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991.
Cristian Dobrota 《Tetrahedron letters》2004,45(44):8153-8156
(S,S)-1,2,5-Triphenylphospholanium tetrafluoroborate salt 2 was conveniently used as chiral ligand precursor in rhodium-catalyzed asymmetric hydrogenation of methyl (Z)-2-acetamidocinnamate. 31P NMR showed the existence of a solvent-dependent equilibrium between the salt and the free phosphine. 相似文献
992.
The reduction of a series of alkyl mesylates, dimesylates and triflates to the corresponding hydrocarbons was efficiently performed using a reducing system composed of CuCl2·2H2O, an excess of lithium sand and a catalytic amount (5 mol%) of 4,4′-di-tert-butylbiphenyl (DTBB), in tetrahydrofuran at room temperature. The process was also applied to enol and dienol triflates affording alkenes and dienes, respectively. The use of the deuterated copper salt CuCl2·2D2O allowed the simple preparation of the corresponding deuterated products. 相似文献
993.
Dan Donescu Sever Serban Cristian Petcu Cristina Lavinia Nistor Marius Ghiurea Mihai Cosmin Corobea 《Colloid and polymer science》2007,285(13):1455-1462
The styrene (St), butyl acrylate (BuA), and methyl methacrylate (MMA) polymerization in microemulsion in the presence of sodium
dodecylsulfate is studied. This process is conducted in the presence of some comonomers having groups that can participate
in sol–gel processes: 3(trimethyloxysilyl) propyl methacrylate (MPTS), triethoxy vinylsilane (VTES), and a comonomer with
a sulfate group, styrene sodium sulfonate (StSO3Na). It has been observed that stabile latexes are obtained by radical polymerization at pH = 7, followed by a sol–gel process
in the presence of ammonia. Latex particles sizes and zeta potential grow with MTPS concentration and in StSO3Na presence. VTES effect depends on its reactivity in St, MMA, and BuA copolymerization. Glass transition temperature and
thermal decomposing temperature are influences by functional comonomer concentration and chemical structure. The Fourier transform
infrared spectrum and inorganic residue growth after organic part thermal decomposition shows the presence of silica in obtained
latexes. 相似文献
994.
Cristian Enachescu Andreas Hauser Jean-Jacques Girerd Marie-Laure Boillot 《Chemphyschem》2006,7(5):1127-1135
The photophysical properties of the ferric catecholate spin-crossover compounds [(TPA)Fe(R-Cat)]X (TPA=tris(2-pyridylmethyl)amine; X=PF(6) (-), BPh(4) (-); R-Cat=catecholate dianion substituted by R=NO(2), Cl, or H) are investigated in the solid state. The catecholate-to-iron(III) charge-transfer bands are sensitive both to the spin state of the metal ion and the charge-transfer interactions associated with the different catecholate substituents. Vibronic progressions are identified in the near-infrared (NIR) absorption of the low-spin species. Evidence for a low-temperature photoexcitation process is provided. The relaxation dynamics between 10 and 100 K indicate a pure tunneling process below approximately 40 K, and a thermally activated region at higher temperatures. The relaxation rate constants in the tunneling regime at low temperature, k(HL)(T-->0), vary in the range from 0.58 to 8.84 s(-1). These values are in qualitative agreement with the inverse energy-gap law and with structural parameters. A comparison with ferrous spin-crossover complexes shows that the high-spin to low-spin relaxation is generally faster for ferric complexes, owing to the smaller bond length changes for the latter. However, in the present case the corresponding rate constants are smaller than expected based on the single configurational coordinate model. This is attributed to the combined influence of the electronic configuration and the molecular geometry. 相似文献
995.
996.
