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101.
Claudio Bianchini Carlo A. Ghilardi Andrea Meli Stefano Midollini Annabella Orlandini 《Journal of organometallic chemistry》1983,255(2):C27-C30
CO2, COS, and SCNPh react under very mild conditions with the copper(I)-tetrahydroborate complexes [(PR3)2Cu(η2-BH4)] (R = Ph, Cy); CO2 and COS give the complexes [(PR3)2Cu(η2-O2CH)] and [(PR3)2Cu(η2-OSCH)] respectively, whereas SCNPh gives the η2-dithiocarbamate complexes [(PR3)2Cu-(η2-S2CNHPh)]. Addition of PPh3 under CO2 to solutions of [(PPh3)2Cu-(η2-BH4)] gives [(PPh3)3Cu(η1-O2CH)] while addition of PPh3 and NBu4ClO4 under CO2 gives [(PPh3)3Cu(η-O2CH)Cu(PPh3)3] ClO4. 相似文献
102.
Rosanna Bonaccorsi Carlo Petrongolo Eolo Scrocco Jacopo Tomasi 《Theoretical chemistry accounts》1969,15(4):332-343
The C.I. method is applied to already published double- SCF wave functions for OF2, NO
2
–
and CN–. All doubly excited configurations are considered. The second order approximation values presented for those cases are compared with the exact energy values in some minor cases. An attempt has been made to improve the rate of convergency of the process by transforming the canonical SCF occupied orbitals into localized ones and the virtual canonical orbitals into a particular type of localized orbitals. These latter show also an intuitively acceptable spatial conformation.
Work supported by the Consiglio Nazionale delie Ricerche. 相似文献
Zusammenfassung Die CI Methode wird auf bereits bekannte Doppel-Zeta-SCF-Wellenfuntionen für die Systeme OF2, NO 2 – und CN– angewandt. Dabei werden alle doppelt angeregten Konfigurationen berücksichtigt. Um die Konvergenz zu verbessern, werden versuchsweise die kanonischen und besetzten SCF-Orbitale in lokalisierte Orbitale und die virtuellen kanonischen Orbitale in einen besonderen Typ von lokalisierten Orbitalen transformiert. Die letzteren zeigen eine besonders geeignete räumliche Anpassung.
Résumé Pour un calcul de intéraction de configurations, comprenant toutes le configurations à double excitation, on a employé des fonctions d'onde SCF sur une base doublée. Pour le calcul complet on a essayé des formules d'approximation, qu'on a pu vérifier avec le calcul exact sur des cas réduits.Pour améliorer la vélocité de convergence du procés on a transformé les orbitales canoniques SCF en orbitales localisées et aprés on a construit, selon un procedé particulier, des orbitales virtuelles localisées qui montrent une conformation dans l'espace qui est intuitivement satisfaisante.
Work supported by the Consiglio Nazionale delie Ricerche. 相似文献
103.
Andreas Herrmann Markus Rüttimann Carlo Thilgen Franois Diederich 《Helvetica chimica acta》1995,78(7):1673-1704
104.
Hybrid density functional theory (B3LYP) method allows the study of the role of metal ions (Li(+)) in the regioselective opening of 2,3-epoxy alcohols with lithium halides (Cl, Br, I) to the corresponding halohydrins. The theoretical results largely confirm the experimental results, especially with regards to the regioselectivity observed in the opening of the oxirane ring. The C3 halogen attack is always preferred to the C2 attack, with a significant difference in the TS structures with the reaction pathway under kinetic control. The central role of the lithium cation, linked to the oxygen atoms of the epoxy alcohol, is well documented in the reaction mechanisms presented. The energy differences between the two structures of the proposed TS appear to be ascribed to the different contribution of the X-H-O hydrogen bond between the hydroxyl groups of the reactant and the incoming halogen nucleophile. 相似文献
105.
The 3 steps sequential extraction procedure proposed by the Standards Measurements and Testing program (SM&T--formerly BCR) of the European Union has been applied for the speciation of metals in sediments. Results obtained by the application of the BCR standardized procedure were compared to those of two four step sequential extraction procedures, which are different from the BCR procedure only for the introduction of an additional step with NaOCl, as 2nd and 3rd step respectively. Five different metals have been taken into consideration: Cd, Cu, Ni, Pb and Zn. The analytical performances of the laboratory have been evaluated using three certified reference materials: the BCR 601 lake sediment for the BCR sequential extraction procedure, PACS-1 and MESS-1 for total metal concentration. Results showed that the efficiency of NaOCl treatment is higher or at least equal to that of H2O2 treatment and that its selectivity is quite satisfying. Moreover the NaOCl treatment doesn't significantly influence the extraction of the easily reducible fraction. 相似文献
106.
