Search results for "PHOTOCHEMISTRY"
showing 10 items of 2034 documents
Dehydrogenation versus Oxygenation in Two-Electron and Four-Electron Reduction of Dioxygen by 9-Alkyl-10-methyl-9,10-dihydroacridines Catalyzed by Mo…
2004
Dehydrogenation of 10-methyl-9,10-dihydroacridine (AcrH(2)) by dioxygen (O(2)) proceeds efficiently, accompanied by the two-electron and four-electron reduction of O(2) to produce H(2)O(2) and H(2)O, which are effectively catalyzed by monomeric cobalt porphyrins and cofacial dicobalt porphyrins in the presence of perchloric acid (HClO(4)) in acetonitrile (MeCN) and benzonitrile (PhCN), respectively. The cobalt porphyrin catalyzed two-electron reduction of O(2) also occurs efficiently by 9-alkyl-10-methyl-9,10-dihydroacridines (AcrHR; R = Me, Et, and CH(2)COOEt) to yield 9-alkyl-10-methylacridinium ion (AcrR+) and H(2)O(2). In the case of R = Bu(t) and CMe(2)COOMe, however, the catalytic two…
Chemical and electrochemical behaviour of 4,4’,4’’,4’’’-tetrakis(dimethylamino)-tetraphenylethylene in an oxidant environment: Toward a new sensor fo…
2020
Abstract Electrochromic compounds are suitable candidates for being used in sensor design. Here we report the use of 4,4’,4’’,4’’’-tetrakis(dimethylamino)-tetraphenylethylene for detecting both NO2 and SO2. Whereas the sensing mechanism in the case of nitrogen dioxide is a simple chemical oxidation reaction, in the case of sulfur dioxide, the mechanism is much more complex and the reaction requires the presence of t-butylhydroperoxide to take place. By modifying the detection conditions both compounds can be detected in gas phase. Additionally, a wide electrochemical study has been carried out to understand the role played by the t-butylhydroperoxide in the reaction with sulfur dioxide.
Singlet and triplet energy transfer rate acceleration by additions of clusters in supramolecular pigment-organometallic cluster assemblies
2011
Both S(1) and T(1) energy transfer rates (porphyrin → cluster) increase from mono- to di- to tetracarboxylate[tetraphenyl-(zinc)porphyrin] adducts with [Pd(3)(dppm)(3)(CO)](2+) clusters.
Blue-emitting pyrene-based aggregates.
2015
The self-assembling features and gel formation of two pyrene imidazoles are presented. The supramolecular aggregation of these synthesised molecules results in an unusual blue-monomeric emission, which is rationalized by a combined experimental and theoretical investigation.
Unexpected photochemistry and charge-transfer complexes of [CB(11)H(12)](-) carborane.
2008
Although the [CB(11)H(12)](-) carborane does not exhibit an absorption band in UV, its triplet excited state can be generated upon 308 nm laser excitation; also unexpectedly carborane acts as electron donor forming a charge transfer complex with methylviologen that upon illumination gives rise to viologen radical cation.
Multielectron transfer in a dicopper(II) anthraquinophane.
2013
The new dinuclear copper(II) metallacyclophane with the non-innocent N,N'-1,4-bis(oxamate)-9,10-anthraquinone bridging ligand possesses a dual multielectron redox behavior featuring stepwise one-electron oxidation of the antiferromagnetically coupled Cu(II) ions and two-electron reduction of the anthraquinone spacers in a π-stacked anti conformation.
The first metamagnetic one-dimensional molecular material with nickel(ii) and end-to-end azido bridges
2001
A novel single azido bridged one-dimensional Ni(II) chain, which represents the first metamagnetic one-dimensional metal–azido system with only end-to-end azido bridges, has been synthesised and characterised by a low temperature magnetic study. Lloret Pastor, Francisco, Francisco.Lloret@uv.es
Mass spectra of chlorinated veratroles (1,2-dimethoxybenzenes)
1987
The behaviour of all nine chlorinated veratroles (1,2-dimethoxybenzenes) under electron impact has been investigated. The most common fragmentation processes are interpreted using metastable ion analysis and deuterium labelled compounds. For all compounds studied, the most common fragmentation route seems to be the primary loss of a methyl radical followed by loss of carbon monoxide. The ion formed has a well-known quinonoid structure and fragments by several routes elucidated by metastable ion analysis. In general, the spectra of the positional isomers are shown to be practically similar and it is apparent that e.g. the 3- and 4-chloro isomers can be differentiated only from the abundance …
Identification of microplastics using 4‐dimethylamino‐4′‐nitrostilbene solvatochromic fluorescence
2021
In this work, we introduce the use of 4-dimethylamino-4'-nitrostilbene (DANS) fluorescent dye for applications in the detection and analysis of microplastics, an impendent source of pollution made of synthetic organic polymers with a size varying from less than 5 mm to nanometer scale. The use of this dye revealed itself as a versatile, fast and sensitive tool for readily discriminate microplastics in water environment. The experimental evidences herein presented demonstrate that DANS efficiently absorbs into a variety of polymers constituting microplastics, and its solvatochromic properties lead to a positive shift of the fluorescence emission spectrum according to the polarity of the poly…
Frequency selective excitation of single chromophores within shape-persistent multichromophoric dendrimers
2003
Isolated multichromophoric dendrimers containing four perylenemonoimide chromophores were investigated in a confocal microscope which allowed imaging of the same set of dendrimers over a wide temperature range. Emission spectra at low temperature (2 K) reveal narrow zero-phonon lines although the electron-phonon coupling is not negligible. By using fluorescence excitation spectroscopy, the sharp purely electronic zero-phonon lines of single chromophores within a single multichromophoric unit could be isolated in the frequency domain. Selective excitation into a higher energy chromophoric site is followed by rapid directional energy transfer into the lowest energy site from which emission th…