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Atomically-defined graphene nanoribbons (GNRs), which are narrow strips of graphene that feature a quantum confinement-induced bandgap, have shown great promise for applications in the next generation of semiconductor devices. Although numerous studies have demonstrated the bottom-up synthesis of all-carbon GNRs, a comparatively limited number of reports have focused on the preparation of nitrogen-doped GNRs, with two general types of architectures demonstrated to date. Herein, we describe the design, synthesis, and characterization of a new class of nitrogen-containing GNRs consisting of repeating tetrabenzopentacene molecular subunits. Our findings may afford additional possibilities and opportunities with regard to the directed bottom-up synthesis of heteroatom-doped, carbon-based nanoscale electronics. (C) 2020 Elsevier Ltd. All rights reserved.

π-stacked organic electronic materials are tunable light absorbers with many potential applications in optoelectronics. The optical properties of such molecules are highly dependent on the nature and energy of electron-hole pairs or excitons formed upon light absorption, which in turn are determined by intra- and intermolecular electronic and vibrational excitations. Here, we present a first-principles approach for describing the optical spectrum of stacked organic molecules with strong vibronic coupling. For stacked perylene tetracarboxylic acid diimides, we describe optical excitations by using the time-dependent density functional theory with a Franck-Condon Herzberg-Teller approximation of vibronic effects and validate our approach with comparison to experimental ultraviolet-visible (UV-vis) absorption measurements of solvated model systems. We determine that for larger macromolecules, unlike for single molecules, the sampling of the ground-state potential energy surface significantly influences the optical absorption spectrum. We account for this effect by applying our analysis to ∼100 structures extracted from equilibrated molecular dynamics simulations and averaging the optical spectrum over the entire ensemble. Additionally, we demonstrate that intermolecular electronic coupling within the stacks results in multiple low-energy electronically excited states that all contribute to the optical spectrum. This study provides a computationally feasible recipe for describing the spectroscopic properties of stacked organic chromophores via first-principles density functional theory.

Electrical doping of organic semiconductors is critical for their use in electrical devices. However, many high-performance semiconductors exhibit drastically reduced solubilities when doped in solution, making it difficult to deconvolute the roles of doping and morphological changes on their electrical properties. Here, we report the synthesis of a semiconducting polymer based on poly(3,4-propylenedioxythiophene) (ProDOT) substituted with oligo(ethylene glycol) (EG) side chains that is designed to solvate dopant molecules. When doped with F4TCNQ in solution, the polymer P(ProDOT-EG) undergoes efficient charge transfer while remaining soluble with no indication of aggregation. The electrical conductivity of thin films cast from heavily doped solutions is ∼1 S/cm; optical spectroscopy reveals that the doping efficiency is reduced upon formation of the solid film. Diffusion of F4TCNQ from the vapor phase into films of neutral P(ProDOT-EG) yields comparable conductivities to films cast from doped solutions. ...

Mixing simple additives into poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) dispersions can greatly enhance the thermoelectric properties of the cast films with little manufacturing cost, but design rules for many of these additives have yet to emerge. We show that controlling stoichiometry in ionic liquid (I.L.) additives can decouple morphological and electronic modifications to PEDOT:PSS and enhance its power factor by over 2 orders of magnitude. Blending I.L. additives with a 1:1 stoichiometry between cationic imidazolium (Im+) derivatives and anionic bis(trifluoromethane)sulfonamide (TFSI–) groups into PEDOT:PSS dispersions raised the film conductivity to ∼1000 S/cm. The Seebeck coefficient, which gives insight into the electronic structure as well as thermoelectric performance, remained unchanged. This behavior mimics that of popular high-boiling solvent additives such as dimethyl sulfoxide and ethylene glycol, which restructure the film morphology to enhance carrier mobility. B...

Polyquinolines have attracted attention as functional materials due to their excellent combination of optical, electrical, chemical, thermal, and mechanical properties. However, only a handful of synthetic routes for the preparation of these polymers have been established to date. Here, we demonstrate the preparation of polyquinolines via an AA/BB-type aza-Diels–Alder polymerization reaction. This approach requires only commercial starting materials and two straightforward synthetic steps to furnish the desired products in high yield. Overall, our modular and general route may afford new opportunities for the rational design and preparation of quinoline-based materials.

Polyquinolines have been studied since the early 1970s due to their favorable chemical, optical, electrical, and mechanical properties. However, surprisingly few synthetic strategies have been developed for the preparation of these polymers. Herein, we demonstrate the application of the aza-Diels–Alder (Povarov) reaction for the synthesis of soluble polyquinolines from a bifunctional monomer. Our approach furnishes polyquinolines with a unique architecture and connectivity in only two synthetic steps from inexpensive, commercially available reagents. The reported strategy may therefore represent a welcome addition to the polymer chemist’s toolkit by providing ready access to a diverse library of polyquinoline-type materials.

