (R = H (1a), MeOCH(2) (2a), EtOCH(2) (3a), (n)PrOCH(2) (4a)) and fac-[(99m)Tc(CO)(3){RNHCH(2)CH(pz)(2)}](+) (R = H (5a), MeO(CH(2))(2) (6a)) (pz = pyrazolyl). At the no carrier added level, complexes 1a-6a were obtained in high radiochemical yield (> 98%) by reaction of fac-[(99m)Tc(CO)(3)(H(2)O)(3)](+) with the corresponding tripod chelator in aqueous medium. All these complexes display a high in vitro and in vivo stability, except 6a which metabolizes in vivo yielding fac-[(99m)Tc(CO)(3){HO(CH(2))(2)NHCH(2)CH(pz)(2)}](+) (7a). Biological studies in mice have shown that among the radiotracers evaluated in this work, 3a, anchored by a tris(pyrazolyl)methane chelator bearing an ethyl methyl ether substituent, has the highest heart uptake (3.6 +/- 0.5%ID g(-1) at 60 min p.i.). Complex 3a presents also the best heart: blood, heart: liver and heart: lung ratios, appearing as the most promising as a potential myocardial imaging agent. The chemical identity of 1a-7a was ascertained by HPLC comparison with the previously reported fac-[Re(CO)(3){HC(pz)(3)}]Br (1) and with the novel fac-[Re(CO)(3){RC(pz)(3)}]Br (R = MeOCH(2) (2), EtOCH(2) (3), (n)PrOCH(2)(4)) and fac-[Re(CO)(3){RNHCH(2)CH(pz)(2)}]Br (R = H (5), MeO(CH(2))(2) (6) HO(CH(2))(2) (7)). The novel Re(I) tricarbonyl complexes, 2-7, were characterized by the common analytical techniques, including single crystal X-ray diffraction analysis. The solid state structure confirmed the presence of facial and tridentate (kappa(3)-N(3)) anchor ligands. Solution NMR studies have also shown that this kappa(3)-N(3) coordination mode is retained in solution for all complexes (2-7).     

Molecular dynamics simulations of charged dendrimers: low-to-intermediate half-generation PAMAMs

We have performed atomistic molecular dynamics simulations of PAMAM dendrimers of generations 0.5, 1.5, 2.5, 3.5, and 4.5. The simulated systems comprise the charged dendrimer and its counterions embedded in a dielectric continuum (i.e., without explicit solvent). Structural properties of these dendrimers, like the radius of gyration, the principal moments of inertia, and the segment density profiles, were evaluated from the simulations. The average radius of gyration obtained for the intermediate half-generations 2.5, 3.5, and 4.5 follows the same scaling law that was previously inferred from simulations of full-generation PAMAMs, Rg approximately M1/3, and is characteristic of space-filling objects. The low half-generations 0.5 and 1.5 deviate, however, to greater Rg values. The shape of the smaller dendrimers is approximately that of a prolate ellipsoid, which becomes more spherical for higher generations. The segment density profiles show features identical to those obtained in other simulations of flexible-chain dendrimers, like dendron-backfolding. Two slightly different configurations, in terms of size and shape, were identified for generation 2.5. The radial distributions of counterions extracted from the simulations compare well with the solutions of Poisson-Boltzmann cell model, and the dendrimer's effective charge was estimated using the Bjerrum criterion. The influence of electrostatic interactions in the dendrimer's conformation due to repulsion between the charged end-groups and its relation to counterion effects is discussed for the several generations simulated. The form factors calculated from the simulations are compared with the model of a homogeneous ellipsoid of revolution. The overall results are in agreement with the previously established morphological transition of PAMAM dendrimers toward a more spherical and compact conformation above generations 3 or 4.     

Nicotine: on the potential role of ionic liquids for its processing and purification

Marked solubility differences of nicotine in the ionic liquids [C(2)mim][NTf(2)], [C(2)mim][EtOSO(3)], and [C(n)mim]Cl, 6 相似文献