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131.
Davide Bonifazi Gianluca Accorsi Nicola Armaroli Fayi Song Amit Palkar Luis Echegoyen Markus Scholl Paul Seiler Bernhard Jaun Franois Diederich 《Helvetica chimica acta》2005,88(7):1839-1884
We report the synthesis and physical properties of novel fullerene–oligoporphyrin dyads. In these systems, the C‐spheres are singly linked to the terminal tetrapyrrolic macrocycles of rod‐like meso,meso‐linked or triply‐linked oligoporphyrin arrays. Monofullerene–mono(ZnII porphyrin) conjugate 3 was synthesized to establish a general protocol for the preparation of the target molecules (Scheme 1). The synthesis of the meso,meso‐linked oligopophyrin–bisfullerene conjugates 4 – 6 , extending in size up to 4.1 nm ( 6 ), was accomplished by functionalization (iodination followed by Suzuki cross‐coupling) of the two free meso‐positions in oligomers 21 – 23 (Schemes 2 and 3). The attractive interactions between a fullerene and a ZnII porphyrin chromophore in these dyads was quantified as ΔG=−3.3 kcal mol−1 by variable‐temperature (VT) 1H‐NMR spectroscopy (Table 1). As a result of this interaction, the C‐spheres adopt a close tangential orientation relative to the plane of the adjacent porphyrin nucleus, as was unambiguously established by 1H‐ and 13C‐NMR (Figs. 9 and 10), and UV/VIS spectroscopy (Figs. 13–15). The synthesis of triply‐linked diporphyrin–bis[60]fullerene conjugate 8 was accomplished by Bingel cyclopropanation of bis‐malonate 45 with two C60 molecules (Scheme 5). Contrary to the meso,meso‐linked systems 4 – 6 , only a weak chromophoric interaction was observed for 8 by UV/VIS spectroscopy (Fig. 16 and Table 2), and the 1H‐NMR spectra did not provide any evidence for distinct orientational preferences of the C‐spheres. Comprehensive steady‐state and time‐resolved UV/VIS absorption and emission studies demonstrated that the photophysical properties of 8 differ completely from those of 4 – 6 and the many other known porphyrin–fullerene dyads: photoexcitation of the methano[60]fullerene moieties results in quantitative sensitization of the lowest singlet level of the porphyrin tape, which is low‐lying and very short lived. The meso,meso‐linked oligoporphyrins exhibit 1O2 sensitization capability, whereas the triply‐fused systems are unable to sensitize the formation of 1O2 because of the low energy content of their lowest excited states (Fig. 18). Electrochemical investigations (Table 3, and Figs. 19 and 20) revealed that all oligoporphyrin arrays, with or without appended methano[60]fullerene moieties, have an exceptional multicharge storage capacity due to the large number of electrons that can be reversibly exchanged. Some of the ZnII porphyrins prepared in this study form infinite, one‐dimensional supramolecular networks in the solid state, in which the macrocycles interact with each other either through H‐bonding or metal ion coordination (Figs. 6 and 7). 相似文献
132.
Sabrina Castellano Marisabella Santoriello Pietro Campiglia Giovanna Cardillo Alessia Bertamino Isabel Gomez-Monterrey Ettore Novellino Gianluca Sbardella 《Tetrahedron letters》2009,50(49):6869-6871
An inexpensive and regioselective approach to dihydrothieno[3,2-g]quinoline-4,9-dione is reported. A combination of a mild version of Skraup reaction with a sequential substitution/Michael addition allowed the selective preparation in acceptable yield of a pharmacologically important quinone derivative, previously obtained only in trace and together with the other regioisomer. 相似文献
133.
