4 research outputs found
Perylene-Based Liquid Crystals as Materials for Organic Electronics Applications
Columnar
phases formed by the stacking of disclike molecules with
an intimate π–π overlap forms a 1D pathway for
the anisotropic charge migration along the columns. Columnar phases
have great potential in organic electronic devices to be utilized
as active semiconducting layers in comparison to organic single crystals
or amorphous polymers in terms of processability, ease of handling,
and high charge carrier mobility. Intelligent molecular engineering
of perylene and its derivatives provided access to tune the physical
properties and self-assembly behavior. The columnar phase formed by
perylene derivatives has great potential in the fabrication of organic
electronic devices. There are several positions on the perylene molecule,
which can be functionalized to tune its self-assembly, as well as
optoelectronic properties. Thus, many liquid-crystalline molecules
stabilizing the columnar phase, which are based on perylene tetraesters,
perylene diester imides, and perylene bisimides, have been synthesized
over the years. Their longitudinal and laterally extended derivatives, <i>bay</i>-substituted derivatives exhibiting a columnar phase,
are reported. In addition, several liquid-crystalline oligomers and
polymers based on perylene derivatives were also reported. All such
modifications provide an option to tune the energy levels of frontier
molecular orbitals with respect to the work function of the electrodes
in devices and also the processability of such materials. In this
feature article, we attempt to provide an overview of the molecular
design developed to tune the applicable properties and self-assembly
of perylene derivatives as well as recent developments related to
their application in the fabrication of organic solar cells, organic
light-emitting diodes, and organic field-effect transistors
Liquid-Crystalline Star-Shaped Supergelator Exhibiting Aggregation-Induced Blue Light Emission
A family of closely
related star-shaped stilbene-based molecules
containing an amide linkage are synthesized, and their self-assembly
in liquid-crystalline and gel states was investigated. The number
and position of the peripheral alkyl tails were systematically varied
to understand the structure–property relation. Interestingly,
one of the molecules with seven peripheral chains was bimesomorphic,
exhibiting columnar hexagonal and columnar rectangular phases, whereas
the rest of them stabilized the room-temperature columnar hexagonal
phase. The self-assembly of these molecules in liquid-crystalline
and organogel states is extremely sensitive to the position and number
of alkoxy tails in the periphery. Two of the compounds with six and
seven peripheral tails exhibited supergelation behavior in long-chain
hydrocarbon solvents. One of these compounds with seven alkyl chains
was investigated further, and it has shown higher stability and moldability
in the gel state. The xerogel of the same compound was characterized
with the help of extensive microscopic and X-ray diffraction studies.
The nanofibers in the xerogel are found to consist of molecules arranged
in a lamellar fashion. Furthermore, this compound shows very weak
emission in solution but an aggregation-induced emission property
in the gel state. Considering the dearth of solid-state blue-light-emitting
organic materials, this molecular design is promising where the self-assembly
and emission in the aggregated state can be preserved. The nonsymmetric
design lowers the phase-transition temperatures.The presence of an
amide bond helps to stabilize columnar packing over a long range because
of its polarity and intermolecular hydrogen bonding in addition to
promoting organogelation
Self-Assembled <i>anti</i>-Napthalene-3,4:9,10-bis(benzimidazole)s: Stabilizing Room Temperature Columnar Phase with Ambipolar Conductivity
The
isolation of syn- and anti-perinone
derivatives and the room temperature columnar self-assembly
of an anti-perinone compound with ambipolar conductivity
are reported. These compounds displayed a wide absorption range encompassing
the entire visible spectrum with a low band gap
Perylo[1,12‑<i>b</i>,<i>c</i>,<i>d</i>] Thiophene Tetraesters: A New Class of Luminescent Columnar Liquid Crystals
PeryloÂ[1,12-<i>b</i>,<i>c</i>,<i>d</i>] thiophene tetraesters exhibiting wide-range
hexagonal columnar
phase have been synthesized. These compounds also exhibit good homeotropic
alignment in the liquid-crystalline phase which is very important
for the device fabrication. These compounds showed sky-blue luminescence
in solution under the long-wavelength UV light. With high solubility
and high quantum yield these compounds can serve as standards to measure
quantum yields of unknown samples. This new class of materials is
promising, considering the emissive nature and stabilization of hexagonal
columnar mesophase over a wide thermal range and ease of synthesis