126,650 research outputs found
Bis-Spiro-Oxetane and Bis-Spiro-Tetrahydrofuran Pyrroline Nitroxide Radicals: Synthesis and Electron Spin Relaxation Studies
No full textSynthesis of bis-spiro-oxetane and
bis-spiro-tetrahydrofuran pyrroline
nitroxide radicals relies on the Mitsunobu reaction-mediated double
cyclizations of N-Boc protected pyrroline tetraols.
Structures of the nitroxide radicals are supported by X-ray crystallography.
In a trehalose/sucrose matrix at room temperature, the bis-spiro-oxetane
nitroxide radical possesses electron spin coherence time, Tm ≈ 0.7 μs. The observed enhanced Tm is most likely associated with strong hydrogen
bonding of oxetane moieties to the trehalose/sucrose matrix
Photochromism of naphthoxazine-spiro-indolines
No full textNaphthoxazine-spiro-indolines (NOSIs) can exist in a colourless and a coloured form.
These compounds can interconvert between these two forms either photochemically or
thermally and are resilient to degradation even after repeated cycles of colouration and
bleaching. Absorption spectra of both the stable colourless form and the energetically less
stable coloured form have been measured.
Several NOSI compounds have been shown to photoconvert to the coloured form with an
efficiency of between 0.06–0.74, depending upon the compound conditions under which
the conversion is brought about. The factors which have been varied in this work are: the
basicity of the 6'-substituent; the size of the N-alkyl group within these compounds; and
the nature solvent or matrix in which the reaction occurs. Electron donation from the
6'-group has been shown to increase the quantum yield of the forward reaction whereas
solvent polarity increases have been shown to reduce the quantum yield. [Continues.
Spiro-Linked Ter-, Penta-, and Heptafluorenes as Novel Amorphous Materials for Blue Light Emission
No full textA series of spiro-linked oligofluorenes were synthesized that exhibit blue emission with
photoluminescence quantum yields in some cases exceeding 0.50 in neat spin-coated films.
Differential scanning calorimetry revealed highly variable glass transition temperatures. A
longer conjugation length is desired for better stability against thermally activated
crystallization, and a shorter pendant is desired for a higher glass transition temperature
at a given conjugation length. In contrast to poly(2,7-(9,9-di-n-octylfluorene)), prolonged
heating of spiro-oligo(fluorene) films resulted in no changes in morphology, emissive color,
and photoluminescence quantum yield. The propensity of spiro-oligo(fluorene)s to thermally
activated crystallization was rationalized with molecular shapes predicted by molecular
mechanics simulations
Novel Oxidative Transformation of Indenoisoquinolines to Isoquinoline-3-spiro-3‘-phthalides in the Presence of Osmium Tetraoxide and 4-Methylmorpholine <i>N</i>-Oxide
No full textNovel Oxidative Transformation of
Indenoisoquinolines to
Isoquinoline-3-spiro-3‘-phthalides in the
Presence of Osmium Tetraoxide and
4-Methylmorpholine N-Oxid
Novel Oxidative Transformation of Indenoisoquinolines to Isoquinoline-3-spiro-3‘-phthalides in the Presence of Osmium Tetraoxide and 4-Methylmorpholine <i>N</i>-Oxide
No full textNovel Oxidative Transformation of
Indenoisoquinolines to
Isoquinoline-3-spiro-3‘-phthalides in the
Presence of Osmium Tetraoxide and
4-Methylmorpholine N-Oxid
Photochromism of naphthoxazine-spiro-indolines
No full textNaphthoxazine-spiro-indolines (NOSIs) can exist in a colourless and a coloured form.
These compounds can interconvert between these two forms either photochemically or
thermally and are resilient to degradation even after repeated cycles of colouration and
bleaching. Absorption spectra of both the stable colourless form and the energetically less
stable coloured form have been measured.
Several NOSI compounds have been shown to photoconvert to the coloured form with an
efficiency of between 0.06–0.74, depending upon the compound conditions under which
the conversion is brought about. The factors which have been varied in this work are: the
basicity of the 6'-substituent; the size of the N-alkyl group within these compounds; and
the nature solvent or matrix in which the reaction occurs. Electron donation from the
6'-group has been shown to increase the quantum yield of the forward reaction whereas
solvent polarity increases have been shown to reduce the quantum yield. [Continues.
All in One: A Versatile n‑Perovskite/p-Spiro-MeOTAD p–n Heterojunction Diode as a Photovoltaic Cell, Photodetector, and Memristive Photosynapse
No full textWith
their excellent optoelectronic properties, halide perovskite
(HP) semiconductors have witnessed successful applications in many
fields, such as solar cells, LEDs, photodetectors, transistors, and
memristors. Exploiting their fascinating physical nature for the development
of single nanodevices with multifunctionalities is significant yet
remains challenging. We report a multifunctional device based on the
n-perovskite/p-spiro-MeOTAD p–n heterojunction diode that enables
the integration of photovoltaic, photodetection, and photosynaptic
functions in a single device. The device exhibits a high photoelectronic
conversion efficiency (PCE) of 17.64% under AM 1.5G illumination and
excellent photodetection characteristics including a low drive voltage
of 0.01 V, a short response time of 0.17 s, high switching repeatability,
and stability. Coupled with the superior photomemristive effect of
the device that can be used for the emulation of short- and long-term
memory formation of visual synapses, these results suggest that the
HP-based p–n heterojunction devices hold great potential in
multifunctional integrated device applications
Eversive Maps of Bounded Convex Domains in â„‚n+1
No full textA duality principle, relating the geometry of the Kobayashi metric with the CR geometry of the boundaries of smoothly bounded, strongly convex domains in â„‚n+1, is established. A characterization of the holomorphic Jacobi vector fields of those domains is also given
Musical motives in performance timing data
No full textData archive to accompany Musical motives in performance: A study of absolute timing patterns (Spiro, Gold, Rink), in Mathemusical Conversations: Mathematics and Computation in Music Performance and Composition (ed. Smith, Chew). This archive contains the data supporting the Formal Concept Analysis investigation reported in the book chapter above. The files are organized according to the manifest contained in the README.TXT file in the archive. OAL files are intended for use with the ConExp package (http://conexp.sourceforge.net/)
Synthesis of and a Comparative Study on the Inhibition of Muscle and Liver Glycogen Phosphorylases by Epimeric Pairs of d-Gluco- and d-Xylopyranosylidene-spiro-(thio)hydantoins and <i>N</i>-(d-Glucopyranosyl) Amides
No full textd-Gluco- and d-xylopyranosylidene-spiro-hydantoins and -thiohydantoins were prepared from
the parent sugars in a six-step, highly chemo-, regio-, and stereoselective procedure. In the
key step of the syntheses C-(1-bromo-1-deoxy-β-d-glycopyranosyl)formamides were reacted with
cyanate ion to give spiro-hydantoins with a retained configuration at the anomeric center as
the major products. On the other hand, thiocyanate ions gave spiro-thiohydantoins with an
inverted anomeric carbon as the only products. On the basis of radical inhibition studies, a
mechanistic rationale was proposed to explain this unique stereoselectivity and the formation
of C-(1-hydroxy-β-d-glycopyranosyl)formamides as byproducts. Enzyme assays with a and b
forms of muscle and liver glycogen phosphorylases showed spiro-hydantoin 12 and spiro-thiohydantoin 14 to be the best and equipotent inhibitors with Ki values in the low micromolar
range. The study of epimeric pairs of d-gluco and d-xylo configurated spiro-hydantoins and
N-(d-glucopyranosyl)amides corroborated the role of specific hydrogen bridges in binding the
inhibitors to the enzyme
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