Abstract  The determination of the dispersive component of surface free energies (gamma(s)d) at different temperatures and Lewis acid-base parameters of 1-allyl-3-methylimidazolium chloride ionic liquid ([AMIM]Cl) were investigated by means of inverse gas chromatography (IGC). Four n-alkanes, including n-hexane (C6), n-heptane (C7), n-octane (C8) and n-nonane (C9), were chosen as the apolar probes to characterize the dispersive component of the surface free energies at 343.15, 353.15, 363.15 and 373.15 K, respectively; and dichloromethane (DCM), trichloromethane (TCM), tetrahydrofuran (THF), ethyl acetate (EtAc), acetone (Acet) as the polar probes to estimate the Lewis acid-base parameters to judge the interactions between [AMIM] Cl and the solvents. The IGC characterizations encompassed the adsorption thermodynamic parameters to acid-base surface interactions, including the standard enthalpy (deltaHa(s)) and the free energy change of adsorption (deltaGa(s)) at different temperatures. The results showed that the Lewis acid parameter Ka of [AMIM] Cl was 0.34, and the base parameter Kb was 1.68, which indicated it was Lewis amphoteric with predominantly basic character. Furthermore, the free energy of adsorption deltaGa(s) was also figured out. It was found that the gamma(s)d of the [AMIM] Cl were 52.26, 50.82, 46.08 and 42.05 mJ/m2 at 343.15, 353.15, 363.15 and 373.15 K, respectively. The results are of great importance to the study of the surface properties and the application of ionic liquid.

Abstract  OBJECTIVE: To study the chemical constituents in the seeds of Oroxylum indicum.

METHOD: Twenty compounds were isolated and purified by silica gel, and Sephadex LH-20 column chromatography, and their structures were determined by spectroscopic analysis including NMR and MS.

RESULT: Twenty compounds were isolated and identified as oroxin A (1), oroxin B (2), chrysin (3), baicalein (4), quercetin (5), apigenin (6), kaempferol (7), quercetin-3-O-ara-binopyranoside (8), lupeol C9), lup-20 (29)-ene-2alpha,3beta-diol (10), pinosylvin (11), dihydropinosylvin (12), cholest-5-ene-3, 7-diol (13), rengyol (14), isorengyol (15), zarzissine (16), (E) -pinosylvin-3-O-beta-D-glucopyranoside (17), adenosine (18), sitosterol (19) and daucosterol (20).

CONCLUSION: Compounds 11-13 and 15-18 were obtained from the genus Oroxylum for the first time, and except compound 18, the remaining 6 compounds were obtained from the family Bignoniaceae for the first time.

Abstract  Human C8 and C9 have a key role in forming the pore-like "membrane attack complex" (MAC) of complement on bacterial cells. A possible mechanism for membrane insertion of these proteins was suggested when studies revealed a structural similarity between the MACPF domains of the C8α and C8β subunits and the pore-forming bacterial cholesterol-dependent cytolysins (CDCs). This similarity includes a pair of α-helical bundles that in the CDCs refold during pore formation to produce two transmembrane β-hairpins (TMH1 and TMH2). C9 is the major pore-forming component of the MAC and is also likely to contain two TMH segments because of its homology to C8α and C8β. To determine their potential for membrane insertion, the TMH sequences in C8α and those predicted to be in C9 were substituted for the TMH sequences in perfringolysin O (PFO), a well-characterized CDC. Only chimeric proteins containing TMH2 from C8α (PFO/αT2) or C9 (PFO/C9T2) could be expressed in soluble, active form. The PFO/αT2 and PFO/C9T2 chimeras retained significant hemolytic activity, formed pore-like structures on membranes, and could combine with PFO to form hemolytically active mixed complexes that were functionally similar to PFO alone. These results provide experimental evidence in support of the hypothesis that TMH segments in C8α and those predicted to be in C9 have a direct role in MAC membrane penetration and pore formation.

