Color‐Tunable Solid‐State Fluorescence Emission from Carbazole‐Based BODIPYs

Several carbazole‐based boron dipyrromethene (BODIPY) dyes were synthesized by organometallic approaches. Thiazole, benzothiazole, imidazole, benzimidazole, triazole, and indolone substituents were introduced at the 1‐position of the carbazole moiety, and boron complexation of each dipyrrin generated the corresponding compounds 1 , 2 a , and 3 – 6 . The properties of these products were investigated by UV/Vis and fluorescence spectroscopy, cyclic voltammetry, X‐ray crystallography, and DFT calculations. These compounds exhibited large Stokes shifts, and compounds 1 , 2 a , and 3 – 5 fluoresced both in solution and in the solid state. Complex 2 a showed the highest fluorescence quantum yield (Φ_F) in the solid state, therefore boron complexes of the carbazole–benzothiazole hybrids 2 b – f , which had several different substituents, were prepared and the effects of the substituents on the photophysical properties of the compounds were examined. The fluorescence properties showed good correlation with the results of crystal‐packing analyses, and the dyes exhibited color‐tunable solid‐state fluorescence.     

The influence of a quaternary ammonium salt and MMT on the in situ intercalative polymerization of PMMA

Poly(methylmetacrylate)/montmorillonite (PMMA)/(MMT) nanocomposites were prepared by a one-step in situ intercalative solution polymerization involving the simultaneous modification of the MMT with a quaternary ammonium salt (cetyl-trimethylammonium bromide (CTMAB)), polymerization and polymer intercalation. Using benzoyl peroxide as an initiator, intercalated nanocomposites were formed and characterized by NMR, DSC, TGA, XRD, TEM and SEC. It was observed that it was not the MMT, but rather the CTMAB, that influences the polymerization reaction, especially the reaction yield, the molar mass averages and the molar mass distribution of the PMMA. The thermal stability of the PMMA was improved by the addition of both the MMT and/or the CTMAB.     

A bifunctional catalyst for carbon dioxide fixation: cooperative double activation of epoxides for the synthesis of cyclic carbonates

We have developed a very active bifunctional porphyrin catalyst showing a high turnover number (TON = 103,000) for the synthesis of cyclic carbonates from CO(2) and epoxides under solvent-free conditions.     

Chiral porphyrin dimer with a macrocyclic cavity for intercalation of aromatic guests

Chiral diporphyrin receptor 1, which has a macrocyclic cavity to sandwich aromatic guest molecules via double π-π stacking interactions, enabled the naked-eye detection of an aromatic explosive as well as chiral discrimination in NMR.     

Photochemical and phototoxic properties of ethyl 1,4-dihydro-8-nitro-4-oxoquinoline-3-carboxylate, a new quinoline derivative

The present study demonstrates photoinduced generation of superoxide radical anion and singlet oxygen upon UVA irradiation of ethyl 1,4-dihydro-8-nitro-4-oxoquinoline-3-carboxylate (DNQC), and its cytotoxic/phototoxic effects on murine leukemia L1210 cells. The formation of reactive oxygen species (ROS) was investigated by EPR spectroscopy using in situ spin trapping technique and 4-hydroxy-2,2,6,6-piperidine (TMP) for singlet oxygen ((1)O(2)) detection. The EPR spectra monitored upon photoexcitation of aerated solutions of DNQC in dimethylsulfoxide evidenced the efficient activation of molecular oxygen via Types I and II mechanisms. The cytotoxic/phototoxic effects of DNQC, analysis of cell cycle, induction of apoptosis/necrosis, DNA damage and molecular mechanism of apoptotic death of L1210 cells in dark and in the presence of UVA irradiation were compared. DNQC induced a different cytotoxic/phototoxic effect, which was concentration- and time-dependent. The four highest tested concentrations of non-photoactivated and photoactivated DNQC induced immediate cytotoxic/phototoxic effect after 24h cultivation of L1210 cells. This effect decreased with the time of treatment. The irradiation increased the sensitivity of leukemia cell line on DNQC, but the cell sensitivity decreased with time of processing. Quinolone derivative DNQC significantly induced direct DNA strand breaks in L1210 cells, which were increased with the irradiation of cells. The DNA damage generated by DNQC alone/with combination of UVA irradiation induced cell arrest in G(0)/G(1) and G(2)/M phases, decrease in the number of L1210 cells in Sphase and apoptotic cell death of certain part of cell population after 24 h of influence. DNQC alone/with combination of UVA irradiation induced apoptosis in L1210 cells through ROS-dependent mitochondrial pathway.     