Roberta Ragni Enrico Orselli Gregg S. Kottas Omar Hassan Omar Francesco Babudri Adriana Pedone Francesco Naso Gianluca M. Farinola Prof. Dr. Luisa De Cola Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(1):136-148
The synthesis and photophysical and electrochemical characterisation of new heteroleptic iridium complexes with electron‐withdrawing sulfonyl groups and fluorine atoms bound to phenylpyridine ligands are reported. The emission energy of these materials strongly depends on the position of the sulfonyl groups and on the number of fluorine substituents. A 90 nm wide tuning range of photoluminescence from the blue‐green (λem=468 nm) of iridium(III)bis[2‐(4′‐benzylsulfonyl)phenylpyridinato‐N,C2′][3‐(pentafluorophenyl)‐pyridin‐2‐yl‐1,2,4‐triazolate] to the orange (λem=558 nm) of iridium(III)bis[2‐(3′‐benzylsulfonyl)phenylpyridinato‐N,C2′](2,4‐decanedionate) has been achieved. Emission quantum yields ranging from 47 to 71 % have also been found for degassed solutions of the complexes, and a surprisingly high value of 16 % was recorded for iridium(III)bis[2‐(5′‐benzylsulfonyl‐3′,6′‐difluoro)phenylpyridinato‐N,C2′](2,4‐decanedionate) in air‐equilibrated dichloromethane. A unusual stereochemistry of the benzylsulfonyl‐substituted dimer and heteroleptic complexes has been detected by 1H NMR spectroscopy, and is characterised by the mutual cis disposition of the pyridyl nitrogen atoms of the phenylpyridine ligands, which differs from the most common trans arrangement reported in the literature. 相似文献
134.
Serena Staccioli Maria Altamura Gianluca Giorgi Antonio Triolo 《Journal of mass spectrometry : JMS》2009,44(7):1081-1086
Di(hydroxybutyl) ether (DHBE), a liver protecting drug, is composed of a mixture of three regioisomers: 4‐(3‐hydroxybutoxy)‐2‐butanol (1), 3‐(4‐hydroxy‐2‐butoxy)‐1‐butanol (2), and 3‐(3‐hydroxybutoxy)‐1‐butanol (3). Unequivocal differentiation of each regioisomer of DHBE was rapidly obtained without isolation of the single components, using GC‐MS with electron ionization (EI). The mass spectrum of 1 showed a rearrangement ion at m/z 118, characteristic of the 3‐hydroxybutyl chain, deriving from loss of acetaldehyde from the molecular ion, whereas 2 and 3 were characterized by the ion at m/z 117, expected from α‐cleavage of the 4‐hydroxy‐2‐butyl chain. The species at m/z 118, in turn, loses a water molecule via a mechanism involving both alcohol hydrogens, as shown by deuterium exchange experiments. Both this finding and theoretical calculations support a mechanism in which the loss of acetaldehyde in 1 occurs via a cyclic intermediate, stabilized by a strong hydrogen bond between the alcohol oxygen bearing the charge and the other alcohol oxygen, and involves initial hydrogen transfer from the former to the latter. The EI spectrum of 2, having two 4‐hydroxy‐2‐butyl chains, showed the fragmentations expected from classical fragmentation rules of aliphatic ethers and alcohols, whereas the EI spectrum of 3, bearing one 4‐hydroxy‐2‐butyl and one 3‐hydroxybutyl chain, showed essentially the characteristic fragments of both chains. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
135.
Austin Nevin Daniela Comelli Iacopo Osticioli Lucia Toniolo Gianluca Valentini Rinaldo Cubeddu 《Analytical and bioanalytical chemistry》2009,395(7):2139-2149
The assessment of the influence of natural and artificial ageing on the spectrofluorescence of triterpenoid varnishes dammar
and mastic is the focus of this work. Both Fourier transform infrared (FTIR) microscopy using attenuated total reflectance
and Raman spectroscopy have been employed for complementary molecular analysis of samples. Synchronous fluorescence spectroscopy,
excitation emission spectroscopy, and statistical analysis of data have been used to monitor changes in the optical properties
of varnish samples. Assessment of naturally and artificially aged samples using excitation emission spectroscopy suggests
that extensive exposure to visible light does not lead to easily appreciable differences in the fluorescence of mastic and
dammar; cluster analysis has been used to assess changes, which occur with artificial ageing under visible light, indicating
that differences in the fluorescence spectra of aged triterpenoids may be insufficient for their discrimination. The results
highlight significant differences between the initial fluorescence of films of dammar and mastic and the fluorescence, which
develops with ageing and oxidation, and specific markers, which change with ageing in FTIR and Raman spectra, have been identified. 相似文献
136.
