Picosecond Switchable Azo Dyes.

Azo dyes that combine electron-withdrawing thiazole/benzothiazole heterocycles and electron-donating amino groups within the very same covalent skeleton exhibit relaxation times for their thermal isomerization kinetics within milli- and microsecond timescales at room temperature. Notably, the thermal back reaction of the corresponding benzothiazolium and thiazolium salts occurred much faster, within the picosecond temporal domain. In fact, these new light-sensitive platforms are the first molecular azo derivatives capable of reversible switching between their trans and cis isomers in a subnanosecond timescale under ambient conditions.

Interface engineering and solid-state organization for triindole-based p-type organic thin-film transistors.

Inspired by the excellent device performance of triindole-based semiconductors in electronic and optoelectronic devices, the relationship between the solid-state organization and the charge-transporting properties of an easily accessible series of triindole derivatives is reported herein. The vacuum-evaporated organic thin-film transistors (OTFTs) exhibited a non ideal behaviour with a double slope in the saturation curves. Moreover, the treatment of the gate insulator of the OTFT device with either a self-assembled monolayer (SAM) or a polymer controls the molecular growth and the film morphology of the semiconducting layer, as shown by X-ray diffraction (XRD) analyses, atomic force microscopy (AFM) and theoretical calculations.

Solid-state organization of n-type carbazole-based semiconductors for organic thin-film transistors.

The development of new organic semiconductors has been mainly led by the search for new π-conjugated cores, but recently the use of flexible side chains is attracting more and more attention to control the molecular packing and order in the solid state to improve the charge-transporting properties. In this work, the charge transport properties of a series of tricyanovinyl-substituted carbazole-based materials with different alkyl chain lengths have been investigated and correlated with the respective intermolecular interactions and molecular packings via X-ray diffraction (XRD) studies.

Tuning the ambipolar charge transport properties of tricyanovinyl-substituted carbazole-based materials.

A series of push-pull carbazole-based compounds has been experimentally and theoretically characterized in combination with the X-ray analysis of the corresponding single crystals. The introduction of the strong electron-withdrawing tricyanovinyl group in the carbazole core affords electron-transporting ability in addition to the characteristic hole-transporting properties exhibited by donor carbazole derivatives.

Stable All-Organic Radicals with Ambipolar Charge Transport.

A series of neutral long-lived purely organic radicals based on the stable [4-(N-carbazolyl)-2,6-dichlorophenyl]bis(2,4,6-trichlorophenyl)methyl radical adduct (Cbz-TTM) is reported herein. All compounds exhibit ambipolar charge-transport properties under ambient conditions owing to their radical character. High electron and hole mobilities up to 10 and 10  cm  V  s , respectively, were achieved.

Spatially close azo dyes with sub-nanosecond switching speeds and exceptional temporal resolution.

Photoswitchable bis-azo dyes with an outstanding temporal resolution of 10(15) times between the thermal relaxation rates of their two constituting photochromes are reported. Remarkably, the close spatial proximity of both azo photochromes in these molecular assemblies translates in an unprecedented 10(3) -fold acceleration of the thermal isomerization rate of their faster azo unit compared to the one displayed by the isolated counterpart. Indeed, the relaxation time of the fast-isomerizing platform of the herein reported bis-azobenzenes is as low as 200 ps under ambient conditions.

A photoswitchable bis-azo derivative with a high temporal resolution.

The novel photoswitchable bis-azo derivative reported herein shows a high temporal resolution of 2 × 10(8) times between the thermal relaxation rates of its two constituting photochromes. Moreover, the slow and fast azo building blocks of this molecular construct can be triggered by using UV and visible light, respectively.

Molecular photo-oscillators based on highly accelerated heterocyclic azo dyes in nematic liquid crystals.

Benzothiazole-pyrrole-based azo dyes greatly enhance their thermal isomerisation rate by up to 160 times when they are under the influence of the nematic mean field yielding the LC-based photochromic oscillators with the highest oscillation frequencies reported so far (2.6 kHz at 298 K).

Charge transfer states in stable neutral and oxidized radical adducts from carbazole derivatives.

In this paper we report the spectral properties of the stable radical adducts 1(•)-3(•), which are formed by an electron donor moiety, the carbazole ring, and an electron acceptor moiety, the polychlorotriphenylmethyl radical. The molecular structure of radical adduct 1(•) in the crystalline state shows a torsion angle of approximately 90° between the phenyl and the carbazole rings due to steric interactions. They exhibit a charge transfer band in the visible range of the electronic spectrum.