One-Pot Divergent Synthesis of a 13-Ring Triquinone and its Facile Conversion to a [4.4.4]Tridecastarphene.

Acenes are notable for their optoelectronic properties. Starphenes are structurally related molecules possessing three acene arms that radiate linearly from a central benzene ring (i.e., linearly annellated triphenylenes). Large starphenes have been prepared using convergent syntheses involving transition metal catalyzed cyclotrimerizations of either preformed acenes or arynes. Here, we report a one-pot divergent synthesis of a 13-ring triquinone that readily converts to a [4.4.4]tridecastarphene derivative. The one-pot procedure involves the sequential reactions of three 1,4-anthraquinones with o--quinodimethane derivatives that are generated sequentially from a trisulfone precursor. The resulting [4.4.4]tridecastarphene derivative bearing p-(t-butyl)phenyl substituents was characterized by 1H NMR, 13C NMR and UV-vis spectroscopies, as well as mass spectrometry, cyclic voltammetry, differential pulse voltammetry and DFT calculations. Theoretical and experimental studies reveal a relatively high-lying HOMO orbital (about -4.70 to -4.86 eV) and a relatively small HOMO-LUMO gap (2.1 eV), suggesting utility as a p-type organic semiconductor. Our [4.4.4]tridecastarphene photooxidizes in CH2Cl2 solution exposed to ambient light and air with a half-life of 150 minutes at room temperature, but shows no sign of degradation after 12 months in the solid-state. Our [4.4.4]tridecastarphene shows excellent solubility in various organic solvents including dichloromethane, chloroform and toluene, potentially enabling printed electronic applications.

Kinetically stabilized 1,3-diarylisobenzofurans and the possibility of preparing large, persistent isoacenofurans with unusually small HOMO-LUMO gaps.

DFT calculations demonstrate that an isoacenofuran of any size possesses a smaller HOMO-LUMO gap than the corresponding acene bearing an isoelectronic π-system (i.e., the same total number of rings). Isoacenofurans show limited stability due in part to the highly reactive 1,3-carbons of the furan ring. Both 1,3-dimesitylisobenzofuran and 1,3-di(2',4',6'-triethylphenyl)isobenzofuran, each bearing sterically congesting ortho-alkyl groups on their phenyl substituents, have been synthesized and shown to adopt non-planar conformations with the ortho-alkyl groups located above and below the most reactive 1,3-carbons of the furan ring. These bulky substituents provide a strong measure of kinetic stabilization. Thus, 1,3-dimesitylisobenzofuran and 1,3-di(2',4',6'-triethylphenyl)isobenzofuran are significantly less reactive than 1,3-diphenylisobenzofuran toward the strong dienophiles DMAD and acrylonitrile. The insights gained here suggest that the synthesis of large, persistent, kinetically stabilized isoacenofurans with unusually small HOMO-LUMO gaps is achievable. As such, these molecules deserve increased attention as potential p-type organic semiconductors.

Effects of LRRK2 Inhibitors in Nonhuman Primates.

Toxicology studies in nonhuman primates were conducted to evaluate selective, brain penetrant inhibitors of LRRK2. GNE 7915 was limited to 7-day administration in cynomolgus monkeys at 65 mg/kg/day or limited to 14 days in rhesus at 22.5 mg/kg b.i.d. due to physical signs. Compound 25 demonstrated acceptable tolerability at 50 and 225 mg/kg b.i.d. for 7 days in rhesus monkeys. MK-1468 was tolerated during 7-day administration at 100, 200 or 800 mg/kg/day or for 30-day administration at 30, 100, or 500 mg/kg b.i.d. in rhesus monkeys. The lungs revealed hypertrophy of type 2 pneumocytes, with accumulation of intra-alveolar macrophages. Transmission electron microscopy confirmed increased lamellar structures within hypertrophic type 2 pneumocytes. Hypertrophy and hyperplasia of type 2 pneumocytes with accumulation of intra-alveolar macrophages admixed with neutrophils were prominent at peripheral lungs of animals receiving compound 25 or MK-1468. Affected type 2 pneumocytes were immuno-positive for pro-surfactant C, but negative for CD11c, a marker for intra-alveolar macrophages. Accumulation of collagen within alveolar walls, confirmed by histochemical trichrome stain, accompanied changes described for compound 25 and MK-1468. Following a 12-week treatment-free interval, animals previously receiving MK-1468 for 30 days exhibited remodeling of alveolar structure and interstitial components that did not demonstrate reversibility.

