18 research outputs found
Effect of Substituent Position on the Photophysical Properties of Triphenylpyrrole Isomers
The charge distribution, molecular
structure, and morphological packing significantly affect the photophysical
properties of organic photoluminescent materials. In this work, two
triphenylpyrrole isomers, 1,2,5- (TPP1) and 1,3,4- (TPP2), were first
synthesized and characterized. Because of their different substituent
positions, TPP1 possesses aggregation-caused emission quenching (ACQ)
behavior while TPP2 exhibits aggregation-induced emission (AIE). Their
different photoluminescent properties were systematically investigated
by using UVâvis absorption spectroscopy, fluorescence spectroscopy,
density functional theory (DFT) calculations, and single-crystal structure
analysis. The results indicate that substituent position of the two
phenyl groups predominately affects the charge distribution of the
isomers and determines their molecular packing structures, which further
cause the different restriction of intramolecular rotation (RIR) capabilities
of phenyl rings, thus resulting in different luminescence properties
of these two triphenylpyrrole isomers under different aggregate states
Synthesis of Polyquinolines via One-Pot Polymerization of Alkyne, Aldehyde, and Aniline under Metal-Free Catalysis and Their Properties
A novel synthetic
route to polyquinolines with 6-substituted quinoline
as the structural unit was developed based on the polymerization of
alkyneâaldehyde monomers and aniline derivatives under the
catalysis of Lewis acid BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>.
The polymerization was conducted in dichloroethane at 100 °C
for 36 h under air atmosphere, affording polyquinolines with molecular
weights up to 13âŻ100 and good solubility in most organic solvents.
The substituents in aniline exhibited significant effects on the molecular
weight, yield, and solubility of the produced polyquinolines. The
structures of prepared polymers were characterized and confirmed by
GPC, NMR, and FT-IR. The thermogravimetry (TGA) and differential scanning
calorimetry (DSC) analysis suggests that the polyquinolines are highly
thermal stable. Further photoluminescence behaviors of the prepared
polyquinolines were investigated. Based on the characterization results
and small molecule reaction mechanism, the polymerization pathway
of the polyquinolines was proposed. Our work has provided a novel
simple strategy for the preparation of multifunctional polyquinolines
with unique architectures by one-pot synthesis under metal-free catalysis
1,4-Selective Polymerization of 1,3-Cyclohexadiene and Copolymerization with Styrene by Cationic Half-Sandwich Fluorenyl Rare Earth Metal Alkyl Catalysts
The
regioselective coordinationâinsertion polymerization of 1,3-cyclohexadiene
(CHD) and copolymerization with styrene (S) could be achieved by cationic
half-sandwich fluorenyl rare earth metal alkyl catalysts generated
by treating half-sandwich fluorenyl rare earth metal dialkyl complexes
Fluâ˛LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(THF)<sub>n</sub> (<b>1</b>â<b>10</b>) with an activator
(such as [Ph<sub>3</sub>C]Â[BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>] (<b>A</b>), [PhNHMe<sub>2</sub>]Â[BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>] (<b>B</b>), or BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> (<b>C</b>)) and Al<sup><i>i</i></sup>Bu<sub>3</sub>. The homopolymerization of CHD afforded polyÂ(CHD)Âs with complete
1,4 selectivity (1,4 selectivity up to 100%). The copolymerization
of CHD with styrene gave new random CHDâS copolymers with CHD
content ranging from 22 to 74 mol % containing 1,4-linked CHDâCHD,
alternating CHDâS, and syndiotactic SâS sequences unavailable
previously. The activity of the copolymerization and the comonomer
compositions and sequences of the resulting CHDâS copolymers
could be easily controlled by changing the substituted fluorenyl ligand,
the metal center, the activator, the temperature, and the molar ratio
of comonomers. The residual CâC double bonds of the random
CHDâS copolymers could be further epoxidized by <i>meta</i>-chloroperoxybenzoic acid (<i>m</i>CPBA) at room temperature
to prepare high-performance polymers with polar groups and reactive
sites in the polymer backbone. Such functionalization could improve
the solubility, dying, acidity, and surfactivity of these copolymer
materials
1,4-Selective Polymerization of 1,3-Cyclohexadiene and Copolymerization with Styrene by Cationic Half-Sandwich Fluorenyl Rare Earth Metal Alkyl Catalysts
The
regioselective coordinationâinsertion polymerization of 1,3-cyclohexadiene
(CHD) and copolymerization with styrene (S) could be achieved by cationic
half-sandwich fluorenyl rare earth metal alkyl catalysts generated
by treating half-sandwich fluorenyl rare earth metal dialkyl complexes
Fluâ˛LnÂ(CH<sub>2</sub>SiMe<sub>3</sub>)<sub>2</sub>(THF)<sub>n</sub> (<b>1</b>â<b>10</b>) with an activator
(such as [Ph<sub>3</sub>C]Â[BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>] (<b>A</b>), [PhNHMe<sub>2</sub>]Â[BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>] (<b>B</b>), or BÂ(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> (<b>C</b>)) and Al<sup><i>i</i></sup>Bu<sub>3</sub>. The homopolymerization of CHD afforded polyÂ(CHD)Âs with complete
1,4 selectivity (1,4 selectivity up to 100%). The copolymerization
of CHD with styrene gave new random CHDâS copolymers with CHD
content ranging from 22 to 74 mol % containing 1,4-linked CHDâCHD,
alternating CHDâS, and syndiotactic SâS sequences unavailable
previously. The activity of the copolymerization and the comonomer
compositions and sequences of the resulting CHDâS copolymers
could be easily controlled by changing the substituted fluorenyl ligand,
the metal center, the activator, the temperature, and the molar ratio
of comonomers. The residual CâC double bonds of the random
CHDâS copolymers could be further epoxidized by <i>meta</i>-chloroperoxybenzoic acid (<i>m</i>CPBA) at room temperature
to prepare high-performance polymers with polar groups and reactive
sites in the polymer backbone. Such functionalization could improve
the solubility, dying, acidity, and surfactivity of these copolymer
materials
Photoelectric Covalent Organic Frameworks: Converting Open Lattices into Ordered DonorâAcceptor Heterojunctions
Ordered
one-dimensional open channels represent the typical porous
structure of two-dimensional covalent organic frameworks (COFs). Here
we report a general synthetic strategy for converting these open lattice
structures into ordered donorâacceptor heterojunctions. A three-component
topological design scheme was explored to prepare electron-donating
intermediate COFs, which upon click reaction were transformed to photoelectric
COFs with segregated donorâacceptor alignments, whereas electron-accepting
buckyballs were spatially confined within the nanochannels via covalent
anchoring on the channel walls. The donorâacceptor heterojunctions
trigger photoinduced electron transfer and allow charge separation
with radical species delocalized in the Ď-arrays, whereas the
charge separation efficiency was dependent on the buckyball content.
