Redox- and Charge-State Dependent Trends in 5, 6, and 7-Membered Boron Heterocycles: A Neutral Ligand Coordination Chemistry Approach to Boracyclic Cations, Anions, and Radicals.

ConspectusBoron heterocycles represent an important subset of heteroatom-incorporated rings, attracting attention from organic, inorganic, and materials chemists. The empty p orbital at the boron center makes them stand out as quintessential Lewis acidic molecules, also serving as a means to modulate electronic structure and photophysical properties in a facile manner. As boracycles are ripe for extensive functionalization, they are used in catalysis, chemical biology, materials science, and continue to be explored as chemical synthons for conjugated materials and reagents.

Synthesis and Ring-Opening Metathesis Polymerization of a Strained -Silacycloheptene and Single-Molecule Mechanics of Its Polymer.

The - and -isomers of a silacycloheptene were selectively synthesized by the alkylation of a silyl dianion, a novel approach to strained cycloalkenes. The -silacycloheptene (-SiCH) was significantly more strained than the isomer, as predicted by quantum chemical calculations and confirmed by crystallographic signatures of a twisted alkene. Each isomer exhibited distinct reactivity toward ring-opening metathesis polymerization (ROMP), where only -SiCH afforded high-molar-mass polymer under enthalpy-driven ROMP.

Approaching Dianionic Tetraoxadiborecine Macrocycles: 10-Membered Bora-Crown Ethers Incorporating Borafluorenate Units.

The addition of non-benzenoid quinones, acenapthenequinone or aceanthrenequinone, to the 9-carbene-9-borafluorene monoanion (1) affords the first examples of dianionic 10-membered bora-crown ethers (2-5), which are characterized by multi-nuclear NMR spectroscopy ( H, C, B), X-ray crystallography, elemental analysis, and UV/Vis spectroscopy. These tetraoxadiborecines have distinct absorption profiles based on the positioning of the alkali metal cations. When compound 4, which has a vacant C B O cavity, is reacted with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, a color change from purple to orange serves as a visual indicator of metal binding to the central ring, whereby the Na ion coordinates to four oxygen atoms.

Systematic Electronic and Structural Studies of 9-Carbene-9-Borafluorene Monoanions and Transformations into Luminescent Boron Spirocycles.

The impact of the exact spatial arrangement of the alkali metal on the electronic properties of 9-carbene-9-borafluorene monoanions is assessed, and a series of [K][9-CAAC-9-borafluorene] complexes (-) have been isolated (CAAC = cyclic(alkyl)(amino) carbene, (2,6-diisopropylphenyl)-4,4-diethyl-2,2-dimethyl-pyrrolidin-5-ylidene). Compound , which contains [B]-K(THF) interactions, is compared to charge-separated -, which were prepared by capturing the potassium cations with 18-crown-6, 2.2.

Activation of Carbon Dioxide by 9-Carbene-9-borafluorene Monoanion: Carbon Monoxide Releasing Transformation of Trioxaborinanone to Luminescent Dioxaborinanone.

The first structurally characterized example of a trioxaborinanone () is produced by the reaction of a 9-carbene-9-borafluorene monoanion and carbon dioxide. When compound is heated or irradiated with UV light, carbon monoxide (CO) is released, and a luminescent dioxaborinanone () is formed. Notably, carbon monoxide releasing molecules (CORMs) are of interest for their ability to deliver a specific amount of CO.

The clinical impact of lumbar epidural steroid injections prior to spine surgery for lumbar spinal stenosis.

Introduction: Lumbar spinal stenosis is a common finding in the adult population. Lumbar Epidural Steroid Injections (ESIs) are often used in management of this condition, with conflicting evidence regarding their efficacy. Previous research has suggested a negative impact of ESIs on the postoperative outcomes when ESIs are administered preoperatively prior to spine surgery in this population.

Isolation of Stable Borepin Radicals and Anions.

Borepin, a 7-membered boron-containing heterocycle, has become an emerging molecular platform for the development of new materials and optoelectronics. While electron-deficient borepins are well-established, reduced electron-rich species have remained elusive. Herein we report the first isolable, crystalline borepin radical (2 a, 2 b) and anion (3 a, 3 b) complexes, which have been synthesized by potassium graphite (KC ) reduction of cyclic(alkyl)(amino) carbene-dibenzo[b,d]borepin precursors.

Air-Stable Thermoluminescent Carbodicarbene-Borafluorenium Ions.

