Photochemistry of 1,N-Diiodoalkanes
This article reviews the photochemistry of 1,n-diiodoalkanes, with special emphasis on the involved intermediates. Photolysis of 1,1-diiodomethane produces homolytic cleavage of the C–I bond to give the α-iodo radical, which in solid matrix cannot dissociate but collapses to isodiiodomethane. However, in solution subsequent electron-transfer produces the α-iodo cation, which is able to achieve cyclo-propanation of olefins. In the case of 1,2-diiodides, their photolysis gives rise to β-iodoalkyl radicals which usually lose iodine very rapidly, forming a carbon-carbon double bond. Homolytic cleavage of 1,n-diiodoalkanes (n>2) affords n-iodo radicals which are stabilized by participation o…
Purcell-enhancement of the radiative PL decay in perylenediimides by coupling with silver nanoparticles into waveguide modes
In this work, an interesting approach to enhance the coupling between excitons and plasmons is proposed by integrating highly luminescent perylenediimides (PDIs) and Ag metal nanoparticles (MNPs) in the core of a multilayer dielectric waveguide. The combination of the weak plasmonic coupling and the high scattering of MNPs gives rise to a significant improvement of the PDI photoluminescence and Purcell factor (PF) in forward-scattering geometry. Furthermore, when the PDI-MNP system is used as the core of a multilayer waveguide, a Purcell factor enhancement larger than 10 is observed, which is explained by an increase in the exciton-plasmon coupling under the light confinement in the wavegui…
Diels–Alder reaction on perylenediimides: synthesis and theoretical study of core-expanded diimides
A one-step reaction for the fusion of aromatic rings to one or both bay areas of perylenediimides using benzynes is presented. Yields as high as 70% for naphthoperylenendiimide 2 and 80% for dibenzocoronenediimide 3 are obtained. The reaction is also carried out using substituted benzynes, heteroaromatic benzynes and substituted perylenediimides. A combined experimental/theoretical approach, based on measuring redox and absorption/emission properties and performing density functional theory calculations, indicates that increasing the π-skeleton of PDIs transversally leads to significant and unexpected changes in the electronic, redox and optical properties. The observed trends are rationali…
Alkoxy-styryl DCDHF fluorophores
A photostable dicyanomethylenedihydrofuran fluorophore which contains electron-donating alkoxy groups is described. This chromophore is highly environmentally-sensitive, which is a remarkable property for a fluorescent reporter. Its light excitation also enables, in low viscous solvents, the formation of dark states whose radical or triplet nature is ruled out.
Mechanistic studies on the photogeneration of o- and p-xylylenes from α,α′-dichloroxylenes
Two-colour two-laser techniques have unambiguously proved that photolysis of the o-/p-(chloromethyl)benzyl radical leads to the sequential two-photon generation of o-/pxylylene from α,α'-dichloro-o-/p-xylene. Perez Prieto, Julia, Julia.Perez@uv.es
Efficient Optical Amplification in a Sandwich-Type Active-Passive Polymer Waveguide Containing Perylenediimides
Polymer waveguides doped with luminescent materials serve as a suitable flexible platform for active elements (lasers and amplifiers) in on-chip optical circuits. However, at present, the best parameters (lowest thresholds) achieved with these devices are obtained with the use of the stripe excitation technique in the framework of which external illumination of an active material along the whole length of the waveguide is realized that is not convenient for the waveguide on-chip integration and requires high peak energies due to the large excitation area. In the present work, an elegant method is proposed to overcome this obstacle and provide efficient active material pumping along the whol…