The Structure of Boron Monoxide.

Boron monoxide (BO), prepared by the thermal condensation of tetrahydroxydiboron, was first reported in 1955; however, its structure could not be determined. With the recent attention on boron-based two-dimensional materials, such as borophene and hexagonal boron nitride, there is renewed interest in BO. A large number of stable BO structures have been computationally identified, but none are supported by experiments. The consensus is that the material likely forms a boroxine-based two-dimensional material. Herein, we apply advanced 11B NMR experiments to determine the relative orientations of B(B)O2 centers in BO. We find that the material is composed of D2h-symmetric O2B-BO2 units that organize to form larger B4O2 rings. Further, powder diffraction experiments additionally reveal that these units organize to form two-dimensional layers with a random stacking pattern. This observation is in agreement with earlier density functional theory (DFT) studies that showed B4O2-based structures to be the most stable.

Thermal Unequilibrium of PdSn Intermetallic Nanocatalysts: From In Situ Tailored Synthesis to Unexpected Hydrogenation Selectivity.

Effective control on chemoselectivity in the catalytic hydrogenation of C=O over C=C bonds is uncommon with Pd-based catalysts because of the favored adsorption of C=C bonds on Pd surface. Here we report a unique orthorhombic PdSn intermetallic phase with unprecedented chemoselectivity toward C=O hydrogenation. We observed the formation and metastability of this PdSn phase in situ. During a natural cooling process, the PdSn nanoparticles readily revert to the favored Pd3 Sn2 phase. Instead, using a thermal quenching method, we prepared a pure-phase PdSn nanocatalyst. PdSn shows an >96 % selectivity toward hydrogenating C=O bonds of various α,ß-unsaturated aldehydes, highest in reported Pd-based catalysts. Further study suggests that efficient quenching prevents the reversion from PdSn- to Pd3 Sn2 -structured surface, the key to the desired catalytic performance. Density functional theory calculations and analysis of reaction kinetics provide an explanation for the observed high selectivity.

Facile Fabrication of Hierarchical MOF-Metal Nanoparticle Tandem Catalysts for the Synthesis of Bioactive Molecules.

Multifunctional metal-organic frameworks (MOFs) that possess permanent porosity are promising catalysts in organic transformation. Herein, we report the construction of a hierarchical MOF functionalized with basic aliphatic amine groups and polyvinylpyrrolidone-capped platinum nanoparticles (Pt NPs). The postsynthetic covalent modification of organic ligands increases basic site density in the MOF and simultaneously introduces mesopores to create a hierarchically porous structure. The multifunctional MOF is capable of catalyzing a sequential Knoevenagel condensation-hydrogenation-intramolecular cyclization reaction. The unique selective reduction of the nitro group to intermediate hydroxylamine by Pt NPs supported on MOF followed by intramolecular cyclization with a cyano group affords an excellent yield (up to 92%) to the uncommon quinoline N-oxides over quinolines. The hierarchical MOF and polyvinylpyrrolidone capping agent on Pt NPs synergistically facilitate the enrichment of substrates and thus lead to high activity in the reduction-intramolecular cyclization reaction. The bioactivity assay indicates that the synthesized quinoline N-oxides evidently inhibit the proliferation of lung cancer cells. Our findings demonstrate the feasibility of MOF-catalyzed direct synthesis of bioactive molecules from readily available compounds under mild conditions.

Linear focal elastosis: histopathologic diagnosis of an uncommon dermal elastosis.

BACKGROUND: Linear focal elastosis is an uncommon dermal elastosis that occurs predominantly on the back. Although first described in the lumbar region of elderly white men, more recent reports note similar findings on the trunk and limbs of adolescent Asian men. METHODS: We present a typical case of an eighty-three year old white man with a one-year history of asymptomatic linear yellow and erythematous plaques on his lumbar region. RESULTS: Light microscopic examination revealed skin with an unremarkable epidermis with coarsely clumped elastic fibers in the reticular dermis, which were highlighted by an elastic tissue stain. CONCLUSION: The histopathologic differential diagnosis includes pseudoxanthoma elasticum, connective tissue nevus, elastofibroma, and solar elastosis. Although some of these diagnoses can be excluded by histologic examination, correlation with the clinical findings is necessary to arrive at the correct diagnosis of linear focal elastosis. Linear focal elastosis is an uncommon dermal elastosis that was originally described as asymptomatic linear yellow plaques in the lumbar region in elderly white males 1. Recent reports have extended the spectrum of this entity to include red-yellow linear atrophic to raised plaques on the trunks and limbs of adolescent males, predominantly of Asian descent. Twenty-one cases of linear focal elastosis have been reported in the literature. We report an additional case of linear focal elastosis in an elderly male and review the literature.

Congenital Spitz nevus clinically mimicking melanoma.

The differentiation between atypical variants of Spitz nevus and melanoma is often difficult given the many clinical and histopathologic similarities between the two. We report a case of an infant with a congenital scalp lesion exhibiting clinical features of melanoma, including variegation and regression of pigmentation and a rapidly changing appearance. Histologic examination of the excised lesion revealed a benign congenital Spitz nevus. This case emphasizes the need for clinical and histologic correlation in determining the benign or malignant nature of atypical pigmented lesions in infants.