Abstract  The sesquiterpene lactone parthenolide has recently attracted considerable attention owing to its promising antitumor properties, in particular in the context of stem-cell cancers including leukemia. Yet, the lack of viable synthetic routes for re-elaborating this complex natural product has represented a fundamental obstacle toward further optimization of its pharmacological properties. Here, we demonstrate how this challenge could be addressed via selective, late-stage sp(3) C-H bond functionalization mediated by P450 catalysts with tailored site-selectivity. Taking advantage of our recently introduced tools for high-throughput P450 fingerprinting and fingerprint-driven P450 reactivity prediction, we evolved P450 variants useful for carrying out the highly regioselective hydroxylation of two aliphatic sites (C9 and C14) in parthenolide carbocyclic backbone. By chemoenzymatic synthesis, a panel of novel C9- and C14-modified parthenolide analogs were generated in order to gain initial structure-activity insights on these previously inaccessible sites of the molecule. Notably, some of these compounds were found to possess significantly improved antileukemic potency against primary acute myeloid leukemia cells, while exhibiting low toxicity against normal mature and progenitor hematopoietic cells. By identifying two 'hot spots' for improving the anticancer properties of parthenolide, this study highlights the potential of P450-mediated C-H functionalization as an enabling, new strategy for the late-stage manipulation of bioactive natural product scaffolds.

Abstract  Bacterial populations co-ordinate gene expression collectively through quorum sensing (QS), a cell-to-cell communication mechanism employing diffusible signal molecules. The LysR-type transcriptional regulator (LTTR) protein PqsR (MvfR) is a key component of alkyl-quinolone (AQ)-dependent QS in Pseudomonas aeruginosa. PqsR is activated by 2-alkyl-4-quinolones including the Pseudomonas quinolone signal (PQS; 2-heptyl-3-hydroxy-4(1H)-quinolone), its precursor 2-heptyl-4-hydroxyquinoline (HHQ) and their C9 congeners, 2-nonyl-3-hydroxy-4(1H)-quinolone (C9-PQS) and 2-nonyl-4-hydroxyquinoline (NHQ). These drive the autoinduction of AQ biosynthesis and the up-regulation of key virulence determinants as a function of bacterial population density. Consequently, PqsR constitutes a potential target for novel antibacterial agents which attenuate infection through the blockade of virulence. Here we present the crystal structures of the PqsR co-inducer binding domain (CBD) and a complex with the native agonist NHQ. We show that the structure of the PqsR CBD has an unusually large ligand-binding pocket in which a native AQ agonist is stabilized entirely by hydrophobic interactions. Through a ligand-based design strategy we synthesized and evaluated a series of 50 AQ and novel quinazolinone (QZN) analogues and measured the impact on AQ biosynthesis, virulence gene expression and biofilm development. The simple exchange of two isosteres (OH for NH₂) switches a QZN agonist to an antagonist with a concomitant impact on the induction of bacterial virulence factor production. We also determined the complex crystal structure of a QZN antagonist bound to PqsR revealing a similar orientation in the ligand binding pocket to the native agonist NHQ. This structure represents the first description of an LTTR-antagonist complex. Overall these studies present novel insights into LTTR ligand binding and ligand-based drug design and provide a chemical scaffold for further anti-P. aeruginosa virulence drug development by targeting the AQ receptor PqsR.

Abstract  Mesoporous silicas are synthesised using 1,3,5-trimethylbenzene (TMB) and heptanes as pore expanders. Small-angle X-ray diffraction and N-2 adsorption-desorption isotherms at 77 K were used to characterise the pore structure of the prepared materials. The porosity increased with the added TMB amount for samples using TMB as a pore expander and a total pore value of 2.48 cm(3)/g was obtained, representing an increase by a factor of 2.4 as compared with mesoporous silica without TMB addition. For samples with heptanes as a pore expander, the pore volume increased with synthesis temperature. The mesoporous silica synthesised at 52 degrees C had a total pore volume of 2.38 cm(3)/g.

Abstract  Sterically encumbered nitrosocarbonyl derivatives of mesitylene or anthracene undergo ene reactions with 3-methylbut-2-en-1-ol to give the corresponding the 5-hydroxyisoxazolidine adducts in fair yields. According to the proposed mechanism, these heterocycles are derived from the anti-Markovnikov orientation of the ene reaction. The isoxazolidin-5-yl acetate derivatives are synthons of choice for the preparation of N,O-nucleoside analogues containing purine rings by means of the Vorbruggen protocol.