Early-Onset albuminuria and Associated Renal Pathology in Leucine-Rich Repeat Kinase 2 Knockout Rats.

Activating mutations of the leucine-rich repeat kinase 2 (LRRK2) gene are associated with Parkinson disease (PD), prompting development of LRRK2 inhibitors as potential treatment for PD. However, kidney safety concerns have surfaced from LRRK2 knockout (KO) mice and rats and from repeat-dose studies in rodents administered LRRK2 inhibitors. To support drug development of this therapeutic target, we conducted a study of 26 weeks' duration in 2-month-old wild-type and LRRK2 KO Long-Evans Hooded rats to systematically examine the performance of urinary safety biomarkers and to characterize the nature of the morphological changes in the kidneys by light microscopy and by ultrastructural evaluation. Our data reveal the time course of early-onset albuminuria at 3 and 4 months in LRRK2 KO female and male rats, respectively. The increases in urine albumin were not accompanied by concurrent increases in serum creatinine, blood urea nitrogen, or renal safety biomarkers such as kidney injury molecule 1 or clusterin, although morphological alterations in both glomerular and tubular structure were identified by light and transmission electron microscopy at 8 months of age. Diet optimization with controlled food intake attenuated the progression of albuminuria and associated renal changes.

Contaminated Stream Water as Source for Escherichia coli O157 Illness in Children.

In May 2016, an outbreak of Shiga toxin-producing Escherichia coli O157 infections occurred among children who had played in a stream flowing through a park. Analysis of E. coli isolates from the patients, stream water, and deer and coyote scat showed that feces from deer were the most likely source of contamination.

STP position paper: interpreting the significance of increased alveolar macrophages in rodents following inhalation of pharmaceutical materials.

The Scientific and Regulatory Policy Committee of the Society of Toxicologic Pathology (STP) appointed a working group to address risk assessment for increases in alveolar macrophages following inhalation of pharmaceutical materials. This position paper provides recommendations for inhalation study-specific terminology and interpretation based on literature and information from marketed inhaled drugs. Based on a weight-of-the-evidence approach, and with appropriate consideration of the physical and pharmacological characteristics of the compound, uncomplicated increases in the size or number of alveolar macrophages in nonclinical species are interpreted as nonadverse.

Syntheses, characterizations and reactions of acene-2,3-dicarbaldehydes.

Here, we report improved syntheses, detailed characterizations and reactions of a series of acene-2,3-dicarbaldehydes including tetracene-2,3-dicarbaldehyde. DFT calculations corroborate and complement the experimental results. Tetracene-2,3-dicarbaldehyde and the benchmark organic semiconductor pentacene have isoelectronic π-systems and similar HOMO-LUMO gaps. Tetracene-2,3-dicarbaldehyde is soluble in a host of organic solvents (e.g., DMF, toluene, THF, chloroform, dichloromethane) and shows excellent photooxidative resistance in solution phases exposed to light and air. Further, it is readily sublimed from the solid-state without decomposition, and can be functionalized using different chemistries. We have demonstrated the utility of acene-2,3-dicarbaldehydes as reactants in the syntheses of novel α,α'-diaryl-2,3-acenedimethanols and acenotropones via Grignard reactions and double-aldol condensation reactions, respectively. The acenotropones were further reacted with concentrated H2SO4 to generate hydroxyacenotropylium ions that exhibit long wavelength absorption in the visible and near-IR regions. The optical gap measured for hydroxyanthracenotropylium ion is 1.3 eV. The results gained here implicate acene-2,3-dicarbaldehydes as potential high-value organic semiconductors and as precursors to a host of interesting molecules and materials.

