Position Of Substituent Groups Research Articles

NMR analysis of the side-group substituents in welan gum in comparison to gellan gum

The physicochemical properties and applications of polysaccharides are highly dependent on their chemical structures, including the monosaccharide composition, degree of substitution, and position of substituent groups in the backbone. The occurrence of side groups or side chains in the chain backbone of polysaccharides is often an essential factor influencing their conformational and physicochemical properties. Welan gum produced by the fermentation of Sphingomonas sp. ATCC 31555 microorganisms has been widely used in food, construction, and oil drilling fields. While understanding the physicochemical properties of welan gum solution has been highly developed, there is still little information about the determination strategy of the glycosyl side groups in welan gum. In this study, the NMR method was established to quantitatively determine the substituent groups in the chain backbone of welan gum. The delicate chemical structures of welan gum obtained at different fermentation conditions were clarified. The composition and content of side substituents were also identified by high-performance liquid chromatography to confirm the accuracy of NMR analysis. The quantitative determination of substituent groups in gellan gum based on NMR analysis was also elaborated for comparison. This work provides insights for profoundly understanding the structure-function relationship of welan gum.

Modulating Chlorination Position on Polymer Donors for Highly Efficient Nonfullerene Organic Solar Cells

Introducing substituent groups has been regarded as an effective method to construct highly efficient polymer donors. However, the correlation between the position of substituent groups and the device performance of polymer donors has rarely been carefully studied and compared. Herein, Cl atoms are introduced into the BDT‐based thienyl side chains and BDD‐based thienyl π‐bridges to obtain two chlorinated donor−acceptor (D−A) polymer donors H1 and H2, respectively. By systematically comparing the photovoltaic properties of H1 and H2, it is found that the device performance of polymer donors is sensitive to the position of chlorine atoms. The nonfullerene organic solar cells (OSCs) based on H1:IT‐4F and H1:Y6 display a superior power conversion efficiency (PCE) of 12.34 and 15.62%, whereas the PCE of H2:IT‐4F and H2:Y6 is 11.04 and 13.80%. As the H1‐based blend shows more desirable aggregation morphology, more preferential face‐on orientation, and more efficient extraction dissociation occurs. The current work demonstrates that the position of chlorine substitution can be reasonably optimized for state‐of‐the‐art polymer donors in the highly efficient nonfullerene OSCs.

Structure-activity relationship toward electrocatalytic nitrogen reduction of MoS2 growing on polypyrrole/graphene oxide affected by pyridinium-type ionic liquids

MoS2 with different crystal structures and phase compositions have in-situ grown on the surface of pyridinium-type ionic liquids functionalized polypyrrole/graphene oxide (pyridinium-ILs/PPy/GO) and exhibited different electocatalytic performance towards Nitrogen reduction reaction (NRR), affected by the difference of crystal structure and phase compositions of MoS2 resulting from the induction of substituent groups in pyridinium. Combining the results of NRR performance tests with material characterizations determined by XRD, XPS and Raman spectra to explore the structure-activity relationship toward NRR of MoS2/pyridinium-ILs/PPy/GO, pyridinium-ILs with a group containing amino in the para- or ortho-position can be beneficial to induce 1T-MoS2 with good crystallinity, resulting in the satisfying NH3 yield, but poor stability, while the hydroxyl group at the para-position in pyridinium-ILs only induce 2H-MoS2 indexed to JCPDS file number 75-1539, not conducive to nitrogen fixation. Surprisingly, the most excellent NRR electroactivity is achieved by MoS2/pyridinium-ILs/PPy/GO synthesized using 2-amino-3-hydroxypyridine with the excellent lamellar hierarchical inorganic/organic micro-/nanostructures. It may be attributed to the confinement effect caused by the stereo hindrance composed of amino group at the ortho-position and hydroxyl group at the meta-position in pyridinium-ILs, resulting in 1T/2H-MoS2 nanoplates with rich defects indexed to JCPDS file number 37-1492 growing on pyridinium-ILs/PPy/GO. Therefore, the kind and position of substituent groups in pyridinium played an essential role for the crystal structure and phase compositions of MoS2 growing on pyridinium-ILs/PPy/GO, and further affected the NRR performance, which would provide a new thought and method for the reasonable design and performance optimization of electrocatalysts based on transition metal dichalcogenides for electrocatalysis.

