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91.
Hao-Jung Chang Mykhailo V. Bondar Dr. Natalia Munera Dr. Sylvain David Dr. Olivier Maury Dr. Gerard Berginc Dr. Boris Le Guennic Dr. Denis Jacquemin Dr. Chantal Andraud Dr. David J. Hagan Dr. Eric W. Van Stryland 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(17):e202104072
The fast relaxation processes in the excited electronic states of functionalized aza-boron-dipyrromethene (aza-BODIPY) derivatives ( 1 – 4 ) were investigated in liquid media at room temperature, including the linear photophysical, photochemical, and nonlinear optical (NLO) properties. Optical gain was revealed for nonfluorescent derivatives 3 and 4 in the near infrared (NIR) spectral range under femtosecond excitation. The values of two-photon absorption (2PA) and excited-state absorption (ESA) cross-sections were obtained for 1–4 in dichloromethane using femtosecond Z-scans, and the role of bromine substituents in the molecular structures of 2 and 4 is discussed. The nature of the excited states involved in electronic transitions of these dyes was investigated using quantum-chemical TD-DFT calculations, and the obtained spectral parameters are in reasonable agreement with the experimental data. Significant 2PA (maxima cross-sections ∼2000 GM), and large ESA cross-sections ∼10−20 m2 of these new aza-BODIPY derivatives 1–4 along with their measured high photostability reveal their potential for photonic applications in general and optical limiting in particular. 相似文献
92.
Anna Bonfiglio Lenka Pallova Dr. Vincent César Dr. Christophe Gourlaouen Dr. Stéphane Bellemin-Laponnaz Dr. Chantal Daniel Dr. Federico Polo Dr. Matteo Mauro 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(51):11751-11766
A novel class of phosphorescent cationic heterobimetallic IrIII/MI complexes, where MI=CuI ( 4 ) and AuI ( 5 ), is reported. The two metal centers are connected by the hybrid bridging 1,3-dimesityl-5-acetylimidazol-2-ylidene-4-olate (IMesAcac) ligand that combines both a chelating acetylacetonato-like and a monodentate N-heterocyclic carbene site coordinated onto an IrIII and a MI center, respectively. Complexes 4 and 5 have been prepared straightforwardly by a stepwise site-selective metalation with the zwitterionic [(IPr)MI(IMesAcac)] metalloproligand (IPr=1,3-(2,6-diisopropylphenyl)-2H-imidazol-2-ylidene) and they have been fully characterized by spectroscopic, electrochemical, and computational investigation. Complexes 4 and 5 display intense red emission arising from a low-energy excited state that is located onto the “Ir(C^N)” moiety featuring an admixed triplet ligand-centered/metal-to-ligand charge transfer (3IL/1MLCT) character. Comparison with the benchmark mononuclear complexes reveals negligible electronic coupling between the two distal metal centers at the electronic ground state. The bimetallic systems display enhanced photophysical properties in comparison with the parental congeners. Noteworthy, similar non-radiative rate constants have been determined along with a two-fold increase of radiative rate, yielding brightly red-emitting cyclometalating IrIII complexes. This finding is ascribed to the increased MLCT character of the emitting state in complexes 4 and 5 due to the smaller energy gap between the 3IL and 1MLCT manifolds, which mix via spin–orbit coupling. 相似文献
93.
Sanz E Valeriani C Zaccarelli E Poon WC Pusey PN Cates ME 《Physical review letters》2011,106(21):215701
In supercooled liquids, vitrification generally suppresses crystallization. Yet some glasses can still crystallize despite the arrest of diffusive motion. This ill-understood process may limit the stability of glasses, but its microscopic mechanism is not yet known. Here we present extensive computer simulations addressing the crystallization of monodisperse hard-sphere glasses at constant volume (as in a colloid experiment). Multiple crystalline patches appear without particles having to diffuse more than one diameter. As these patches grow, the mobility in neighboring areas is enhanced, creating dynamic heterogeneity with positive feedback. The future crystallization pattern cannot be predicted from the coordinates alone: Crystallization proceeds by a sequence of stochastic micronucleation events, correlated in space by emergent dynamic heterogeneity. 相似文献
94.
