Double Aromatic Rings Research Articles

Ultraviolet electronic spectroscopy of heavily substituted naphthalene derivatives

Context. The so-called bump spectral signature observable on interstellar extinction curves, peaking at 217.5 nm, is commonly assigned to π* ← π transitions from carbonaceous carriers, but the exact nature of the carbonaceous carriers remains debated. Aims. To constrain the chemical structures associated with the bump carriers, we record and compare the UV spectra of a large variety of carbonaceous molecules to this interstellar feature. Methods. Large carbonaceous molecules, such as polycyclic aromatic hydrocarbons (PAHs), were produced by a combustion process stabilized at low pressure under rich flame conditions. Species were extracted and probed through resonance enhanced multiphoton ionization spectroscopy coupled to a time-of-flight mass spectrometer. Masses and absorption profiles of the carbonaceous molecules were measured, and their spectra were compared to the bump feature. Results. Species showing a specific mass progression starting at mass 128 u visible up to mass 394 u with a characteristic progression of +14 u present a common electronic absorption band profile peaking asymptotically around 220 nm. The first masses were assigned to a naphthalene C10H8 molecule and two of its derivatives: C10H7CH3 and C10H7C2H5. The mass progression of +14 u is explained by successive H atom substitutions by CH3 functional groups. This mass distribution was thus assigned to naphthalene derivatives with large aliphatic carbon substitution. This derivative family shows an electronic band assigned to S3 ← S0 transitions involving electron promotion within the π aromatic orbitals of the naphathlene chromophore. More importantly, after a few substitutions, the position of the band converges asymptotically to a value close to the interstellar bump signature, independent of the molecule size. Conclusions. Based on the asymptotic behavior of the larger members in the species distribution, a similar band position is expected from double aromatic ring substructures within hydrogenated amorphous carbons (HACs). Similar to the conclusions of previous works, we find substituted naphthalene units as substructures of interstellar HACs to be good candidates as carriers of the bump feature.

Simple, fast and inexpensive quantification of glycolate in the urine of patients with primary hyperoxaluria type 1

In primary hyperoxaluria type 1 excessive endogenous production of oxalate and glycolate leads to increased urinary excretion of these metabolites. Although genetic testing is the most definitive and preferred diagnostic method, quantification of these metabolites is important for the diagnosis and evaluation of potential therapeutic interventions. Current metabolite quantification methods use laborious, technically highly complex and expensive liquid, gas or ion chromatography tandem mass spectrometry, which are available only in selected laboratories worldwide. Incubation of ortho-aminobenzaldehyde (oABA) with glyoxylate generated from glycolate using recombinant mouse glycolate oxidase (GO) and glycine leads to the formation of a stable dihydroquinazoline double aromatic ring chromophore with specific peak absorption at 440 nm. The urinary limit of detection and estimated limit of quantification derived from eight standard curves were 14.3 and 28.7 µmol glycolate per mmol creatinine, respectively. High concentrations of oxalate, lactate and L-glycerate do not interfere in this assay format. The correlation coefficient between the absorption and an ion chromatography tandem mass spectrometry method is 93% with a p value < 0.00001. The Bland–Altmann plot indicates acceptable agreement between the two methods. The glycolate quantification method using conversion of glycolate via recombinant mouse GO and fusion of oABA and glycine with glyoxylate is fast, simple, robust and inexpensive. Furthermore this method might be readily implemented into routine clinical diagnostic laboratories for glycolate measurements in primary hyperoxaluria type 1.

Synthesis and Characterization of Non-leaching Inorgano- and Organo-montmorillonites and their Bactericidal Properties Against Streptococcus Mutans

