12 research outputs found
B<sub>2</sub>N<sub>2</sub>‑Dibenzo[<i>a</i>,<i>e</i>]pentalenes: Effect of the BN Orientation Pattern on Antiaromaticity and Optoelectronic Properties
Two BN units were
embedded in dibenzo[<i>a</i>,<i>e</i>]pentalene
with different orientation patterns, which significantly
modulated its antiaromaticity and optoelectronic properties. Importantly,
the vital role of the BN orientation in conjugated molecules with
more than one BN unit was demonstrated for the first time. This work
indicates a large potential of the BN/CC isosterism for the development
of new antiaromatic systems and highlights the importance of precise
control of the BN substitution patterns in conjugated materials
Synthesis of Stable Nanographenes with OBO-Doped Zigzag Edges Based on Tandem Demethylation-Electrophilic Borylation
A tandem demethylation-aryl
borylation strategy was developed to
synthesize OBO-doped tetrabenzo[<i>a,f,j,o</i>]perylenes
(namely “bistetracenes”) and tetrabenzo[<i>bc,ef,kl,no</i>]coronenes (namely “peritetracenes”). The OBO-doped
bistetracene analogues exhibited excellent stability and strong fluorescence,
in contrast to the unstable all-carbon bistetracene. Single-crystal
X-ray analysis for OBO-doped bistetracene revealed a twisted double
[5]helicene structure, indicating that this synthesis is applicable
to new heterohelicenes. Importantly, cyclodehydrogenation of the bistetracene
analogues successfully produced the unprecedented heteroatom-doped
peritetracenes, which opened up a new avenue to periacene-type nanographenes
with stable zigzag edges
Synthesis of Stable Nanographenes with OBO-Doped Zigzag Edges Based on Tandem Demethylation-Electrophilic Borylation
A tandem demethylation-aryl
borylation strategy was developed to
synthesize OBO-doped tetrabenzo[<i>a,f,j,o</i>]perylenes
(namely “bistetracenes”) and tetrabenzo[<i>bc,ef,kl,no</i>]coronenes (namely “peritetracenes”). The OBO-doped
bistetracene analogues exhibited excellent stability and strong fluorescence,
in contrast to the unstable all-carbon bistetracene. Single-crystal
X-ray analysis for OBO-doped bistetracene revealed a twisted double
[5]helicene structure, indicating that this synthesis is applicable
to new heterohelicenes. Importantly, cyclodehydrogenation of the bistetracene
analogues successfully produced the unprecedented heteroatom-doped
peritetracenes, which opened up a new avenue to periacene-type nanographenes
with stable zigzag edges
Fusion at the Non-K-Region of Pyrene: An Alternative Strategy To Extend the π‑Conjugated Plane of Pyrene
A large fused pyrene derivative <b>TTTP</b> was facilely developed through fusion at the non-K-region of pyrene, which represents the first example of extending such a π-conjugated plane at its non-K-region. The investigation of its photophysical properties and other characterizations indicated that <b>TTTP</b> exhibited strong aggregation behaviors and self-assembled into highly ordered one-dimensional nanowires due to its large π-conjugated plane
Synthesis, Structure, and Chiroptical Properties of a Double [7]Heterohelicene
The synthesis of
11a,25a-dibora-11,12,25,26-tetraoxatetranaphtho[1,2-<i>a</i>:2′,1′-<i>f</i>:1″,2″-<i>j</i>:2‴,1‴-<i>o</i>]perylene, a double
[7]heterohelicene containing OBO units, has been achieved via tandem
demethylation-borylation, representing the highest double helicene
reported thus far with all six-membered rings. Single-crystal X-ray
analysis clearly demonstrated a significantly twisted structure with
the terminal aromatic rings overlapping at both ends, giving the first
example of a double helicene with intramolecular π-layers. Such
structural features resulted in a high theoretical isomerization barrier
of 45.1 kcal/mol, which is the highest value for all the double helicenes
ever reported, rendering the achieved molecule with high chiral stability.