Abstract  We have synthesised first generation (G1) of mesitylene-based polyamine dendrimer by following the convergent approach. The polyamine dendrimer was characterised by the usual spectroscopic techniques including liquid chromatography coupled with mass spectrometry. To develop polycationic functionalised carbon nanotubes (f-CNTs) as advanced systems for the delivery of nucleic acid, we attached G1 polyamine dendrimer onto the surface of single-walled CNTs (SWCNTs). The f-SWCNTs were characterised by thermogravimetric analysis and transmission electron microscopy. The nanotubes after functionalisation with polyamine dendrimer showed good dispersibility in highly polar solvents.

Abstract  AlCl(3) promoted Friedel-Crafts acylation between 4-tert-butylbenzoyl chloride and mesitylene was investigated. The donor-acceptor complex was observed as the major species. Kinetic investigation demonstrated that the reaction was first-order on the donor-acceptor complex and zero-order on ArH, suggesting that the donor-acceptor complex was not the true reactive species. However, the acylium ion was almost invisible with a fairly low concentration under live reaction conditions. It was approved as the true reactive species through kinetic data ("kinetic capture") in the AlCl(3) promoted Friedel-Crafts acylation reaction.

Abstract  Mesoporous titanosilicate of cubic Pm3n structure was prepared for the first time using cetyltriethylammonium (CTEA(+)) bromide as pore-directing agent in alkaline condition (pH around 9) with the aid of NaCl salt. The alkaline synthesis condition facilitated the incorporation of Ti(IV) into the silica framework as well as the assembly of mesoporous silica with zeolite seeds. Two kinds of silica sources were used. The material prepared with sodium silicate was named Ti-SBA-1-alk, and the other named Ti-ZSBA-1 was prepared with the seeds of titanosilicalite-1 (TS-1). The studies by UV-Vis and Ti K-edge XANES spectra indicated that the Ti(IV) in Ti-SBA-1-alk was favorably in tetrahedral (T-d) coordination and should be incorporated into the framework of mesoporous silica, whereas a larger amount of Ti(IV) in Ti-ZSBA-1 was in octahedral coordination. In oxidation of 2,3,6-trimethylphenol (TMP) to 2,3,5-trimethylbenzoquinone (TMBQ) using hydrogen peroxide as the oxidant, the mesoporous titanosilicate materials were found to be efficient catalysts, while only trace TMP conversion was observed over TS-1 due to its small zeolitic pores. In comparison of mesoporous titanosilicate materials in similar pore diameters, Ti-SBA-1-alk and Ti-ZSBA-1 both of cubic Pm3n structure gave higher TMBQ selectivities than Ti-MCM-41 of 2D channeling pores, attributing to the better diffusion of the phenoxyl radicals in the three-dimensional pores. Moreover, Ti-SBA-1-alk which contained more T-d-coordinated Ti(IV) showed higher catalytic activities than Ti-ZSBA-1. (C) 2014 Elsevier Inc. All rights reserved.

Abstract  Herein, we report a special case of pseudo-β-hairpin formation by tetrapetide sequences featuring a two-membered Ant-Pro dipeptide motif (Ant = anthranilic acid and Pro = proline) at the loop region. These folded structures uniquely feature the presence of C9- and C17-H-bonding patterns at reverse turn and interstrand regions, respectively. Their hairpin nucleation and folding propensities have been expounded using solution and solid state studies of distinct stereochemically altered sequences.

Abstract  Firefighters wear fireproof clothing and self-contained breathing apparatus (SCBA) during rescue and fire suppression activities to protect against acute effects from heat and toxic chemicals. Fire services are also concerned about long-term health outcomes from chemical exposures over a working lifetime, in particular about low-level exposures that might serve as initiating events for adverse outcome pathways (AOP) leading to cancer. As part of a larger US National Institute for Occupational Safety and Health (NIOSH) study of dermal exposure protection from safety gear used by the City of Chicago firefighters, we collected pre- and post-fire fighting breath samples and analyzed for single-ring and polycyclic aromatic hydrocarbons as bioindicators of occupational exposure to gas-phase toxicants. Under the assumption that SCBA protects completely against inhalation exposures, any changes in the exhaled profile of combustion products were attributed to dermal exposures from gas and particle penetration through the protective clothing. Two separate rounds of firefighting activity were performed each with 15 firefighters per round. Exhaled breath samples were collected onto adsorbent tubes and analyzed with gas-chromatography-mass spectrometry (GC-MS) with a targeted approach using selective ion monitoring. We found that single ring aromatics and some PAHs were statistically elevated in post-firefighting samples of some individuals, suggesting that fire protective gear may allow for dermal exposures to airborne contaminants. However, in comparison to a previous occupational study of Air Force maintenance personnel where similar compounds were measured, these exposures are much lower suggesting that firefighters' gear is very effective. This study suggests that exhaled breath sampling and analysis for specific targeted compounds is a suitable method for assessing systemic dermal exposure in a simple and non-invasive manner.