AbstractThe direct application of heavy metal- and quaternary ammonium-based antibacterial agents can cause inconvenience such as irritation, short-term applicability, discoloration of the tissue, and environmental concerns. The immobilization of these agents on montmorillonite (Mnt) was expected to diminish these effects by hindering direct contact of the ions with the target tissues. The objective of the present study was, therefore, to prepare inorgano(I)- and organo(O)-montmorillonites (I/O-Mnt) and to determine their potential uses in such biomedical applications. Na-montmorillonite (Mnt-Na) was modified by hydrothermal and microwave irradiation methods using Cu2+/Zn2+, and quaternary ammonium and/or anionic surfactants. The effect of the structures formed by immobilization on Mnt surfaces on antibacterial activity was investigated. Quaternary ammonium surfactants were cetyltrimethyl ammonium bromide (CTAB) with a linear alkyl chain, cetylpyridinium chloride (CPC) with a single aromatic ring, and benzethonium chloride (BZT) with double aromatic rings. N-lauroyl sarcosinate (SR) was the anionic surfactant. The samples were subjected to thermogravimetric (TGA) and scanning electron microscopy (SEM) analyses. Desorption tests showed that the antibacterial efficacy against Streptococcus mutans stemmed from I/O-Mnt and not from the ions released from the material surfaces to the aqueous phase. The results of the antibacterial studies showed that the existence of a linear alkyl chain and a double aromatic ring were the structural factors causing the greatest antibacterial effect. The time-kill tests revealed that Mnt-CTA, Mnt-BZT, and Mnt-CP-SR were effective against Streptococcus mutans within 5 min of contact. With the new findings, they were identified as possible selective and potent bactericidal agents and promising candidates for biomedical applications.

Interplay of distributions of multiple guest molecules in block copolymer micelles: A dissipative particle dynamics study

HypothesisDelivery of multiple payloads using the same micelle is of significance to achieve multifunctional or synergistic effects. The interacting distribution of different payloads in micelles is expected to influence the loading stability and capacity. It is highly desirable to explore how intermolecular interactions affect the joint distribution of multi-payloads. ExperimentsDissipative Particle Dynamics simulations were performed to probe the loading of three payloads: decane with a linear carbon chain, butylbenzene with an aromatic ring connected to carbon chain, and naphthalene with double aromatic rings, within poly(β-amino ester)-b-poly(ethylene glycol) micelles. Properties of core-shell micelles, e.g., morphological evolution, radial density distribution, mean square displacement, and contact statistics, were analyzed to reveal payloads loading stability and capacity. Explorations were extended to vesicular, multi-compartment, double helix, and layer-by-layer micelles with more complex inner structures. FindingsDifferent payloads have their own preferred locations. Decane locates at the hydrophilic/hydrophobic interface, butylbenzene occupies both the hydrophilic/hydrophobic interface and the hydrophobic core, while naphthalene enters the hydrophobic core. More efficient delivery of multi-payloads is achieved since the competition of payloads occupying preferred locations is minimized. The fusion of micelles encapsulating different payloads suggests that specific payloads will move to their preferred positions without interfering other payloads.

Layered Yttrium Hydroxide as a Host for Enhancing the UV‐Protective Capacity and Photostability of Benzophenone‐5

AbstractLayered yttrium hydroxide (LYH) was explored as a host material for a highly efficient organic UV‐absorber, 2‐hydroxy‐4‐methoxybenzophenone‐5‐sulfonic acid (BP5), with the intercalation of BP5 anions into the interlayer galleries of LYH. On the basis of the powder X‐ray diffraction (XRD) pattern and Infrared (IR) spectra of the resulting BP5‐LYH hybrid, it was suggested that the double aromatic rings of BP5 anion are arranged parallel to the hydroxocation layers in the interlayer space in LYH. Thermogravimetry (TG) curves indicated the incomplete inclusion of BP5 anions due to the insufficiency of the lateral area of the interlayer space in LYH to accommodate the parallel arrangement of fully exchanged BP5 anions. The UV absorption band of BP5 was so broad as to absorb over the full UV range after intercalation in the LYH host. Long‐term use tests showed that BP5 was not significantly released from the LYH matrix in artificial seawater. This hybrid was well dispersed in a PVA solution to produce transparent BP5‐LYH/PVA composite UV‐filter films. The BP5‐LYH hybrid exhibited excellent photostability in PVA composites, maintaining complete UV‐filtering performance under simulated sunlight. A BP5‐LYH hybrid could therefore be a promising candidate not only as a UV‐filter that does not release BP5 into aquatic systems but also as a transparent outdoor UV‐screening polymer film whose single species covers the full UV range.