Ligand Substituent Effects on the Spin-Crossover Behaviors of Dinuclear Iron(II) Compounds.

Six analogue compounds with the general formula [Fe2( xL)5(NCS)4]· yMeOH ( x = o-Cl, y = 3 for compound 1; x = m-Cl, y = 5 for 2; x = p-Cl, y = 1 for 3; x = o-Me, y = 2 for 4; x = m-Me, y = 2 for 5; x = p-Me, y = 3 for 6; L = N-phenylmethylene-4-amino-1,2,4-triazole) were synthesized. The two Fe(II) ions are triply bridged by the triazole groups of three xL ligands and each Fe(II) is further capped with two NCS- groups and one more xL ligand. These compounds show regular patterns in their magnetic properties that depend on the positions the substituent groups (-Cl or -Me) ride, i.e., ortho-substituted compounds 1 and 4 undergo complete one-step spin crossover (SCO), while meta-substituted compounds 2 and 5 display incomplete one-step SCO with lower transition temperatures, and para-substituted compounds 3 and 6 are in the high-spin states in all temperature ranges. Structural analyses reveal that the molecular geometry and intermolecular interactions of these compounds, which should account for the differences in magnetic properties, are obviously depend on the positions of substituent groups (steric effect), despite them being electron-withdrawing chlorine or electron-donating methyl, whereas theoretical calculations confirm that the electronic effects of substituent groups exert no effect on the magnetic properties.

Interaction of phenolic acids with trypsin: Experimental and molecular modeling studies.

Trypsin is a kind of protease for digestion and food processing, whose activity can be inhibited by phenolic acids in plant foods. However, most reports explained the inhibitory difference of phenolic acids based on the number and position of substituent groups, which failed to reveal the comprehensive inhibitory mechanism. In this work, the inhibitory effects of 11 common phenolic acids on trypsin were investigated. Amongst the tested cinnamic and benzoic acid derivatives, caffeic acid and gallic acid showed the strongest anti-trypsin activity with a noncompetitive inhibition pattern, respectively. The fluorescence analysis displayed that both the quenching rate constant (Kq) and binding constant (KA) of caffeic acid were higher than those of gallic acid. Molecular docking illustrated their different binding modes with trypsin. The ONIOM calculations revealed that the binding capacity of caffeic acid was higher than that of gallic acid, which could explain their difference in their inhibitory behaviors.

HPLC Method for Analysis of Bioactive Compound fromMomordica charantia

Momordica charantia commonly known as bitter melon/gourd, a member of Cucarbitaceae. Qualitative phytochemical analysis of Momordica charantia confirms the presence of photochemicals like flavonoids, saponins, terpenoids, coumarins, emodins, alkaloids, proteins, etc. HPLC is a simple, accurate and selective technique for separation and quantification of anthraquinone and flavonoid and phenols from leaf sample of bitter gourd. The most common method for chromatographic determination of anthraquinone is the HPLC method. Anthraquinones are a class of natural products encompassing several hundreds of compounds, differing in the nature and positions of substituent groups. Many anthraquinones have potential therapeutic value, since antimicrobial, insecticidal, antitumor, anticongestive, hypotensive and sedative properties have been assigned to these compounds.

Controlled Release Kinetics in Hydroxy Double Salts: Effect of Host Anion Structure

Nanodimensional layered metal hydroxides such as layered double hydroxides (LDHs) and hydroxy double salts (HDSs) can undergo anion exchange reactions releasing intercalated anions. Because of this, these metal hydroxides have found applications in controlled release delivery of bioactive species such as drugs and pesticides. In this work, isomers of hydroxycinnamate were used as model compounds to systematically explore the effects of anion structure on the rate and extent of anion release in HDSs. Following intercalation and subsequent release of the isomers, it has been demonstrated that the nature and position of substituent groups on intercalated anions have profound effects on the rate and extent of release. The extent of release was correlated with the magnitude of dipole moments while the rate of reaction showed strong dependence on the extent of hydrogen bonding within the layers. The orthoisomer showed a more sustained and complete release as compared to the other isomers.