The (<i>P</i>,<i>P</i>)- and (<i>M</i>,<i>M</i>)-isomers were separated by chiral HPLC and the
chiroptical properties were investigated, revealing opposite circular
dichroism responses
Fused Bis-Benzothiadiazoles as Electron Acceptors
Fused
bis-benzothiadiazoles with different molecular geometries, namely,
linear benzoquinone-fused bis(benzothiadiazole) (Q-BBT) and V-shaped
sulfone-fused bis(benzothiadiazole) (S-BBT), were synthesized. Single
crystal analysis of Q-BBT and S-BBT revealed profoundly distinct packing
modes, which must be ascribed to the different molecular shapes. Experimental
and theoretical studies indicated that both compounds give rise to
electron-accepting materials. This work thus also contributes to the
diversity of electron acceptors based on bis-benzothiadiazole moieties
and highlights the important role of molecular shape for the solid-state
packing of organic conjugated materials
A Straightforward Strategy toward Large BN-Embedded π‑Systems: Synthesis, Structure, and Optoelectronic Properties of Extended BN Heterosuperbenzenes
A straightforward
strategy has been used to construct large BN-embedded
π-systems simply from azaacenes. BN heterosuperbenzene derivatives,
the largest BN heteroaromatics to date, have been synthesized in three
steps. The molecules exhibit curved π-surfaces, showing two
different conformations which are self-organized into a sandwich structure
and further packed into a π-stacking column. The assembled microribbons
exhibit good charge transport properties and photoconductivity, representing
an important step toward the optoelectronic applications of BN-embedded
aromatics
Epindolidione-Based Conjugated Polymers: Synthesis, Electronic Structures, and Charge Transport Properties
Development of new electron-deficient
building blocks is essential to donor–acceptor conjugated polymers.
Herein, epindolidione (EPD) as electron-deficient unit was integrated
into conjugated polymers for the investigation of field-effect transistors
for the first time. We systematically studied the electronic structures
and charge transport properties of the EPD-based donor–acceptor
polymers. They exhibit <i>p</i>-type transport characteristics
with the highest mobility of up to 0.40 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>, thus demonstrating its great potential as
a building block for polymer field-effect transistors and photovoltaics
Impacts of Stereoisomerism on Molecular Packing and Charge Transport of Imide-Fused Corannulene Derivatives
Two
chiral tertiary carbon centers bearing one mesityl group at
each center are introduced into the molecular backbone of imide-fused
corannulene derivatives to produce four stereoisomers (i.e., (<i>S</i>, <i>S</i>), (<i>R</i>, <i>R</i>), (<i>R</i>, <i>S</i>), or (<i>S</i>, <i>R</i>) configurations on two chiral carbons) in one
pot, which are separated into two portions through column chromatography
over silica gel. Portion 1, containing a pair of enantiomers ((<i>S</i>, <i>S</i>) and (<i>R</i>, <i>R</i>)), adopts layered packing in the crystal. Portion 2, consisting
of a pair of mesomers ((<i>R</i>, <i>S</i>) and
(<i>S</i>, <i>R</i>)), exhibits columnar packing
in their cocrystal. Theoretical calculations are performed on these
two packing motifs, revealing that Portion 1 displays hole-dominated
transport, whereas Portion 2 shows electron-dominated transport
Monitoring the On-Surface Synthesis of Graphene Nanoribbons by Mass Spectrometry
We present a mass spectrometric approach
to characterize and monitor
the intermediates of graphene nanoribbon (GNR) formation by chemical
vapor deposition (CVD) on top of Au(111) surfaces. Information regarding
the repeating units, lengths, and termini can be obtained directly
from the surface sample by a modified matrix-assisted laser desorption/ionization
(MALDI) method. The mass spectrometric results reveal ample oxidative
side reactions under CVD conditions that can be drastically diminished
by the introduction of protective H<sub>2</sub> gas at ambient pressure.
Simultaneously, the addition of hydrogen extends the lengths of the
oligophenylenes and thus the final GNRs. Moreover, the prematurely
formed cyclodehydrogenation products during the oligomer growth can
be assigned by the mass spectrometric technique. The obtained mechanistic
insights provide valuable information for optimizing and upscaling
the bottom-up fabrication of GNRs. Given the important role of GNRs
as semiconductors, the mass spectrometric analysis provides a readily
available tool to characterize and improve their structural perfection