Dependence of Interfacial Charge Transfer on Bifunctional Aromatic Molecular Linkers in CdSe Quantum Dot Sensitized TiO2 Photoelectrodes

Quantum dot (QD) sensitization of TiO2 is a powerful method to improve its performance as a photoanode material in solar energy conversion. The efficiency of sensitization depends strongly on the rate of interfacial electron transfer (ET) from the QDs to TiO2. To understand the key factors affecting the ET, arene-substituted (ortho, meta, and para) bifunctional linkers with single or double aromatic rings were employed to link CdSe QDs to TiO2 and control the strength of their interaction as well as the rate of interfacial ET. Interestingly, the para-substituted aromatic linker, 4-mercaptobenzoic acid (4MBA) with the longest distance between the carboxyl and thiol groups, shows the best photoelectrochemical (PEC) performance, when compared to those of ortho-subtituted (2-mercaptobenzoic acid, 2MBA) and meta-substituted (3-mercaptobenzoic acid, 3MBA) aromatic linkers. Two other bifunctional linkers with double aromatic rings, 4′-mercapto-[1,1′-biphenyl]-4-carboxylic acid (4M1B4A) and 6-mercapto-2-naphthioc...

New alkylresorcinols from the fruits of Embelia ribes

Nine new alkylresorcinols, designated as embelialkylresorcinols A-I (1–9), along with five known compounds (10–14) were isolated from the fruits of Embelia ribes. Their structures were elucidated by extensive spectroscopic analysis (1D, 2D NMR and HRESIMS), optical rotation data and modified Mosher method. Notably, embelialkylresorcinols A-H (1–8), possessing double aromatic rings linked with an aliphatic chain, are reported from the genus of Embelia (Myrsinaceae) for the first time. Most of the isolated compounds were evaluated for cytotoxic activity, and the results indicated that compounds 3, 5, 6 and 8 displayed moderate cytotoxicity against three human cancer cell lines (Hep3B, A549 and HCC1806) with IC50 values ranging from 23.06 to 41.49 μM.

Distribution of extra-framework cations and water molecules in synthetic high-silica (Na, Cs)-rho-zeolite

We determined the distribution of extra-framework cesium and sodium atoms, as well as water molecules in the cavities of synthetic high-silica (Si/Al = 3.7) (Na, Cs)-rho-zeolite (Cs3.2Na6.7H0.3[Al10.2Si37.8O96] · 41H2O, Im-3m, a = 14.979(1) A) from X-ray powder diffraction data by applying the Rietveld and the maximum entropy methods. Extra-framework Cs and Na cations are found in α-cavities facing eight- and six-membered rings and in the center of the double aromatic ring D8R.

Quantum Mechanical Design of Efficient Second-Order Nonlinear Optical Materials Based on Heteroaromatic Imido-Substituted Hexamolybdates: First Theoretical Framework of POM-Based Heterocyclic Aromatic Rings

This work was inspired by a previous report (Janjua et al. J. Phys. Chem. A 2009, 113, 3576-3587) in which the nonlinear-optical (NLO) response strikingly improved with an increase in the conjugation path of the ligand and the nature of hexamolybdates (polyoxometalates, POMs) was changed into a donor by altering the direction of charge transfer with a second aromatic ring. Herein, the first theoretical framework of POM-based heteroaromatic rings is found to be another class of excellent NLO materials having double heteroaromatic rings. First hyperpolarizabilities of a large number of push-pull-substituted conjugated systems with heteroaromatic rings have been calculated. The β components were computed at the density functional theory (DFT) level (BP86 geometry optimizations and LB94 time-dependent DFT). The largest β values are obtained with a donor (hexamolybdates) on the benzene ring and an acceptor (-NO(2)) on pyrrole, thiophene, and furan rings. The pyrrole imido-substituted hexamolybdate (system 1c) has a considerably large first hyperpolarizability, 339.00 × 10(-30) esu, and it is larger than that of (arylimido)hexamolybdate, calculated as 0.302 × 10(-30) esu (reference system 1), because of the double aromatic rings in the heteroaromatic imido-substituted hexamolybdates. The heteroaromatic rings act as a conjugation bridge between the electron acceptor (-NO(2)) and donor (polyanion). The introduction of an electron donor into heteroaromatic rings significantly enhances the first hyperpolarizabilities because the electron-donating ability is substantially enhanced when the electron donor is attached to the heterocyclic aromatic rings. Interposing five-membered auxiliary fragments between strong donor (polyanion) or acceptor (-NO(2)) groups results in a large computed second-order NLO response. The present investigation provides important insight into the NLO properties of (heteroaromatic) imido-substituted hexamolybdate derivatives because these compounds exhibit enhanced hyperpolarizabilities compared to typical NLO arylimido hexamolybdates and heterocyclic aromatic rings reported in the literature.

