Search results for "ROS"
showing 10 items of 59694 documents
Effect of Iodination on the Photophysics of the Laser Borane anti-B18H22: Generation of Efficient Photosensitizers of Oxygen
2019
Treatment of the laser borane anti-B18H22 (compound 1) with iodine in ethanol gives the monoiodinated derivative 7-I-anti-B18H21 (compound 2) in 67% yield, or, by reaction with iodine or ICl in the presence of AlCl3 in dichloromethane, the diiodinated derivative 4,4'-I2-anti-B18H20 (compound 3) in 85% yield. On excitation with 360 nm light, both compounds 2 and 3 give strong green phosphorescent emissions (λmax = 525 nm, ΦL = 0.41 and λmax = 545 nm, ΦL = 0.71 respectively) that are quenched by dioxygen to produce O2(1Δg) singlet oxygen with quantum yields of ΦΔ = 0.52 and 0.36 respectively. Similarly strong emissions can be stimulated via the nonlinear process of two-photon absorption when …
Photo-Chromium: Sensitizer for Visible-Light-Induced Oxidative C−H Bond Functionalization-Electron or Energy Transfer?
2017
The chromium(III) sensitizer [Cr(ddpd)2]3+ - based on an earth-abundant metal center - possesses a unique excited state potential energy landscape (ddpd = N,N'-dimethyl-N,N'-dipyridine-2-ylpyridine-2,6-diamine). The very large energy gap between the redox active and substitutionally labile 4T2 state and the long-lived low-energy 2E spin-flip state enables a selective, efficient sensitization of triplet dioxygen to give singlet dioxygen. Ultrafast intersystem crossing after the Franck Condon point from the 4T2 to the 2E excited state within 3.5 ps precludes intermolecular electron transfer pathways from the ultrashort-lived excited 4T2 state. This specific excited state reactivity enables a …
Co–Co and Co–Fe cyano-bridged pentanuclear clusters based on a methylpyrazinyl-diamine tetradentate ligand: spin crossover and metal substitution eff…
2017
A pentanuclear [CoII3CoIII2] cluster complex has been developed by a solvothermal synthesis. Its highly stable metal-mixed Fe–Co derivatives display robust spin crossover (T1/2 = 268 K) controlled by the degree of substitution.
A spin-crossover complex based on a 2,6-bis(pyrazol-1-yl)pyridine (1-bpp) ligand functionalized with a carboxylate group
2014
Combining Fe(ii) with the carboxylate-functionalized 2,6-bis(pyrazol-1-yl)pyridine (bppCOOH) ligand results in the spin-crossover compound [Fe(bppCOOH)2](ClO4)2 which shows an abrupt spin transition with a T1/2 of ca. 380 K and a TLIESST of 60 K due to the presence of a hydrogen-bonded linear network of complexes.
