Charge-sensitive vibrational modes in the (EDT-TTF-OX)2AsF6 chiral molecular conductors

Infrared and Raman spectra of three chiral molecular conductors (EDT-TTF-OX)₂AsF₆, comprising of two salts based on enantiopure EDT-TTF-OX donor molecules and one based on their racemic mixture, have been measured as a function of temperature. In the frequency range of the C=C stretching vibrations of EDT-TTF-OX, charge-sensitive modes are identified based on theoretical calculations for neutral and oxidized EDT-TTF-OX using density functional theory (DFT) methods. The positions of C=C stretching modes in both Raman and infrared spectra of the (EDT-TTF-OX)₂AsF₆ materials are analyzed assuming a linear relationship between the frequency and charge of the molecule. The charge density on the EDTTTF-OX donor molecule is estimated to be +0.5 in all investigated materials and does not change with temperature. Therefore we suggest, that M-I transition observed in (EDT-TTF-OX)₂AsF₆ chiral molecular conductors at low temperature is not related to the charge ordering mechanism.     

Study of the shock-induced acceleration of hexane droplets

An experimental study of the interaction of a shock wave with a hexane droplet is presented. The main goal of the experiments was to record images of the process and measure basic parameters describing movement, dispersion and evaporation of the droplets engulfed by a shock wave propagating in air. A shock tube with a visualization section was used for this research. Photography of the process allowed one to measure the positions, velocities and sizes of mist clouds created by the interaction processes. Analysis of the pictures shows that there is no qualitative difference between cases for different size droplets, but shock Mach number had a significant effect on the process. Quantitative analysis shows that under certain conditions, a catastrophic breakup mechanism of dispersion occurred. The droplets are shattered into a mist cloud before they achieve mechanical equilibrium with the surrounding gas. The approximate time for the complete dispersion and acceleration of the fuel droplet varies from 300 to 500 μs, and depends both on the droplet diameter and shock velocity. The dispersion time is controlled principally by the droplet diameter, and to a lesser extent, the shock Mach number. This paper is based on work that was presented at the 20th International Colloquium on the Dynamics of Explosions and Reactive Systems, Montreal, Canada, July 31–August 5, 2005.     

Correction to: Unexpected Z/E isomerism of N-methyl-O-phosphothioyl benzohydroxamic acids,their oxyphilic reactivity and inertness to amines

Structural Chemistry - A Correction to this paper has been published: https://doi.org/10.1007/s11224-021-01744-8     

Towards More Photostable,Brighter, and Less Phototoxic Chromophores: Synthesis and Properties of Porphyrins Functionalized with Cyclooctatetraene

Free base and zinc porphyrins functionalized with cyclooctatetraene (COT), a molecule known as a good triplet-state quencher, have been obtained and characterized in detail by structural, spectral, and photophysical techniques. Substitution with COT leads to a dramatic decrease of the intrinsic lifetime of the porphyrin triplet. As a result, photostability in oxygen-free solution increases by two to three orders of magnitude. In non-degassed solutions, improvement of photostability is about tenfold for zinc porphyrins, but the free bases become less photostable. Similar quantum yields of photodegradation in free base and zinc porphyrins containing the COT moiety indicate a common mechanism of photochemical decomposition. The new porphyrins are expected to be much less phototoxic, since the quantum yield of singlet oxygen formation strongly decreases because of the shorter triplet lifetime. The reduction of triplet lifetime should also enhance the brightness and reduce blinking in porphyrin chromophores emitting in single-molecule regime, since the duration of dark OFF states will be shorter.     

Charged spray generation for gas cleaning applications

The paper presents results of experimental investigation of properties of charged sprays generated by two types of pressure atomizers with charging by induction. Among other possible methods of charged spray generation, the induction charging has been considered due to its most practical importance. The goal of this research is to optimise the charging process with respect to obtain droplets of required size and charge for their application for exhaust gas cleaning from submicron particles in electrostatic scrubber used for the removal of PM from Diesel engine exhausts. Electrostatic scrubbers use electrostatic forces in order to deposit fine charged particles onto oppositely charged droplets.     

Semiderivative real filter for microoptical elements quality control

The article presents a proposal for a new method of automatic quality control of microlenses arrays, which is based on a semiderivative real filter. The use of the semiderivative filter for examining pure-phase objects involves modifying the spatial frequency. The basis of the proposed setup is a 4f correlator setup with coherent light. The phase object examined is placed in the input plane of the correlator. Next, the light passes through a filter located in the frequency plane, which gives an intensity signal. In the output plane a charge-coupled device (CCD) camera registers the light intensity, the range of which informs the shape of the phase object. The proposed method is shift invariant, so it allows for examination of single elements or a set of micro-optical elements simultaneously. Additionally, the same setup allows for measuring the phase of objects whose thickness is either considerably smaller or much bigger than 2π.     