Insights into antioxidant activity of 1-adamantylthiopyridine analogs using multiple linear regression

A data set of 1-adamantylthiopyridine analogs (1–19) with antioxidant activity, comprising of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide dismutase (SOD) activities, was used for constructing quantitative structure–activity relationship (QSAR) models. Molecular structures were geometrically optimized at B3LYP/6-31g(d) level and subjected for further molecular descriptor calculation using Dragon software. Multiple linear regression (MLR) was employed for the development of QSAR models using 3 significant descriptors (i.e. Mor29e, F04[N–N] and GATS5v) for predicting the DPPH activity and 2 essential descriptors (i.e. EEig06r and Mor06v) for predicting the SOD activity. Such molecular descriptors accounted for the effects and positions of substituent groups (R) on the 1-adamantylthiopyridine ring. The results showed that high atomic electronegativity of polar substituent group (R = CO2H) afforded high DPPH activity, while substituent with high atomic van der Waals volumes such as R = Br gave high SOD activity. Leave-one-out cross-validation (LOO-CV) and external test set were used for model validation. Correlation coefficient (QCV) and root mean squared error (RMSECV) of the LOO-CV set for predicting DPPH activity were 0.5784 and 8.3440, respectively, while QExt and RMSEExt of external test set corresponded to 0.7353 and 4.2721, respectively. Furthermore, QCV and RMSECV values of the LOO-CV set for predicting SOD activity were 0.7549 and 5.6380, respectively. The QSAR model's equation was then used in predicting the SOD activity of tested compounds and these were subsequently verified experimentally. It was observed that the experimental activity was more potent than the predicted activity. Structure–activity relationships of significant descriptors governing antioxidant activity are also discussed. The QSAR models investigated herein are anticipated to be useful in the rational design and development of novel compounds with antioxidant activity.

Spectroscopic and In Silico Evaluation of Interaction of DNA with Six Anthraquinone Derivatives

Anthraquinones consist of several hundreds of derivatives that differ in the nature and positions of substituent groups which are known to have several biological activities including antitumor properties. Interaction of molecules with DNA persists to be an extremely vital parameter while endeavouring to formulate therapeutics. In this study, few anthraquinone derivatives such as 1,2-dihydroxyanthraquinone (alizarin), 1,4-dihydroxyanthraquinone (quinizarin), 1,8-dihydroxyanthraquinone (danthron), 1,2,4-trihydroxyanthraquinone (purpurin), 1,4-diaminoanthraquinone, and 1-methylaminoanthraquinone were analyzed for its possible interaction with calf-thymus DNA through spectroscopy and in silico analysis. Our UV spectroscopic results indicate that all selected anthraquinones interact with DNA probably by external binding. Molar extinction coefficient has been calculated for chosen six anthraquinones. FT-IR results suggest that significant shifts of peaks as well as disappearance of certain characteristic peaks were indicators of the plausible interaction going on due to dye-DNA adduct formation. Among the six dyes used, purpurin showed better results and indicates the relatively strong binding affinity with DNA. Our molecular modeling results also show that purpurin has comparatively higher DNA interaction with a score of -6.18 compared with the ethidium bromide of -5.02 and intercalate the DNA.

Computational study of pyrazine‐based derivatives and their N‐oxides as high energy materials

Gas‐phase heats of formation (HOF), solid‐phase HOF, detonation properties, electronic structure and thermal stability for a series of polynitro pyrazine derivatives containing three heterocycles have been investigated using density functional theory. It is found that the nitro group is an efficient tool to improve HOF of pyrazine derivatives. Furthermore, detonation velocities and detonation pressures of these compounds are evaluated using empirical Kamlet–Jacobs equations. As a result, it indicates that the nitro group is useful to enhance detonation properties. Detonation velocities of five compounds are 9.67, 9.20, 9.74, 9.76 and 9.87 km/s, respectively, which are significantly larger than that of HMX (9.10 km/s). Bond dissociation energy is also performed to investigate their thermal stability, showing that thermal stability of these compounds is little affected by nitro groups or the position of substituent groups. Considering solid‐phase HOF, detonation properties and thermal stability, some of pyrazine derivatives can be potential high energy density materials. Copyright © 2013 John Wiley & Sons, Ltd.

