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101.
Marin ML Zaragoza RJ Miranda MA Diaba F Bonjoch J 《Organic & biomolecular chemistry》2011,9(9):3180-3187
Under radical reaction conditions, two different and competitive reaction pathways were observed for N-(α-methylbenzyl)trichloroacetamides with a N-3-cyclohexenyl substituent: 1,4-hydrogen translocation and radical addition to a double bond. However, for radicals with an acyclic alkenyl side chain, the direct cyclisation process was exclusively observed. The dichotomy between translocation and direct radical cyclisation in these substrates has been theoretically studied using density functional theory (DFT) methods at the B3LYP/6-31G** computational level. 相似文献
102.
Conjugated polymers have attracted considerable attention in the last few decades due to their potential for optoelectronic applications. A key step that needs optimisation is charge carrier separation following photoexcitation. To understand better the dynamics of the exciton prior to charge separation, we have performed simulations of the formation and dynamics of localised excitations in single conjugated polymer strands. We use a nonadiabatic molecular dynamics method which allows for the coupled evolution of the nuclear degrees of freedom and of multiconfigurational electronic wavefunctions. We show the relaxation of electron-hole pairs to form excitons and oppositely charged polaron pairs and discuss the modifications to the relaxation process predicted by the inclusion of the Coulomb interaction between the carriers. The issue of charge photogeneration in conjugated polymers in dilute solution is also addressed. 相似文献
103.
Wang Y Urban C Rodríguez-Fernández J Gallego JM Otero R Martín N Miranda R Alcamí M Martín F 《The journal of physical chemistry. A》2011,115(45):13080-13087
Formation of self-assembled chains of tetrathiafulvalene (TTF) on the Cu(100) surface has been investigated by scanning tunneling microscopy and density functional theory calculations that include semiempirical van der Waals (vdW) interaction corrections. The calculations show that the chain structures observed in the experiments can only be explained by including the vdW interactions. The molecules are tilted along the chain in order to achieve maximal intermolecular interaction. The chains are metastable on the surface, which is consistent with the experimental observation that they disappear after annealing. The fact that all TTF chains observed in the experiment are short might be possibly explained by the interplay between the stabilizing vdW molecule-molecule interaction and the destabilizing rearrangement of surface atoms due to the strong molecule-substrate interaction. 相似文献
104.
Yeh YC Patra D Yan B Saha K Miranda OR Kim CK Rotello VM 《Chemical communications (Cambridge, England)》2011,47(11):3069-3071
A new class of quaternary ammonium derivatives has been used to synthesize cationic CdSe/ZnS quantum dots with exceptional stability in water as well as in biological media. 相似文献
105.
106.
Nadezhda Rangelova Lachezar Radev Sanchi Nenkova Isabel M. Miranda Salvado Maria H. Vas Fernandes Michael Herzog 《Central European Journal of Chemistry》2011,9(1):112-118
Methylcellulose (MC) / SiO2 organic / inorganic hybrid materials have been prepared from MC and methyltriethoxysilane or ethyltrimethoxysilane, and characterized
by XRD, FTIR and AFM. XRD showed peak shifts. FTIR shows intermolecular hydrogen bonding between MC and SiO2. AFM depicts surface roughness which depends on the silica precursor and MC content.
相似文献
107.
M. Agostinha R. Matos Margarida S. Miranda Natália A. B. Pinto Victor M. F. Morais N. Dhananjaya Joel F. Liebman 《Molecular physics》2013,111(14):1885-1894
The standard (p°?=?0.1?MPa) molar enthalpy of formation for solid and gaseous diphenic anhydride (2,2′-biphenyldicarboxylic anhydride, dibenz[c,e]oxepin-5,7-dione) was derived from the standard molar enthalpy of combustion, in oxygen, at T?=?298.15?K, measured by static bomb combustion calorimetry, and the standard molar enthalpy of sublimation, at T?=?298.15?K, measured by Calvet microcalorimetry: ?(258.4?±?4.9) kJ?mol?1. In addition, ab initio and density functional theory calculations have been performed at a variety of levels. The degree of aromaticity of diphenic anhydride is discussed in the context of other oxygen-containing (ring and keto) heterocycles and related carbocycles: this species is surprisingly destabilized. 相似文献
108.
109.
A. Cruz Orea I. Delgadillo H. Vargas J.L. Pichardo J.J. Alvarado-Gil L.C.M. Miranda 《Solid State Communications》1996,100(12):855-859
The photoacoustic technique is used in semiconductor two-layer systems for the determination of thermal properties and thermal expansion coefficient. The two-layer systems studied were amorphous silicon-glass and Al0.2Ga0.8As---GaAs. Our results show that the proposed method is a reliable technique for the characterization of other semiconductor two-layers systems. 相似文献
110.
J. M. Garcia O. Sanchez P. Segovia J. E. Ortega J. Alvarez A. L. Vazquez de Parga R. Miranda 《Applied Physics A: Materials Science & Processing》1995,61(6):609-613
We observe the partial confinement of the twodimensional electron gas of ans-p-like surface state by the regular step distribution of several vicinal Cu(111) surfaces. The spatial distribution of the surface state is visualized by scanning tunneling microscopy. Local tunneling spectroscopy reveals a shift of the maximum of the density of states of the surface state towards the Fermi level, which correlates with the size of the terraces. The average shift is also measured by angle-resolved photoemission and found to be consistent with a one-dimensional Kronig-Penney model. 相似文献