Abstract  Dietary unsaturated fatty acids (FA) are intensively hydrogenated in the rumen, resulting in reduced amount of poly-unsaturated fatty acids (PUFA) and accumulation of several biohydrogenation (BH) products. In this study, BH of PUFA originating from different oilseeds (linseed, soya beans, sunflower seed and rapeseed) present in crushed oilseeds or their free oils were assessed in vitro. The assay substrates were incubated in buffered rumen fluid for 0, 6, 12 and 24 h. After incubation, the FA pattern of the incubated samples was analysed using gas chromatography. Biohydrogenation is defined as disappearance of double bonds (DB) calculated from the contents of unsaturated FA. After 24-h incubation, the DB contents of all oilseeds were reduced (p < 0.001) by 40-60%. The reduction was higher (p < 0.001) for the crushed form compared with the oil form. In addition, linseed and sunflower seed known as oilseeds with high contents of linolenic acid C18:3 c9,12,15 (LNA) and linoleic acid C18:2 c9,12 (LA), respectively, showed a higher (p < 0.001) accumulation of the BH intermediates conjugated linoleic acid (CLA, isomer C18:2 c9t11) and vaccenic acid (C18:1 t11) for the crushed form, when compared with the oil. These results suggest an inherent effect of the physical form of the assay oilseeds on in vitro BH. Changes in FA pattern during BH in vitro can be attributed to both source and physical form of the assay oilseeds. However, further investigations are warranted to ensure whether the observed in vitro effects on ruminal BH can be confirmed in vivo.

Abstract  The chemical profile of the cuticle and internal tissues of four species of Culicoides have been studied for the first time by gas chromatography-mass spectrometry. The chemical composition of females of C. obsoletus s.l. and C. lupicaris, vectors of diverse viral diseases, have been compared with that of other biting midges, such as C. kibunensis and C. fascipennis, and the non-biting midge Forcipomyia bipunctata. A total of 61 compounds belonging to 8 major chemical classes were identified in cuticular and internal tissues in n-hexane extracts. The compounds include carboxylic acids (CAs) (C6-C20), with C16:0, C16:1 and C18:1 being dominant, branched hydrocarbons (C29 to C38 mono/di/trimethylalkanes), linear hydrocarbons (C15 to C33, mainly odd chain carbons), terpenes (geranylacetone, geranylgeraniol acetate, squalene, terpenic alcohol), steroids (cholesterol), aldehydes (C9-C10 and even chain C20 to C30), and esters. The chemical profile depends on the species and whether the extracts are external (cuticle) or internal. The contents of linear and branched hydrocarbons and aldehydes was high in cuticular extracts but practically absent in internal tissues, which were, in contrast, rich in CAs, terpenes and steroids. The results are discussed and compared with other Culicoides midges and mosquito-related species.

