Diverse reactions of a fluorostannylenoid towards ethynes.

Fluoro(dialkyl)stannylenoid 2 exhibits unique reactivity towards ethynes with acetylenic hydrogen and those with trimethylsilyl groups, though the corresponding free dialkylstannylene 1 is inactive against those ethynes. Stannylenoid 2 reacts smoothly with gaseous ethyne and phenylethyne at room temperature, giving the corresponding diethynylstannanes, di(phenylethynyl)stannane 3 and diethynylstannane 6, respectively, in good yields with the concomitant evolution of H2. Trimethylsilyl-substituted ethynes such as 1-trimethylsilyl-(2-phenyl)ethyne and 1,2-bis(trimethylsilyl)ethyne react similarly to give 3 and bis(trimethylsilylethynyl)stannane 8, respectively. Rather unexpectedly, the reaction of 2 with (trimethylsilyl)ethyne affords 1,2-bis(ethenylstannyl)ethyne 7 in a good yield. The reactions of 2 with methyl and ethyl propynoates give the same products 4 and 5 as those obtained during the reaction of dialkylstannylene 1 without CsF. Pathways involving the nucleophilic attack of cesium acetylide to an ethyne-complexed stannylene were proposed, while the detailed mechanisms remain unknown. The structure of 7 was studied by single crystal X-ray diffraction analysis.

Excitation Wavelength Dependent Fluorescence of an ESIPT Triazole Derivative for Amine Sensing and Anti-Counterfeiting Applications.

Excitation wavelength dependent (Ex-De) emission materials have potential applications in anti-counterfeiting labels and bioimaging. Nevertheless, few purely organic chromophores are used in these areas. In this study, multiple excited states were incorporated into a molecule that was excited state intramolecular proton transfer (ESIPT) active, with the goal of manipulating the relaxation pathways of the excited states. The triazole derivative exhibits Ex-De photoluminescence (PL), and the maximum PL wavelength is located at 526 nm and 593 nm under a series of excitation wavelengths. Spectral identification indicates that the excimer and ESIPT processes are responsible for the green (526 nm) and orange (593 nm) fluorescence, respectively. Importantly, the quick response code and test strip prepared with this triazole derivative can be used for anti-counterfeiting and food spoilage detection applications, respectively. This research opens the door for developing novel Ex-De materials for anti-counterfeiting purposes.

The Effect of Substituent Position on Excited State Intramolecular Proton Transfer in Benzoxazinone Derivatives: Experiment and DFT Calculation.

The preparation and the photophysical behaviour of two benzoxazinone derivatives isomers 2-(1-hydroxynaphthalen-2-yl)-4H-benzo[e][1, 3]oxazin-4-one(1) and 2-(3-hydroxynaphthalen-2-yl)-4H-benzo[e][1, 3]oxazin-4-one(2) designed for displaying were reported. The effect of substituent position and solvent effect on the excited state intramolecular proton transfer (ESIPT) dynamics and the spectroscopic properties were investigated using a combined theoretical (i.e., time-dependent density function theory (DFT)) and experimental (i.e., steady-state absorption and emission spectra and time-resolved fluorescence spectra) study. The results showed that compound 1 would facilitate ESIPT process and favored the keto tautomer emission, while compound 2 suppressed the ESIPT process and favored the enol emission.

Synthesis of α-haloenamides via zinc halide mediated direct addition of benzhydryl halides to ynamides.

A regio- and stereoselective synthesis of highly substituted α-haloenamides was described via the zinc halide mediated direct addition of benzhydryl halides to ynamides under mild conditions. The products α-haloenamides were further transformed into multisubstituted enamides via Suzuki and Sonogashira cross-coupling reactions.

Rapid differentiation of ortho-, meta-, and para-isomers of halogenated phenylmethylidene hydrazinecarbodithioates by metal complexation and electrospray ionization mass spectrometry.

