Search results for "PHOTOCHEMISTRY"

Stereospecific Polymerization of Isoprene with Nd(BH4)3(THF)3/MgBu2 as Catalyst

2004

The neodymium trisborohydride Nd(BH 4 ) 3 - (THF) 3 (THF = tetrahydrofuran) has been used as a catalyst precursor for isoprene polymerization for the first time. Associated to an excess of Al(Et) 3 , the resulting catalyst is moderately active, giving a mixture of cis- and trans- polymer. Addition of a stoichiometric amount of MgBu 2 to Nd(BH 4 ) 3 (THF) 3 affords a stereospecific catalyst providing trans-1,4-polyisoprene, more than 96% regular. That dual component Nd/Mg system also shows a better efficiency and good control of the molecular weights. A molecular structure is tentatively attributed to a bimetallic active species, based on 1 H NMR experiments.

Hydrogen bond-mediated conjugates involving lanthanide diphthalocyanines and trifluoroacetic acid (Lnpc2@TFA): Structure, photoactivity, and stability

2020

The interaction between lanthanide diphthalocyanine complexes, LnPc2 (Ln = Nd, Sm, Eu, Gd, Yb, Lu

Photocatalytic activity of nano and microcrystalline TiO2 hybrid systems involving phthalocyanine or porphyrin sensitizers

2011

Hybrid photocatalysts based on TiO(2)-anatase matrix, representing the both micro- and nano-structures, impregnated with selected lanthanide diphthalocyanine and metalloporphyrin sensitizers, were compared to evaluate their activity and effectiveness in a water suspension catalytic system designed to degrade 4-nitrophenol (4-NP) in a UV-stimulated reaction. Either type of the anatase catalyst was proved to be effective in mineralizing of 4-NP. However, kinetic studies confirmed that the composite's efficiency basically depends on the nature of the macromolecular sensitizer and to a minor extent on the dimensions (micro/nano) of the TiO(2) particles. The apparent higher activity observed for…

Homoleptic Phosphoraneiminato Complexes of Rare Earth Elements as Initiators for Ring-Opening Polymerization of Lactones.

2000

CO Oxidation on Cationic Gold Clusters: A Theoretical Study

2008

Aiming at understanding the elementary steps governing the oxidation of CO catalyzed by dispersed or supported gold nanoclusters, the reactivity of molecular species, such as O2 and CO, on neutral and positively charged Au13 clusters have been studied using a DFT approach. Two CO oxidation mechanisms have been simulated, involving respectively the adsorption of CO and O2 on adjacent catalytic sites (two-sites mechanism) and the competitive interaction of the reactants on the same site (single-site mechanism). It is demonstrated that in the former scheme a definite interaction of CO and O2 with both the charged and neutral cluster is effective, but that a chemical reaction between the adsorb…

Visible-light photoredox catalyzed synthesis of pyrroloisoquinolines via organocatalytic oxidation/[3 + 2] cycloaddition/oxidative aromatization reac…

2014

Beilstein journal of organic chemistry 10, 1233-1238 (2014). doi:10.3762/bjoc.10.122

1H and13C n.m.r. spectra of dichloro(trans-2-chlorovinyl)arsine

1977

Proton and carbon magnetic resonance spectra of Lewisite or dichloro(trans-2-chlorovinyl)arsine have been measured and the results are compared with the n.m.r. spectral parameters of other trans-1,2-substituted ethylenes. The coupling constants can be rationalized by substituent electronegativity. The chemical shifts show an unusually large paramagnetic effect from the AsCl2 group.

Fluoride-induced modulation of ionic transport in asymmetric nanopores functionalized with “caged” fluorescein moieties

2016

[EN] We demonstrate experimentally and theoretically a nanofluidic fluoride sensing device based on a single conical pore functionalized with "caged" fluorescein moieties. The nanopore functionalization is based on an amine-terminated fluorescein whose phenolic hydroxyl groups are protected with tert-butyldiphenylsilyl (TBDPS) moieties. The protected fluorescein (Fcn-TBDPS-NH2) molecules are then immobilized on the nanopore surface via carbodiimide coupling chemistry. Exposure to fluoride ions removes the uncharged TBDPS moieties due to the fluoride-promoted cleavage of the silicon-oxygen bond, leading to the generation of negatively charged groups on the fluorescein moieties immobilized on…

Understanding and exploiting long-lived near-infrared emission of a molecular ruby

2018

Coordination chemistry reviews 359, 102 - 111 (2018). doi:10.1016/j.ccr.2018.01.004

Excited State Tuning of Bis(tridentate) Ruthenium(II) Polypyridine Chromophores by Push-Pull Effects and Bite Angle Optimization: A Comprehensive Exp…

2013

The synergy of push-pull substitution and enlarged ligand bite angles has been used in functionalized heteroleptic bis(tridentate) polypyridine complexes of ruthenium(II) to shift the (1) MLCT absorption and the (3) MLCT emission to lower energy, enhance the emission quantum yield, and to prolong the (3) MLCT excited-state lifetime. In these complexes, that is, [Ru(ddpd)(EtOOC-tpy)][PF6 ]2 , [Ru(ddpd-NH2 )(EtOOC-tpy)][PF6 ]2 , [Ru(ddpd){(MeOOC)3 -tpy}][PF6 ]2 , and [Ru(ddpd-NH2 ){(EtOOC)3 -tpy}][PF6 ]2 the combination of the electron-accepting 2,2';6',2''-terpyridine (tpy) ligand equipped with one or three COOR substituents with the electron-donating N,N'-dimethyl-N,N'-dipyridin-2-ylpyridin…