Borenium ions, originally synthesized as fundamentally important laboratory curiosities, have attracted significant attention due to their applications in catalysis and frustrated Lewis pair chemistry. However, investigations of the materials properties of these types of compounds are exceptionally rare. Herein, we report the synthesis, molecular structures, and optical properties of a new class of air-stable borenium ions, stabilized by the strongly donating carbodicarbene (CDC) ligand (, , ).

Reactions of 9-Carbene-9-Borafluorene Monoanion and Selenium: Synthesis of Boryl-Substituted Selenides and Diselenides.

Reactions of 9-carbene-9-borafluorene monoanion () with elemental selenium and selenium-containing reagents are reported. When compound is reacted with grey selenium in THF, various boryl-substituted selenides and diselenides are produced (), including molecules resulting from migration of the carbene ligand Dipp group (Dipp = 2,6-diisopropylphenyl). However, when a similar reaction between and grey selenium is performed in toluene in the presence of 18-crown-6, boryl-substituted selenide is obtained as the sole boron-containing product.

Stabilization of the Elusive 9-Carbene-9-Borafluorene Monoanion.

Two-electron reduction of carbene-supported 9-bromo-9-borafluorenes with excess KC , Na, or Li-naphthalenide affords six N-heterocyclic carbene (NHC)- or cyclic(alkyl)(amino) carbene (CAAC)-stabilized borafluorene anions (3-8)-the first isolated and structurally authenticated examples of the elusive 9-carbene-9-borafluorene monoanion. The electronic structure, bonding, and aromaticity of the boracyclic anions were comprehensively investigated via computational studies. Compounds 5 and 8 react with metal halides via salt elimination to give new B-E (E=Au, Se, Ge)-containing materials (9-12).

The Artificial Sweetener, Erythritol, Has Insecticidal Properties Against Pear Psylla (Hemiptera: Psyllidae).

Erythritol is a dietary sweetener that is used for low-calorie or diabetic diets. Although safe for human consumption, erythritol is lethal to certain Dipteran pests, but insecticidal effects of erythritol on phloem-feeding insects have yet to be examined. Our goal was to determine whether erythritol has insecticidal activity against pear psylla, Cacopsylla pyricola (Foerster) (Hemiptera: Psyllidae).

Need for recovery in relation to effort from work and health in four occupations.

Objective: To examine three levels of need for recovery (NFR) after work in relation to effort from work demands, demand compensatory strategies, effort-moderating or -reversing resources, and health including health behaviors. A further purpose was to examine occupational characteristics determining NFR.

Methods: 5000 engineers, carpenters, nurses, and home care nurses were invited to participate.

Leaf temperatures mediate alpine plant communities' response to a simulated extended summer.

We use a quantitative model of photosynthesis to explore leaf-level limitations to plant growth in an alpine tundra ecosystem that is expected to have longer, warmer, and drier growing seasons. The model is parameterized with abiotic and leaf trait data that is characteristic of two dominant plant communities in the alpine tundra and specifically at the Niwot Ridge Long Term Ecological Research Site: the dry and wet meadows. Model results produce realistic estimates of photosynthesis, nitrogen-use efficiency, water-use efficiency, and other gas exchange processes in the alpine tundra.

Implicit and Explicit Attention to Pictures and Words: An fMRI-Study of Concurrent Emotional Stimulus Processing.

The present study utilized functional magnetic resonance imaging (fMRI) to examine the neural processing of concurrently presented emotional stimuli under varying explicit and implicit attention demands. Specifically, in separate trials, participants indicated the category of either pictures or words. The words were placed over the center of the pictures and the picture-word compound-stimuli were presented for 1500 ms in a rapid event-related design.

Structural study by solid-state (71)Ga NMR of thin film transistor precursors.

Solid-state (71)Ga NMR was used to investigate the structures of several heterometallic Group 13 hydroxo-aquo clusters, [Ga13-xInx (μ3-OH)6(μ2-OH)18(H2O)24](NO3)15 which are envisioned for thin film transistors. The characterization of these clusters in the solid state provides additional information in understanding the synthesis, structure and speciation of these precursors for high-quality, ultrasmooth thin films. Yet important structural information regarding these clusters - including the exact composition, isomeric structure, and coordination environments - were unknown prior to this precise NMR spectroscopy study.

Small-bowel dislocation during long-term MRI observation - insights in intestinal physiology.