Abstract  The half structure of the symmetrical macrodiolide aplasmomycin A was synthesized by alkylation of a C3-C10 α-sulfonyl ketone subunit, prepared from (R)-pulegone and protected as a C3 ortholactone with (2R,3R)-butanediol, by a protected 15,16-dihydroxy (12E)-allylic chloride representing C11-C17. The latter was obtained from (2S,3R)-1,2-epoxy-3-butanol and propargyl alcohol. Regio- and stereoselective 5-exo-trig cyclization of the ene diol moiety in this segment, mediated by N-bromosuccinimide, led to the (2R,3S,5R)-tetrahydrofuran substructure of aplasmomycin A. Attachment of an α-acetic ester at the C3 carboxylic acid and esterification of the 3'-hydroxyl group of the tetrahydrofuran as its α-bromoacetate enabled coupling of two aplasmomycin half structures as an α-acyloxy acetate. Mukaiyama macrolactonization of this hydroxy acid afforded a symmetrical 36-membered diolide. Base-mediated double Chan rearrangement of this bis α-acyloxy dilactone caused ring contraction to the 34-membered macrocycle of desboroaplasmomycin A while generating the transannular 2-hydroxy-3-hemiketal motif of the natural product in the correct configuration. Final incorporation of boron into the tetraol core produced aplasmomycin A, isolated as its sodium borate. Extension of this route to the unsymmetrical macrodiolide boromycin was accomplished by modifications that included reversal of C12-C13 olefin geometry to (Z) for the southern half structure along with stereoselective hydride reductions of the C9 ketone that produced (9R) and (9S) alcohols for northern and southern half structures, respectively. Coupling of these half structures was made using an α-acyloxy ester linkage as for aplasmomycin A, but ring closure in this case was orchestrated via a blocked C16 alcohol that left open the C15 hydroxyl group of the southern half for Mukaiyama macrolactonization. A double Chan rearrangement of the resulting 35-membered macrocycle produced the 33-membered diolide of desborodesvalinylboromycin which had been obtained previously by degradation of natural boromycin. Insertion of boron into the tetraol core followed by esterification of the C16 alcohol with a masked d-valine and final deprotection furnished boromycin as its zwitterionic (Böeseken) complex.

Abstract  Three different model reactions (methylcyclohexane, m-xylene and 1,3,5-trimethylbenzene transformations) were studied over a series of partially Na-exchanged H-EU-1 zeolites. In the case of methylcyclohexane transformation, the catalytic activity was shown to be directly correlated to the concentrations and strength distribution of the acid sites. Consequently, a maximum in activity and turn-over frequency (TOF) was obtained for an exchange ratio comprised between 26% and 34%, for which the proportion of very strong acid sites was very high. An acidity activity correlation, based on the Polanyi principle, was successfully applied to this reaction. This was not the case for m-xylene and 1,3,5-trimethylbenzene transformations. During those reactions, the activity and TOF decreased with the protonic site concentration, hence with the increase of the exchange ratio, the activity loss being more pronounced for low exchange ratios. Poisoning experiments using gamma-collidine indicated that two kinds of external acid sites could be distinguished, depending on their locations, that is, at the pore mouths and in 12-ring pockets. The fast exchange by sodium cations of the latter sites, which would be particularly active in m-xylene and 1,3,5-trimethylbenzene transformations, could explain the evolution of these activities. (C) 2012 Elsevier Inc. All rights reserved.

Abstract  A new class of functionalised dicationic ionic liquids, containing a central cationic unit capped by a basic functionality (imidazole), has been synthesised. These salts have been characterised in isotropic solution using proton and 2D-NMR spectroscopy, and their thermal stability has been studied by DSC and TGA. All these novel salts contain the 1-(1-imidazolylmethyl)-3,5-di{1-(3'-octylimidazolyInnethyl)}-benzene cation as a defining structural motif. Salts of both singly and doubly charged anions were prepared and, in particular, the selected monoanions (Br-, [BF4](-), or [NTf2](-)) differ in size, shape and hydrogen-bonding ability, whereas the dianions differ in the nature of the spacer, such as 1,4-benzenedicarboxylate, 2,6-naphthalenedicarboxylate, 1,5- and 2,6-naphthalenedisulfonate, 1,4-butanedicarboxylate, and 1,6-hexanedicarbmlate. These ionic liquids exhibit the presence of different conformers in solution, whose distribution is affected by the nature of the anion. The nature of the anion also affects their thermal stability.