Selective oxidation processes of organic substances in water by means of photocatalytic systems

Selective oxidation of benzyl alcohol into benzaldehyde in anoxic acidic aqueous solution, through a TiO2/Cu(II)/solar UV photocatalytic system, has been investigated both in a laboratory scaled reactor equipped with a high-pressure mercury lamp as well as in a solar pilot plant. During the laboratory experiments, benzaldehyde gave best results, in terms of yield, equal to 35% with respect to the initial benzyl alcohol concentration. A partial conversion of benzaldehyde to benzoic acid has also been observed. Traces of hydroxylated by-products have also been detected. On the basis of the formation of these species, a production of HO radicals has been thus inferred. The study has suggested that different operative parameters, such as the composition and amount of TiO2 photocatalyst, pH, ionic inorganic components in water, and the initial concentration of Cu(II) ions, play an important role in the photocatalytic selective oxidation of benzyl alcohol. The mechanism of photocatalytic selective oxidation of benzyl alcohol into benzaldehyde and benzaldehyde into benzoic acid has been investigated in the presence of TiO2 catalyst and cupric ions, as electron acceptor, in water at a pH = 2.0 and under deaerated conditions. A competitive adsorption has been proposed in which the aromatic substrates are adsorbed on the TiO2 surface and react with the positive holes. Whereas Cu(II) ions are reduced to Cu(0) by the photogenerated electrons. A new kinetic model has been developed by writing a set of mass balance equations for the main species involved in the photocatalytic oxidation process. The resulting mathematical model has been used for the analysis of the data collected at different starting substrates’ concentrations. During each of the selective photoxidation runs, it satisfactorily predicts the concentrations of Cu(II) species, organic substrates, and intermediates. The effect of ionic components, which compete with benzyl alcohol and benzaldehyde for the reaction with positive holes on the catalyst surface and behave as scavengers towards HO radicals, has been taken into account in the model. The values of some rate constants of the reactions of the holes with benzyl alcohol, benzaldehyde, Cu(II) species, and inorganic anions (sulfates and di-hydrogenophosphates), not available in the literature, have been estimated by a proper optimizing procedure. 7 The conversion of hydroxybenzyl alcohols, methoxybenzyl alcohols and nitrobenzyl alcohol into the corresponding aldehydes has been attempted by using the same process. The presence and position of substituent groups in the aromatic alcohols structure change the photocatalytic oxidation rates and product selectivities with respect to that previously observed for unsubstituted benzyl alcohol. In particular, the presence of both electron donating (hydroxy, methoxy groups) and electron withdrawing (nitro group) on the aromatic ring of the substrate causes a detrimental effect on the selectivity of the process with respect to that of benzyl alcohol. The technical feasibility of selective photocatalytic oxidation of benzyl alcohol to benzaldehyde, in aqueous solutions and in presence of cupric ions, has been then investigated in a solar pilot plant with Compound Parabolic Collectors. Under deaerated conditions, the presence of reduced copper species has been proved by XPS analysis. The results indicated that, at the end of the process, cupric species can be easily regenerated and reused, through a re-oxidation of reduced copper that is produced during the photolytic run, with air or oxygen in dark conditions. A figure-of-merit (ACM), proposed by the International Union of Pure and Applied Chemistry (IUPAC) and based on the collector area, has been estimated, under the proposed conditions, with the aim to provide a direct link to the solar-energy efficiency independently of the nature of the system. Generally speaking, it can be considered that the lower ACM values are, the higher is the system efficiency.

