New zwitterionic bisulfite compounds of aldehydes, such as pyridine-2-carbaldehyde
(1)
and qunoline-2-carbaldehydes
(2)
, were for the first time spectroscopically characterized and structurally ...studied. In the crystal structures, molecules
1
and
2
are connected
via
intermolecular OH⋯−O
3
S and NH
+
⋯−O
3
S interactions to form hydrogen-bonded chains. The oxidation of a solution of
2
in dimethyl sulfoxide with atmospheric air afforded quinaldil
(3)
and quinaldoin
(4).
In the crystalline state, compound
4
exists as the enediol tautomer formed by strong intramolecular hydrogen bonds.
8-Phenyl- and 8-(4-nitrophenyl)-BODIPYs with thien-2-ylthio- and (2,2'-dithien-5-yl)-thio-substitution at the 3,5-positions were synthesized. 2-Thienylthio derivatives were obtained using two ...different sequences, i.e., via nucleophilic substitution in the corresponding 1,9-dichlorodipyrromethenes, followed by BODIPY formation and via the same reaction using 3,5-dichloro-BODIPY dyes. The "dipyrromethene route" was observed to result in better overall yields. All the dyes were characterized by UV-Vis and fluorescence spectroscopy as well as cyclic voltammetry (CVA) studies. The UV-Vis spectra exhibited slight dependence on the thiophene chain length. The thienylthio derivatives fluoresce with modest quantum yields; conversely, no fluorescence has been detected for their dithienylthio counterparts. 8-Phenyl-3,5-di(thien-2-ylthio)-BODIPY was characterized by X-ray crystallography, which showed the layered arrangement of the molecules. The thienyl fragments of different molecules in the same layer form pairs alike H-aggregates, whereas the BODIPYs moieties in the different layers are arranged in a J-aggregate fashion. Solid fluorescence was observed for these crystals with a broad emission from 600 nm to longer than 850 nm. The CVA results correspond to those for known substituted BODIPYs except for the unusually high current observed for the oxidation process of the dithienyl derivatives with respect to the reduction process. This finding indicates oxidative film deposition.
Complexes {(NMe
2
H
2
)Ln(TDA)(HCOO) ∙ 0.5H
2
O)} are prepared by the solvothermal synthesis in a water–dimethylformamide (1 : 1) system from a mixture of 1,2,3-triazole-4,5-dicarboxylic acid (H
3
...TDA), NaOH, and Ln(NO
3
)
3
(Ln = Eu, Gd). The crystal structure of the europium complex is determined by X-ray structure analysis (CIF file CCDC no. 1939689). This compound is shown to be the ionic metal-organic framework, where the cavities in the anionic structure of Eu(TDA)(HCOO)
–
are partially occupied by the dimethylammonium cations and water molecules. The study of the luminescence spectra of the gadolinium derivative gives the energy of the triplet level of the H
3
TDA ligand (~25 300 cm
–1
), the value of which makes it possible to efficiently sensitize the luminescence of rare-earth metal ions, in particular, Eu
3+
. The decay kinetics and the emission and excitation spectra of the heterometallic derivatives {(NMe
2
H
2
)Gd
1 –
x
Eu
x
(TDA)(HCOO) ∙ 0.5H
2
O)} are studied. The dilution of europium with gadolinium results in a substantial decrease in the concentration quenching of the europium luminescence and an increase in the observed lifetimes of the excited state of Eu
3+
.
8-Phenyl- and 8-(4-nitrophenyl)-BODIPYs with thien-2-ylthio- and (2,2′-dithien-5-yl)-thio-substitution at the 3,5-positions were synthesized. 2-Thienylthio derivatives were obtained using two ...different sequences,
i.e.
,
via
nucleophilic substitution in the corresponding 1,9-dichlorodipyrromethenes, followed by BODIPY formation and
via
the same reaction using 3,5-dichloro-BODIPY dyes. The "dipyrromethene route" was observed to result in better overall yields. All the dyes were characterized by UV-Vis and fluorescence spectroscopy as well as cyclic voltammetry (CVA) studies. The UV-Vis spectra exhibited slight dependence on the thiophene chain length. The thienylthio derivatives fluoresce with modest quantum yields; conversely, no fluorescence has been detected for their dithienylthio counterparts. 8-Phenyl-3,5-di(thien-2-ylthio)-BODIPY was characterized by X-ray crystallography, which showed the layered arrangement of the molecules. The thienyl fragments of different molecules in the same layer form pairs alike H-aggregates, whereas the BODIPYs moieties in the different layers are arranged in a J-aggregate fashion. Solid fluorescence was observed for these crystals with a broad emission from 600 nm to longer than 850 nm. The CVA results correspond to those for known substituted BODIPYs except for the unusually high current observed for the oxidation process of the dithienyl derivatives with respect to the reduction process. This finding indicates oxidative film deposition.
Novel thienyl- and dithienylthio-BODIPYs were synthesized, which displayed unusual crystal packing and luminescence.
