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31.
Valrie Niddam Martial Medou Jean Dessolin Carole Trabaud Michel Camplo Jean-Louis Kraus 《Journal of heterocyclic chemistry》1997,34(3):829-833
Synthetic approaches of N-α-hydroxyalkyl amides or urea derivatives are described. In particularly, a new 1,4,6-oxadiazocine-2,5,8-trione was obtained by condensation of glyoxylic acid on urea derivatives in acidic catalysis condition. 相似文献
32.
Francesco Talotta Martial Boggio-Pasqua Prof. Dr. Leticia González 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(50):11522-11528
The design of photoswitchable transition metal complexes with tailored properties is one of the most important challenges in chemistry. Studies explaining the underlying mechanisms are, however, scarce. Herein, the early relaxation dynamics towards NO photoisomerization in trans-[RuCl(NO)(py)4]2+ is elucidated by means of non-adiabatic dynamics, which provided time-resolved information and branching ratios. Three deactivation mechanisms (I, II, III) in the ratio 3:2:4 were identified. Pathways I and III involve ultrafast intersystem crossing and internal conversion, whereas pathway II involves only internal conversion. 相似文献
33.
Hall KF Boggio-Pasqua M Bearpark MJ Robb MA 《The journal of physical chemistry. A》2006,110(50):13591-13599
On the basis of an extensive ab initio electronic structure study of the ground and excited-state potential energy surfaces of the naphthalene radical cation (N*+), we propose a mechanism for its ultrafast nonradiative relaxation from the second excited state (D2) down to the ground state (D0), which could explain the experimentally observed photostability [Zhao, L.; Lian, R.; Shkrob I. A.; Crowell, R. A.; Pommeret, S.; Chronister, E. L.; Liu, A. D.; Trifunac, A. D. J. Phys. Chem. A., 2004, 108, 25]. The proposed photophysical relaxation pathway involves internal conversion from the D2 state down to the D0 state via two consecutive, accessible, sloped conical intersections (CIs). The two crossings, D0/D1 and D1/D2, are characterized at the complete active space self-consistent field (CASSCF) level. At this level of theory, the D0/D1 crossing is energetically readily accessible, while the D1/D2 CI appears too high in energy to be involved in internal conversion. However, the inclusion of dynamic correlation effects, via single point CASPT2 calculations including excitations out of the valence pi- and sigma-orbitals, lowers the D0 and D2 state energies with respect to D1. Extrapolations at the CASPT2 level predict that the D1/D2 crossing is then significantly lower in energy than with CASSCF indicating that with a higher-level treatment of dynamic correlation it may be energetically accessible following vertical excitation to D2. N*+ is proposed as one of the species contributing to a series of diffuse infrared absorption bands originating from interstellar clouds. Understanding the mechanism for photostability in the gas phase, therefore, has important consequences for astrophysics. 相似文献
34.
Lucjan Strekowski J. Christian Mason Hyeran Lee Martial Say Gabor Patonay 《Journal of heterocyclic chemistry》2004,41(2):227-232
Three methods were used to synthesize a series of the title compounds. The ketones absorb in the visible region, and upon protonation (pH<6) they are converted to hydroxy‐substituted heptamethine cyanines that show an intense absorption in the near‐infrared region (>700 nm). The conversion is reversible and depends solely on pH conditions. 相似文献
35.
Khanh-Duy Huynh Houssein Ibrahim Martial Toffano Giang Vo-Thanh 《Tetrahedron: Asymmetry》2010,21(11-12):1542-1548
A new class of β-amino alcohol and diamine ligands was prepared from isosorbide as a chiral renewable resource. The original wedge-shaped structure of isosorbide offers an interesting chiral pocket to promote the metal-catalyzed enantioselective reduction of ketones by transfer hydrogenation. 相似文献
36.
Michael J.?BearparkEmail author Martial?Boggio-Pasqua 《Theoretical chemistry accounts》2003,110(2):105-114
By using a parameterised Heisenberg Hamiltonian coupled to a molecular mechanics force field, excited-state geometries were optimised for three conjugated hydrocarbon radicals: cyclopentadienyl, phenalenyl (perinaphthenyl), and triphenylmethyl. The results are compared with ab initio calculations, and with recent spectroscopic measurements.
Electronic Supplementary Material is available in the online version of this article at http://dx.doi.org/10.1007/s00214-003-0461-3 相似文献
37.
Martial Mazars 《Molecular physics》2013,111(9):1241-1260
The purpose of this work is to carry out a comparison between the Ewald quasi-2D and Lekner summation methods. These methods were derived to treat the long-range electrostatic interactions in systems periodic in two directions, but bound in the third. The comparison is performed by Monte Carlo simulations on a very simple system, a bilayer of point ions; samplings of the phase space, average energies and structure functions are compared. When correctly implemented, the Lekner summation method is found to be in close agreement with the Ewald quasi-2D method; otherwise, a very complicated bias may plague computations. 相似文献
38.
Near-field coupling between an excited atom and a surface-polariton mode can dramatically modify atomic branching ratios, because of surface-induced enhancement of a resonant decay channel. We show here that Cs(6D(3/2)) transfer towards Cs(7P(1/2)) (at lambda = 12.15 microm), negligible in free space, becomes efficient in the vicinity (< or =100 nm) of a sapphire window, due to a 12 microm resonance in the surface-polariton modes. The experiment relies on a selective reflection probing on the 7P(1/2)-10D(3/2) transition. 相似文献
39.
Moritz Antlanger Martial Mazars Ladislav Šamaj Gerhard Kahl Emmanuel Trizac 《Molecular physics》2014,112(9-10):1336-1349
A planar array of identical charges at vanishing temperature forms a Wigner crystal with hexagonal symmetry. We take off one (reference) charge in a perpendicular direction, hold it fixed, and search for the ground state of the whole system. The planar projection of the reference charge should then evolve from a sixfold coordination (centre of a hexagon) for small distances to a threefold arrangement (centre of a triangle), at large distances d from the plane. The aim of this paper is to describe the corresponding non-trivial lattice transformation. For that purpose, two numerical methods (direct energy minimisation and Monte Carlo simulations), together with an analytical treatment, are presented. Our results indicate that the d = 0 and d → ∞ limiting cases extend for finite values of d from the respective starting points into two sequences of stable states, with intersecting energies at some value dt; beyond this value the branches continue as metastable states. 相似文献
40.
Nicolas Leuenberger Neil Robinson Martial Saugy 《Analytical and bioanalytical chemistry》2013,405(30):9617-9623
MicroRNAs (miRNAs) are small non-coding RNAs that regulate a variety of biological processes. Cell-free miRNAs detected in blood plasma are used as specific and sensitive markers of physiological processes and some diseases. Circulating miRNAs are highly stable in body fluids, for example plasma. Therefore, profiles of circulating miRNAs have been investigated for potential use as novel, non-invasive anti-doping biomarkers. This review describes the biological mechanisms underlying the variation of circulating miRNAs, revealing that they have great potential as a new class of biomarker for detection of doping substances. The latest developments in extraction and profiling technology, and the technical design of experiments useful for anti-doping, are also discussed. Longitudinal measurements of circulating miRNAs in the context of the athlete biological passport are proposed as an efficient strategy for the use of these new markers. The review also emphasizes potential challenges for the translation of circulating miRNAs from research into practical anti-doping applications. 相似文献