A review of optically pumped far-infrared laser lines from methanol isotopes

The technique of optical pumping in polar molecules is the most efficient for Far-Infrared (FIR) laser generation, providing also a versatile and powerful tool for molecular spectroscopy in this spectral region. Methanol (CH₃OH) and its isotopic varieties are the best media for optically pumped FIR laser, with over thousand lines observed, and the most widely used for investigations and applications. In this sense, it is important organize and make available catalogues of FIR laser lines as complete as possible. Since the last critical reviews of 1984 [1] on methanol and its isotopic varieties [2,3,4], over hundred papers have been published dealing with hundreds of new FIR laser lines. In 1992 a review of FIR laser lines from CH₃OH was presented [5]. In this communication we extend this work to the other methanol isotopes, namely CH₃OD, CD₃OH, CD₃OD,¹³CH₃OH,¹³CD₃OH,¹³CD₃OD, CH₃ ¹⁸OH, CH₂DOH, CHD₂OH and CH₂DOD.Work supported by FAPESP, CNPq, FAEP-Brasil, and CNR-Italia     

IR and FIR spectroscopy of 13CD3OH around the 10P(22) and 10P(24) CO2 laser lines: New FIR laser emissions,frequency measurements and assignments

By using high resolution infrared Fourier transform data on ¹³CD₃OH and the 10P(22) and 10P(24) lines of a waveguide CO₂ laser to optically pump this methanol isotope, eight new FIR laser lines were observed. The frequencies of five laser lines were directly measured by heterodyne detection with already known laser lines. Particularly interesting are the lines pumped by the 10P(24) line, since a triade of emissions could be completely assigned.     

Energy spectra of the stable boundary layer: A theoretical model

Summary A derivation of spectral energy functions for stable atmospheric boundary layers is presented for a local similarity regime. Previous studies of this nocturnal atmospheric conditions were usually carried through purely kinematic modellizations. In this study, the atmospheric turbulence energy content is derived from a dynamical viewpoint. This is achieved through the use of the energy balance relation obtained by Rotta from Navier-Stokes equations. The result is an appropriate physical rooting of the spectral energy curves known as Kaimal’s Isopleths. The authors of this paper have agreed to not receive the proofs for correction.     

Molecular distillation

Applied Biochemistry and Biotechnology - In this work, important results from simulations are presented, showing the potentiality of the molecular distillation process for recovering vitamin E from...     

Cyclam kappa4 to kappa3 ligand denticity change upon mono-n-substitution with a carboxypropyl pendant arm in a ruthenium nitrosyl complex

The complex fac-[Ru(NO)Cl2(kappa(3)N(4),N(8),N(11)(1-carboxypropyl)cyclam)]Cl.H2O (1-carboxypropyl)cyclam=3-(1,4,8,11-tetraazacyclotetradecan-1-yl)propionic acid) was prepared in a one pot reaction by mixing equimolar amounts of RuNOCl 3 and (1-carboxypropyl)cyclam and was characterized by X-ray crystallography, electrospray ionization tandem mass spectrometry (ESI-MS/MS), elemental analysis, NMR, and electronic and vibrational (IR) spectroscopies. fac-[Ru(NO)Cl 2(kappa(3)N(4),N(8),N(11)(1-carboxypropyl)cyclam)]Cl.H2O crystallizes in the triclinic, space group P1, No. 2, with unit cell parameters of a=8.501(1) A, b=9.157(1) A, c=14.200(1) A, alpha=72.564(5) degrees , beta=82.512(5) degrees , gamma=80.308(5) degrees , and Z=2. The Ru-N interatomic distance and bond angle in the [Ru-NO] unit are 1.739(2) A and 167.7(2) degrees , respectively. ESI-MS/MS shows characteristic dissociation chemistry that initiates by HCl or NO loss. The IR spectrum displays a nu(NO) at 1881 cm(-1) indicating a nitrosonium character. The electronic spectrum shows absorptions bands at 264 nm (log epsilon=3.27), 404 nm (log epsilon=2.53), and 532 nm (log epsilon=1.88). (1)H and (13)C NMR are in agreement with the proposed molecular structure, which shows a very singular architecture where the cyclam ring N (with the carboxypropyl pendant arm) is not coordinated to the ruthenium resulting in a kappa(3) instead of the expected kappa(4) denticity.     