We present a search for charged Higgs bosons in top quark decays. We analyze the e+jets, μ+jets, ee, eμ, μμ, τe and τμ final states from top quark pair production events, using data from about 1 fb−1 ...of integrated luminosity recorded by the DØ experiment at the Fermilab Tevatron Collider. We consider different scenarios of possible charged Higgs boson decays, one where the charged Higgs boson decays purely hadronically into a charm and a strange quark, another where it decays into a τ lepton and a τ neutrino and a third one where both decays appear. We extract limits on the branching ratio B(t→H+b) for all these models. We use two methods, one where the tt¯ production cross section is fixed, and one where the cross section is fitted simultaneously with B(t→H+b). Based on the extracted limits, we exclude regions in the charged Higgs boson mass and tanβ parameter space for different scenarios of the minimal supersymmetric standard model.
We report observation of the electroweak production of single top quarks in ppover collisions at sqrts=1.96 TeV based on 2.3 fb(-1) of data collected by the D0 detector at the Fermilab Tevatron ...Collider. Using events containing an isolated electron or muon and missing transverse energy, together with jets originating from the fragmentation of b quarks, we measure a cross section of sigma(ppover --> tb + X, tqb + X) = 3.94 + or - 0.88 pb. The probability to measure a cross section at this value or higher in the absence of signal is 2.5 x 10(-7), corresponding to a 5.0 standard deviation significance for the observation.
We present a measurement of the W boson mass using data corresponding to 4.3 fb(-1) of integrated luminosity collected with the D0 detector during Run II at the Fermilab Tevatron pp collider. With a ...sample of 1,677,394 W → eν candidate events, we measure M(W) = 80.367 ± 0.026 GeV. This result is combined with an earlier D0 result determined using an independent Run II data sample, corresponding to 1 fb(-1) of integrated luminosity, to yield M(W) = 80.375 ± 0.023 GeV.
The synthesis, structure, optical and redox properties as well as photovoltaic studies of iridium(
iii
) complexes with cyclometalated 2-arylbenzimidazoles decorated with various polyaromatic ...fragments and an ancillary aromatic β-diketone are reported. Despite the strong preference of the iridium(
iii
) ion to form bis- or tris-cyclometalated complexes in which the metal participates in five-membered metallacycles, the cyclometalation of the benzimidazole ligands containing rigid π-extended systems yields dimeric complexes containing strained five- or six-membered metallacycles and allows for generating an extremely rare monocyclometalated complex. X-ray crystallography shows that the steric strain observed in the dimers is retained in heteroleptic diketonate complexes which is also corroborated by gas-phase DFT calculations. While emission maxima and redox potentials of the heteroleptic complexes exhibit just a moderate variation upon the change of the cyclometalated ligands, the extension of the π-system of the benzimidazole ligands give the complexes remarkable light absorption in the visible spectral range, which meets the requirements for application in dye-sensitized solar cells. At the titania photoanodes, these iridium dyes retain their optical properties and exhibit power conversion efficiencies under standard AM 1.5 G conditions comparable to those of other iridium-based sensitizers. These results demonstrate that the size and position of the π-extended fragment in cyclometalated ligands can modulate not only the electronic structure of the corresponding iridium(
iii
) complexes, but also affect their composition, structure and reactivity that may find implications in future design of emerging iridium dyes, emitters and catalysts.
Cyclometalation of 2-arylbenzimidazoles decorated with various polyaromatic fragments leads to formation of strongly absorbing iridium dyes applicable in DSSC and enables access to structurally diverse iridium(
iii
) complexes.
In this work, the results of the measurements of characteristics of 40-cm and 2-m scintillation counters irradiated by a particle beam with a momentum of 7 GeV/c from the accelerator of the Institute ...for High Energy Physics are presented. The scintillators used in counters are BC-404 and BC-408 scintillators. The counters are viewed from both ends by R1828-01 photomultiplier tubes. The PMT signal spectra are well described by a convolution of the Landau and Gaussian distributions. Their width is determined mainly by fluctuations of ionization energy losses. The time distributions of the signals obey the Gaussian law. For the 40-cm counter, the time resolution is σ(
T
) = 88 ps; for the 2-m counter, it varies from 120–160 ps in its center to ~100 ps near the end.
The muon system of the Run II DØ detector Abazov, V.M.; Alkhazov, G.; Baldin, B. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2005, Letnik:
552, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We describe the design, construction, and performance of the upgraded DØ
muon system for Run II of the Fermilab Tevatron collider. Significant improvements have been made to the major subsystems of ...the DØ
muon detector: trigger scintillation counters, tracking detectors, and electronics. The Run II central muon detector has a new scintillation counter system inside the iron toroid and an improved scintillation counter system outside the iron toroid. In the forward region, new scintillation counter and tracking systems have been installed. Extensive shielding has been added in the forward region. A large fraction of the muon system electronics is also new.
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