Transformation of Iodosulfuron-Methyl into Ionic Liquids Enables Elimination of Additional Surfactants in Commercial Formulations of Sulfonylureas

Efficient use of herbicides for plant protection requires the application of auxiliary substances such as surfactants, stabilizers, wetting or anti-foaming agents, and absorption enhancers, which can be more problematic for environment than the herbicides themselves. We hypothesized that the combination of sulfonylurea (iodosulfuron-methyl) anion with inexpensive, commercially available quaternary tetraalkylammonium cations could lead to biologically active ionic liquids (ILs) that could become a convenient and environment-friendly alternative to adjuvants. A simple one-step synthesis allowed for synthesizing iodosulfuron-methyl based ILs with high yields ranging from 88 to 96% as confirmed by UV, FTIR, and NMR. The obtained ILs were found to possess several favorable properties compared to the currently used sodium salt iodosulfuron-methyl, such as adjustable hydrophobicity (octanol-water partition coefficient) and enhanced stability in aqueous solutions, which was supported by molecular calculations showing cation–anion interaction energies. In addition, soil mobility and volatility of ILs were more beneficial compared to the parental herbicide. Herbicidal activity tests toward oil-seed rape and cornflower revealed that ILs comprising at least one alkyl chain in the decyl to octadecyl range had similar or better efficacy compared to the commercial preparation without addition of any adjuvant. Furthermore, results of antimicrobial activity indicated that they were practically harmless or slightly toxic toward model soil microorganisms such as Pseudomonas putida and Bacillus cereus.     

Spectroscopic Studies of Fluorescence Effects in Bioactive 4-(5-Heptyl-1,3,4-Thiadiazol-2-yl)Benzene-1,3-Diol and 4-(5-Methyl-1,3,4-Thiadiazol-2-yl)Benzene-1,3-Diol Molecules Induced by pH Changes in Aqueous Solutions

This paper presents the results of stationary fluorescence spectroscopy and time-resolved spectroscopy analyses of two 1,3,4-thiadiazole analogues, i.e. 4-(5-methyl-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (C1) and 4-(5-heptyl-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (C7) in an aqueous medium containing different concentrations of hydrogen ions. An interesting dual florescence effect was observed when both compounds were dissolved in aqueous solutions at pH below 7 for C1 and 7.5 for C7. In turn, for C1 and C7 dissolved in water at pH higher than the physiological value (mentioned above), single fluorescence was only noted. Based on previous results of investigations of the selected 1,3,4-thiadiazole compounds, it was noted that the presented effects were associated with both conformational changes in the analysed molecules and charge transfer (CT) effects, which were influenced by the aggregation factor. However, in the case of C1 and C7, the dual fluorescence effects were visible in a higher energetic region (different than that observed in the 1,3,4-thiadiazoles studied previously). Measurements of the fluorescence lifetimes in a medium characterised by different concentrations of hydrogen ions revealed clear lengthening of the excited-state lifetime in a pH range at which dual fluorescence effects can be observed. An important finding of the investigations presented in this article is the fact that the spectroscopic effects observed not only are interesting from the cognitive point of view but also can help in development of an appropriate theoretical model of molecular interactions responsible for the dual fluorescence effects in the analysed 1,3,4-thiadiazoles. Furthermore, the study will clarify a broad range of biological and pharmaceutical applications of these compounds, which are more frequently used in clinical therapies.

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Graphical Abstract Upper left corner – C7 molecule at high pH, right upper corner - fluorescence emission spectrum for C7 dissolved in H₂O at high pH (7–12) - single fluorescence. Bottom left corner – C7 molecule at low pH (1–7), lower right corner - fluorescence emission spectrum for C7 dissolved in water at low pH – two fluorescence emissions. The circles indicate the group related to dissociation of molecules at low and high pH and the additional long circles indicate C1 or a molecule with a shorter acyl chain.

     

Intramolecular transformation of an antifungal antibiotic nystatin A1 into its isomer,iso‐nystatin A1 – structural and molecular modeling studies

Nystatin A₁, a polyene macrolide antifungal antibiotic, in a slightly basic or acidic solution undergoes an intramolecular transformation, yielding a structural isomer, the translactonization product, iso‐nystatin A₁ with lactone ring diminished by two carbon atoms. Structural evidence is provided by advanced NMR and Mass Spectrometry (MS) studies. Molecular dynamics simulations and quantum mechanics calculations gave the insight into the course and mechanism of the transformation and its effect on the conformation of the subject molecule. Copyright © 2016 John Wiley & Sons, Ltd.