Photophysics of boron difluoride chelates with dihalogenated tetraphenyl-<Emphasis Type="Italic">ms</Emphasis>-azadipyrromethenes

Spectral, luminescent, and photophysical properties of the BF₂ chelates with dichloroand dibromotetraphenyl-ms-azadipyrromethene (derivatives of tetraphenyl-aza-BODIPY) have been studied experimentally and theoretically by quantum chemistry methods. The positions of fluorescence bands, quantum yields, and lifetimes were measured experimentally. The rate constants of intramolecular photophysical processes have been estimated, and the quantum yields of fluorescence and phosphorescence and the lifetimes of excited states have been calculated. Complete energy schemes of electronically excited states and photophysical processes in the molecules of the compounds under study have been built on the basis of calculation results. The decrease in the fluorescence quantum yields upon excitation into the second absorption band and the absence of the phosphorescence of the chelates have been explained.     

Chromium(II) Complexes with Hydroxyethylidenediphosphonic Acid

The complex formation of chromium(II) with hydroxyethylidenediphosphonic acid (HEDP, H₅L) in an aqueous solution is studied by spectrophotometry. The pH region is determined where the HEDP complexonates of chromium(II) are stable. The effect of pH on the complexation and the composition of the coordination sphere of the complex ions is shown. The optimum conditions for the practical application of HEDP as a stabilizing ligand are chosen. The instability constants for tetra-, tri-, di-, and monoprotonated and neutral chromium(II) hydroxyethylidenediphosphonate complexes were calculated, whose pK were found to be 1.21, 2.43, 6.87, 12.60, 19.40, respectively. A new complex of chromium(II), Na₄[Cr(H₂L)₂ · 2H₂O] · 4H₂O, was isolated from a solution and characterized using elemental, IR spectroscopic, and thermographic analyses.     

Effects of Hydrogen Peroxide on In Vitro Cultures of Tea (Camellia sinensis L.) Grown in the Dark and in the Light: Morphology,Content of Malondialdehyde,and Accumulation of Various Polyphenols

Tea plants (Camellia sinensis L.) are phenol-accumulating crops that are widely used for public health. The healing effect of tea leaf products is due to the biosynthesis of such phenolic compounds (PCs) as flavans, which have P-vitamin capillary-strengthening activity. Due to their limited habitat and the value of their specialized metabolites of a phenolic nature, a promising approach is to establish in vitro cultures from them that retain the ability to form PCs, which is characteristic of ex vivo tea plants. The aim of this study was to investigate the effect of exogenic H₂O₂ (0.01 mM; 0.1 mM; 1 mM) on the growth, morphology, degree of stress response, and accumulation of various phenolic compounds in tea plant callus cultures of different ages (24 or 36 days) grown under different cultivation conditions (darkness or light). According to the results obtained, the H₂O₂ effect on tea callus cultures of different ages did not cause changes in their morphophysiological characteristics, both after 2 h of exposure (rapid response of callus culture, RRCC) and after 48 h (delayed response of callus culture, DRCC). The determination of the malondialdehyde (MDA) content, which serves as an indicator of changes in the level of lipid peroxidation (LPO) and the presence of stress responses in plant cells, indicated either its maintenance at the control level, a decrease, or an increase. All these effects depended on the growth conditions of the tea callus cultures (darkness or light), their age, the duration of exposure (rapid or delayed response), and the H₂O₂ concentration. Similar trends were noted for the total content of PCs as well as the amount of flavans, proanthocyanidins (soluble and insoluble forms), and lignin. The plant cell responses reflected changes in its adaptation programs, when specialized metabolites act as a target for the action of H₂O₂, thereby contributing to an increase in their resistance.     

Stability of Dibromo-Dipyrromethene Complexes Coordinated with B,Zn, and Cd in Solutions of Various Acidities

The spectral luminescent properties of dipyrromethenates halogenated with bromine on both ends of the long axis and coordinated using boron fluoride, zinc, or cadmium in neutral ethanol and acidified with hydrochloric acid solutions were studied. The constants of the acid–base equilibrium of the complexes in the proton-donor solvents in the ground and excited states was determined. The mechanisms of complex protonation were discussed, depending on the structure of the compounds. The electronic structures of the neutral and protonated compounds were modeled and analyzed based on the quantum-chemical method. The structures and spectral-luminescence properties were calculated using the SMD model of ethanol solvent using the TD-DFT theory with the B3LYP functional and the composite def2-SVP/def2-TZVP/def2-TZVPP_ECP basis sets, depending on the atomic number of the elements.     

Synthesis and Structure of (2E)-3-Aryl(hetaryl)-2-[5-bromo-4-aryl(hetaryl)-1,3-thiazol-2-yl]acrylonitriles

Russian Journal of General Chemistry - Bromination of (2E)-3-aryl(hetaryl)-2-[4-aryl(hetaryl)-1,3-thiazol-2-yl]acrylonitriles proceeds regioselectively at the C5 atom of the thiazole ring with the...     

Synthesis and Properties of New Fluorine-Containing Thieno[2,3-b]pyridine Derivatives

Russian Journal of General Chemistry - Cyanothioacetamide reacted with 1,1,5,5-tetrafluoroacetylacetone to give 4,6-bis(difluoromethyl)-2-thioxo-1,2-dihydropyridine-3-carbonitrile, and alkylation...     

Pseudo-Five-Component Stereoselective Synthesis of Highly Functionalized 3-Azabicyclo[3.3.1]nona-2,7-dienes

Russian Journal of General Chemistry - The reaction of aromatic aldehydes with malononitrile, ethyl or butyl cyanoacetate and acetylacetone in the presence of NaOH under mild conditions (EtOH,...     

Synthesis of hydrophobic derivatives of muramyldipeptides

Methyl esters of the cyclohexyl-, phenethyl-, (2-naphthyl)methyl-, and 2-(1-naphthyl)ethyl -glycosides of N-acetylmuramyl-L-analyl-D-isoglutamine have been synthesized. The corresponding glycosides of N-acetylglucosamine were obtained by glycosylating the alcohols with the peracetate of -glucosaminyl chloride in the presence of HgI₂, followed by deacetylation. Subsequent benzylidenation and alkylation with -L-chloropropionic acid led to glycosylmuramic acids, the condensation of which with the dipeptide and final debenzylidenation gave the desired glycopeptides.Simferopol' State University, 333036, Ukraine, Crimea, Simferopol', ul. Yaltinskaya, 4. Translated from Khimiya Priodnykh Soedinenii, Vol. 33, No. 1, pp. 79–86, January–February, 1997.     

Deformation and annealing textures of rolled nickel single crystals

Textural and structural analysis is conducted on nickel single crystals of unstable orientation in a compression deformed (=83%) and annealed state. The formation of different deformation textures (DT) on opposite surfaces of compressed crystals is established. The relief and band structure corresponds to two-component DT {110} 112, observed in the compression plane. Annealing (573°K) leads to the appearance of recrystallization grains on the two component DT side {110} 112. Orientationally, the first recrystallization grains correspond to the intersection of the peripheral portions of the texture maxima associated with both components of DT. On the side with DT {123} 212, indications of recrystallization were not observed. Application of the texture method with defocus allowed the comparison of the state of the lattice in the regions of the crystal having different orientations. The experimentally observed inhomogeneity of the development of the structure for primary recrystallization is explained by the inhomogeneity of the deformed structure and by orientational factors.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 45–50, June, 1986.