7 research outputs found
Mobility of Long-Lived Fullerene Radical in Solid State and Nonlinear Temperature Dependence
A singly bonded fullerene dimer [C<sub>60</sub>R]<sub>2</sub> in
the solid state thermally generates a pair of fullerene radicals C<sub>60</sub>R<sup>•</sup> that dissociate reversibly and irreversibly
upon heating and cooling of the solid. The temperature dependence
of the electron mobility of the solid shows striking nonlinearity,
caused by the dissociation of a strongly interacting radical pair
into two free radicals, which interact with the neighboring fullerene
molecules to increase the mobility 10 times to a value of 1.5 ×
10<sup>–3</sup> cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>. The nonlinearity is due to the plastic crystalline
nature of fullerene crystals
Thermoresponsive Shuttling of Rotaxane Containing Trichloroacetate Ion
A thermoresponsive rotaxane shuttling system was developed with a trichloroacetate counteranion of an ammonium/crown ether-type rotaxane. Chemoselective thermal decomposition of the ammonium trichloroacetate moiety on the rotaxane yielded the corresponding nonionic rotaxane accompanied by a positional change of the crown ether on the axle. The rotaxane skeleton facilitated effective dissociation of the acid, markedly lowering the thermal decomposition temperature
Geometric Complementarity in Assembly and Guest Recognition of a Bent Heteroleptic <i>cis</i>-[Pd<sub>2</sub><b>L</b><sup><b>A</b></sup><sub>2</sub><b>L</b><sup><b>B</b></sup><sub>2</sub>] Coordination Cage
Due to the inherent
difficulties in achieving a defined and exclusive
formation of multicomponent assemblies against entropic predisposition,
we present the rational assembly of a heteroleptic [Pd<sub>2</sub><b>L</b><sup><b>A</b></sup><sub>2</sub><b>L</b><sup><b>B</b></sup><sub>2</sub>]<sup>4+</sup> coordination
cage achieved through the geometric complementarity of two carefully
designed ligands, <b>L</b><sup><b>A</b></sup> and <b>L</b><sup><b>B</b></sup>. With PdÂ(II) cations as rigid nodes,
the pure distinctly angular components readily form homoleptic cages,
a [Pd<sub>2</sub><b>L</b><sup><b>A</b></sup><sub>4</sub>]<sup>4+</sup> strained helical assembly and a [Pd<sub>4</sub><b>L</b><sup><b>B</b></sup><sub>8</sub>]<sup>8+</sup> box-like
structure, both of which were characterized by X-ray analysis. Combined,
however, the two ligands could be used to cleanly assemble a <i>cis</i>-[Pd<sub>2</sub><b>L</b><sup><b>A</b></sup><sub>2</sub><b>L</b><sup><b>B</b></sup><sub>2</sub>]<sup>4+</sup> cage with a bent architecture. The same self-sorted product
was also obtained by a quantitative cage-to-cage transformation upon
mixing of the two homoleptic cages revealing the [Pd<sub>2</sub><b>L</b><sup><b>A</b></sup><sub>2</sub><b>L</b><sup><b>B</b></sup><sub>2</sub>]<sup>4+</sup> assembly as the thermodynamic
minimum. The structure of the heteroleptic cage was examined by ESI-MS,
COSY, DOSY, and NOESY methods, the latter of which pointed toward
a <i>cis</i>-conformation of ligands in the assembly. Indeed,
DFT calculations revealed that the angular ligands and strict PdÂ(II)
geometry strongly favor the <i>cis</i>-[Pd<sub>2</sub><b>L</b><sup><b>A</b></sup><sub>2</sub><b>L</b><sup><b>B</b></sup><sub>2</sub>]<sup>4+</sup> species. The robust nature
of the <i>cis</i>-[Pd<sub>2</sub><b>L</b><sup><b>A</b></sup><sub>2</sub><b>L</b><sup><b>B</b></sup><sub>2</sub>]<sup>4+</sup> cage allowed us to probe the accessibility
of its cavity, which could be utilized for shape recognition toward
stereoisomeric guests. The ability to directly combine two different
backbones in a controlled manner provides a powerful strategy for
increasing complexity in the family of [Pd<sub>2</sub><b>L</b><sub>4</sub>] cages and opens up possibilities of introducing multiple
functionalities into a single self-assembled architecture
Assessment of Anterior Cingulate Cortex (ACC) and Left Cerebellar Metabolism in Asperger's Syndrome with Proton Magnetic Resonance Spectroscopy (MRS)
<div><p>Purpose</p><p>Proton magnetic resonance spectroscopy (<sup>1</sup>H MRS) is a noninvasive neuroimaging method to quantify biochemical metabolites <i>in vivo</i> and it can serve as a powerful tool to monitor neurobiochemical profiles in the brain. Asperger’s syndrome (AS) is a type of autism spectrum disorder, which is characterized by impaired social skills and restrictive, repetitive patterns of interest and activities, while intellectual levels and language skills are relatively preserved. Despite clinical aspects have been well-characterized, neurometabolic profiling in the brain of AS remains to be clear. The present study used proton magnetic resonance spectroscopy (<sup>1</sup>H MRS) to investigate whether pediatric AS is associated with measurable neurometabolic abnormalities that can contribute new information on the neurobiological underpinnings of the disorder.</p><p>Methods</p><p>Study participants consisted of 34 children with AS (2–12 years old; mean age 5.2 (±2.0); 28 boys) and 19 typically developed children (2–11 years old; mean age 5.6 (±2.6); 12 boys) who served as the normal control group. The <sup>1</sup>H MRS data were obtained from two regions of interest: the anterior cingulate cortex (ACC) and left cerebellum.</p><p>Results</p><p>In the ACC, levels of N-acetylaspartate (NAA), total creatine (tCr), total choline-containing compounds (tCho) and myo-Inositol (mI) were significantly decreased in children with AS compared to controls. On the other hand, no significant group differences in any of the metabolites were found in the left cerebellum. Neither age nor sex accounted for the metabolic findings in the regions.</p><p>Conclusion</p><p>The finding of decreased levels of NAA, tCr, tCho, and mI in the ACC but not in left cerebellar voxels in the AS, suggests a lower ACC neuronal density in the present AS cohort compared to controls.</p></div
Participant Characteristics and Demographics.
<p>Participant Characteristics and Demographics.</p
Positions of the measurement voxel in ACC (anterior cingulate cortex) and left cerebellum and representative spectra from each voxel.
<p>(LEFT) Positions of the measurement voxel in the anterior cingulate cortex (ACC) and left cerebellum. (RIGHT) Representative short TE and J-edited spectra obtained.</p