Probing intramolecular CH-π interactions in o-quinodimethane adducts of [60]fullerene using variable temperature NMR.

Several o-quinodimethane adducts of [60]fullerene were synthesized and their intramolecular aryl CH-fullerene π interactions were studied using variable temperature-NMR (VT-NMR). Evaluation of the rate constants associated with the first-order transition states for cyclohexene boat-to-boat inversions enables quantification of ΔG(‡) values for each inversion. A comparison between two constitutional isomers, only one of which is capable of intramolecular CH-π interactions, provides a lower limit of 0.95 kcal/mol for each aryl CH-fullerene π interaction.

An improved synthesis of pentacene: rapid access to a benchmark organic semiconductor.

Pentacene is an organic semiconductor used in a variety of thin-film organic electronic devices. Although at least six separate syntheses of pentacene are known (two from dihydropentacenes, two from 6,13-pentacenedione and two from 6,13-dihydro-6,13-dihydroxypentacene), none is ideal and several utilize elevated temperatures that may facilitate the oxidation of pentacene as it is produced. Here, we present a fast (-2 min of reaction time), simple, high-yielding (≥ 90%), low temperature synthesis of pentacene from readily available 6,13-dihydro-6,13-dihydroxypentacene. Further, we discuss the mechanism of this highly efficient reaction. With this improved synthesis, researchers gain rapid, affordable access to high purity pentacene in excellent yield and without the need for a time consuming sublimation.

Design, synthesis, and characterization of a persistent nonacene derivative.

A significant technical barrier (i.e., facile oxidative degradation) that has prevented the preparation of large acenes has now been breached. Using a combination of experimentally and theoretically derived substituent effects, the design, synthesis, isolation, and characterization of the first persistent nonacene derivative is described. The molecular design strategy includes placement of arylthio (or alkylthio) substituents on the terminal rings of the nonacene skeleton, effectively converting an open-shell singlet diradical into a closed-shell system. These powerful substituent effects appear to be suitable for the synthesis of other persistent, soluble, large acene derivatives required for advanced thin-film organic semiconductor applications.

Exploiting substituent effects for the synthesis of a photooxidatively resistant heptacene derivative.

Substituent effects have been exploited to produce an unusually persistent heptacene derivative. In total, four new heptacene derivatives with varying levels of photooxidative resistance (1 < 2 < 3 < 4) have been synthesized. A combination of p-(t-butyl)thiophenyl substituents at positions 7 and 16 (i.e., arylthio substituents attached to the most reactive ring) and o-dimethylphenyl substituents at positions 5, 9, 14, and 18 (i.e., steric resistance on neighboring rings) make heptacene derivative 4 especially resistant to photooxidation. It persists for weeks as a solid, for 1-2 days in solution if shielded from light, and for several hours in solution when directly exposed to both light and air. Heptacene derivative 4 has been fully characterized. It possesses a small HOMO-LUMO gap of 1.37 eV.

Field-assisted nanopatterning of metals, metal oxides and metal salts.

The tip-based nanofabrication method called field-assisted nanopatterning or FAN has now been extended to the transfer of metals, metal oxides and metal salts onto various receiving substrates including highly ordered pyrolytic graphite, passivated gold and indium-tin oxide. Standard atomic force microscope tips were first dip-coated using suspensions of inorganic compounds in solvent. The films prepared in this manner were non-uniform and contained inorganic nanoparticles. Tip-based nanopatterning on chosen substrates was conducted under high electric field conditions. The same tip was used for both nanofabrication and imaging. Arbitrary patterns were formed with dimensions that ranged from tens of microns to sub-20 nm and were controlled by tuning the tip bias during fabrication. Most tip-based nanopatterning techniques are limited in terms of the type of species that can be deposited and the type of substrates onto which the deposition occurs. With the successful deposition of inorganic species reported here, FAN is demonstrated to be a truly versatile tip-based nanofabrication technique that is useful for the deposition of a wide variety of both organic and inorganic species including small molecules, large molecules and polymers.