Two new Ru(II) diimine chromophores, each containing a single photochromic dianthryl unit, have been prepared and characterized. The photoluminescence from the Ru(II) complexes is modulated by the photochromic action of the dianthryl species, which serves as a triplet energy transfer quencher in one photochromic state. The coupling of the dianthryl photochromic action to the Ru(II) complex emission permits nondestructive photoluminescence readout of binary information photochemically recorded on the molecular level. Luminescent images stored on polystyrene films that contain these molecules maintained their integrity for periods of months with no apparent degradation or variation in the image resolution, suggesting their durability for long-term storage in read-only memory applications. 相似文献
107.
Mario Di Braccio Giorgio Roma Gian Carlo Grossi Giovanni Ciarallo 《Journal of heterocyclic chemistry》1992,29(1):25-31
The reaction of 2-[(N-acyl, N-alkyl or phenyl)amino]-4H-pyrido[1,2-a]pyrimidin-4-ones 8a-g with the N,N-dimethylformamide/phosphorus oxychloride Vilsmeier reagent 1 (95°, 90 minutes) afforded 1-alkyl or phenyl-2H-dipyrido[1,2-a:2′,3′-d]pyrimidine-2,5(1H)?diones, 3-alkyl substituted or not, 10a-g . The starting compounds 8 were prepared by treating 2-amino-4H-pyrido[1,2-a]pyrimidin-4-ones N-alkyl substituted 7a,b or N-phenyl substituted 4 with excess anhydrides (130°, 7 hours) when the 2-(alkylamino) derivatives 7 were used in the reaction, compounds 8 were obtained along with very small amounts of 3-acyl-2-(alkylamino)-4H-pyrido[1,2-a]pyrimidin-4-ones 9 . 相似文献
108.
109.
Domenici V Geppi M Veracini CA Zakharov AV 《The journal of physical chemistry. B》2005,109(39):18369-18377
In this work, the rotational-diffusion coefficients D(parallel) and D(perpendicular) for the ferroelectric smectogen (+)-(S)-4-[4'-(1-methylheptyloxy)] biphenyl 4-(10-undecenyloxy)benzoate have been studied by means of 2H NMR spectroscopy in the smectic C phase, using a new theoretical approach (Domenici,V.; Geppi, M.; Veracini, C. A. Chem. Phys. Lett. 2003, 382, 518). The analysis of spin-lattice relaxation times has been performed in terms of the diffusional constant and the activation energy of the internal and overall molecular-reorientational motions, and the results are compared to the smectic A (SmA) phase. Moreover, from the 2H NMR data in the SmA phase, the dielectric permittivity and the dielectric relaxation time functions are investigated using a theoretical approach. The longitudinal and transverse components of the real Rchigammaomega and imaginary chigammaomega (gamma = parallel, perpendicular) parts of the complex susceptibility tensor and the nematic-like rotational-viscosity coefficients, lambda2 and lambda5, are calculated. 相似文献
110.
Moret I Gambaro A Piazza R Corami F Ravazzi C Andreoli C Truzzi C Lambertucci L Scarponi G 《Annali di chimica》2004,94(5-6):373-387
During the period March 1997-March 1998 dimethyl sulphide (DMS), dimethylsulphoniopropionate (DMSP) and carbon disulphide (CS2) were determined weekly in the water of the Lagoon of Venice, Italy (at three stations located in the Giudecca Canal, the San Secondo Canal and the Rio di San Nicolò). At the same time, the following hydrological and biological variables were also measured: tide height, temperature, transmittance, fluorescence, pH, salinity, chlorinity, sulphate, ammonia, nitrite, nitrate, phosphate, silicate, chlorophyll a, phaeopigments, phytoplankton (abundance and biomass). Principal component analysis (PCA), applied as a dimension reduction tool, made it possible to summarize multivariate information in a small number of components, which highlighted the relationships between the temporal evolutions of the sulphur compounds with hydrological and biological variables in the seasonal biogeochemical cycle of the lagoon. In particular the overall temporal cycle, which begins with the development of biological activity in late winter and spring, followed by the predominance of degradation processes during the late summer and the remineralization of nutrients in autumn, is clearly described in the plane of the first two principal components, together with the interrelationships between all the relevant variables. 相似文献