RATIONALE: Development of mass spectrometry (MS)-based methods for isomeric differentiation remains a challenging analytical task, and has attracted the interest of many research groups. It is relevant to develop a general method to differentiate the isomeric halogenated phenylmethylidene hydrazinecarbodithioates (MX, X = F, Cl, Br). METHODS: Diluted CH3 CN solutions containing NiCl2 and a title isomer (MX) were analyzed by electrospray ionization tandem mass spectrometry (ESI-MS(n)) in a quadrupole ion trap instrument equipped with an ESI source. Theoretical calculations were performed using the density functional theory (DFT) method at the uB3LYP/6-31+G(2d,p) level. RESULTS: In MS(3) experiments, the complex [MX + SCH3 + Ni](+) ion, resulting from dissociation of the ESI-generated complex [2MX - H + Ni](+) ion, undergoes ligand-exchange reactions with residual gas molecules, such as water, acetonitrile, and nitrogen in the ion trap, and the o-isomers [Mo-X + SCH3 + Ni](+) were found to undergo the characteristic HX elimination reactions to afford several unique ions. Each set of three isomers [MX + SCH3 + Ni](+) show significantly different reactivity, which has been corroborated by MS(4) experiments and theoretical calculations. CONCLUSIONS: A rapid method based on metal complexation and tandem mass spectrometric (MS(n)) analysis has been developed to differentiate three sets of positional isomers of halogenated phenylmethylidene hydrazinecarbodithioates (MX, X = F, Cl, Br).

On the origin of the methyl radical loss from deprotonated ferulic and isoferulic acids: electronic excitation of a transient structure.

Formation of radical fragments from even-electron ions is an exception to the "even-electron rule". In this work, ferulic acid (FA) and isoferulic acid (IFA) were used as the model compounds to probe the fragmentation mechanisms and the isomeric effects on homolytic cleavage. Elimination of methyl radical and CO2 are the two competing reactions observed in the CID-MS of [FA - H](-) and [IFA - H](-), of which losing methyl radical violates the "even-electron rule". The relative intensity of their product ions is significantly different, and thereby the two isomeric compounds can be differentiated by tandem MS. Theoretical calculations indicate that both the singlet-triplet gap and the excitation energy decrease in the transient structures, as the breaking C-O bond is lengthened. The methyl radical elimination has been rationalized as the intramolecular electronic excitation of a transient structure with an elongating C-O bond. The potential energy diagrams, completed by the addition of the energy barrier of the radical elimination, have provided a reasonable explanation of the different CID-MS behaviors of [FA - H](-) and [IFA - H](-).

[The effect of compressive stress on the factors for liver regeneration in hepatocytes Chang cell line].

OBJECTIVE: To investigate the effect of compressive stress on the factors for liver regeneration including NF-kappaB, signal transducers and activators of transcription 3 (STATS), c-fos and c-jun in hepatocytes Chang cell line. METHODS: Human hepatocytes Chang cell line were subjected to compressive stress at 1000 microstain or 2000 microstain, expression of NF-kappaB P65, p-STAT3, c-fos and c-jun were detected by Western blot or RT-PCR at 30 min, 1 h, 2 h, 3 h, 4 h, 6 h after application of compressive stress to indicate the priming of hepatocytes proliferation. RESULTS: Enhanced expressions of NF-kappaB P65 and p-STAT3 were observed in hepatocytes under compressive stress indicated by Western blot, the magnitude of compressive stress loaded significantly affected the level of expression of NF-kappaB P65 at 2 h (P = 0.046) and p-STAT3 at 1 h (P = 0.039), the peak of expression of p-STAT3 was at 30 minutes after stress-loading while NF-kappaB P65 was at 1 hour; RT-PCR showed that expression of c-fos was not significantly different between 1000 microstain and 2000 microstain at each time point, and expression of c-jun was significantly different at 30 minutes (P = 0.026), 1 h (P = 0.031), 2 h (P = 0.033) after compressive stress loading. CONCLUSION: These results indicate that compressive stress may play an important role in initiating the process of liver regeneration.