Effective cleavage of ditertiary glycols via vanadium(V)-catalyzed aerobic oxidation

The aerobic oxidation of ditertiary glycols catalyzed by oxytrichlorovanadium resulted in carbon-carbon bonds cleavage producing the ketones efficiently.     

Chemical forces in terms of the electron density

A previous study of the small deformations produced by the molecular environment in the atomic densities has concluded that these deformations reflect and support all the concepts of the empirical structural chemistry. In the present work the study is extended to the chemical forces. Four types are distinguished: Van der Waals, Pauli, bonding and nuclear unscreening forces. For each type, the origin, the associated density deformations, the force generated by these deformations and the main role played by this force are investigated. It is stressed that Van der Waals complexes, usual molecules, conformers and chemical processes can be described in terms of these four forces, and are determined by the balance between them. It is proved that simple models for the density are often sufficient for semiquantitative predictions of forces, and can be very helpful for rationalizing the chemical properties and behavior. Developments are illustrated and supported with specific examples. Contribution to the Serafin Fraga Memorial Issue. Financial support: Dirección General de Investigación Científica y Técnica (CTQ2004-06615/BQU).     

Effects of vapor‐phase‐formaldehyde treatments on thermal conductivity and diffusivity of ramie fibers in the range of low temperature

To understand the influence to thermal conductivity by bridging in the polymer fibers, the thermal conductivity, and thermal diffusivity of ramie fiber and those bridged by formaldehyde (HCHO) using vapor‐phase method (VP‐HCHO treatment) were investigated in the lower temperature range. The thermal conductivities of ramie fiber with and without VP‐HCHO treatments decreased with decreasing temperature. Thermal diffusivities of ramie fiber with and without VP‐HCHO treatments were almost constant in the temperature range of 250–50 K, and increased by decreasing temperature below 50 K. Thermal conductivity and thermal diffusivity of ramie fiber decreased by VP‐HCHO treatment. The crystallinities and orientation angles of ramie fibers with and without VP‐HCHO treatment were measured using solid state NMR and X‐ray diffraction. These were almost independent of VP‐HCHO treatment. Although tensile modulus decreased slightly by VP‐HCHO treatment, the decrease could not explain the decrease in thermal conductivity and diffusivity with decreasing sound velocity. The decrease of the thermal diffusivity and thermal conductivity by VP‐HCHO treatment suggested the possibility of the reduction of the mean free path of phonon by HCHO in VP‐HCHO treated ramie fiber. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2754–2766, 2005     

Nonplanar Shocks and Solitons in a Strongly Coupled Adiabatic Plasma: the Roles of Heavy Ion Dynamics and Nonextensitivity

An investigation has been made on heavy ion‐acoustic (HIA) nonplanar shocks and solitons in an unmagnetized, collisionless, strongly coupled plasma whose constituents are strongly correlated adiabatic inertial heavy ions, weakly correlated nonextensive distributed electrons and Maxwellian light ions. By using appropriate nonlinear equations for our strongly coupled plasma system and the well‐known reductive perturbation technique, a modified Burgers (mB) equation and a modified Korteweg‐de Vries (mK‐dV) equation have been derived. They are also numerically solved in order to investigate the basic features (viz. polarity, amplitude, width, etc.) of cylindrical and spherical shock/solitary waves in such a strongly coupled plasma system. The roles of heavy ion dynamics, nonextensivity of electrons, and other plasma parameters arised in this investigation have significantly modified the basic features of the cylindrical and spherical HIA solitary and shock waves. The findings of our results obtained from this theoretical investigation may be useful in understanding the nonlinear phenomena associated with the cylindrical and spherical HIA waves both in space and laboratory plasmas. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)