Nonanuclear Spin-Crossover Complex Containing Iron(II) and Iron(III) Based on a 2,6-Bis(pyrazol-1-yl)pyridine Ligand Functionalized with a Carboxylat…
2016
The synthesis and magnetostructural characterization of [Fe(III)3(μ3-O)(H2O)3[Fe(II)(bppCOOH)(bppCOO)]6](ClO4)13·(CH3)2CO)6·(solvate) (2) are reported. This compound is obtained as a secondary product during synthesis of the mononuclear complex [Fe(II)(bppCOOH)2](ClO4)2 (1). The single-crystal X-ray diffraction structure of 2 shows that it contains the nonanuclear cluster of the formula [Fe(III)3(μ3-O)(H2O)3[Fe(II)(bppCOOH)(bppCOO)]6](13+), which is formed by a central Fe(III)3O core coordinated to six partially deprotonated [Fe(II)(bppCOOH)(bppCOO)](+) complexes. Raman spectroscopy studies on single crystals of 1 and 2 have been performed to elucidate the spin and oxidation states of iron …
Bowl-shape electron donors with absorptions in the visible range of the solar spectrum and their supramolecular assemblies with C 60
2012
We describe the synthesis, electronic, optical and photophysical properties of a family of three electron-donor bowl-shaped organic molecules that absorb light in the whole range of the visible spectrum (up to 800 nm in one case), and associate C60 in solution with binding constants in the range of 104–102 M−1 as measured from both UV-vis and fluorescence titrations in several solvents. These molecules are π-extended derivatives of tetrathiafulvalene, based on a truxene core to which two or three units of dithiole are covalently attached. The inclusion of the bulky dithiole groups is responsible for their bowl-shape geometry, which allows them to associate with C60, and their electron-donor…
Microporous Triptycene‐Based Affinity Materials on Quartz Crystal Microbalances for Tracing of Illicit Compounds
2019
Triptycene-based organic molecules of intrinsic microporosity (OMIMs) with extended functionalized π-surfaces are excellent materials for gas sorption and separation. In this study, the affinities of triptycene-based OMIM affinity materials on 195 MHz high-fundamental-frequency quartz crystal microbalances (HFF-QCMs) for hazardous and illicit compounds such as piperonal and (-)-norephedrine were determined. Both new and existing porous triptycene-based affinity materials were investigated, resulting in very high sensitivities and selectivities that could be applied for sensing purposes. Remarkable results were found for safrole - a starting material for illicit compounds such as ecstasy. A …
Theoretical investigation of the spin crossover transition states of the addition of methane to a series of Group 6 metallocenes using minimum energy…
2016
International audience; Density functional calculations are reported on the addition of methane to Group 6 metallocenes, M(η-C5H5)2 (M), M(CH2(η-C5H4)2) (a-M) and M(η-C5Me5)2 (M*) where M = Mo and W. Full geometry optimisations were carried out on the singlet and triplet 16 electron complexes, 1[M] and 3[M], the η2-methane complexes, 1[M(η2-CH4)], and the hydridomethyl adducts, 1[M(CH3)(H)]. The triplet state for [M] was found to be more stable for all six metallocenes, the difference being least in the case of the ansa-bridged system. Formation of the hydridomethyl complexes was exoenergetic for all tungsten systems and for a-Mo, the other two Mo systems being endoenergetic. Minumum energy…
Cobalt Clusters with Cubane-Type Topologies Based on Trivacant Polyoxometalate Ligands.
2016
Four novel cobalt-substituted polyoxometalates having cobalt cores exhibiting cubane or dicubane topologies have been synthesized and characterized by IR, elemental analysis, electrochemistry, UV-vis spectroscopy, X-ray single-crystal analysis, and magnetic studies. The tetracobalt(II)-substituted polyoxometalate [Co4(OH)3(H2O)6(PW9O34)](4-) (1) consists of a trilacunary [B-α-PW9O34](9-) unit which accommodates a cubane-like {Co(II)4O4} core. In the heptacobalt(II,III)-containing polyoxometalates [Co7(OH)6(H2O)6(PW9O34)2](9-) (2), [Co7(OH)6(H2O)4(PW9O34)2]n(9n-) (3), and [Co7(OH)6(H2O)6(P2W15O56)2](15-) (4), dicubane-like {Co(II)6Co(III)O8} cores are encapsulated between two heptadentate [B…
Theoretical study on the decomposition mechanism of bisphenol A polycarbonate induced by the combined effect of humidity and UV irradiation.
2020
Polycarbonate (PC) is a good material for covering and protecting cultural heritage sites because of its durability, mechanical properties, and transparency. When bisphenol A polycarbonate is subjected to weathering conditions this polymer shows several degradation processes depending on the irradiation wavelength, humidity and temperature. In particular, the combined effects of humidity and UV irradiation speed up the PC molecular weight reduction. In this work, the decomposition mechanisms associated to the hydrolysis process are scrutinized and the effects of UV irradiation on the hydrolysis process are evaluated throughout the Density Functional Theory (DFT) approach. It was found that …