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101.
Branchi B Bergamini G Fiandro L Ceroni P Alvino A Doddi G Vögtle F Klärner FG 《Dalton transactions (Cambridge, England : 2003)》2011,40(6):1356-1364
Complexation of Zn(II) ions by cyclam cored dendrimers appended with four (G0), eight (G1) and 16 naphthyl chromophores (G2) at the periphery have been investigated in CH?CN-CH?Cl? 1?:?1 (v/v) solution by absorption and emission, ESI-mass and 1H NMR spectroscopy. The results obtained can be interpreted by the formation of complexes of 2?:?1 dendrimer to metal stoichiometry, at low metal ion concentration, and 1?:?1 complexes upon further addition of Zn(II) ions, for all the dendrimer generations. Upon addition of a molecular clip C2? consisting of two anthracene sidewalls bridged by a benzene group with two sulfate substituents in the para positions, heteroleptic complexes of general formula [GnZnC] are formed. Interestingly, in these complexes, a very efficient quenching (practically 100%) of the dendrimer naphthyl luminescence and sensitization (ca. 90%) of the clip anthracene emission take place. The complex [G2ZnC] exhibits a very high molar absorption coefficient in the UV spectral region owing to the 16 naphthyl chromophores of the dendrimer and the two anthracene units of the clip (ε = 1.7 × 10? M?1 cm?1 at 263 nm). Furthermore, the excitation energy absorbed by the naphthyl chromophores is efficiently funneled to the two anthracene units of the clip, which emits in the blue spectral region. 相似文献
102.
Menichini F Tundis R Bonesi M de Cindio B Loizzo MR Conforti F Statti GA Menabeni R Bettini R Menichini F 《Natural product research》2011,25(8):789-799
The chemical composition of the essential oil of Citrus medica L. cv. Diamante peel obtained by hydrodistillation, cold-pressing and supercritical carbon dioxide extraction techniques was determined by GC/MS analysis. Forty-six components were fully characterised. Limonene and γ-terpinene were the major components of the oils obtained by hydrodistillation (HD) and cold-pressing (CP), while citropten was the major constituent in the oil obtained by supercritical carbon dioxide extraction (SFE). Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities were evaluated. The essential oil obtained by hydrodistillation exerted the highest inhibitory activity against BChE (IC?? value of 154.6 μg mL?1) and AChE (IC?? value of 171.3 μg mL?1. Interestingly, the oil obtained by cold-pressing exhibited a selective inhibitory activity against AChE. The essential oils have also been evaluated for the inhibition of NO production in LPS induced RAW 264.7 macrophages. The oil obtained by hydrodistillation exerted a significant inhibition of NO production with an IC?? value of 17 μg mL?1 (IC?? of positive control 53 μg mL?1). 相似文献
103.
Muniz-Miranda M Del Rosso T Giorgetti E Margheri G Ghini G Cicchi S 《Analytical and bioanalytical chemistry》2011,400(2):361-367
We investigated the chemisorption of self-assembled monolayers of sulfur-functionalized 4-amino-7-nitrobenzofurazan on gold
and silver nanoisland films (NIFs) by means of surface-enhanced fluorescence (SEF) and surface-enhanced Raman scattering (SERS).
The ligand is a push–pull molecule, where an intramolecular charge transfer occurs between an electron-donor and an electron-acceptor
group, thus exhibiting nonlinear optical properties that are related to both SERS and SEF effects. The presence of different
heteroatoms in the molecule ensures the possibility of chemical interaction with both silver and gold substrates. The SERS
spectra suggest that furazan is bound to silver via lone pairs of the nitrogen atoms, whereas the ligand is linked to gold
via a sulfur atom. Silver NIFs provide more efficient enhancement of both fluorescence and Raman scattering in comparison
with gold NIFs. The present SEF and SERS investigation could provide useful information for foreseeing changes in the nonlinear
responses of this push–pull molecule. 相似文献
104.