Computational studies on polynitropurines as potential high energy density materials

As part of a search for high energy density materials (HEDMs), a series of purine derivatives with nitro groups were designed computationally. The relationship between the structures and the performances of these polynitropurines was studied. Density functional theory (DFT) at the B3LYP/6-311G** level was employed to evaluate the heats of formation (HOFs) of the polynitropurines by designing an isodesmic reaction method. Results indicated that the HOFs were influenced by the number and positions of substituent groups. Detonation properties were evaluated using the Kamlet-Jacobs equations, based on the theoretical densities and heats of formation of the polynitropurines. The relative stabilities of the polynitropurines were studied via the pyrolysis mechanism and the UB3LYP/6-311G** method. Homolysis of the ring-NO2 bond is predicted to be the initial step in the thermal decomposition of these purine derivatives. Considering their detonation properties and relative stabilities, the tetranitropurine (D1) derivatives may be regarded as potential candidates for practical HEDCs. These results may provide useful information for further investigations.

Selective C–C bond cleavage of cyclopentadiene rings assisted by ferric chloride to synthesize water-soluble pyrylium salts

A facile procedure for C–C bond cleavage of cyclopentadiene rings is reported, and a series of water-soluble pyrylium tetrachloroferrates (Py–Fes) were synthesized. Different photoluminescence properties of Py–Fes were simply tuned by changing the types and positions of substituent groups.

Anti-Neoplastic Activity of Two Flavone Isomers Derived from Gnaphalium elegans and Achyrocline bogotensis

Over 4000 flavonoids have been identified so far and among these, many are known to have antitumor activities. The basis of the relationships between chemical structures, type and position of substituent groups and the effects these compounds exert specifically on cancer cells are not completely elucidated. Here we report the differential cytotoxic effects of two flavone isomers on human cancer cells from breast (MCF7, SK-BR-3), colon (Caco-2, HCT116), pancreas (MIA PaCa, Panc 28), and prostate (PC3, LNCaP) that vary in differentiation status and tumorigenic potential. These flavones are derived from plants of the family Asteraceae, genera Gnaphalium and Achyrocline reputed to have anti-cancer properties. Our studies indicate that 5,7-dihydroxy-3,6,8-trimethoxy-2-phenyl-4H-chromen-4-one (5,7-dihydroxy-3,6,8-trimethoxy flavone) displays potent activity against more differentiated carcinomas of the colon (Caco-2), and pancreas (Panc28), whereas 3,5-dihydroxy-6,7,8-trimethoxy-2-phenyl-4H-chromen-4-one (3,5-dihydroxy-6,7,8-trimethoxy flavone) cytototoxic action is observed on poorly differentiated carcinomas of the colon (HCT116), pancreas (Mia PaCa), and breast (SK-BR3). Both flavones induced cell death (>50%) as proven by MTT cell viability assay in these cancer cell lines, all of which are regarded as highly tumorigenic. At the concentrations studied (5–80 µM), neither flavone demonstrated activity against the less tumorigenic cell lines, breast cancer MCF-7 cells, androgen-responsive LNCaP human prostate cancer line, and androgen-unresponsive PC3 prostate cancer cells. 5,7-dihydroxy-3,6,8-trimethoxy-2-phenyl-4H-chromen-4-one (5,7-dihydroxy-3,6,8-trimethoxy flavone) displays activity against more differentiated carcinomas of the colon and pancreas, but minimal cytotoxicity on poorly differentiated carcinomas of these organs. On the contrary, 3,5-dihydroxy-6,7,8-trimethoxy-2-phenyl-4H-chromen-4-one (3,5-dihydroxy-6,7,8-trimethoxy flavone) is highly cytotoxic to poorly differentiated carcinomas of the colon, pancreas, and breast with minimal activity against more differentiated carcinomas of the same organs. These differential effects suggest activation of distinct apoptotic pathways. In conclusion, the specific chemical properties of these two flavone isomers dictate mechanistic properties which may be relevant when evaluating biological responses to flavones.