2,3-Bis(bromo-meth-yl)-1,4-diphenyl-benzene.

In the title compound, C(20)H(16)Br(2), the terminal phenyl groups are twisted away from the central ring by approximately 55 and -125° (average of four dihedral angles each), respectively. The crystal structure is stabilized by a combination of inter-molecular and intra-molecular inter-actions including inter-molecular π-π stacking inter-actions [C atoms of closest contact = 3.423 (5) Å].

1,2-Dimethyl-4,5-diphenyl-benzene determined on a Bruker SMART X2S benchtop crystallographic system.

The title compound, C(20)H(18), has two crystallographically independent mol-ecules in the asymmetric unit. The phenyl substituents of mol-ecule A are twisted away from the plane defined by the central benzene ring by 131.8 (2) and -52.7 (3)°. The phenyl substituents of mol-ecule B are twisted by -133.3 (2) and 50.9 (3)°. Each mol-ecule is stabilized by a pair of intra-molecular C(aryl, sp(2))-H⋯π inter-actions, as well as by several inter-molecular C(methyl, sp(3))-H⋯π inter-actions.

2,5-Dichloro-thio-phene 1,1-dioxide.

The complete mol-ecule of the title compound, C(4)H(2)Cl(2)O(2)S, is generated by crystallographic twofold symmetry, with the S atom lying on the rotation axis. In the crystal, the molecules are linked by C-H⋯O hydrogen bonds..

Hydrogenation of single-wall carbon nanotubes using polyamine reagents: combined experimental and theoretical study.

We combine experimental observations with ab initio calculations to study the reversible hydrogenation of single-wall carbon nanotubes using high boiling polyamines as hydrogenation reagents. Our calculations characterize the nature of the adsorption bond and identify preferential adsorption geometries at different coverages. We find the barrier for sigmatropic rearrangement of chemisorbed hydrogen atoms to be approximately 1 eV, thus facilitating surface diffusion and formation of energetically favored, axially aligned adsorbate chains. Chemisorbed hydrogen modifies the structure and stability of nanotubes significantly and increases the inter-tube distance, thus explaining the improved dispersability in solvents like methanol, ethanol, chloroform, and benzene.

Substituent effects in pentacenes: gaining control over HOMO-LUMO gaps and photooxidative resistances.

A combined experimental and computational study of a series of substituted pentacenes including halogenated, phenylated, silylethynylated and thiolated derivatives is presented. Experimental studies include the synthesis and characterization of six new and six known pentacene derivatives and a kinetic study of each derivative under identical photooxidative conditions. Structures, HOMO-LUMO energies and associated gaps were calculated at the B3LYP/6-311+G**//PM3 level while optical and electrochemical HOMO-LUMO gaps were measured experimentally. The combined results provide for the first time a quantitative assessment of HOMO-LUMO gaps and photooxidative resistances for a large series of pentacene derivatives as a function of substituents. The persistence of each pentacene derivative is impacted by a combination of steric resistance and electronic effects as well as the positional location of each substituent. Silylethynyl-substituted pentacenes like TIPS-pentacene possess small HOMO-LUMO gaps but are not the longest lived species under photooxidative conditions, contrary to popular perception. A pentacene derivative with both chlorine substituents in the 2,3,9,10 positions and o-alkylphenyl substituents in the 6,13 positions is longer lived than TIPS-pentacene. Of all the derivatives studied, alkylthio- and arylthio-substituted pentacenes are most resistant to photooxidation, possess relatively small HOMO-LUMO gaps and are highly soluble in a variety of organic solvents. These results have broad implications for the field of organic molecular electronics where OFET, OLED, and other applications can benefit from highly persistent, solution processable pentacene derivatives.