The performance of devices from organic semiconductors is often governed by charge transfer phenomena at structurally and electronically complex interfaces, which remain challenging to access and study with excellent chemical and temporal resolution. Herein, we report the preparation and X-ray spectroscopic characterization of well-defined model organic-inorganic interfaces. We discover an unexpected trend for our systems' associated charge transfer times, and we rationalize this trend with density functional theory calculations. Our findings hold relevance for understanding interfacial charge transfer phenomena in a variety of organic, biological, and bioinspired systems.

Electrochemistry of self-assembled DNA monolayers represents an attractive strategy for understanding the intrinsic properties of DNA and for developing DNA-based sensors. Thus, there is much interest in the discovery and characterization of new redox-active probes for application in DNA-based technologies. Herein, we report a detailed study of the electrochemical properties of a perylene-3,4,9,10-tetracarboxylic diimide base surrogate, when incorporated at various positions within a DNA monolayer. We demonstrate that the redox chemistry of this perylenediimide probe is mediated by the DNA base pair stack, dependent on its location within the DNA monolayer, and activated thermally. The electrochemical features and general synthetic flexibility of the perylenediimide base surrogate appear favorable for assays that leverage DNA-mediated charge transport.

X-ray pair distribution function (PDF) analysis has been applied to five carbon-supported platinum nanoparticles with sizes ranging from 1.78(2) to 11.2(2) nm. Debye (θD) and Einstein (θE) temperatures were extracted from temperature-dependent PDF peak widths. A monotonic decrease in (θD) with nanoparticle diameter was found and could be well explained by the effect of increased surface area except in the case of the 1.78(2) nm diameter nanoparticle where the measured Debye temperature is significantly depressed from that predicted. This suggests an anomalous bond softening in the smallest sample.

Advanced molecular electronic components remain vital for the next generation of miniaturized integrated circuits. Thus, much research effort has been devoted to the discovery of lossless molecular wires, for which the charge transport rate or conductivity is not attenuated with length in the tunneling regime. Herein, we report the synthesis and electrochemical interrogation of DNA-like molecular wires. We determine that the rate of electron transfer through these constructs is independent of their length and propose a plausible mechanism to explain our findings. The reported approach holds relevance for the development of high-performance molecular electronic components and the fundamental study of charge transport phenomena in organic semiconductors.

Graphene nanoribbons (GNRs) are promising candidate materials for the next generation of nanoscale electronics. Described herein is the synthesis of 2,4,6-substituted benzoquinolines, which constitute building blocks for nitrogen-doped GNRs. The presented facile and modular aza-Diels–Alder chemistry accommodates the installation of diverse functionalities at the crowded benzoquinolines’ 2 positions. Given the general utility of the benzoquinoline motif, these findings hold relevance not only for carbon-based electronics but also for a range of chemical disciplines.

© 2015 American Chemical Society. Perylene-3,4,9,10-tetracarboxylic diimides (PTCDIs) are a well-known class of organic materials. Recently, these molecules have been incorporated within DNA as base surrogates, finding ready applications as probes of DNA structure and function. However, the assembly dynamics and kinetics of PTCDI DNA base surrogates have received little attention to date. Herein, we employ constant temperature molecular dynamics simulations to gain an improved understanding of the assembly of PTCDI dimers and trimers. We also use replica-exchange molecular dynamics simulations to elucidate the energetic landscape dictating the formation of stacked PTCDI structures. Our studies provide insight into the equilibrium configurations of multimeric PTCDIs and hold implications for the construction of DNA-inspired systems from perylene-derived organic semiconductor building blocks. (Figure Presented).

Graphene nanoribbons (GNRs) represent promising materials for the next generation of nanoscale electronics. However, despite substantial progress towards the bottom-up synthesis of chemically and structurally well-defined all-carbon GNRs, strategies for the preparation of their nitrogen-doped analogs remain at a nascent stage. This scarce literature precedent is surprising given the established use of substitutional doping for tuning the properties of electronic materials. Herein, we report the synthesis of a previously unknown class of polybenzoquinoline-based materials, which have potential as GNR precursors. Our scalable and facile approach employs few synthetic steps, inexpensive commercial starting materials, and straightforward reaction conditions. Moreover, due to the importance of quinoline derivatives for a variety of applications, the reported findings may hold implications across a diverse range of chemical and physical disciplines.