A thiadiazole-capped nanoribbon with 18 linearly fused rings

Polycyclic aromatic hydrocarbons that extend over 2 nm in one dimension are seen as monodisperse graphene nanoribbons, which have attracted significant attention for a broad range of applications in organic electronics and photonics. Herein we report the synthesis of a stable bisthiadiazole-capped pyrene-containing nanoribbon with 18 linearly fused rings (NR-18-TD). Thanks to the presence of alternating tert-butyl and tri-iso-butylsilyl groups, NR-18-TD is highly soluble in organic solvents and therefore its structure and fundamental optoelectronic, redox and electrical properties could be unambiguously established. This work illustrates that NR-18-TD is a promising soluble NR-based n-type semiconductor for applications in organic electronics.

Thiadizoloquinoxaline-Based N-Heteroacenes as Active Elements for High-Density Data-Storage Device

A novel thiadiazoloquinoxaline (TQ)-based donor-acceptor (D-A)-type N-heteroacene (Py-1-TQ) has been demonstrated for promising applications in organic multilevel resistive memory devices. Compared with its counterparts (Py-0-TQ and Py-2-TQ), which show flash-type binary memory behaviors, Py-1-TQ exhibits excellent nonvolatile write-once-read-many-times-type ternary memory effects with high ON2/ON1/OFF current ratios (10^5.8:10^3.4:1), which can be attributed to the different electron-withdrawing abilities between the pyrazine unit and TQ species that can induce stepwise D-A charge-transfer processes. These results suggest that TQ-based N-heteroacenes can be potentially useful in ultrahigh-density data-storage devices through the rational D-A tuning.

Tetraalkoxyphenanthrene-Fused Thiadiazoloquinoxalines: Synthesis, Electronic, Optical, and Electrochemical Properties, and Self-Assembly

π-Extended thiadiazoloquinoxaline (TQ) derivatives 1a,b-3a,b, in which a tetraalkoxyphenanthrene moiety is annulated with the TQ core and benzene rings are incorporated via the ethynylene spacer, were synthesized. They display absorption bands reaching into 750 nm and possess the electron-affinity comparable to [60]fullerene. The CF₃- and OMe-substituents on the benzene rings have moderate effects on modulation of the HOMO and LUMO levels. Tetraalkoxyphenanthrene-fused TQs 1a,b-3a,b aggregate in the solid state and assemble in solution through π-π stacking interactions. The self-assembly of 1a,b-3a,b into 1D superstructures was confirmed, and the difference in the alkoxy groups and the solvents for self-assembly proved to change their morphology. Comparison of the properties of 1a and those of reference compounds 4 and 5 clarified the effects of both the fusion of the phenanthrene moiety and the introduction of ethynylene spacers on the properties.

Pyrene-fused bisphenazinothiadiazoles with red to NIR electroluminescence

Deep red and NIR electroluminescence from pyrene-fused bisphenazinothiadiazoles.

Theory guided systematic molecular design of benzothiadiazole–phenazine based self-assembling electron-acceptors

A systematic theory-guided molecular design of electron acceptors to reveal the impact of each structural subunit on the electronic properties.

Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds: Synthetic Routes, Properties, and Applications

Two-dimensionally extended, polycyclic heteroaromatic molecules (heterocyclic nanographenes) are a highly versatile class of organic materials, applicable as functional chromophores and organic semiconductors. In this Review, we discuss the rich chemistry of large heteroaromatics, focusing on their synthesis, electronic properties, and applications in materials science. This Review summarizes the historical development and current state of the art in this rapidly expanding field of research, which has become one of the key exploration areas of modern heterocyclic chemistry.

HOMO stabilisation in π-extended dibenzotetrathiafulvalene derivatives for their application in organic field-effect transistors

Three new organic semiconductors, in which either two methoxy units are directly linked to a dibenzotetrathiafulvalene (DB-TTF) central core and a 2,1,3-chalcogendiazole is fused on the one side, or four methoxy groups are linked to the DB-TTF, have been synthesised as active materials for organic field-effect transistors (OFETs). Their electrochemical behaviour, electronic absorption and fluorescence emission as well as photoinduced intramolecular charge transfer were studied. The electron-withdrawing 2,1,3-chalcogendiazole unit significantly affects the electronic properties of these semiconductors, lowering both the HOMO and LUMO energy levels and hence increasing the stability of the semiconducting material. The solution-processed single-crystal transistors exhibit high performance with a hole mobility up to 0.04 cm(2)  V(-1)  s(-1) as well as good ambient stability.

A compact tetrathiafulvalene-benzothiadiazole dyad and its highly symmetrical charge-transfer salt: ordered donor π-stacks closely bound to their acceptors

A compact and planar donor-acceptor molecule 1 comprising tetrathiafulvalene (TTF) and benzothiadiazole (BTD) units has been synthesised and experimentally characterised by structural, optical, and electrochemical methods. Solution-processed and thermally evaporated thin films of 1 have also been explored as active materials in organic field-effect transistors (OFETs). For these devices, hole field-effect mobilities of μFE = (1.3±0.5)×10(-3) and (2.7±0.4)×10(-3)  cm(2)  V s(-1) were determined for the solution-processed and thermally evaporated thin films, respectively. An intense intramolecular charge-transfer (ICT) transition at around 495 nm dominates the optical absorption spectrum of the neutral dyad, which also shows a weak emission from its ICT state. The iodine-induced oxidation of 1 leads to a partially oxidised crystalline charge-transfer (CT) salt {(1)2I3}, and eventually also to a fully oxidised compound {1I3}⋅1/2I2. Single crystals of the former CT compound, exhibiting a highly symmetrical crystal structure, reveal a fairly good room temperature electrical conductivity of the order of 2 S cm(-1). The one-dimensional spin system bears compactly bonded BTD acceptors (spatial localisation of the LUMO) along its ridge.

Low-LUMO pyrene-fused azaacenes

A series of pyrene-fused azaacenes with four and six linearly fused rings that possess LUMO levels between -3.7 and -4.3 eV is reported. These LUMO values are remarkably lower than those typically observed for pyrene-fused azaacenes, even for systems with sixteen linearly fused rings, and are comparable to those observed for state-of-the-art n-azaacenes.

The Epitaxial Growth of Self-Assembled Ternaphthalene Fibers on Muscovite Mica

The morphology and structure of 2,2':6',2″-ternaphthalene (NNN) deposited on muscovite mica(001) substrates was investigated by scanning force microscopy (SFM) and specular X-ray diffraction measurements. Consistently, both methods reveal the coexistence of needle-like structures with a {111} contact plane and {001} orientated island-like crystallites, which are built up by almost upright standing NNN molecules. Both orientations are characterized by a well-defined azimuthal alignment relative to the substrate surface, which is analyzed by X-ray diffraction pole figure (XRD-PF) measurements. Based on XRD-PF and SFM analysis, the azimuthal alignment of {001} orientated crystallites is explained by ledge-directed epitaxy along the fibers' sidewalls. These fibers are found to orient along two dominant directions, which is verified and explained by a doubling of the energetically preferred molecular adsorption site by mirror symmetry of the substrate surface. The experimental findings are confirmed by force-field simulations and are discussed based on a recently reported growth model.