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Protective groups that can be selectively removed under mild conditions are an essential aspect of carbohydrate chemistry. Groups that can be selectively removed by visible light are particularly attractive because carbohydrates are transparent to visible light. Here, different BODIPY protecting groups were explored for their utility during glycan synthesis. A BODIPY group bearing a boron difluoride unit is stable during glycosylations but can be cleaved with green light as illustrated by the assembly of a trisaccharide.

An abdominal aortic aneurysm (AAA) is a pathological widening of the aortic wall characterized by loss of smooth muscle cells (SMCs), extracellular matrix degradation, and local inflammation. This condition is often asymptomatic until rupture occurs, leading to high morbidity and mortality rates. Diagnosis is often accidental, and for now, the only available treatment option remains surgical intervention. Circular RNAs (circRNAs) are RNA loops that originated from backsplicing, which have received increasing attention as a novel class of functional non-coding RNAs contributing to cardiovascular physiology and disease. Their high structural stability, combined with a remarkable enrichment in body fluids, make circRNAs promising disease biomarkers. We aimed to investigate the contribution of circRNAs to AAA pathogenesis and their potential application as biomarkers for AAA diagnosis. Combined circRNA array and quantitative real-time PCR analysis revealed the presence of differentially expressed circular transcripts stemming from AAA-relevant geneloci. Among these, the circRNA to the Ataxia-telangiectasia mutated gene (cATM) was upregulated in human AAA tissue specimens, in AAA patient-derived SMCs, and serum samples collected from aneurysm patients. In control primary aortic SMCs, cATMincreased upon angiotensin II stimulation, while its silencing triggered apoptosis. Furthermore, doxorubicin could induce cATM expression, supporting a link with acute stress response in SMCs. Constitutively higher cATMexpressing AAA patient-derived SMCs were less vulnerable to oxidative stress-induced cell death and survival pathways enriched when compared to control SMCs. Taken together, this data supports the role ofcATMin adapting SMCs to oxidative stress in the vascular AAA micromilieu. This molecular signature provides an additional parameter to be included in procedures for AAA screening in combination with already established practices.

A new strategy to stabilize free radicals electronically is described by conjugating formally antiaromatic substituents to the free radical. With an antiaromatic substituent, the radical acts as an electron sink to allow configuration mixing of a low-energy zwitterionic state that provides antiaromaticity relief to the substituent. A combination of X-ray crystallography, VT-EPR and VT-UV/Vis spectroscopy, as well as computational analysis, was used to investigate this phenomenon. We find that this strategy of antiaromaticity relief is successful at stabilizing radicals, but only if the antiaromatic substituent is constrained to be planar by synthetically imposed conformational restraints that enable state mixing. This work leads to the counterintuitive finding that increasing the antiaromaticity of the radical substituent leads to greater radical stability, providing proof of concept for a new stereoelectronic approach for stabilizing free radicals.

BODIPY-based photocages release substrates by excitation with wavelengths in the visible to near-IR regions. The recent development of more efficient BODIPY photocages spurred us to evaluate the scope and efficiency of these second-generation boron-methylated green-light and red-light-absorbing BODIPY photocages. Here, we show that these more photosensitive photocages release amine, alcohol, phenol, phosphate, halides, and carboxylic acid derivatives with much higher quantum yields than first-generation BODIPY photocages and excellent chemical yields. Chemical yields are near-quantitative for the release of all functional groups except the photorelease of amines, which react with concomitantly photogenerated singlet oxygen. In these cases, high chemical yields for photoreleased amines are restored by irradiation under an inert atmosphere. The photorelease quantum yield has a weak relationship with the leaving group p

Phenol dearomatization is one of several oxidation reactions enabled by hypervalent iodine reagents. However, the presence of a proposed free phenoxenium intermediate in phenol dearomatization is a matter of debate in the literature. Here, we report the unambiguous detection of a free phenoxenium intermediate in the reaction of an electron-rich phenol, 2,4,6-trimethoxyphenol, and (diacetoxyiodo)benzene using UV-vis and resonance Raman spectroscopies. In contrast, we predominantly detect single electron oxidation products of less electron-rich phenols or alkoxy-substituted aromatics in their reaction with (diacetoxyiodo)benzene using UV-vis and electron paramagnetic resonance (EPR) spectroscopies. We conclude that the often-postulated free phenoxenium intermediate, while possible with highly stabilizing substituents, is unlikely to be a general mechanistic pathway in the reaction of typical phenols with hypervalent iodine reagents. The polar solvent 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) or the use of more strongly oxidizing hypervalent iodine reagents, such as [bis(trifluoroacetoxy)iodo]benzene (PIFA) or [hydroxy(tosyloxy)iodo]benzene (HTIB), can help reduce the formation of radical byproducts and favors the formation of phenoxenium intermediates.