Kemel Arafet Natalia Serrano-Aparicio Alessio Lodola Adrian J. Mulholland Florenci V. Gonzlez Katarzyna
widerek Vicent Moliner 《Chemical science》2021,12(4):1433
The SARS-CoV-2 main protease (Mpro) is essential for replication of the virus responsible for the COVID-19 pandemic, and one of the main targets for drug design. Here, we simulate the inhibition process of SARS-CoV-2 Mpro with a known Michael acceptor (peptidyl) inhibitor, N3. The free energy landscape for the mechanism of the formation of the covalent enzyme-inhibitor product is computed with QM/MM molecular dynamics methods. The simulations show a two-step mechanism, and give structures and calculated barriers in good agreement with experiment. Using these results and information from our previous investigation on the proteolysis reaction of SARS-CoV-2 Mpro, we design two new, synthetically accessible N3-analogues as potential inhibitors, in which the recognition and warhead motifs are modified. QM/MM modelling of the mechanism of inhibition of Mpro by these novel compounds indicates that both may be promising candidates as drug leads against COVID-19, one as an irreversible inhibitor and one as a potential reversible inhibitor.QM/MM simulations identify the mechanism of reaction of N3, a covalent peptidyl inhibitor of SARS-CoV-2 main protease. Modelling of two novel proposed compounds, B1 and B2, suggests that reversibility of covalent inhibition could be tailored. 相似文献
997.
Cristian Silvestru Florin Illie Ionel Haiduc 《Journal of organometallic chemistry》1987,330(3):315-324
Di- and tri-organotin(IV) diphenyldithiophosphinates, R2Sn(S2PPh2)2 (R = Me, n-Bu, Bz, Ph) and R3SnS2PPh2 (R = Me, Cy, Bz, Ph) were prepared by reaction of the corresponding organotin chlorides or oxides with diphenyldithiophosphinic acid or its ammonium salt. All the compounds were characterized by IR and 1H NMR spectra. For R2Sn(S2PPh2)2 (R = Me, Ph) and Ph3SnS2PPh2 mass spectra and tin-119m Mössbauer spectra were also recorded. Monodentate bonding of the dithiophosphinic ligand and tetrahedral structures are proposed for the triorganotin derivatives, while in diorganotin compounds there appears to be distorted octahedral geometry around tin, with anisobidentate dithiophosphonic ligands. 相似文献
998.
Accurate ground-state intermolecular potential-energy surfaces are obtained for the HCCH-He, Ne, and Ar van der Waals complexes. The interaction energies are calculated at the coupled cluster singles and doubles including connected triple excitations level and fitted to analytic functions. For the three complexes we start with systematic basis set studies carried out at several intermolecular geometries, and using augmented correlation consistent polarized valence basis sets x-aug-cc-pVXZ (x=-,d; X=D,T,Q,5), also extended with a set of 3s3p2d1f1g midbond functions. The aug-cc-pVQZ-33211 surfaces of HCCH-He, Ne, and Ar complexes are characterized by absolute minima of -24.22, -50.20, and -122.17 cm(-1) at distances R between the rare-gas atom and the HCCH centers of mass of 4.35, 3.95, and 3.99 A, respectively; and at angles between the vector R and the HCCH main symmetry axis of 0 degrees , 43.3 degrees , and 60.6 degrees . The results are compared and considerably improve those previously available. 相似文献
999.
1000.
Ren von der Stück Maren Krause Dana Brünink Stefan Buss Nikos L. Doltsinis Cristian A. Strassert Axel Klein 《无机化学与普通化学杂志》2022,648(1):e202100278
Cyclometalated Pd(II) complexes generally show inferior luminescence properties compared with their Pt(II) analogues. The established approach employing tridentate cyclometalating ligands has allowed us to create a series of square planar Pd(II) complexes [Pd( )X] from their protoligands H (2-(6-phenylpyridin-2-yl)thiazoles and -benzothiazoles; coligands X=Cl, Br, I) with extensive variations at the Carene group (phenyl, naphthyl, fluorenyl), the central Npyridine (pyridine, 4-phenylpyridine, 3,5-di-tert-butyl-4-phenylpyridine), and the peripheral Nthiazole (thiazole, benzothiazole) to probe for structural factors that might enhance efficient luminescence. Long-wavelength bands at 400–500 nm were assigned to transitions into mixed ligand-centred/metal-to-ligand charge transfer (MLCT) states based on time-dependent (TD)DFT calculations. The MLCT contributions are rather low, in agreement with relatively long lifetimes and high photoluminescence quantum yields of up to 0.79 recorded in frozen glassy solvent matrices at 77 K along with emission bands showing pronounced vibrational progressions and peaking at about 520 nm. No photoluminescence was observed at 298 K in solution. Variation of the ligand allowed to shift the experimental absorption energies from about 2.4 to 2.7 eV, in good agreement with the electrochemical band gaps (2.58 to 2.81 eV). The theoretical absorption and emission spectra excellently reproduced the experimental trends. 相似文献