Isomeric ruthenium terpyridine complexes [Ru(trpy)(L)Cl]n+ containing the unsymmetrically bidentate acceptor L=3-amino-6-(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine. Synthesis, structures, electrochemistry, spectroscopy and DFT calculations

The isomeric title complexes were obtained in almost equimolar ratio from the reaction of Ru(trpy)Cl3 and L. Crystal structure analyses of the perchlorate hemihydrates, electrochemical and spectroscopic (NMR, UV/VIS, EPR) studies, supported by DFT calculations, reveal distinct differences between the isomeric redox series [1]n+(tetrazine-Nt trans to Cl) and [2]n+(pyrazolyl-Np trans to Cl; n= 0, 1, 2). The latter system with the pi acceptors trpy and tetrazine in the equatorial plane and the pyrazolyl and chloride donors in the axial positions exhibits facilitated oxidation, lower energy MLCT transitions, more balanced chelate coordination, and a higher g anisotropy in the oxidised (RuIII) state. According to partially resolved EPR spectra of one-electron reduced neutral compounds and they have the unpaired electron predominantly in the tetrazine ring of L.     

Research in the imidazole series. 93. Synthesis of derivatives of benzimidazolyl-1-acetic acid

A simple method has been developed for obtaining esters of benzimidazolyl-1-acetic acid and its 2-alkyl (or aralkyl) derivatives, by reaction of benzimidazoles with esters of chloroacetic or bromoacetic acid in DMF in the presence of anhydrous potassium carbonate. The method of synthesis of amides of these acids has been simplified.For Communication 92, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 29, No. 5, pp. 656–658, May, 1993.     

Reactions of diisobutyl- and diethylaluminum hydrides with α-acetylenes

Conclusions To obtain Al vinyl compounds R₂A1CH=CHR' by reacting R₂AlH with HC=CR', we must use weakly acid acetylenes (alkyl acetylenes) and perform the reaction in aliphatic hydrocarbons at a low temperature in excess acetylene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 910–912, April, 1968.     

Studies in the imidazole series

6,7-Dimethylbenzimidazo[2,1-b]thiazolid-3-one was synthesized, and its reactions with aldehydes, isatin, nitroso compounds, and arene diazonium salts were studied. As a result, ylidene and imino derivatives and azo coupling products were obtained. According to the IR spectra, the azo coupling products have 6,7-dimethylbenzimidazo[2,1-b]thiazolidine-2,3-dione 2-arylhydrazone structures.See [1] for communication LVI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 822–825, June, 1971.     

Mass spectra of pyrrolo [1,2-a]benzimidazole and imidazo[1,2-a]benzimidazole derivatives

The closeness of the electronic structures of the ions formed in the first act of disintegration of the ions is responsible for the monotypic character of the subsequent fragmentation of pyrrolo[1,2-a]benzimidazole and imidazo[1,2-a]benzimidazole derivatives. The mass-spectrometric disintegration of the investigated systems has something in common with the fragmentation of thiazolo[3,2-a]benzimidazole derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, 1124–1127, August, 1975.     

Effects of Periodic Excitation on the Flow Around a D-Shaped Cylinder at Low Reynolds Numbers

The baseline and forced flow around a bluff body with semi-elliptical D-shape was investigated by solving the 2D Navier–Stokes equations at low Reynolds numbers. A D-shape rather than the canonic circular-cylinder was selected due to the fixed separation points in the latter, enabling to study a pure wake rather than boundary-layer control. The correlation between Strouhal and Reynolds numbers, the mean drag, the lift and drag oscillations vs. the Reynolds number and wake structure were investigated and compared to experimental and numerical data. Effects of open-loop forcing, resulting from the influence of zero-mass-flux actuators located at the fixed separation points, were studied at a Reynolds number of 150. Fluidic rather than body motion or volume forcing was selected due to applicability considerations. The motivation for the study was to quantify the changes in the flow field features, as captured by Proper Orthogonal Decomposition (POD) analysis, due to open-loop forcing, inside and outside the “lock-in” regime. This is done in order to evaluate the suitability of low-order-models based on POD modes of this changing flow field, for future feed-back flow control studies. The evolution of the natural and the excited vortices in the Kármán wake were also investigated. The formation and convection regions of the vortex evolution were documented. It was found that the forcing causes an earlier detachment of the vortices from the boundary-layers, but does not affect their circulation or convection speeds. The results of the POD analysis of the near-wake flow show that the influence of the bluff body shape (“D”-shaped versus circular cylinder) on the baseline POD wake modes is small. It was found that the eigenfunctions (mode-shapes) of the POD velocity modes are less sensitive to slot excitation than the vorticity modes. As a result of the open-loop excitation, two types of mode-shape-change were observed: a mode can be exchanged with a lower-energy mode or shifted to a low energy level. In the latter case, the most energetic mode becomes the “actuator” mode. The evolution of one-slot excitation on still fluid (“Synthetic jet”) was studied and compared to published data and to “actuator” modes with external flow present. Based on the current findings, it is hypothesized that the cross-flow velocity POD modes are suitable for feedback control of wake flow using periodic excitation, due to their low sensitivity to the excitation as compared to the streamwise velocity or vorticity modes.     

Triazole-based chromogenic and non-chromogenic receptors for halides

We designed and synthesized a series of triazole-based receptors for anion recognition. Our studies demonstrated that an amide-linked triazole unit is a promising moiety for anion recognition. We synthesized various chromogenic and non-chromogenic receptors based on this moiety. Receptor 11 binds very strongly (K = 102,750 M⁻¹) to fluoride. Receptor 18 changes color from faint yellow to orange upon binding to fluoride.     

Effect of the shape and size of the cell on the compressive strength of honeycomb cores

The effect of cell shape and size and panel thickness on the strength of honeycomb materials is studied. Three types (shapes) of core cells are investigated: 1) regular (symmetric) hexahedral; 2) hexahedral offset by one-half pitch; 3) reinforced hexahedral. It is found that the strength of the investigated types of core increases in the following order; 1) cores with hexahedral cells offset by one-half pitch; 2) cores with regular hexahedral cells, and 3) cores with reinforced hexahedral cells. It is shown that cores with reinforced cells obey all the laws characteristic of other cores. It is confirmed that the facing strengthens the core material.Mekhanika Polimerov, Vol. 1, No. 3, pp. 29–32, 1965     

Visualizing Microglia with a Fluorescence Turn‐On Ugt1a7c Substrate

Microglia, the brain‐resident macrophage, are involved in brain development and contribute to the progression of neural disorders. Despite the importance of microglia, imaging of live microglia at a cellular resolution has been limited to transgenic mice. Efforts have therefore been dedicated to developing new methods for microglia detection and imaging. Using a thorough structure–activity relationships study, we developed CDr20, a high‐performance fluorogenic chemical probe that enables the visualization of microglia both in vitro and in vivo. Using a genome‐scale CRISPR‐Cas9 knockout screen, the UDP‐glucuronosyltransferase Ugt1a7c was identified as the target of CDr20. The glucuronidation of CDr20 by Ugt1a7c in microglia produces fluorescence.