Pseudocapacitors harness unique charge-storage mechanisms to enable high-capacity, rapidly cycling devices. Here we describe an organic system composed of perylene diimide and hexaazatrinaphthylene ...exhibiting a specific capacitance of 689 F g
at a rate of 0.5 A g
, stability over 50,000 cycles, and unprecedented performance at rates as high as 75 A g
. We incorporate the material into two-electrode devices for a practical demonstration of its potential in next-generation energy-storage systems. We identify the source of this exceptionally high rate charge storage as surface-mediated pseudocapacitance, through a combination of spectroscopic, computational and electrochemical measurements. By underscoring the importance of molecular contortion and complementary electronic attributes in the selection of molecular components, these results provide a general strategy for the creation of organic high-performance energy-storage materials.
Perylene diimide (PDI) is a workhorse of the organic electronics community. However, the vast majority of designs that include PDI substitute the core with various functional groups to encourage ...intimate cofacial contacts between largely planar PDIs. Over the past several years, we have observed the counterintuitive result that contorting the planar aromatic core of PDI leads to higher performing photovoltaics, photodetectors, batteries, and other organic electronic devices. In this Perspective, we describe how different modes of contortion can be reliably installed into PDI-based molecules, oligomers, and polymers. We also describe how these different contortions modify the observed optical and electronic properties of PDI. For instance, contorting PDIs into bowls leads to high-efficiency singlet fission materials, while contorting PDIs into helicene-like structures leads to nonlinear amplification of Cotton effects, culminating in the highest g-factors so far observed for organic compounds. Finally, we show how these unique optoelectronic properties give rise to higher performance organic electronic devices. We specifically note how the three-dimensional structure of these contorted aromatic molecules is responsible for the enhancements in performance we observe. Throughout this Perspective, we highlight opportunities for continued study in this rapidly developing organic materials frontier.
Here we report the synthesis of two polyhelicene frameworks consisting, from end-to-end, of 18 and 24 fused benzene rings. The latter exhibits the largest electronic circular dichroism in the visible ...spectrum of any molecule. These shape-persistent helical nanoribbons incorporate multiple helicenes, a class of contorted polycyclic aromatic molecules consisting of ortho-annulated rings. These conjugated, chiral molecules have interesting chemical, biological, and chiroptical properties; however, there are very few helicenes with extraordinary chiroptical response over a broad range of the visible spectruma key criterion for applications such as chiral optoelectronics. In this report, we show that coupling the polyhelicene framework with multiple perylene-diimide subunits elicits a significant chiroptic response. Notably, the molar circular dichroism increases faster than the absorptivity of these molecules as their helical axis lengthens. Computational analysis reveals that the greatly amplified circular dichroism arises from exciton-like interactions between the perylene-diimide and the helicene moieties. We predict that even greater chiroptic enhancement will result from further axial elongation of these nanoribbons, which can be readily enabled via the iterative synthetic method presented herein.
Electron Delocalization in Perylene Diimide Helicenes Schuster, Nathaniel J.; Paley, Daniel W.; Jockusch, Steffen ...
Angewandte Chemie (International ed.),
October 17, 2016, Letnik:
55, Številka:
43
Journal Article
Recenzirano
Odprti dostop
We report two new helicenes derived from the double fusion of an acene with two perylene diimide (PDI) subunits. These PDI‐helicene homologs exhibit very different structural and electronic ...properties, despite differing by only a single ring in the link between the PDI units. The shorter inter‐PDI link brings the two PDI subunits closer together, and this results in the collision of their respective π‐electron clouds. This collision facilitates intramolecular through‐space electronic delocalization when the PDI‐helicene is reduced.
Two helicenes were synthesized by double fusion of an acene with two perylene diimide (PDI) subunits. These PDI‐helicene homologs show different structural and electronic properties, despite differing by only a single ring in the link between the PDI units. The shorter link brings the two PDI subunits closer together, and this results in the collision of their respective π‐electron clouds.
A new intersection between reaction chemistry and electronic circuitry is emerging from the ultraminiaturization of electronic devices. Over decades chemists have developed a nuanced understanding of ...stereoelectronics to establish how the electronic properties of molecules relate to their conformation; the recent advent of single-molecule break-junction techniques provides the means to alter this conformation with a level of control previously unimagined. Here we unite these ideas by demonstrating the first single-molecule switch that operates through a stereoelectronic effect. We demonstrate this behaviour in permethyloligosilanes with methylthiomethyl electrode linkers. The strong σ conjugation in the oligosilane backbone couples the stereoelectronic properties of the sulfur-methylene σ bonds that terminate the molecule. Theoretical calculations support the existence of three distinct dihedral conformations that differ drastically in their electronic character. We can shift between these three species by simply lengthening or compressing the molecular junction, and, in doing so, we can switch conductance digitally between two states.