Abstract  We have monitored the speeds of evaporating helium atoms dissolved in liquid octane, isooctane, 1-methylnaphthalene, dodecane, squalane, ethylene glycol, and two jet fuels. In all cases, the average kinetic energies of the evaporating He atoms exceed the Maxwellian value of 2RT. The energies roughly track solvent surface tensions; this correlation may reflect the tighter packing and attractions of interfacial solvent molecules that restrict the gaps through which He atoms escape. Mixtures of dodecane, squalane, and 1-methylnaphthalene generate He evaporation energies that lie between the pure liquid values. We find, however, that He atoms evaporate from pure 1-methylnaphthalene with kinetic energies lower than expected based on its high surface tension, perhaps because the sideways packing of the aromatic rings provides more direct channels for the escaping He atoms. Additionally, He evaporates from two complex fuel mixtures, Jet A and JP-8, with nearly identical energies, implying that the extra additives in JP-8 do not segregate to the surface in ways that alter the dynamics of evaporation.

Abstract  Pathogenic mutations involving DNA repeat expansions are responsible for over 20 different neuronal and neuromuscular diseases. All result from expanded tracts of repetitive DNA sequences (mostly microsatellites) that become unstable beyond a critical length when transmitted across generations. Nearly all are inherited as autosomal dominant conditions and are typically associated with anticipation. Pathologic unstable repeat expansions can be classified according to their length, repeat sequence, gene location and underlying pathologic mechanisms. This review summarizes the current contribution of mutant pluripotent stem cells (diseased human embryonic stem cells and patient-derived induced pluripotent stem cells) to the research of unstable repeat pathologies by focusing on particularly large unstable noncoding expansions. Among this class of disorders are Fragile X syndrome and Fragile X-associated tremor/ataxia syndrome, myotonic dystrophy type 1 and myotonic dystrophy type 2, Friedreich ataxia and C9 related amyotrophic lateral sclerosis and/or frontotemporal dementia, Facioscapulohumeral Muscular Dystrophy and potentially more. Common features that are typical to this subclass of conditions are RNA toxic gain-of-function, epigenetic loss-of-function, toxic repeat-associated non-ATG translation and somatic instability. For each mechanism we summarize the currently available stem cell based models, highlight how they contributed to better understanding of the related mechanism, and discuss how they may be utilized in future investigations.

Abstract  The soraphens are natural products that exhibit a molecular structure different from what would have been expected by following its polyketidal assembly line. The most significant differences are the presence of a hemiketal instead of a trisubstituted double bond and a double bond at C9 and C10 where a saturated carbon chain was expected. We were interested in the biological activity of the soraphens with architectures as described by the polyketide synthase since we hypothesized that these modifications reflect the evolutionary optimization of the soraphens. Herein we describe four additional derivatives of the so-called paleo-soraphens and their biological profiling to provide a picture of the hypothetical evolutionary optimization of this family of natural products. The syntheses required a unified and convergent strategy and their biological profiling was performed with the aid of impedance measurements. The results of these biological experiments are consistent with the proposed evolutionary optimization of the soraphens.

Abstract  CONTEXT: Viola tianshanica Maxim. (Violaceae) is a perennial herb distributed in Central Asia, especially in the Xinjiang Uygur Autonomous Region (XUAR) of China. Preliminary study showed that the ethanol extract of the herb exhibited the anti-complement activity against the classical pathway, but the active components responsible for this capacity remain unknown and are yet to be studied.

OBJECTIVE: The objective of this study was the isolation and identification of the anti-complement constituents of V. tianshanica.

MATERIALS AND METHODS: The ethyl acetate and n-butanol fractions from the ethanol extract of V. tianshanica were purified. The structures of the isolates were identified by spectroscopic methods, and comparing their spectral data with those reported in the literature. All the isolates (0.02-2.50 mg/mL) were evaluated for their anti-complement activity against the classical and alternative pathways.

RESULTS: Twenty-one phenolic compounds including 15 flavonol O-glycosides (1-15), one flavone 6,8-di-C-glycoside (16), one flavone aglycone (17), and four phenolic acid derivatives (18-21) were isolated and identified. Bioassay showed that 11 compounds inhibited the classical pathway and the alternative pathway with CH50 and AP50 values of 0.113-1.210 mM and 0.120-1.579 mM, respectively. Preliminary mechanistic study using complement-depleted sera demonstrated that 1 acted on C1q, C2, C4, and C9 components, 16 on C1q, C4, and C5, and 21 on C1q, C3, C4, and C9.