Galactans from Cryptonemia species . Part II: Studies on the system of galactans of Cryptonemia seminervis (Halymeniales) and on the structure of major fractions

Cryptonemia seminervis biosynthesizes a family of d, l-hybrid galactans based on the classical 3-linked β- d-galactopyranosyl→4-linked α- d- and α- l-galactopyranosyl alternating sequence (A-units→B-units) with major amounts of α- d- and α- l-galactose and 3,6-anhydro- d- and l-galactose and lesser percentages of 3,6-anhydro-2- O-methyl- l-galactose, 2- O-methyl-, 4- O-methyl- and 6- O-methylgalactoses. The dispersion of structures in this family is based on five structural factors, namely: (a) the amount and position of substituent groups as sulfate (major), pyruvic acid ketals, methoxyl and glycosyl side-chain (4- O-methyl galactopyranosyl and/or xylosyl); (b) the ratio galactose/3,6-anhydrogalactose in the B-units; (c) the ratio d, l-galactoses and d, l-3,6-anhydrogalactoses also in the B-units, (d) the formation of diads and (e) the sequence of the diads in the linear backbone. Considering these variables it is not unexpected to find in the fractions studied at least 18 structural units producing highly complex structures. Structural studies carried out in two major fractions (S2S-3 and S2S-4) showed that these galactans were formed mainly by β- d-galactopyranosyl 2-sulfate (20 and 11.9 mol %), β- d-galactopyranosyl 2-sulfate 4,6- O-(1′-carboxyethylidene) (8.9 and 6.0 mol %) and β- d-galactopyranosyl 2,6-sulfate (5.4 and 18.6 mol %), together with 3,6-anhydro-α- l-galactopyranosyl (11.4 and 7.3 mol %) and 3,6-anhydro-α- l-galactopyranosyl 2-sulfate (4.9 and 15.4 mol %) and minor quantities of 12–15 other structural units. Preparative alkaline treatment carried out on fraction (S2S-3) produced a quantitative formation of 3,6-anhydro α- l-galactopyranosyl units from precursor units (α- l-galactose 6-sulfate and α- l-galactose 2,6-sulfate). Kinetic studies on this 3,6-anhydro cyclization show a rate constant of 5.2 × 10 4 s −1 indicating diads of the type G→L6S/2,6S. Data from chemical, spectroscopic and kinetic studies suggest that, in S2S-3, the agaran block in the d, l-hybrid galactan is composed of the following diads: G(6R)→L6S/2,6S and G2S(P)(2,6S)→LA(2S)(2R)(2M) and the carrageenan block of G2S(P)→D(2S)(2,3S)(3S)(3,6S) in a molar ratio of agaran to carrageenan structures of ∼2:1.

Novel Cholesteric Glassy Liquid Crystals Comprising Benzene Functionalized with Hybrid Chiral-Nematic Mesogens

With 4′-cyanobiphenyl-4-yl benzoate nematogens chemically bonded to a benzene core via enantiomeric 2-methylpropyl spacers, a new series of cholesteric glassy liquid crystals has been synthesized for an investigation of structure−property relationships. Glass-forming ability, phase-transition temperatures, and stability against crystallization are affected by both the number and the position of substituent groups on the benzene ring with 1,3,5-trisubstituted system possessing the most favorable set of properties, Tg at 73 °C and Tc at 295 °C. With (S)-3-bromo-2-methylpropanol as the chiral precursor, left-handed helical stacking was observed for all the cholesteric GLCs reported herein. Films of the 1,3,5-trisubstituted and meta-disubstituted systems show a selective reflection wavelength, λR, at 413 and 422 nm, respectively, whereas that of the ortho-isomer exhibits a λR at 860 nm. Replacing one of the hybrid chiral-nematic mesogen in the 1,3,5-trisubstituted system by a nematogen loosens the helical pit...

Kinetics of substitution reactions of hexacoordinate cobalt(III) complexes with phenoxyacetic acid herbicides

Phenoxy herbicides are proved to be potential chelating agents in the metal complexation showing substitution reactions following second order kinetics. The reactions of cis-[Co(en) 2 (H 2 O) 2 ] 3+ with a series of substituted phenoxyacetic acids proved to be biomolecular and second order rate constants (log k) values are found to be linearly dependent on the Hammett substituent constants (σ) of respective phenoxyacetic acids. The high value of regression coefficient (r = 0.82) indicates that reactivities of these herbicides depend on number, nature and position of substituent group in the benzene ring. Further, the kinetic and thermodynamic stability of these complexes are also interpreted on the basis of equilibrium and rate constant data. The rate and equilibrium constants, spectral changes and their linear correlations with Hammett substituent constants (σ) for both biologically active and inactive phenoxyacetic acids are of comparable magnitudes, thereby ruling out the possibility of chelation as a possible mode of action of these herbicides.