Theoretical Study on the Considerable Second-Order Nonlinear Optical Properties of Naphthylimido-Substituted Hexamolybdates

The static first hyperpolarizabilities and origin of nonlinear optical (NLO) properties of [(2-methylnaphthyl)imido]hexamolybdates derivatives have been investigated by density functional theory (DFT). The [(2-methylnaphthyl)imido]hexamolybdate has considerable large first hyperpolarizability, 6.780 x 10(-30) esu, and it is larger than that of [(2,6-dimethylphenyl)arylimido]hexamolybdate due to the double aromatic rings in the naphthylimido ligand. The naphthylimido ligand acts as an electron-donor and the polyanion acts as an electron-acceptor. The substituent position on the naphthylimido is a key factor to determine the first hyperpolarizability of (naphthylimido)hexamolybdate derivatives. The derivative, which the iodine atom locates on the para nitrogen on the naphthylimido ligand, has the largest betao(o) value among the iodine-substituted derivatives. It suggests that the iodine atom is quasi linear with nitrogen and Mo, which is bonded to thenitrogen atom, could generate a large static electronic field and give the large contribution to NLO response.The introducing of electron-donors significantly enhances the first hyperpolarizabilities of (naphthylimido)hexamolybdates comparing with the electron-acceptors as the electron-donating ability is significantly enhanced when the electron-donor is attached to the naphthylimido segment. The present investigation provides important insight into NLO properties of (arylimido)molybdate derivatives.

Pyrolysis of polystyrene in a batch-type stirred vessel

Isothermal pyrolysis of PS was investigated in the relatively low temperature range of 370 to 400 °C, using a stirred tank of batch-type with respect to the liquid phase; the gas phase was operated in an open system. To maintain an isothermal condition, the stirring speed was 80 rpm. At the initial stage of pyrolysis at each temperature, the first-order kinetic law was found to be operative. The activation energy was evaluated to be 224 kJ/mol a value close to the previously reported one. The main liquid products were single and double aromatic ring species: styrene, α-methylstyrene, toluene and 1,3-diphenylpropane, 1,3-diphenylbutene. The yield of styrene was much larger than any other product and amounted to ca. 70 % by weight. The present reactor, operated in an open system with respect to the gas phase, tends to suppress the scission of volatile diphenyl radicals because of short residence times of these radicals.

Effects of photo-excitation and organic vapor treatment on vapor sorption behavior of sputtered fluoropolymer films

Investigation of sorption capacities for volatile organic compounds of radio-frequency-sputtered fluoropolymer films has revealed that they are affected by the applied voltage and by supplemental photo-excitation using ultraviolet light irradiation during sputtering. The photo-assisted effects of producing unsaturated carbons on the sputtered tetrafluoroethylene film are revealed by infrared, electron spin resonance, and X-ray photoelectron spectroscopies. Measurements of sorption capacities and computational chemical calculation for six-membered cyclic hydrocarbons revealed that the π-character of the solute molecule is a decisive molecular descriptor for sorption behavior of the sputtered fluoropolymers. The π-character of the sputtered fluoropolymer films can be enhanced by a photo-assisted effect, which can also increase the affinities for π-characterized solutes by π– π interaction. This is further clarified by the fact that the photo-assisted fluoropolymer film has a larger sorption capacity for highly π-conjugated double aromatic ring systems (C 10H 8): naphthalene than for slightly π-conjugated, but polar, isomer: azulene. It was also found that saturated organic vapor ( p-xylene and 2-butanone) sorption can enhance the sorption capacities of the sputtered fluoropolymer by restructuring induced by solvation and radical reaction.