Search results for "Benzene"
showing 10 items of 1701 documents
Azobenzene Polyesters Used as Gate-Like Scaffolds in Nanoscopic Hybrid Systems
2012
The synthesis and characterisation of new capped silica mesoporous nanoparticles for on-command delivery applications is reported. Functional capped hybrid systems consist of MCM-41 nanoparticles functionalised on the external surface with polyesters bearing azobenzene derivatives and rhodamine¿B inside the mesopores. Two solid materials, Rh-PAzo8-S and Rh-PAzo6-S, containing two closely related polymers, PAzo8 and PAzo6, in the pore outlets have been prepared. Materials Rh-PAzo8-S and Rh-PAzo6-S showed an almost zero release in water due to steric hindrance imposed by the presence of anchored bulky polyesters, whereas a large delivery of the cargo was observed in the presence of an esteras…
Influence of preparation conditions on the catalytic performance of mo/h-zsm-5 for methane dehydroaromatization
2021
[EN] Methane, the main component of natural gas, is an interesting source of chemicals and clean liquid fuels, and a promising alternative raw material to oil. Among the possible direct routes for methane conversion, its aromatization under non-oxidative conditions has received increasing attention, despite the low conversions obtained due to thermodynamic limitations, because of its high selectivity to benzene. Mo/H-ZSM-5, the first bifunctional zeolite-catalyst proposed for this reaction, is still considered as one of the most adequate and has been widely studied. Although the mono- or bifunctional nature of the MDA mechanism is still under debate, it is generally accepted that the Mo spe…
Photomodulation of Two-Dimensional Self-Assembly of Azobenzene-Hexa-peri-hexabenzocoronene-Azobenzene Triads
2019
International audience; Achieving exquisite control over self-assembly of functional polycyclic aromatic hydrocarbons (PAH) and nanographene (NG) is essential for their exploitation as active elements in (nano)technological applications. In the framework of our effort to leverage their functional complexity, we designed and synthesized two hexa-peri-hexabenzocoronene (HBC) triads, pAHA and oAHA, decorated with two light-responsive azobenzene moieties at the pseudo-para and ortho positions, respectively. Their photoisomerization in solution is demonstrated by UV–vis absorption. 1H NMR measurements of oAHA suggested 23% of Z-form can be obtained at a photostationary state with UV irradiation …
Thermo- and Light-Responsive Polymers Containing Photoswitchable Azobenzene End Groups
2009
Telechelic thermo- and light-responsive polymers based on poly(oligo(ethylene glycol) methyl ether methacrylate) P(OEGMA) with azobenzene functionalities at the end groups were synthesized. In a reversible addition−fragmentation chain transfer (RAFT) polymerization using a functionalized chain transfer agent (CTA) containing a pentafluorophenyl (PFP) activated ester, oligo(ethylene glycol) methyl ether methacrylate (OEGMA, Mn ∼ 300 g mol−1) could successfully be polymerized with good control over molecular weight, very high conversions, and narrow molecular weight distributions. Polymers derived from this CTA possessed an activated ester at the α-end of the polymer chain as well as a dithio…
5,11,17,23-Tetra-tert-butyl-25,26,27,28-tetrapentoxycalix[4]arene
2005
The molecule of the title compound, C64H96O4, adopts the typical pinched-cone conformation. The dihedral angles between the reference plane (defined by the C atoms of the methylene bridges) and the benzene rings are 86.88 (4), 136.64 (5), 87.22 (4) and 133.99 (4)°.
Green determination of the presence of volatile organic compounds in vehicle repair shops through passive sampling.
2012
A simple, fast and green direct analytical methodology has been developed to evaluate the concentration level of volatile organic compounds (VOCs) in indoor areas of vehicle repair shops using membrane devices as passive samplers. VOCs retained in the samplers were directly determined without any sample pre-treatment and avoiding the use of solvents by head space (HS) coupled to gas chromatography-mass spectrometry (GC-MS) in only 20 min. Benzene, toluene, tetrachloroethene, m,p-xylene and o-xylene were found at concentration levels from 0.1 to 11.2 mg m(-3).
Mesophase behaviour of 2,5-dibenzoyloxy-p-benzoquinone derivatives and tetrahydrobenzene tetraesters
1991
Abstract The synthesis of 2,5-dibenzoyloxy-p-benzoquinone derivatives, their products after reduction and tetraesters from tetrahydroxybenzene prepared from those products is described. Their phase behaviour was investigated by differential scanning calorimetry and polarizing microscopy and is discussed in terms of their detailed structure.
Synthesis and characterization of chiral azobenzene dye functionalized Janus dendrimers
2008
Abstract Eight bischromophoric bisMPA based polyester Janus dendrimers emanating from a pentaerythritol core were synthesized and their properties evaluated. 4-((4-(Ethyl(2-(2-(6-methoxynaphthalen-2-yl)propanoyloxy)ethyl)amino)-phenyl)diazenyl)-benzoic acid and 4-((4-(ethyl(2-(2-(6-methoxynaphthalen-2-yl)propanoyloxy)-ethyl)-amino)phenyl)diazenyl)-3-nitrobenzoic acid were attached to the dendritic polyester skeleton to make chiral dendrimers up to the second generation. The structures and the purity of the molecules were verified with 1H NMR, 13C NMR, ESI TOF mass spectrometry, and elemental analysis. Spectral properties were evaluated with UV–vis and CD spectrometer. The compounds displaye…
The two-dimensional iron(ii)–thiocyanate–4,4′-bipyridine coordination network
2010
The crystal structures of eight solvates of {Fe(4,4′-bipyridine)2(NCS)2}n have been determined. All of them contain a layered iron–bipyridine–thiocyanate framework formed from approximately square infinite two-dimensional (4,4) iron–bipyridine grids, with the solvent molecules hosted between adjacent layers. All the structures contain the iron(II) centres in the high-spin electronic configuration, and magnetic susceptibility measurements on the toluene and nitrobenzene solvates do not reveal any spin-crossover behaviour.
The catalytic reduction of nitrobenzene at the [MoVIO2(O2CC(S)(C6H5)2)2]2? complex intercalated in a Zn(II)-Al(III) layered double hydroxide host: A …
2001
The heterogeneous reduction of nitrobenzene by thiophenol catalyzed by the dianionic bis(2-sulfanyl-2,2-diphenylethanoxycarbonyl) dioxomolybdate(VI) complex, [MoVIO2(O2CC(S)(C6H5)2)2]2−, intercalated into a Zn(II)–Al(III) layered double hydroxide host [Zn3−xAlx(OH)6]x+, has been investigated under anaerobic conditions. Aniline was found to be the only product formed through a reaction consuming six moles of thiophenol for each mol of aniline produced. The kinetics of the system have been analyzed in detail. In excess of thiophenol, all reactions follow first-order kinetics (ln([PhNO2]/[PhNO2]0) = −kappt) with the apparent rate constant kapp being a complex function of both initial nitrobenz…