Experimental and theoretical insights into the sequential oxidations of 3π-2spiro molecules derived from oligophenylenes: A comparative study of 1,2-b-DiSpiroFluorene-IndenoFluorene versus 1,2-b-DiSpiroFluorene(tert-butyl)4-IndenoFluorene

International audienceCyclic voltammetry and differential pulse voltammetry have shown too distinct behaviours in the sequential oxidation processes of two closely related compounds, namely 1,2-b-DiSpiroFluorene-IndenoFluorene (1,2-b-DSF-IF) and 1,2-b-DiSpiroFluorene(tert-Butyl)4-IndenoFluorene (1,2-b-DSF(tBu)4-IF). 1,2-b-DSF-IF is oxidized after a reversible one-electron transfer and a subsequent irreversible two-electron transfer. In contrast, 1,2-b-DSF(tBu)4-IF undergoes three well separated chemically reversible one-electron processes. Spectroelectrochemical monitoring of the gradual oxidation of the compounds points to a first oxidation centred on the indenofluorenyl core for both molecules. Consistent with the different electrochemical behaviour, the spectroelectrochemical data after the first oxidation is very different for both compounds and points to a specific electronic structure. This is further studied theoretically by DFT calculations of the molecules in their neutral, cationic and dicationic state which suggest an electronic reorganization in the dication 1,2-b-DSF(tBu)4-IF2+

Intramolecular excimer emission as a blue light source in fluorescent organic light emitting diodes: a promising molecular design

International audienceIntramolecular excimer emission arising from organic molecules as a blue light source in fluorescent Small Molecule Organic Light Emitting Diodes (SMOLEDs) is almost absent from the literature. In this work, three aryl-substituted DiSpiroFluorene-IndenoFluorenes (DSF-IFs 1-3) possessing different fluorescent properties due to their different main emitters have been investigated through a structure-property relationship study. Due to its particular geometry, the rigid DSF-IF platform 2 allows an 'aryl/fluorene/aryl' dimer to be preformed in the ground state leading, in the excited state, to a deep blue fluorescent emission through strong π-π intramolecular interactions between the two 'aryl/fluorene/aryl' arms. 2 has been successfully used as an emitting layer in a SMOLED with electroluminescence arising from electrogenerated intramolecular excimers and the properties of these excimer-based OLEDs have been compared to those of two model compounds (1 and 3). The simple and non-optimized double-layer device displays a deep blue colour (CIE coordinates: 0.19; 0.18) exhibiting a luminance of 510 Cd m−2 with a luminous efficiency of ca. 0.1 Cd A−1. This work is, to the best of our knowledge, the first rational and comparative study describing an intramolecular excimer based-SMOLED

Comparative Electronic Properties of Two Arylene-Cyanovinylene Isomers and of Their Respective Electrogenerated Polymers.

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/4.0/).International audienceTwo arylene-cyanovinylene isomers formed by a phenyl unit substituted in para or meta positions by two cyanovinylene-methylthiophene were synthesized. Their main physicochemical properties were studied in order to point out the influence of the nature of the substitution (para vs meta) of the central phenyl unit on the electronic properties of the two isomers. The anodic electropolymerization of the two compounds was also studied with a main emphasis on the electrochemical behavior of the derived polymers showing that the specific behavior of the para-substituted isomer is maintained in its polymer leading to a polymer with a lower bandgap (1.95 eV) than the polymer obtained from the meta-substituted isomer (2.16 eV)

A robust pure hydrocarbon derivative based on the (2,1-b)-indenofluorenyl core with high triplet energy level.

International audienceA unique (2,1-b)-indenofluorenyl core flanked with two spirofluorene units, possessing a high triplet energy value and excellent thermal/morphological stability, is reported

Properties modulation of organic semi-conductors based on a donor-spiro-acceptor (D-spiro-A) molecular design: new host materials for efficient sky-blue PhOLEDs

International audienceFour high triplet org. semi-conductors based on the donor-spiro-acceptor design (D-spiro-A) have been synthesized. Their physicochem. and photophys. properties have been studied, compared and discussed in light of the nature of their resp. donor/acceptor units. The four compds. have been used as host materials in efficient sky-blue (EQE \textgreater 10% at 10 mA cm-2) phosphorescent org. light emitting diodes

2,5-Thiophene Substituted Spirobisiloles - Synthesis, Characterization, Electrochemical Properties and Performance in Bulk Heterojunction Solar Cells

