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10.1002/chem.201804074
Chemistry - A European Journal
FULL PAPER
1,2,5-Triphenylpyrrole Derivatives with Dual Intense
Photoluminescence in Both Solution and Solid State and their
Solvatochromism, Polymorphic Luminescent Property
Yuanyuan Li,[a] Yunxiang Lei,[b] Lichao Dong,[b] Longlong Zhang,[a] Junge Zhi,*[a] Jianbing Shi,[b] Bin
Tong,[b] Yuping Dong,*[b]
Abstract: Five organic luminophores 1,2,5-triphenylpyrrole (TPP)
derivatives 3a-e containing electron-withdrawing or electron-
donating groups were synthesized by Pd-catalyzed Suzuki coupling
of 1-phenyl-2,5-di(4’-bromophenyl) pyrrole and para-substituted
phenylboronic acid. They possess good thermal stabilities with high
decomposition temperatures above 310 °C. The investigation on the
photophysical properties of the luminogens 3a-e indicated that they
exhibited dual intense photoluminescence in both solution and solid
state due to their twisted conformations, and their fluorescence
quantum yields (ΦF) were 68.7%~94.9% in THF solution and
19.1%~52.0% in solid powder state. The compounds 3a-c with
electron-acceptor exhibited remarkable solvatochromism with large
Stokes shift attributing to their D-π-A structure and intramolecular
charge transfer effect, especially, 3a with aldehyde group displays
obvious red-shift of emission band from 445 nm to 564 nm as
increasing solvent polarity. However, no obvious solvatochromic
behavior was observed for compounds 3d-e containing electron-
donating groups. Moreover, the luminophore 3a exhibited
polymorphic luminescent property and crystallization-induced
emission enhancement feature.
in photoelectric devices and bioprobes.[1] Aggregation-induced
emission (AIE), contrary to the ACQ phenomenon, was
presented by Tang and his coworkers in 2001.[3] A series of
novel fluorophores, silole derivatives with propeller-like
conformation, were developed and exhibited high fluorescence
emission in aggregation and solid state, but nonluminescence in
dilute solution, and the photoluminescence mechanism was
ascribed to the twisted conformation and restriction of
intramolecular motions of the fluorophores in the solid state.[3,4]
AIE-active organic materials have attracted widespread attention
because they provided an effective strategy to avoid
fluorescence quenching in solid state and concentrated solution.
Therefore, series of AIE fluorogens, also extending to
crystallization-induced
/crystallization-induced
emission
enhanced
(CIE),
emission
aggregation-
(AIEE/CIEE)
materials, have been developed and applied in diverse fields as
chem-/bio-sensors, bioimaging, chiral recognition and
optoelectronic devices.[5] However, the fluorescent materials,
whatever they possess AIE feature or ACQ character, only
play an active role in one side, meaning that they can display
high efficient photoluminescence only in dilute solution or solid
state, which limits their wide range practical application.
Recently, several fluorophores were developed in
consequence, which exhibited intense photoluminescence in
both dilute solution and solid state with high fluorescence
quantum efficiencies, and they were going to get much broader
applications.[6,7] Further research revealed that the appropriate
twisted conformations, conjugation-induced rigidity or longer
conjugation length, or increasing steric hindrance in π-
conjugated systems were beneficial to make the fluorescent
materials possess dual strong photoluminescence in both dilute
solution and solid state.[7] Thus, more fluorophores with dual
intense luminescence need to be developed to explore the
luminescent mechanism combining molecular structure with
molecular packing pattern in solution and solid state, and further
enlarge the scope of molecular candidates applicability in
Introduction
The florescent materials with high quantum efficiencies have
attracted great attention for their extensive applications in chem-
/bio-sensors, mechanosensors, optoelectronic conversion
materials, biological probes and so on.[1,2] Conventional organic
fluorophores with π-conjugated structure and planar
conformations often display intense emission in dilute solution,
but the fluorescence is weakened or even quenched in
concentrated solution and solid states mainly attributing to the
delocalization of excitons and strong π-π stacking interaction.
The phenomenon is known as aggregation-caused quenching
(ACQ), and it restricts the fluorophores for practical application
fluorescent
sensors,
biological
imaging,
optics
and
optoelectronics devices, etc.
[a]
Y Li, L Zhang, Associate Prof. J Zhi*
1,2,5-Triphenylpyrrole (TPP) is a kind of conjugated skeleton
to construct AIE/AIEE-active molecules, and TPP derivatives
exhibit potential application in chem-/bio-sensors although 1,2,5-
TPP is AIE-inactive.[8-10] 1,2,5-TPP molecule adopts slightly
twisted conformation with torsion angles of 40.19°, 69.08°, and
40.19o between the pyrrole ring and phenyl rings, and 1,2,5-TPP
exhibits a fluorescence quantum yield (F) of 24.8% in THF and
a lower F of 1.88% in solid state.[8] Thus, five TPP derivatives,
1-phenyl-2,5-di(4’-R-biphenyl) pyrrole (3a-e), were designed by
introducing para-R-phenyl (R: -CHO, -CN, -COOCH3, -OCH3, -
OH) at 2,5-position of pyrrole to extend the conjugated structure
School of Chemistry and Chemical Engineering,
Beijing Key Laboratory of Photoelectronic/Electrophotonic
Conversion Materials,
Beijing Institute of Technology,
5 South Zhongguancun Street, Beijing 100081, (China)
E-mail: zhijunge@bit.edu.cn
Y Lei, L Dong, Associate Prof. B Shi, Prof. B Tong, Prof. Y Dong*
Materials Science and Engineering
Beijing Institute of Technology,
5 South Zhongguancun Street, Beijing 100081, (China)
E-mail: chdongyp@bit.edu.cn
[b]
Supporting information for this article is given via a link at the end of
the document.
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