Temperature-induced physiological stress and reproductive characteristics of the migratory seahorse Hippocampus erectus during a thermal stress simulation.

Inshore-offshore migration occurs frequently in seahorse species, either because of prey opportunities or because they are driven by reproduction, and variations in water temperature may dramatically change migratory seahorse behavior and physiology. The present study investigated the behavioral and physiological responses of the lined seahorse Hippocampus erectus under thermal stress and evaluated the potential effects of different temperatures on its reproduction. The results showed that the thermal tolerance of the seahorses was time dependent. Acute thermal stress (30°C, 2-10 h) increased the basal metabolic rate (breathing rate) and the expression of stress response genes (Hsp genes) significantly and further stimulated seahorse appetite. Chronic thermal treatment (30°C, 4 weeks) led to a persistently higher basal metabolic rate, higher stress response gene expression and higher mortality rates, indicating that the seahorses could not acclimate to chronic thermal stress and might experience massive mortality rates due to excessively high basal metabolic rates and stress damage. Additionally, no significant negative effects on gonad development or reproductive endocrine regulation genes were observed in response to chronic thermal stress, suggesting that seahorse reproductive behavior could adapt to higher-temperature conditions during migration and within seahorse breeding grounds. In conclusion, this simulation experiment indicates that temperature variations during inshore-offshore migration have no effect on reproduction, but promote significantly high basal metabolic rates and stress responses. Therefore, we suggest that the observed high tolerance of seahorse reproduction is in line with the inshore-offshore reproductive migration pattern of lined seahorses.This article has an associated First Person interview with the first author of the paper.

Thermal, sonochemical, and mechanical behaviors of single crystal [60]fullerene nanotubes.

Although related to conventional carbon nanotubes in both shape and construction, fullerene nanowhiskers and fullerene nanotubes have received far less attention. A modified liquid-liquid interfacial precipitation technique is described to produce relatively uniform batches of [60]fullerene nanotubes in high yield. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) reveal that the tubes possess approximately 100-nm inside diameters and 300-nm outside diameters. The [60]fullerene nanotubes degrade slowly at 180 degrees C, eventually collapsing into micron scale [60]fullerene discs and rods, as revealed by optical microscopy and AFM. Ultrasonic cavitation chops [60]fullerene nanotubes into smaller segments within seconds. Longer ultrasonic bathing leads to considerable structural damage in which the sidewalls rupture. Mechanical stress tests using an AFM microscope tip effectively dent and break [60]fullerene nanowhiskers, revealing a hollow interior.

Recombinant rat and mouse growth hormones: risk assessment of carcinogenic potential in 2-year bioassays in rats and mice.

Recombinant rat growth hormone (rrGH) and recombinant mouse growth hormone (rmGH) were developed to evaluate the potential carcinogenicity of each biologically active growth hormone (GH) as assessed in the respective species. Biological activities of rrGH and rmGH were demonstrated by showing an increase in body weight gain and serum levels of insulin-like growth factor-1 (IGF-1) in hypophysectomized rats receiving daily sc injections for 6 days. With the exception of pharmacologically mediated weight gain, rrGH and rmGH had no adverse effects in 5-week oral toxicity studies and no production of anti-recombinant GH antibodies. The high doses selected for the carcinogenicity studies provided systemic exposures of GH up to approximately 10-fold over basal levels. In the 105-week mouse carcinogenicity study, daily sc injections of rmGH at 0.1, 0.2, or 0.5 mg/kg/day were well tolerated and had no effects on survival or incidence of tumors. In the 106-week rat carcinogenicity study, daily sc injections of rrGH at 0.2, 0.4, or 0.8 mg/kg/day had a favorable effect on longevity in female rats administered 0.4 or 0.8 mg/kg/day, an increased weight gain in females and males, and no increase in the incidence of tumors. The absence of carcinogenic effects of recombinant GH administered daily for 2 years to rodents was consistent with publications of clinical experience, indicating a lack of convincing evidence for an increased risk of cancer in children receiving human recombinant GH replacement therapy.