Enhanced Rates of Photoinduced Molecular Orientation in a Series of Molecular Glassy Thin Films.

Photoinduced orientation in a series of molecular glasses made of small push-pull azo derivatives is dynamically investigated for the first time. Birefringence measurements at 632.8 nm are conducted with a temporal resolution of 100 ms to probe the fast rate of the azo orientation induced under polarized light and its temporal stability over several consecutive cycles. To better evaluate the influence of the azo chemical substituents and their electronic properties on the orientation of the whole molecule, a series of push-pull azo derivatives involving a triphenylaminoazo core substituted with distinct electron-withdrawing moieties is studied. All resulting thin films are probed using polarization modulation infrared spectroscopy that yields dynamical linear dichroism measurements during a cycle of orientation followed by relaxation. We show here in particular that the orientation rates of small molecule-based azo materials are systematically increased up to 7-fold compared to those of a reference polymer counterpart. For specific compounds, the percentage of remnant orientation is also higher, which makes these materials of great interest and promising alternatives to azobenzene-containing polymers for a variety of applications requiring a fast response and absolute control over the molecular weight

Red-emitting fluorescent Organic Light emitting Diodes with low sensitivity to self-quenching

International audienceConcentration quenching is a major impediment to efficient organic light-emitting devices. We herein report on Organic Light-Emitting Diodes (OLEDs) based on a fluorescent amorphous red-emitting starbust triarylamine molecule (4-di(4'-tert-butylbiphenyl-4-yl)amino-4'-dicyanovinylbenzene, named FVIN), exhibiting a very small sensitivity to concentration quenching. OLEDs are fabricated with various doping levels of FVIN into Alq3, and show a remarkably stable external quantum efficiency of 1.5% for doping rates ranging from 5% up to 40%, which strongly relaxes the technological constraints on the doping accuracy. An efficiency of 1% is obtained for a pure undoped active region, along with deep red emission (x=0.6; y=0.35 CIE coordinates). A comparison of FVIN with the archetypal DCM dye is presented in an identical multilayer OLED structure

A Comprehensive Study of Structure-Property Relationships for Two-photon Absorbing Triarylamine Molecules Containing Trifluoromethyl.

This work reports on the influence of the Electron Withdrawing Groups (EWG) strength on\ud the one- and two-photon absorption properties of six novel push-pull triarylamine molecules\ud containing trifluoromethyl (CF3). The molecules present octupolar structures with a core\ud based on triarylamine (strong donor group) containing two trifluoromethyl-phenyl arms\ud (acceptor group) and another with distinct EWG strength (H < CN < CHO < NO2 < Cyet <\ud Vin). Linear photophysical properties such as molar absorptivity, one-photon induced\ud fluorescence, solvatochromic Stokes shift measurements, dipole moments, fluorescence\ud quantum yield and lifetimes were investigated using several spectroscopic techniques. For the\ud two-photon absorption measurements we used the open-aperture Z-scan technique with\ud femtosecond pulses operating at low repetition rate (1 KHz)

Synthesis, Mass Spectrometry and Spectroscopic Properties of a Dinuclear Ruthenium Complex Comprising a 20 Å Long Fully Aromatic Bridging Ligand

The luminescent dinuclear ruthenium complex [(bpy)2Ru(bqpy)Ru(bpy)2]4+ (1) comprising the 20 Å long fully aromatic bridging ligand bqpy has been synthesized by successive reactions from suitable precursor complexes. Investigations in electrospray mass spectrometry and 1H NMR spectroscopy have indicated the formation of supramolecular aggregates by strong ð-stacking of the large aromatic parts. Despite the extended aromatic character of the bqpy bridging ligand, electrochemical and spectroscopic studies of the dinuclear complex have shown that the complex is composed of four noninteracting parts: two Ru(bpy)3 2+-type units bridged by two bqpy-localized fragments similar to two fused phenazine moieties

Synthesis, Mass Spectrometry and Spectroscopic Properties of a Dinuclear Ruthenium Complex Comprising a 20 Å Long Fully Aromatic Bridging Ligand

The luminescent dinuclear ruthenium complex [(bpy)2Ru(bqpy)Ru(bpy)2]4+ (1) comprising the 20 Å long fully aromatic bridging ligand bqpy has been synthesized by successive reactions from suitable precursor complexes. Investigations in electrospray mass spectrometry and 1H NMR spectroscopy have indicated the formation of supramolecular aggregates by strong ð-stacking of the large aromatic parts. Despite the extended aromatic character of the bqpy bridging ligand, electrochemical and spectroscopic studies of the dinuclear complex have shown that the complex is composed of four noninteracting parts: two Ru(bpy)3 2+-type units bridged by two bqpy-localized fragments similar to two fused phenazine moieties

Two-photon absorption properties of a novel class of triarylamine compounds

Two-photon absorption spectra of a triarylamine compounds dissolved in toluene were measured using the well-known Z-scan technique, employing 120-fs laser pulse-width. According to the results, an extra band located at around 900 nm was observed only for triarylamine with azoaromatic units. On the other hand, a shift in the two-photon absorption band for triarylamine, with and without azoaromatic units, is observed when different electron donor/acceptors groups are changed. The fitting of the spectra, using sum-over-states model, allowed us to obtain the spectroscopic parameters of each molecule, which appears to be in reasonable agreement with molecules presenting similar structural moieties. (C) 2010 Elsevier B.V. All rights reserved

Photophysics of Binuclear Ru(II) and Os(II) Complexes Based on the Tetrapyrido[3,2-a:2',3'-c:3",2"-h:2'''-3'''-j]phenazine (tpphz) Bridging Ligand

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