Cyclo[2]pyridine[8]pyrrole: An Expanded Porphyrinoid with Three Closed-Shell Oxidation States.

We report here an expanded porphyrinoid, cyclo[2]pyridine[8]pyrrole, 1, that can exist at three closed-shell oxidation levels. Macrocycle 1 was synthesized via the oxidative coupling of two open chain precursors and fully characterized by means of NMR and UV-vis spectroscopies, MS, and X-ray crystallography. Reduction of the fully oxidized form (1, blue) with NaBH4 produced either the half-oxidized (2, teal) or fully reduced forms (3, pale yellow), depending on the amount of reducing agent used and the presence or absence of air. Reduced products 2 or 3 can be oxidized to 1 by various oxidants (quinones, FeCl3, and AgPF6). Macrocycle 1 also undergoes proton-coupled reductions with I-, Br-, Cl-, SO32-, or S2O32- in the presence of an acid. Certain thiol-containing compounds likewise reduce 1 to 2 or 3. This conversion is accompanied by a readily discernible color change, making cyclo[2]pyridine[8]pyrrole 1 able to differentiate biothiols, such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH).

Quinoxaline-fused octaphyrin(2.0.0.0.2.0.0.0). A rudimentary chemosensor.

A quinoxaline-fused octaphyrin(2.0.0.0.2.0.0.0) was synthesized by the FeCl3-induced oxidative coupling of an α-free quinoxaline-fused tetrapyrrole. This macrocycle adopts a figure-of-eight conformation in the solid state and acts as a rudimentary chemosensor in solution. The Lewis basic anions fluoride and hydroxide induce a colour change via a deprotonation mechanism.

What a deep song: The role of music features in perceived depth.

This study examines perceptions of music depth by exploring its relationships to different music features. First, a correlation analysis shows that the perceived depth of music is negatively correlated with valence and arousal and is also related to different music features, including tempo, Mel-frequency cepstrum coefficients, chromagrams, spectral centroids, spectral bandwidth, spectral contrast, spectral flatness, spectral roll-off, and tonal centroid features. Applying machine learning methods, we find that selected music features can predict perceptions of music depth, and a random forest regression (RFR) is found to perform best in this study. Finally, a feature importance analysis shows that the principal component of spectral contrast dominates the RFR-based music depth recognition model, showing that deep music usually has clear and narrow-band audio signals.

Exercise prevents HFD-induced insulin resistance risk: involvement of TNF-α level regulated by vagus nerve-related anti-inflammatory pathway in the spleen.

OBJECTIVES: Regular physical exercise can improve insulin resistance in insulin target tissues. However, the mechanisms about the beneficial effect of exercise on insulin resistance are not yet fully resolved. This study was carried out to address whether insulin resistance improvement by exercise is involved in an anti-inflammatory pathway in the spleen in high-fat diet (HFD) feeding mice. METHODS: Male C57Bl/6J mice with or without subdiaphragmatic vagotomy (sVNS) were subjected to medium-intensity treadmill exercise during HFD feeding. Glucose tolerance test and insulin tolerance test were detected, and spleen acetylcholine level, choline acetyltransferase activity (ChAT), protein kinase C (PKC) and tumor necrosis factor-alpha (TNF-α) were assayed. RESULTS: We found that exercise significantly improves HFD-induced glucose intolerance and insulin resistance, along with an increase in acetylcholine level, ChAT activity, and PKC activity, and decrease in TNF-α level in the system and the spleen from HFD-fed mice. However, sVNS abolished the beneficial effect of exercise on glucose intolerance and insulin resistance, decreased acetylcholine level, ChAT activity, and PKC activity, and increase TNF-α level of the spleen in HFD-mice exercise intervention. CONCLUSIONS: These data reveal that the prevention of HFD-associated insulin resistance by exercise intervention involves reducing splenic TNF-α level, which is mediated by cholinergic anti-inflammatory activity via influencing PKC activity, ChAT activity, and acetylcholine concentration in mice spleen.

Using machine learning analysis to interpret the relationship between music emotion and lyric features.

Melody and lyrics, reflecting two unique human cognitive abilities, are usually combined in music to convey emotions. Although psychologists and computer scientists have made considerable progress in revealing the association between musical structure and the perceived emotions of music, the features of lyrics are relatively less discussed. Using linguistic inquiry and word count (LIWC) technology to extract lyric features in 2,372 Chinese songs, this study investigated the effects of LIWC-based lyric features on the perceived arousal and valence of music. First, correlation analysis shows that, for example, the perceived arousal of music was positively correlated with the total number of lyric words and the mean number of words per sentence and was negatively correlated with the proportion of words related to the past and insight. The perceived valence of music was negatively correlated with the proportion of negative emotion words. Second, we used audio and lyric features as inputs to construct music emotion recognition (MER) models. The performance of random forest regressions reveals that, for the recognition models of perceived valence, adding lyric features can significantly improve the prediction effect of the model using audio features only; for the recognition models of perceived arousal, lyric features are almost useless. Finally, by calculating the feature importance to interpret the MER models, we observed that the audio features played a decisive role in the recognition models of both perceived arousal and perceived valence. Unlike the uselessness of the lyric features in the arousal recognition model, several lyric features, such as the usage frequency of words related to sadness, positive emotions, and tentativeness, played important roles in the valence recognition model.