Treatment of 3 equiv of the potassium salts derived from the β-amino ketones 1-(dimethylamino)-3,3-dimethylbutan-2-one (L1H), 3,3-dimethyl-1-(pyrrolidin-1-yl)butan-2-one (L2H), and 3,3-dimethyl-1-(...

The feasibility of using selective thermal cobalt metal (Co) atomic layer deposition (ALD) as high density Cu–Cu interconnect bonding is demonstrated at a low temperature (200 °C) and with minimal surface pretreatment. A Cu/Gap/Cu structure, which emulates 3-D ICs stacking is fabricated. Cobalt ALD showing seamless interconnection between copper (Cu) pads with 30- $\mu \text{m}$ pitch is demonstrated with greater than 90% yield through electrical measurements, SEM inspection, EDS, and focused ion beam (FIB) cross section.

Photocages are light-sensitive chemical protecting groups that give investigators control over activation of biomolecules using targeted light irradiation. A compelling application of far-red/near-IR absorbing photocages is their potential for deep tissue activation of biomolecules and phototherapeutics. Toward this goal, we recently reported BODIPY photocages that absorb near-IR light. However, these photocages have reduced photorelease efficiencies compared to shorter-wavelength absorbing photocages, which has hindered their application. Because photochemistry is a zero-sum competition of rates, improvement of the quantum yield of a photoreaction can be achieved either by making the desired photoreaction more efficient or by hobbling competitive decay channels. This latter strategy of inhibiting unproductive decay channels was pursued to improve the release efficiency of long-wavelength absorbing BODIPY photocages by synthesizing structures that block access to unproductive singlet internal conversion conical intersections, which have recently been located for simple BODIPY structures from excited state dynamic simulations. This strategy led to the synthesis of new conformationally restrained boron-methylated BODIPY photocages that absorb light strongly around 700 nm. In the best case, a photocage was identified with an extinction coefficient of 124000 M-1 cm-1, a quantum yield of photorelease of 3.8%, and an overall quantum efficiency of 4650 M-1 cm-1 at 680 nm. This derivative has a quantum efficiency that is 50-fold higher than the best known BODIPY photocages absorbing >600 nm, validating the effectiveness of a strategy for designing efficient photoreactions by thwarting competitive excited state decay channels. Furthermore, 1,7-diaryl substitutions were found to improve the quantum yields of photorelease by excited state participation and blocking ion pair recombination by internal nucleophilic trapping. No cellular toxicity (trypan blue exclusion) was observed at 20 μM, and photoactivation was demonstrated in HeLa cells using red light.

An air- and thermally stable aryl dicyanomethyl radical is reported that switches between two dimeric forms-a σ dimer and a π dimer-by changing the solvent. The two dimer forms exhibit unique optical properties leading to solvatochromic behavior. The solvent-responsive behavior of these radicals can be explained by the higher polarizability of the pimer than the σ dimer that leads to pimer stabilization in polar solvents.

Oil skimmer is a useful tool in recovering all types of floating waste oils, greases and fats from water surfaces. Lubricant film flow velocity approximation is an important problem of oil skimmer belt speed adjustment. The adjustment belt speed level is up to several physical parameters of oil types. A thin lubricant film flow velocity on a moving belt oil skimmer can be modeled in a form of a nonlinear differential equation as a boundary value problem. The model is providing the lubricant film flow velocity in each thickness layers. In this research, a centered in space finite difference method and a Quasi-Newton iterative method are proposed to approximate the solutions of the nonlinear thin lubricant film flow velocity model. Their numerical simulations of a thin lubricant film flow velocity on a moving oil skimmer belt with varied physical parameters are investigated. The proposed numerical techniques give good agreement approximated solutions in several moving belts speed levels with the external force factor. These are then useful to achieve the optimum belt oil skimmer speed for each lubricant type.