CONCLUSION: All isolated compounds except 1 and 10 were reported for the first time from V. tianshanica. Compound 16 is the first flavone C-glycoside isolated from the herb. Flavonol O-glycosides and phenolic acids contributed the anti-complement activity of the herb.

Abstract  Efficient photocatalytic oxygenation of toluene occurs under visible light irradiation of 9-mesityl-10-methylacridinium (Acr(+)-Mes) in oxygen-saturated acetonitrile containing toluene and aqueous hydrochloric acid with a xenon lamp for 15 h. The oxygenated products, benzoic acid (70 %) and benzaldehyde (30 %), were formed after the photoirradiation. The photocatalytic reaction is initiated by intramolecular photoinduced electron transfer from the mesitylene moiety to the singlet excited state of the Acr(+) moiety of Acr(+)-Mes, which affords the electron-transfer state, Acr(aEuro cent)-Mes(aEuro cent+). The Mes(aEuro cent+) moiety can oxidize chloride ion (Cl-) by electron transfer to produce chlorine radical (Cl-aEuro cent), whereas the Acr(aEuro cent) moiety can reduce O-2 to O (2) (aEuro cent a') . The Cl-aEuro cent radical produced abstracts a hydrogen from toluene to afford benzyl radical in competition with the bimolecular radical coupling of Cl-aEuro cent. The benzyl radical reacts with O-2 rapidly to afford the peroxyl radical, leading to the oxygenated product, benzaldehyde. Benzaldehyde is readily further photooxygenated to yield benzoic acid with Acr(aEuro cent)-Mes(aEuro cent+). In the case of an aromatic compound with electron-donating substituents, 1,3,5-trimethoxybenzene, photocatalytic chlorination occurred efficiently under the same photoirradiation conditions to yield a monochloro-substituted compound, 2,4,6-trimethoxychlorobenzene.

Abstract  Dinuclear square planar palladium(ii) complexes, [{Pd(ii)La}2(baet)] (La(-) = β-diketonato and baet(2-) = 1,2-diacetyl-1,2-bis(3-methylbutanoyl)ethanato), were prepared and used as chiral dopants to induce chiral nematic phases. The following β-diketones were used as LaH: pentane-2,4-dione (acacH), dibenzoylmethane (dbmH), di-4-nonyloxybenzoylmethane (C9-dbmH) and 3-[4'-(4''-(octyloxy)phenylazo)phenyl]-2,4-dione (C8-azoacacH). When the enantiomers were doped in a nematic liquid crystal, they induced a chiral nematic phase with a helical twisting power (HTP) of 5-50 μm(-1). In particular, the sample doped with [{Pd(ii)(C8-azoacac)}2(baet)] exhibited a reversible change of the circular dichroism spectrum under alternate irradiation at 350 nm and 460 nm. It implied that the HTP changed reversibly in response to the cis-trans isomerization of the coordinated C8-azoacac ligand.

Abstract  Computational studies carried out at density functional theory levels are able to provide reliable chemical information about medium sized compounds as anthocyanins and their aglycons (anthocyanidins). Thus, they indicate that the most stable tautomers in aqueous solution for the main anthocyanidins (excluding pelargonidin) are deprotonated at C4' in the neutral forms, while deprotonations at C5 and C4' characterize the most stable anions in solution. QTAIM electron density analysis (overviewed in brief in the methods section) shows that Lewis structures usually employed give rise to unreliable atomic charges. Thus: (1) The positive charge spreads throughout the whole cation, and is not localized on any specific atom or set of atoms; (2) Neutral forms can be described as enolates where the negative charge is counterbalanced in a different way to that indicated by the typical resonance forms; and (3) The negative charge of anions is mainly spread among three regions of the molecule: the two deprotonated sites and the C9-O1-C2 area. The analysis of a group of complexes formed by a model of cyanin with four common metalic cations (Mg(II), Al(II), Cu(II), Zn(II)), shows: (1) the preference for tetracoordination in Zn(II) and Cu(II) complexes, (2) higher affinity for Cu(II) than for the other metals here studied, and (3) the distortion of electron density in the cyanin ligand affects the whole molecule. This distortion can be described as a continuous polarization where, even, in some cases, the atomic electron populations of those atoms of the ligand that are more directly involved in bonding to the metal increase.