Study on the antioxidant activities of benzofuranones in melt processing of polypropylene

The antioxidant activities of four benzofuranones in melt processing of polypropylene (PP) have been investigated using multiple extrusions. The antioxidant activities of those four benzofuranones with different substituent groups have been evaluated using melt flow index (MFI) and yellowness index (Y.I.) of multiple-extruded PP stabilized with those antioxidants. The change of MFI values indicates as follows: firstly, the position of substituent group has a very important effect on the antioxidant activity of benzofuranone in the melt processing of PP i.e. methyl group of 2′-position may prevent the hydrogen donation of benzofuranone toward PP radicals and make the antioxidant activity of benzofuranone in PP decrease; secondly, electronic property of substituent group of para position to 3-reactive hydrogen has little influence on the antioxidant activity. Furthermore, the theory that the formation of antioxidative products due to the dimerization and disproportionation of benzofuranyl radicals is the main reason that induces the discoloration of stabilized PP has been predicted for the first time.

Looking for high‐energy density compounds among hexaazaadamantane derivatives with CN, NC, and ONO2 groups

AbstractDensity functional theory (DFT) was employed to evaluate the heats of formation (HOFs) for hexaazaadamantane (HAA) derivatives with CN, NC, and ONO2 groups, respectively. This was done by designing isodesmic reactions at the B3LYP/6‐31G* level of theory, where the HAA cage skeletons were kept unbroken to produce more accurate results, and all HOFs for the required reference compounds, NH2CN, NH2NC, NH2ONO2, and (CH2NH)3, were derived from the G3 theory calculation based on the atomization energies. The calculation results show that the HOFs of HAA derivatives are mainly affected by the number and the position of substituent groups, all the obtained HOFs are positive, and the NC derivatives have the most HOFs among the three types of derivatives with the same number of substituent groups. The detonation velocity (D) and detonation pressure (P) were obtained from the empirical Kamlet–Jacobs equations. All the NC and CN derivatives of HAA have lower densities (ρ), heats of explosion (Q), D, and P. However, these properties of ONO2 derivatives are rather high and vary with the number of ONO2 groups. Considering the easiness for synthesis and relative stability, 2,4,6,8‐hexaazaadamantanenitrate is finally recommended as a potential candidate of a high‐energy density compound (HEDC). © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006

Syntheses and Application of Novel Blue Phosphorescent Iridium Complexes to OLEDs

We synthesized novel iridium complexes having a cyano and/or fluorine-containing phenylpyridine ligands for organic light emitting diodes (OLEDs). The optical properties of these complexes were investigated by ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) spectrophotometer. The emission color ranges from blue to green depending on the position of substituent groups. One of the complexes, bis[(5-cyano-2-fluorophenyl)-pyridinato-N,C2'] (dipivaloylnate) iridium (III), with the substituent groups on 2 and 5 positions, showed a greenish blue emission peak at 476 nm. The OLED with a structure of glass substrate / indium-tin-oxide (ITO) / tetraphenyl-benzidine-containing poly (arylene ether sulfone) (TPDPES) doped with tris (4-bromophenyl) aminium hexachloro-antimonate (TBPAH) / 2,2'-Bis[3''-(N,N'-ditolylamino) phenyl]biphenyl (3DTAPBP) / iridium complex-doped 2,2'-Bis[4''-(N -carbazole)phenyl] biphenyl (4CzPBP) / 3-(4-biphenyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (t-Bu-TAZ) / lithium fluoride (LiF)/ aluminum (Al) exhibited the external quantum efficiency of 17 % and the power efficiency of 33 lm/W at 100cd/m2.