Cyanostilben-based derivatives: mechanical stimuli-responsive luminophors with aggregation-induced emission enhancement.

Cyanostilbene derivatives with the aggregation-induced emission enhancement (AIEE) activity are prepared by Knoevenagel and Suzuki reactions. Among them, the dye (Z)-2,3-bis(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl)acrylonitrile (CNS-4) nanoparticle suspension shows the polarity-dependent characteristics of the fluorescence properties. By the fluorescence spectroscopy and transmission electron microscopy (TEM) analysis, the restriction of transfer from the local excited (LE) state to the intramolecular charge-transfer (ICT) state and crystal formation results in a blue-shift in emission and enhances the intensity in the aggregate state. Additionally, the luminophors CNS-3 and CNS-4 possess the AIEE effect as well as mechanochromic fluorescent properties. This mechanofluorochromic behavior originates from the change between the crystalline and the amorphous state.

2,3,4,5-Tetraphenylsilole-based conjugated polymers: synthesis, optical properties, and as sensors for explosive compounds.

A series of linear 2,5-tetraphenylsilole-vinylene-type polymers were successfully synthesized for the first time. The tetraphenylsilole moieties were linked at their 2,5-positions through a vinylene bridge with p-dialkoxybenzenes to obtain polymer PSVB and with 3,6-carbazole to obtain polymer PSVC. For comparison, 2,5-tetraphenylsilole-ethyne-type polymer PSEB was also synthesized, in which the vinylene bridge of PSVB was replaced with an ethyne bridge. Very interestingly, the bridging group (vinylene or ethyne) had a significant effect on the photophysical properties of the corresponding polymers. The fluorescence peak of PSEB at 504 nm in solution originated from the emission of its silole moieties, whereas PSVB and PSVC emitted yellow light and no blueish-green emission from the silole moieties was observed, thus demonstrating that the emissions of PSVB and PSVC were due to their polymer backbones. More importantly, the 2,5-tetraphenylsilole-ethyne polymer exhibited a pronounced aggregation-enhanced emission (AEE) effect but the 2,5-tetraphenylsilole-vinylene polymer was AEE-inactive. Moreover, both AEE-active 2,5-tetraphenylsilole-ethyne polymer and AEE-inactive 2,5-tetraphenylsilole-vinylene polymers were successfully applied as fluorescent chemosensors for the detection of explosive compounds.

The pyrolytic reaction of ketonic hydrazones from S-methyl dithiocarbazate: a combined online GC-MS pyrolysis and DFT study.

The gas-phase pyrolysis of ketonic hydrazones from S-methyl dithiocarbazate R(1)R(2)C=N-NHC(=S)SCH(3) (R(1), R(2) = alkyl or aryl) was investigated by online GC-MS pyrolysis and theoretical calculation. Both of these pyrolytic products, ascribed to methanethiol and the corresponding N-isothiocyanate imines, were detected in the total ion chromatography (TIC) of GC-MS. Calculation results exhibit two stable configurational structures for reactants (Re), which can interconvert with relatively low barriers (<78 kJ/mol). DFT calculations showed that the two unimolecular pyrolytic processes, a direct 1,2-elimination of CH(3)SH for syn-Re and a two-step reaction pathway for trans-Re involving tautomer interconversion followed by decomposition of CH(3)SH, are competitive in the reaction. Both syn-Re and trans-Re exhibit lower critical energies in the propagation step of the radical pyrolysis than that in the unimolecular pyrolysis process (187.76 kJ/mol via 131.91 kJ/mol for syn-Re, and 159.15 kJ/mol via 98.92 kJ/mol for trans-Re). However, much more energy is needed to excite the compound to produce the methylthio radical, with 262.03 and 253.60 kJ/mol for syn-Re and trans-Re, respectively. Therefore, the unimolecular pyrolysis rather than the radical one occurs in the condition of this study.