Manipulating frontier orbital energies of aromatic molecules with substituents is key to a variety of chemical and material applications. Here, we investigate a simple strategy for achieving high-energy in-plane orbitals for aromatics simply by positioning iodine atoms next to each other. The lone pair orbitals on the iodines mix to give a high-energy in-plane σ-antibonding orbital as the highest occupied molecular orbital (HOMO). We show that this effect can be used to manipulate orbital gaps, the symmetry of the highest occupied orbital, and the adopted electronic state for reactive intermediates. This electronic effect is not limited to reactive intermediates, and we demonstrate that this iodine buttressing strategy also can be used to achieve small HOMO-lowest unoccupied molecular orbital (HOMO-LUMO) gaps in organic electronic materials. Iodinated oligomers of several of the most popular conducting polymers are computed to have smaller HOMO-LUMO gaps than the unsubstituted materials. This iodine buttressing approach for generating high-energy in-plane HOMOs is anticipated to be highly general. While the unusual properties of fluorous materials are well established, at the other extreme on the periodic table novel properties of iodous materials may await discovery.

Photoactivation of bioactive molecules allows manipulation of cellular processes with high spatiotemporal precision. The recent emergence of visible-light excitable photoprotecting groups has the potential to further expand the established utility of the photoactivation strategy in biological applications by offering higher tissue penetration, diminished phototoxicity, and compatibility with other light-dependent techniques. Nevertheless, a critical barrier to such applications remains the significant hydrophobicity of most visible-light excitable photocaging groups. Here, we find that applying the conventional 2,6-sulfonation to meso-methyl BODIPY photocages is incompatible with their photoreaction due to an increase in the excited state barrier for photorelease. We present a simple, remote sulfonation solution to BODIPY photocages that imparts water solubility and provides control over cellular permeability while retaining their favorable spectroscopic and photoreaction properties. Peripherally disulfonated BODIPY photocages are cell impermeable, making them useful for modulation of cell-surface receptors, while monosulfonated BODIPY retains the ability to cross the cellular membrane and can modulate intracellular targets. This new approach is generalizable for controlling BODIPY localization and was validated by sensitization of mammalian cells and neurons by visible-light photoactivation of signaling molecules.

Metastable radicals exist in a steady-state equilibrium in solution with dimers, which can be either σ dimers or π dimers. Here, we show that steric hindrance at the

The growth of rhenium nitride and rhenium metal thin films is presented using atomic layer deposition (ALD) with the precursors methyltrioxorhenium and 1,1-dimethylhydrazine. Saturative, self-limiting growth was determined at 340 °C for pulse times of ≥4.0 s for methyltrioxorhenium and ≥0.1 s for 1,1-dimethylhydrazine. An ALD window was observed from 340 to 350 °C with a growth rate of about 0.60 A/cycle. Films grown at 340 °C revealed an root mean square surface roughness of 2.7 nm for a 70 nm thick film and possessed a composition of ReN0.14 with low O and C content of 1.6 and 2.6 at.%, respectively. Enhanced nucleation on in-situ grown TiN, relative to thermal SiO2, enabled a conformality of 98% on high aspect ratio trenched structures. Subjecting the ReN0.14 thin films to thermal or chemical and thermal treatments reduced the nitrogen content to ≤1.6 at.%, yielding a film purity of about 96 at.% rhenium and resistivities as low as 51 µΩ cm. The Re metal film thicknesses on the trenched structures remained intact during the post-deposition annealing treatments and the films did not delaminate from the substrate surfaces.

Nitrenium ions are important reactive intermediates in both chemistry and biology. Although singlet nitrenium ions are well-characterized by direct methods, the triplet states of nitrenium ions have never been directly detected. Here, we find that the excited state of the photoprecursor partitions between heterolysis to generate the singlet nitrenium ion and intersystem crossing (ISC) followed by a spontaneous heterolysis process to generate the triplet p-iodophenylnitrenium ion (np). The triplet nitrenium ion undergoes ISC to generate the ground singlet state, which ultimately undergoes proton and electron transfer to generate a long-lived radical cation that further generates the reduced p-iodoaniline. Ab Initio calculations were performed to map out the potential energy surfaces to better understand the excited state reactivity channels show that an energetically-accessible singlet-triplet crossing lies along the N-N stretch coordinate and that the excited triplet state is unbound and spontaneously eliminates ammonia to generate the triplet nitrenium ion. These results give a clearer picture of the photophysical properties and reactivity of two different spin states of a phenylnitrenium ion and provide the first direct glimpse of a triplet nitrenium ion.

Treatment of the stable N-heterocyclic carbene 1,3-di-tert-butylimidazolin-2-ylidene with 2 equiv of AlH3(NMe3) afforded the structurally unusual ring-expanded dialane complex 1 in 72% yield after ...