Self-assembly of carbon nanotubes on a hollow carbon polyhedron to enhance the potassium storage cycling stability of metal organic framework-derived metallic selenide anodes.

Potassium-ion batteries (PIBs) is increasingly studied because of their suitable redox potential and high natural abundance. However, potential anode materials with long-term cycling stability are still in high demand because of the large radius of K+. Herein, an MOF-derived hierarchical carbon structure and the self-assembly of CNTs on hollow carbon polyhedrons are used as carbon matrices to disperse and stabilize metal selenides(Co-Se@CNNCP). When the hybrid is utilized in PIBs, it displays a specific capacity of 410 mA h g-1 at 0.1 A g-1 after 80 cycles and 253 mA h g-1 at 0.5 A g-1 after 200 cycles with a capacity retention of 100%, while the metal selenides dispersed on hollow carbon polyhedrons without CNTs (Zn-Co-Se@NCP) lose 86% of their capacity after 200 cycles. The superior cycling stability of the hybrid is mainly attributed to the large amounts of CNTs suppressing the agglomeration of the metal selenide nanoparticles on the surface, and the hollow carbon polyhedrons cause a high structural integrity during the repreated K+ insertion and extraction process. This work offers a feasible route to design a hierarchical carbon matrix for use as the anode materials of PIBs with long-term cycling stability.

Rational design of MoSe2 nanosheet-coated MOF-derived N-doped porous carbon polyhedron for potassium storage.

For potassium-ion battery (PIB), it remains a huge challenge to develop an appropriate anode material to compensate the large radius of K+. MoSe2 shows great potential for efficient K+ insertion/extraction due to its unique lamellar structures with an interlayer spacing of 6.46 Å. However, pure MoSe2 has low electronic conductivity and agglomerates during long-term cycling. In the present work, MoSe2 nanosheets were fabricated on the N-doped porous carbon polyhedron (NPCP). The obtained product was designated as NPCP@MoSe2 and functioned as anode materials for PIBs. NPCP@MoSe2 displayed a promising reversible capacity (325 mAh/g at 100 mA/g after 80 cycles), long-term cycling performance (128 mAh/g at 500 mA/g after 800 cycles), and superior rate property at 5000 mA/g. The enhanced electrochemical performance of NPCP@MoSe2 could be attributed to the rational design of hybrid structures. Notably, the hollow NPCP provide a large contact area for the interactions among the electrolytes and electro-active materials as well as partly buffer the volume expansion. The synergistic effects between MoSe2 and NPCP could mitigate the agglomeration of MoSe2 nanosheets. Besides, the uniformly doping N elements enhanced the conductivity of the carbon matrix, and the N-group also provided potential binding active sites for K-ion accommodation. This work paves the ideas for the design of novel anode materials with high specific capacity, good cycling stability and outstanding rate capability for PIBs.

Doubly N-confused phlorin and phlorinone analogue.

A doubly N-confused phlorin and phlorinone analogue were synthesized from a ß,ß'-linked dipyrromethane precursor and characterized by means of NMR and UV-Vis spectroscopies, X-ray crystallography, and electrochemistry. Solvents have a considerable impact on the optical absorption of the doubly N-confused phlorin so that it can differentiate simple alcohols such as methanol and ethanol.

Hierarchical Ni-Co-O-C-P hollow tetragonal microtubes grown on Ni foam for efficient overall water splitting in alkaline media.

Exploring low-cost and highly efficient non-noble bifunctional electrocatalysts with high performances for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential for large-scale sustainable energy systems. Herein, the Ni-Co-O-C-P hollow tetragonal microtubes grown on 3D Ni foam (Ni-Co-O-C-P/NF) was synthesized via a one-step solvothermal method and followed by a simple carbon coating and in situ phosphorization treatment. Benefiting from the unique open and hierarchical nano-architectures, the as prepared Ni-Co-O-C-P/NF presents a high activity and durability for both the HER and OER in alkaline media. The overall-water-splitting reaction requires a low cell voltage (1.54 V @ 10 mA cm-2) in 1 M KOH when Ni-Co-O-C-P/NF is used as both the anode and cathode. The highly flexible structure can provide a large amount of exposed active sites and shorten the mass transport distance. Furthermore, bimetallic phosphides also favor the electrocatalysis due to the higher electronic conductivity and the synergetic effect. This work demonstrated a promising bifunctional electrocatalyst for water electrolysis in alkaline media with potential in future applications.

Construction of Hierarchical MoSe2 Hollow Structures and Its Effect on Electrochemical Energy Storage and Conversion.