Electric fields have been proposed as having a distinct ability to catalyze chemical reactions through the stabilization of polar or ionic intermediate transition states. Although field-assisted ...catalysis is being researched, the ability to catalyze reactions in solution using electric fields remains elusive and the understanding of mechanisms of such catalysis is sparse. Here we show that an electric field can catalyze the cis-to-trans isomerization of 3cumulene derivatives in solution, in a scanning tunneling microscope. We further show that the external electric field can alter the thermodynamics inhibiting the trans-to-cis reverse reaction, endowing the selectivity toward trans isomer. Using density functional theory-based calculations, we find that the applied electric field promotes a zwitterionic resonance form, which ensures a lower energy transition state for the isomerization reaction. The field also stabilizes the trans form, relative to the cis, dictating the cis/trans thermodynamics, driving the equilibrium product exclusively toward the trans.
Nanoscale Atoms in Solid-State Chemistry Roy, Xavier; Lee, Chul-Ho; Crowther, Andrew C. ...
Science (American Association for the Advancement of Science),
07/2013, Letnik:
341, Številka:
6142
Journal Article
Recenzirano
Odprti dostop
We describe a solid-state material formed from binary assembly of atomically precise molecular clusters. Co₆Se₈(PEt₃)₆C₆₀₂ and Cr₆Te₈(PEt₃)₆C₆₀₂ assembled into a superatomic relative of the cadmium ...iodide (Cdl₂) structure type. These solid-state materials showed activated electronic transport with activation energies of 100 to 150 millielectron volts. The more reducing cluster Ni₉Te₆(PEt₃)₈ transferred more charge to the fullerene and formed a rock-salt—related structure. In this material, the constituent clusters are able to interact electronically to produce a magnetically ordered phase at low temperature, akin to atoms in a solid-state compound.
Single-molecule topological insulators are promising candidates as conducting wires over nanometre length scales. A key advantage is their ability to exhibit quasi-metallic transport, in contrast to ...conjugated molecular wires which typically exhibit a low conductance that decays as the wire length increases. Here, we study a family of oligophenylene-bridged bis(triarylamines) with tunable and stable mono- or di-radicaloid character. These wires can undergo one- and two-electron chemical oxidations to the corresponding mono-cation and di-cation, respectively. We show that the oxidized wires exhibit reversed conductance decay with increasing length, consistent with the expectation for Su–Schrieffer–Heeger-type one-dimensional topological insulators. The 2.6-nm-long di-cation reported here displays a conductance greater than 0.1G0, where G0 is the conductance quantum, a factor of 5,400 greater than the neutral form. The observed conductance–length relationship is similar between the mono-cation and di-cation series. Density functional theory calculations elucidate how the frontier orbitals and delocalization of radicals facilitate the observed non-classical quasi-metallic behaviour.Designing long and highly conducting molecular wires has been a great challenge for decades. It has now been shown that a singly oxidized 2.6-nm-long oligophenylene-bridged bis(triarylamine) can show a single-molecule junction conductance over 0.1G0.
Despite numerous organic semiconducting materials synthesized for organic photovoltaics in the past decade, fullerenes are widely used as electron acceptors in highly efficient bulk-heterojunction ...solar cells. None of the non-fullerene bulk heterojunction solar cells have achieved efficiencies as high as fullerene-based solar cells. Design principles for fullerene-free acceptors remain unclear in the field. Here we report examples of helical molecular semiconductors as electron acceptors that are on par with fullerene derivatives in efficient solar cells. We achieved an 8.3% power conversion efficiency in a solar cell, which is a record high for non-fullerene bulk heterojunctions. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor-acceptor interfaces. Atomic force microscopy reveals a mesh-like network of acceptors with pores that are tens of nanometres in diameter for efficient exciton separation and charge transport. This study describes a new motif for designing highly efficient acceptors for organic solar cells.
One-dimensional sp-hybridized carbon wires, including cumulenes and polyynes, can be regarded as finite versions of carbynes. They are likely to be good candidates for molecular-scale conducting ...wires as they are predicted to have a high-conductance. In this study, we first characterize the single-molecule conductance of a series of cumulenes and polyynes with a backbone ranging in length from 4 to 8 carbon atoms, including 7cumulene, the longest cumulenic carbon wire studied to date for molecular electronics. We observe different length dependence of conductance when comparing these two forms of carbon wires. Polyynes exhibit conductance decays with increasing molecular length, while cumulenes show a conductance increase with increasing molecular length. Their distinct conducting behaviors are attributed to their different bond length alternation, which is supported by theoretical calculations. This study confirms the long-standing theoretical predictions on sp-hybridized carbon wires and demonstrates that cumulenes can form highly conducting molecular wires.
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