A Comparison of Differently Synthesized Gold‐coated Magnetic Nanoparticles as ‘Dispersible Electrodes’

Gold‐coated magnetic nanoparticles (Au@MNPs) have attracted significant interest in electrochemistry in recent years. This is especially the case with their application as dispersible electrodes where modified Au@MNPs are dispersed into a solution, selectively bind to the analyte of interest and are then brought to an electrode via application of a magnetic field for measurement. This paper characterizes four types of Au@MNPs with different sizes, shapes, and method of synthesis as dispersible electrodes. The Au@MNPs were characterized by transmission electron microscopy and X‐ray photoelectron spectroscopy and scanning electron microscopy. In addition, the electrochemical behaviour of Au@MNPs was investigated using cyclic voltammetry. The four sorts of Au@MNPs were evaluated with regards to the three main features required in the dispersible electrodes approach, well‐defined morphology, well‐defined electrochemistry and fast response to a magnetic field. The Cubic‐Au@MNPs, which presents the simplest synthetic route, showed the best electrochemical stability and performance, responding quickly to a magnet and had a well defined shape.     

Structural and spectroscopic characterization of epiisopiloturine-metal complexes,and anthelmintic activity vs. S. mansoni

Epiisopiloturine (EPI), extracted from leaves of Pilocarpus microphyllus, a plant originally from the Amazon and Savanna regions in Brazil, was described as a potential drug against Schistosomiasis, a neglected severe disease. Herein, EPI was complexed with copper(II) or zinc(II) salts and the isolated species, [Cu(epi)₄](ClO₄)₂ (1) and [Zn(epi)₂Cl₂] (2), were structurally and spectroscopically characterized. By using X-ray diffraction, the crystal structures of both metal complexes were determined, indicating a square pyramidal geometry for copper for 1 and a tetrahedral environment around zinc for 2. EPR spectra of 1 show a typical tetragonal environment around the central metal ion with some tetrahedral distortion, both in the solid state and in frozen acetonitrile solution, in accordance with crystallographic data. For 2, NMR spectra have bands consistent with a tetrahedral species in solid state or in DMSO-d₆ solution. These spectroscopic characterization data were further supported by Density Functional Theory calculations, showing that these metal complexes are also stable in solution. Those metal complexes were tested against adult worms of Schistosoma mansoni, in comparison to the free alkaloid as anthelmintic agent. Coordination with copper(II) improved the alkaloid schistosomicidal properties, while binding to zinc(II) decreased its activity.     

Gas-phase electrophilic addition promoted by CH(3)S(+)=CH(2) ions on aromatic systems

The gas-phase methylenation reaction between CH(3)S(+)=CH(2) and alkylbenzenes, aniline, phenol and alkyl phenyl ethers, which yields [M + CH](+) and CH(3)SH, has been studied by Fourier transform ion cyclotron resonance (FT-ICR) techniques and computational chemistry at the DFT level. The methylthiomethyl cation is less reactive than methoxymethyl and, unlike the latter, is unreactive toward benzene. The calculations suggest that reaction with toluene should proceed primarily by addition at the para and ortho positions resulting in a benzyl-type ion. Reaction with aniline-2,3,4,5,6-d(5) reveals that elimination of CH(3)SD is kinetically favored by a factor of 5 over elimination of CH(3)SH. Experiments with C(6)H(6)ND(2) and theoretical calculations suggest that methylenation at the nitrogen atom is energetically favorable and likely, but the observed results may reflect some H/D scrambling, which occurs after attack at a ring position. By comparison, reaction with phenol-2,3,4,5,6-d(5) reveals that methylenation followed by elimination of CH(3)SD is kinetically favored by a factor of 3.8 over elimination of CH(3)SH. For phenol, the theoretical calculations suggest that attack by CH(3)S(+)=CH(2) at the para or ortho position is the only low-energy pathway for methylenation. However, a low-energy pathway for hydrogen scrambling is predicted by the calculations originating from the exit complex, [CH(3)SH(...) CH(2)=C(6)H(4)=OH](+), of reaction at a ring position.     

Equilibrium states of self-assembly systems: Monte Carlo simulations

We investigated the equilibrium states of the self-assembly of amphiphilic molecules in water. The amphiphiles are represented by chains of the type H1T4, where H is the hydrophilic part of the molecule and T is its hydrophobic portion formed by four monomers. We have performed Monte Carlo simulations on a two-dimensional lattice, in which each water molecule occupies a single site, and the amphiphiles occupy five sites of the lattice. We have determined the aggregate distribution curves for the system at low concentration and fixed temperature. We have shown that the criterion to determine the equilibrium states of the system, based on the stabilization of energy curves as a function of the simulation time, is not reliable. The best way to ensure that the equilibrium state was reached was to follow the route to equilibrium of all aggregate sizes of the system.