The paper deals with solutions of a differential inclusion constrained to a compact convex set Ω. Here F is a compact, possibly non-convex valued, Lipschitz continuous multifunction, whose convex closure co F satisfies a strict inward pointing condition at every boundary point x∈∂Ω. Given a reference trajectory x?(⋅) taking values in an ε-neighborhood of Ω, we prove the existence of a second trajectory x:[0,T]?Ω which satisfies . As shown by an earlier counterexample, this bound is sharp. 相似文献
105.
106.
Oriano Francescangeli Bin Yang Emo Chiellini Giancarlo Galli Annino Sante Angeloni Michele Laus 《Liquid crystals》1993,14(4):981-990
An X-ray study is performed on powder specimens and on stretched oriented fibres of two liquid crystalline polyacrylates containing the azobenzene mesogenic unit with either a 4'-n-pentyloxy (sample 1-4) or 4'-n-hexyloxy (sample 1-5) substituent. The X-ray diffraction patterns of both samples showed the presence of a bilayer smectic C mesophase with the mesogneic groups tilted by an angle β ∼ 45° (1-4) or β ∼ 38° (1-5) with respect to the layer normal. The electron density profile p(z) along the direction normal to the smectic layers was calculated by Fourier inversion and possible structural models of the smectic mesophase are discussed. A partial interdigitation of the terminal alkyloxy substituents appears to occur. 相似文献
107.
Simona Lai Emanuela Locci Giuseppe Saba Ivan Husu Giancarlo Masci Vittorio Crescenzi Adolfo Lai 《Journal of polymer science. Part A, Polymer chemistry》2003,41(20):3123-3131
Dry and hydrated poly(vinyl alcohol) (PVA) gels with 55% (a‐PVA) and 61% (s‐PVA) syndiotacticity and related PVA/lactyl chitosan (LC) blends have been investigated with 129Xe and cross‐polarization/magic‐angle‐spinning 13C NMR techniques. Although the dry gels exhibit two broad 129Xe resonances in the slow‐to‐intermediate exchange limit, both hydrated gels show three resonances. The corresponding dry blends exhibit two signals, the chemical shifts and line widths of which change with respect to those of pure PVA, whereas one (a‐PVA/LC) or two (s‐PVA/LC) signals appear in the spectra of the hydrated blends. A comparative analysis of the data demonstrates that LC rearranges the domains of the polymeric matrix in both the dry and hydrated blends according to the syndiotacticity of the PVA chains. Information on the molecular motions of the amorphous and swollen polymeric domains in the kilohertz range has been obtained from an analysis of the spin‐lattice relaxation times. These data indicate that the dynamics and arrangement of the PVA chains in the gels are strongly affected by their tacticity and the addition of the copolymer LC. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3123–3131, 2003 相似文献
108.
109.
Antonino Corsaro Ugo Chiacchio Giancarlo Perrini Pierluigi Caramella Giovanni Purrello 《Journal of heterocyclic chemistry》1985,22(3):797-799
Cycloadditions of nitrile oxides to N-mono and unsubstituted β-aminocinnamonitriles are remarkably affected by the hydrogen acceptor ability of the solvent. Addition to C ? N bond predominates in non and weak hydrogen bond acceptor solvents because of the assistance of favourable hydrogen bonding effects. In strong hydrogen bond acceptor solvents the assistance is fully relieved and the regular addition to C ? C bond becomes prevalent. 相似文献
110.
Experimental study on the retention of silica particles in gravitational field-flow fractionation effects of the mobile phase composition 总被引:3,自引:0,他引:3
Pierluigi Reschiglian Dora Melucci Giancarlo Torsi 《Journal of chromatography. A》1996,740(2):245-252
Effects of mobile phase composition can play an effective role in modulating the retention of particles in gravitational field-flow fractionation (GFFF), the simplest and cheapest among field-flow fractionation (FFF) techniques. In the framework of an optimized procedure for the GFFF characterization of particulate systems, an experimental approach to the effects of the mobile phase composition on the retention of silica particles retention is presented. The role of the ionic strength and the presence of surfactant are emphasized, with special regards to the shape of the particles. Moreover, the first experimental evidence of potential-barrier GFFF is reported. 相似文献