Buscemi S Pace A Piccionello AP Pibiri I Vivona N Giorgi G Mazzanti A Spinelli D 《The Journal of organic chemistry》2006,71(21):8106-8113
The hydrazinolysis reaction of 5-perfluoroalkyl-1,2,4-oxadiazoles with hydrazine or methylhydrazine as bidentate nucleophiles has been investigated. The reaction occurred through the addition of the bidentate nucleophile to the C(5)-N(4) double bond of the 1,2,4-oxadiazole followed by ring-opening and ring-closure (ANRORC) involving the second nucleophilic site of the reagent. This ring-closure step could involve either the original C(3) of the 1,2,4-oxadiazole (giving a five-to-five membered ring rearrangement) or an additional electrophilic center linked to it (exploiting a five-to-six membered ring rearrangement). An alternative initial nucleophilic attack may involve the additional electrophilic center linked at C(3), that is the carbonyl group, leading to the formation of the hydrazones which undergo the Boulton-Katritzky rearrangement (BKR). The chosen reaction path is a function of the used nucleophile and of the nature of the substituent at C(3). At variance with previous hypotheses, when methylhydrazine was used, the observed regiochemistry always showed the preferred initial attack by the less hindered NH(2) end of the nucleophile on C(5). Moreover, new spectroscopic evidence allowed the assignment of correct structures to the products formed by reaction of 5-perfluoroalkyl-3-phenyl-1,2,4-oxadiazoles with methylhydrazine. 相似文献
137.
Absolute frequency stabilization of an extended-cavity diode laser at 0.94 μm is reported. The diode laser was frequency locked against rovibrational absorption lines of water vapour by using the frequency modulation spectroscopy technique. The stabilized oscillator shows a short-term frequency stability level of 40 kHz for integration times of 1 s and a long-term frequency drift lower than 10 MHz for observation times longer than 103 s. The frequency-stabilized oscillator system is mounted on a compact breadboard (75 cm×50 cm) and constitutes the seed laser system for the injection of a high-energy DIAL laser transmitter operating in the 0.94-μm spectral region. 相似文献
138.
Carla Gasbarri Maurizio Ronci Antonio Aceto Roshan Vasani Gianluca Iezzi Tullio Florio Federica Barbieri Guido Angelini Luca Scotti 《Molecules (Basel, Switzerland)》2021,26(17)
The aim of this work was to deeply investigate the structure and properties of electrochemically synthesized silver nanoparticles (AgNPs) through high-resolution techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), Zeta Potential measurements, and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS). Strong brightness, tendency to generate nanoclusters containing an odd number of atoms, and absence of the free silver ions in solution were observed. The research also highlighted that the chemical and physical properties of the AgNPs seemed to be related to their peculiar oxidative state as suggested by X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRPD) analyses. Finally, the MTT assay tested the low cytotoxicity of the investigated AgNPs. 相似文献
139.
Calcagni Gianluca Modesto Leonardo Nicolini Piero 《The European Physical Journal C - Particles and Fields》2014,74(8):1-13
Application of the effective action approach to amplitudes with loop integration is studied for collisions on two and three centers with possible gluon emission. A rule is formulated for the integration around pole singularities in the induced vertices which brings the results in agreement with the QCD. It is demonstrated that the amplitudes can be restored from the purely transverse picture by introducing the standard Feynman propagators for intermediate gluons and quarks. 相似文献
140.
We investigate the asymptotic decrease of the Wannier functions for the valence and conduction band of graphene, both in the monolayer and the multilayer case. Since the decrease of the Wannier functions is characterised by the structure of the Bloch eigenspaces around the Dirac points, we introduce a geometric invariant of the family of eigenspaces, baptised eigenspace vorticity. We compare it with the pseudospin winding number. For every value $n \in \mathbb {Z}$ of the eigenspace vorticity, we exhibit a canonical model for the local topology of the eigenspaces. With the help of these canonical models, we show that the single band Wannier function $w$ satisfies $|w(x)| \le {\mathrm {const}} \cdot |x|^{-2}$ as $|x| \rightarrow \infty $ , both in monolayer and bilayer graphene. 相似文献