Metal selenides have attracted increased attention as promising electrode materials for electrochemical energy storage and conversion systems including metal-ion batteries and water splitting. However, their practical application is greatly hindered by collapse of the microstructure, thus leading to performance fading. Tuning the structure at nanoscale of these materials is an effective strategy to address the issue. Herein, we craft MoSe2 with hierarchical hollow structures via a facile bubble-assisted solvothermal method. The temperature-related variations of the hollow interiors are studied, which can be presented as solid, yolk-shell, and hollow spheres, respectively. Under the simultaneous action of the distinctive hollow structures and interconnections among the nanosheets, more intimate contacts between MoSe2 and electrolyte can be achieved, thereby leading to superior electrochemical properties. Consequently, the MoSe2 hollow nanospheres prepared under optimum conditions exhibit optimal electrochemical activities, which hold an initial specific capacity of 1287 mA h g-1 and maintain great capacity even after 100 cycles as anode for Li-ion battery. Moreover, the Tafel slope of 58.9 mV dec-1 for hydrogen evolution reaction is also attained.

Facile solution synthesis of hexagonal Alq3 nanorods and their field emission properties.

A facile self-assembly growth route assisted by surfactant has been developed to synthesize tris(8-hydroxyquinoline)aluminium (Alq(3)) nanorods with regular hexagonal shape and good crystallinity, which exhibit field-emission characteristics with a very low turn-on field of ca. 3.1 V microm(-1) and a high field-enhancement factor of ca. 1300.

N-2-Hydroxybenzaldehyde acylhydrazone-Fe(III) complex: synthesis, crystal structure and its efficient and selective N-methylation.

N-Methyl-N'-2-hydroxybenzaldehyde acylhydrazones have been chemospecifically synthesized in good yield by N-methylation of the Fe(iii) complexes of N-2-hydroxybenzaldehyde acylhydrazones with methyl iodide in tetrahydrofuran. The reaction proceeds with the exclusive formation of the N-methyl derivative without any concurrent O-methylation side reactions. In addition, the N-methylation reaction occurred simultaneously with a complete deprotection step (elimination of the metal ion). As a result, the N-methyl product was obtained in excellent purity without time-consuming chromatographic workup. A free N-2-hydroxybenzaldehyde acylhydrazone ligand could not be methylated under the same conditions.

A facile method to prepare monodispersed CdS/SiO2 composite microspheres and investigation on their photocatalytic properties.

This article presents a facile method to prepare CdS/SiO(2) composite microspheres and their good catalytic properties. In our method, monodispersed SiO(2) particles bearing amino groups (-NH(2)) were synthesized at first and then used as carriers to load nanosized CdS particles to form CdS/SiO(2) composite microspheres. With the addition of CdAc(2) solution to the SiO(2) dispersion, Cd(2+) was attracted to the surfaces of the SiO(2) particles through coordination interaction, and then thioacetamide was added to the dispersion. By heating, S(2-) released and reacted with the Cd(2+), CdS/SiO(2) composite microspheres were obtained accordingly. The photocatalytic properties of the as-prepared composite microspheres were investigated as well. It was found that the composite microspheres have excellent photocatalytic activities for the degradation of dyes comparing with the commercial P-25 TiO(2) catalysts. After using and recycling for three times, the photocatalytic performance still remained very well.

Spectral identification of specific photophysics of cy5 by means of ensemble and single molecule measurements.

The triplet-state characteristics of the Cy5 molecule related to trans-cis isomerization are investigated by means of ensemble and single molecule measurements. Cy5 has been used frequently in the past 10 years in single molecule spectroscopic applications, e.g., as a probe or fluorescence resonance energy transfer acceptor in large biomolecules. However, the unknown spectral properties of the triplet state and the lack of knowledge on the photoisomerization do not allow us to interpret precisely the unexpected single molecule behaviors. This limits the application of Cy5. The laser photolysis experiments demonstrate that the trans triplet state of Cy5 absorbs about 625 nm, the cis ground state absorbs about 690 nm, and the cis triplet state also absorbs about 690 nm. In other words, the T1-Tn absorptions largely overlap the ground-state absorptions for both trans and cis isomers, respectively. Furthermore, the observation of the cis triplet state indicates an important isomerization pathway from the trans-S1 state to the cis-T1 state upon excitation. The detailed spectra presented in this article let us clearly interpret the exact mechanisms responsible for several important and unexpected photophysical behaviors of single Cy5 molecules such as reverse intersystem crossing (RISC), the observation of dim states with a lower emission intensity and slightly red-shifted fluorescence, and unusual energy transfer from donor molecules to dark Cy5 molecules acting as acceptors in single molecule fluorescence resonance energy transfer (FRET) measurements. Spectral results show that the dim state in the single molecule fluorescence intensity time traces originated from cis-Cy5 because of a lower excitation rate, resulting from the red-shifted ground-state absorption of cis-Cy5 compared to that of the trans-Cy5.

Direct observation of delayed fluorescence from a remarkable back-isomerization in Cy5.

The direct observations of delayed fluorescence and phosphorescence from the cyanine dye Cy5 are reported. The delayed fluorescence is generated from the S(1) state of trans-Cy5 through a reserve intersystem crossing from the cis-triplet state T(1) to the trans-singlet state S(1) via thermal activation. The lowest cis-triplet state is evidenced to be involved in the formation of the isomer. The back-isomerization from cis-triplet state to trans-singlet state crossing, a remarkably back-isomerization pathway that has not been reported before, plays a significant role in this unusual delayed fluorescence.