Green Synthesis Of Polycyclic Benzimidazole Derivatives And Organic Semiconductors

Polycyclic benzimidazole derivatives, an important class of compounds in organic electronics and photovoltaics, were prepared using a solvent-free green process based on heating carboxylic acid anhydrides and arylene diamines in the presence of zinc acetate in the solid state. Products were isolated and purified directly by train sublimation of the crude reaction mixtures. The reaction conditions were optimized using various carboxylic acid anhydrides. Optical and electrochemical properties of these materials are also described

Triclinic polymorph of dibenzotetrathiafulvalene

Crystals of the title compound (DBTTF), C14H8S4, feature a triclinic polymorph different from two known monoclinic polymorphs. In this form, there are two independent centrosymmetric half-molecules in the asymmetric unit. Although the molecular orientations are relatively similar to one of monoclinic polymorphs, the packing motif is different

Characterization of New Rubrene Analogues with Heteroaryl Substituents

New rubrene analogues, which are heteroaryl-tetrasubstituted tetracenes, have been developed using a simplified synthesis approach. Their stabilities in solution were improved compared to those of rubrene. The correlation among the molecular structures, crystal structures, and charge transport properties has been investigated and compared with rubrene and various rubrene analogues. Although twisted structures of a tetracene backbone have often been found in single crystal analyses, the planarity might be related to intermolecular interactions rather than the electron donating/withdrawing properties of the heteroaryl side groups. The packing motifs in thiophene-substituted derivatives did not include π-stacking of tetracene cores, which differ from the well-known structure of rubrene. However, furan-substituted derivatives can be crystallized in the π-stacking manner. These differences in the packing structure affect hole transport properties

Synthesis, Physical Properties, and Field-Effect Mobility of Isomerically Pure <i>syn</i>-/<i>anti</i>-Anthradithiophene Derivatives

Isomerically pure <i>syn</i>-/<i>anti</i>-isomers of 2,8-dimethylanthradithiophene (DMADT) were synthesized in five steps and characterized using thermogravimetry, X-ray single crystal analysis, UV–vis absorption, and electrochemical measurements. The physical properties in solution were slightly different for each isomer, whereby the more obvious differences were observed in the solid state. A field-effect transistor using the <i>anti</i>-isomer showed a much higher performance than that using the <i>syn</i>-isomer

Synthesis, Physical Properties, and Field-Effect Mobility of Isomerically Pure <i>syn</i>-/<i>anti</i>-Anthradithiophene Derivatives

Isomerically pure <i>syn</i>-/<i>anti</i>-isomers of 2,8-dimethylanthradithiophene (DMADT) were synthesized in five steps and characterized using thermogravimetry, X-ray single crystal analysis, UV–vis absorption, and electrochemical measurements. The physical properties in solution were slightly different for each isomer, whereby the more obvious differences were observed in the solid state. A field-effect transistor using the <i>anti</i>-isomer showed a much higher performance than that using the <i>syn</i>-isomer

Multiple donor–acceptor design for highly luminescent and stable thermally activated delayed fluorescence emitters

Abstract A considerable variety of donor–acceptor (D–A) combinations offers the potential for realizing highly efficient thermally activated delayed fluorescence (TADF) materials. Multiple D–A type compounds are one of the promising families of TADF materials in terms of stability as well as efficiencies. However, those emitters are always composed of carbazole-based donors despite a wide choice of moieties used in linearly linked single D–A molecules. Herein, we developed a multiple D–A type TADF compound with two distinct donor units of 9,10-dihydro-9,9-dimethylacridine (DMAC) and carbazole as the hetero-donor design. The new emitter exhibits high photoluminescence quantum yield (PLQY) in various conditions including polar media blend and high concentrations. Organic light-emitting diodes (OLEDs) showed a reasonably high external quantum efficiency (EQE). In addition, we revealed that the multiple-D–A type molecules showed better photostability than the single D–A type molecules, while the operational stability in OLEDs involves dominant other factors

Excellent Semiconductors Based on Tetracenotetracene and Pentacenopentacene: From Stable Closed-Shell to Singlet Open-Shell

International audienceDesigning stable open-shell organic materials through the modifications of the π-topology of molecular organic semiconductors have attracted recently considerable attention. However, their uses as an active layer in organic field-effect transistors (OFETs) are very limited and the obtained hole and electron charge mobilities are around 10 −3 cm 2 V −1 s −1. Herein, we disclosed the synthesis of two materials so-called tetraceno-tetracene (TT) and pentacenopentacene (PP) which have low band gap of 1.79 and 1.42 eV, respectively. Their ground state natures have been investigated by different experiments including steady state absorption, electron spin resonance, superconducting quantum interfering device (SQUID) and variable temperature NMR along with DFT calculations. TT and PP have closed-shell and singlet open-shell structures in their ground state, respectively , and possess high stability. Their biradical characteristics were found to be 0.50 and 0.64. The origin of the open-shell character of PP is related to the concomitant opening of two tetracenes with the recovering of two extra aromatic sextets and a small HOMO-LUMO energy gap (gap < 1.5 eV). Thanks to the high stability, thin film OFET devices could be fabricated. In TG-BC configuration PP shows remarkably high hole mobility of 1.4 cm 2 V −1 s −1 while TT exhibits a hole mobility of 0.77 cm 2 V −1 s −1. In configuration of BG-TC, ambipolar behaviors for both were obtained with hole and electron mobilities of 0.21 and 0.01 cm 2 V −1 s −1 for PP and 0.14 and 0.006 cm 2 V −1 s −1 for TT

Synthesis, crystal structure, tropicity and charge transport properties of diindenothienothiophene derivatives

International audienceA set of π-conjugated diindenothienothiophene derivatives (DITTs) which formally possess an extended as-indacene core with 16 π-electrons has been synthesised and their closed-shell configuration has been confirmed by X-ray structure analysis. Bond lengths analysis provides insight into the peculiar bond lengths observed for diindenoacene diradicaloids. The annellation mode at the outer rings has a great impact on the tropicity, optoelectrochemical properties and molecular packing. The featured molecules exhibit low energy band gap with values up to 1.30 eV and have high electron affinities with LUMO energies up to 3.86 eV. Their optical properties are similar to those of benzo-fused indeno[2,1-c]fluorene (BIFs) counterparts possessing formally the as-indacene core. Analysis of the molecule tropicity using NICS and ACID plot shows that the central rings of DITTs are weakly antiaromatic and should be regarded as quinoidal molecules bridged by two sulphur atoms. Three out of four molecules show ambipolar behavior in OFETs with moderate mobilitie