Serge Michalet Laëtitia Payen‐Fattaccioli Chantal Beney Pascale Cégiéla Christine Bayet Gilbert Cartier Diderot Noungoué‐Tchamo Etienne Tsamo Anne‐Marie Mariotte Marie‐Geneviève Dijoux‐Franca 《Helvetica chimica acta》2008,91(6):1106-1117
Phytochemical investigation of barks of Christiana africana led to the identification of cyclopeptide alkaloids, flavonoids, coumarinolignans, iridoids, sesquiterpenoids, and triterpenes. This plant was classified so far in the Tiliaceae family. This study was started while the genomic study of numerous specimens was described in order to establish new criteria for Malvales botanical classification. In the present work, twenty components were identified, belonging to the three major classes of secondary metabolites: alkaloids, phenols, and terpenes. In the first class, cyclopeptides are well‐known compounds in Rhamnaceae and Sterculiaceae. Their presence in Malvaceae (in APG2 sensus) suggests a possible chemical link between the ex‐Tiliaceae and the Malvaceae. 相似文献
95.
K. Lorentz 《Analytical and bioanalytical chemistry》1974,269(3):182-187
Amino acids can be determined as charge-transfer complexes by reaction with p-benzoquinone in the presence of organic solvents. This method combines high sensitivity (? 490=2.5 cm2/μmole α-amino acid and 4.4 cm2 /μmole α,?-amino acid; ? 525=4.65 cm2/μmole proline) and rapid, cheap and simple procedure with good reproducibility, sufficient specifity, stable colour and insensitivity to ammonia and inorganic compounds. Optimal conditions and normal values are reported for the determination of amino nitrogen in serum and urine. 相似文献
96.
Two different cationic redox labels, i.e. a ferroceneammonium ion and a cobaltocenium ion, were covalently attached to two antiepileptics, phenytoin and phenobarbital, respectively. The two labeled drugs possess distinct standard redox potentials of 0.39 V for the phenytoin derivative and −0.92 V for phenobarbital derivative (vs Ag/AgCl, Cl− 0.05 M ) at a carbon paste electrode. After preconcentration in a polyanionic Nafion-loaded carbon paste electrode the positively charged labeled phenytoin and phenobarbital derivatives could be simultaneously detected in concentration ranges which were relevant to the therapeutic ranges of the antiepileptics, with a view to a future dual-analyte immuno- assay. Square-wave voltammetry permitted detection limits of 5×10−8 M (for the phenytoin derivative) and 2.5×10−8 M (for the phenobarbital derivative) for non-simultaneous detection. © 1998 John Wiley & Sons, Ltd. 相似文献
97.
The synthesis of new bioisosteric analogues of farnesyl pyrophosphate where a vinyl pyrophosphonate replaced the pyrophosphate moiety is described. These compounds have been prepared using a Horner–Wadsworth–Emmons procedure and a modified Michelson reaction. They have been evaluated for the inhibition of farnesyl protein transferase. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:654–661, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10081 相似文献
98.
99.
Near the interface between a normal metal and a superconductor, Cooper pairs penetrate into the normal side, giving rise to
the proximity effect. The two electrons of these pairs have entangled spin and orbital degrees of freedom. Nonlocal features
of quantum mechanics can be probed by separating these two electrons. This is achieved with a fork geometry with two normal
leads containing either spin- or energy-selective filters. A signature of entanglement can be detected by measuring the positive
noise cross-correlations in this fork. In the case of energy filters, Bell-inequality checks constitute a definite probe of
entanglement. We formulate Bell-type inequalities in terms of current-current cross-correlations associated with contacts
with varying magnetization orientations. We find maximal violation (as in photons) when a superconductor is the particle source. 相似文献
100.
Rathmann F Lenisa P Steffens E Contalbrigo M Dalpiaz PF Kacharava A Lehrach A Lorentz B Maier R Prasuhn D Ströher H 《Physical review letters》2005,94(1):014801
Polarized antiprotons can be produced in a storage ring by spin-dependent interaction in a purely electron-polarized hydrogen gas target. The polarizing process is based on spin transfer from the polarized electrons of the target atoms to the orbiting antiprotons. After spin filtering for about two beam lifetimes at energies T approximately equal 40-170 MeV using a dedicated large acceptance ring, the antiproton beam polarization would reach P=0.2-0.4. Polarized antiprotons would open new and unique research opportunities for spin-physics experiments in p(-) p interactions. 相似文献