Magnetic resonance imaging (MRI) of the abdomen is a widely established imaging modality in the diagnostic workup of patients suffering from abdominal disorders. Small-bowel motility analyses using MRI have recently been introduced to provide functional information about the intestine not provided by morphological analyses. This is of clinical importance as motility disorders correlate with inflammation.

Differentiation between active and chronic Crohn's disease using MRI small-bowel motility examinations - initial experience.

Aim: To evaluate the influence of locally active Crohn's disease on systemic small-bowel motility in patients with chronic Crohn's disease compared to healthy individuals.

Material And Methods: Fifteen healthy individuals (11 men, four women; mean age 37 years) and 20 patients with histopathologically proven active (n = 15; 10 women, 5 men; mean age 45 years) or chronic (n = 5; four women, one man; mean age 48 years) Crohn's disease were included in this institutional review board-approved, retrospective study. Magnetic resonance imaging (MRI; 1.

Aluminum nanoparticles capped by polymerization of alkyl-substituted epoxides: ratio-dependent stability and particle size.

We report here on the polymerization of epoxide monomers on incipient aluminum nanoparticle cores and the effects of changing the epoxide-capping precursor and the metallic monomer ratio on the resultant stability and particle size of passivated and capped aluminum nanoparticles. When altering the ratio of aluminum to cap monomer precursor, nanoparticles capped with epoxydodecane, epoxyhexane, and epoxyisobutane show a clear decreasing trend in stability with decreasing alkane substituent length. The nanoparticle core size was unaffected by cap ratio or composition.

Synthesis of the hydroxide cluster [Al13(μ3-OH)6(μ-OH)18(H2O)24]15+ from an aqueous solution.

A scalable synthesis of the "flat" tridecameric inorganic cluster [Al(13)(μ(3)-OH)(6)(μ-OH)(18)(H(2)O)(24)](15+) has been realized by treating an aqueous aluminum nitrate solution with a zinc-metal powder at room temperature. Single crystals and polycrystalline samples are readily obtained in yields exceeding 55% relative to the starting reagent Al(NO(3))(3). Products have been characterized by X-ray diffraction and solid-state (27)Al MAS and MQMAS NMR.

High-resolution diffusion tensor imaging of prostate cancer using a reduced FOV technique.

Objective: Diffusion tensor imaging (DTI) offers the promise of improved tumor localization in prostate cancer but the technique suffers from susceptibility-induced artifacts that limit the achievable resolution. The present work employs a reduced field-of-view technique that enables high-resolution DTI of the prostate at 3T. Feasibility of the approach is demonstrated in a clinical study including 26 patients and 14 controls.

Clinical experience in timed arterial compression contrast-enhanced magnetic resonance angiography of the hand.

Purpose: A retrospective analysis of the diagnostic performance of the timed arterial compression (TAC) technique, which allows freezing of the contrast bolus during first-pass contrast-enhanced (CE) magnetic resonance angiography (MRA) to diagnose vascular pathologies in the hand.

Material And Methods: A total of 14 consecutive CE-MRAs of the hand were acquired by using the TAC technique. By inflating a blood pressure cuff up to 200 mm Hg triggered to the arterial contrast filling of the hand, prolonged measurement times up to 144 seconds, with a spatial resolution of 0.

Improved vessel delineation in keyhole time-resolved contrast-enhanced MR angiography using a gadolinium doped flush.

Purpose: To prospectively assess the influence of a gadolinium doped saline flush compared with a pure saline flush on the image quality of the supra-aortic vessels using time-resolved contrast-enhanced MR angiography (4D CE-MRA) in a randomized double blind clinical trial.

Materials And Methods: Twenty-two patients scheduled for contrast-enhanced craniocerebral MRI underwent a supplemental 4D CE-MRA covering the carotids to the superior sinus consisting of 30 dynamics of a T1-weighted 3D gradient-echo sequence (FFE) in sagittal direction. The temporal resolution of 1.

Self-absorption correction for solid-state photoluminescence quantum yields obtained from integrating sphere measurements.

A new method is presented for analyzing the effects of self-absorption on photoluminescence integrating sphere quantum yield measurements. Both the observed quantum yield and luminescence spectrum are used to determine the self-absorption probability, taking into account both the initial emission and subsequent absorption and reemission processes. The analysis is experimentally validated using the model system of the laser dye perylene red dispersed in a polymer film.