International audienceNew spirobisilole molecules containing thienyl (DTSBS) and bis-thienyl (BBTSBS) electron donor groups have been synthesized for use as the donor material in bulk-heterojunction solar cells together with PCBM. The spectroscopic, electrochemical and thermal properties of DTSBS and BBTSBS have been investigated. All these new spirobisiloles exhibit excellent thermal stability. Cyclic voltammetry measurements revealed reversible and irreversible oxidation and irreversible reduction processes. The highest occupied and lowest unoccupied molecular orbital (HOMO/LUMO) energy levels were determined from electrochemical measurements and DFT calculations. The HOMO/LUMO energy levels were estimated to lie in the range -5.2 to -2.3 eV for DTSBS and -4.9 to -2.6 eV for BBTSBS. For both compounds, electropolymerization processes occur at potentials higher than 1.5 V leading to low band gap electrogenerated polymers. Spin-coating-deposited bulk-heterojunction solar cells fabricated with the novel spirobisiloles as donor and PCBM as acceptor displayed open-circuit voltages up to 0.4 V, short-circuit currents around 0.5 mA.cm-2, and power conversion efficiencies approaching 0.1 %

Electron deficient dicyanovinylene-ladder-type pentaphenylene derivative for n-type Organic Field Effect Transistors

International audienceA bridged pentaphenylene derivative functionalized with dicyanovinylene units LPP([double bond, length as m-dash]C(CN)2)2 has been designed, synthesized and characterized. The optical and electrochemical properties have been carefully studied through a combined experimental and theoretical approach and compared with those of two pentaphenylene derivatives bearing methylenes (LPP) or carbonyl (LPP([double bond, length as m-dash]O)2) on the bridgeheads. LPP([double bond, length as m-dash]C(CN)2)2 which possesses a very low LUMO level, ca. −4.02 eV, has been successfully used as an active layer in n-channel OFETs using the epoxy based photoresist SU-8 as a gate insulator. LPP([double bond, length as m-dash]C(CN)2)2 based n-channel OFETs show low voltage functioning (low gate-source and drain-source voltages), high ratio between the on and the off currents (2 × 105), interesting subthreshold swing (S = 1) and excellent stability under electrical stress and in a nitrogen atmosphere. More importantly, we have also shown that LPP([double bond, length as m-dash]C(CN)2)2 based n-channel OFETs present an excellent environmental stability. This work is to the best of our knowledge the first report on bridged pentaphenylene-based semiconductors in n-type OFETs and highlights the potential of such type of material to provide air stable OFETs

2-Substituted vs 4-substituted-9,9′-spirobifluorene host materials for green and blue phosphorescent OLEDs: a structure-property relationship study

Nanotek for organic synthesis, and organic synthesis for nanotekInternational audienceWe report a structure-property relationship study of four 9,9′-spirobifluorene (SBF) derivatives (4-5Pm-SBF, 2-5Pm-SBF, 4-Ph-SBF and 2-Ph-SBF), substituted with either phenyl or pyrimidine at the \C2\ or \C4\ position of the \SBF\ core. Structural, thermal, electrochemical and photophysical properties have been examined and correlated to theoretical calculations in order to study the influence of the nature and the position of the substituent. The emission properties of 4- versus 2-substituted \SBFs\ are noticeably different highlighting, in the excited state, the remarkable effect of substitution in ortho position of SBF. All compounds have been used as host material for green dopant in PhOLEDs with very high performances (2-5Pm-SBF: CE>58 cd/A, PE>35 lm/W, EQE>14%). More importantly, the two 4-substituted \SBFs\ have been used as host materials in blue PhOLEDs, displaying high performance and a decrease of \VTH\ for 4-5Pm-SBF due to the incorporation of the electron-withdrawing pyrimidine

Dérivés du 4-spirobifluorène Une nouvelle famille de matrices hôtes pour des PhOLED

National audienceCet article a pour objectif de faire un état des lieux exhaustif d’une nouvelle famille de semi-conducteurs organiques dérivés du 9,9’-spirobifluorène (SBF) ,substitués en positon 4 (4-SBF) possédant un fort potentiel en tant que matrices hôtes dans des diodes électroluminescentes organiques phosphorescentes (PhOLED). Cet article couvrira plusieurs aspects : après une approche générale sur la stratégie de synthèse des molécules 4-SBF, il donnera une analyse détaillée et comparative de l'ensemble des propriétés (optiques, électrochimiques et thermiques) et mettra en exergue les applications des dérivés 4-SBF en tant que matrice hôte dans des PhOLED

Un design moléculaire unique pour des OLED à excimères à base d'oligophénylènes

National audienceLes dispirofluorène-indénofluorènes associent des dérivés du fluorène aux unités planes et rigides de l'indénofluorène, via deux ponts spiro. L'architecture de ces composés est tridimensionnelle et leurs propriétés électroniques peuvent être modulées par la nature et la géométrie des différents systèmes π. Certaines de ces molécules avec une géométrie autorisant des interactions intramoléculaires entre deux systèmes π " face-à-face " conduisent à une émission bleue (via la formation d'excimères intramoléculaires) qu'il serait impossible d'obtenir par l'émission des systèmes π indépendants. Ce travail décrit l'utilisation d'une source de lumière bleue provenant d'excimères intramoléculaires dans des diodes organiques électroluminescentes