This new donorâacceptor strategy explores both skeletons and
pores of COFs for charge separation and photoenergy conversion
Tuning the Luminescence of MetalâOrganic Frameworks for Detection of Energetic Heterocyclic Compounds
Herein
we report three metalâorganic frameworks (MOFs),
TABD-MOF-1, -2, and -3, constructed from Mg<sup>2+</sup>, Ni<sup>2+</sup>, and Co<sup>2+</sup>, respectively, and deprotonated 4,4â˛-((<i>Z</i>,<i>Z</i>)-1,4-diphenylbuta-1,3-diene-1,4-diyl)Âdibenzoic
acid (TABD-COOH). The fluorescence of these three MOFs is tuned from
highly emissive to completely nonemissive via ligand-to-metal charge
transfer by rational alteration of the metal ion. Through competitive
coordination substitution, the organic linkers in the TABD-MOFs are
released and subsequently reassemble to form emissive aggregates due
to aggregation-induced emission. This enables highly sensitive and
selective detection of explosives such as five-membered-ring energetic
heterocyclic compounds in a few seconds with low detection limits
through emission shift and/or turn-on. Remarkably, the cobalt-based
MOF can selectively sense the powerful explosive 5-nitro-2,4-dihydro-3<i>H</i>-1,2,4-triazole-3-one with high sensitivity discernible
by the naked eye (detection limit = 6.5 ng on a 1 cm<sup>2</sup> testing
strip) and parts per billion-scale sensitivity by spectroscopy via
pronounced fluorescence emission
Tuning the Luminescence of MetalâOrganic Frameworks for Detection of Energetic Heterocyclic Compounds
Herein
we report three metalâorganic frameworks (MOFs),
TABD-MOF-1, -2, and -3, constructed from Mg<sup>2+</sup>, Ni<sup>2+</sup>, and Co<sup>2+</sup>, respectively, and deprotonated 4,4â˛-((<i>Z</i>,<i>Z</i>)-1,4-diphenylbuta-1,3-diene-1,4-diyl)Âdibenzoic
acid (TABD-COOH). The fluorescence of these three MOFs is tuned from
highly emissive to completely nonemissive via ligand-to-metal charge
transfer by rational alteration of the metal ion. Through competitive
coordination substitution, the organic linkers in the TABD-MOFs are
released and subsequently reassemble to form emissive aggregates due
to aggregation-induced emission. This enables highly sensitive and
selective detection of explosives such as five-membered-ring energetic
heterocyclic compounds in a few seconds with low detection limits
through emission shift and/or turn-on. Remarkably, the cobalt-based
MOF can selectively sense the powerful explosive 5-nitro-2,4-dihydro-3<i>H</i>-1,2,4-triazole-3-one with high sensitivity discernible
by the naked eye (detection limit = 6.5 ng on a 1 cm<sup>2</sup> testing
strip) and parts per billion-scale sensitivity by spectroscopy via
pronounced fluorescence emission
Colloidal Synthesis of Air-Stable CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> Quantum Dots by Gaining Chemical Insight into the Solvent Effects
Because of the superior
optical properties and potential applications
in display technology, colloidal synthesis of halide perovskite quantum
dots has been intensively studied. Although great successes have been
made in the fabrication of green emissive CH<sub>3</sub>NH<sub>3</sub>PbBr<sub>3</sub> quantum dots, the fabrication of stable iodide-based
CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> quantum dots remains a
great challenge because of their sensitivity to moisture in the open
air. Even in a glovebox, the colloidal CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> quantum dots obtained from <i>N</i>,<i>N</i>-dimethylformamide suffer from instability caused by fast
degradation within days to weeks. In this work, we investigated the
interactions between perovskite precursors and various polar solvents
as well as their influence on the crystallization of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> in reprecipitation synthesis. By gaining
chemical insight into the coordination effects, we can explain the
degradation of CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> to the
defective crystals with coordinated solvents on the surface and/or
intrinsic inner iodine vacancies. On the basis of this understanding,
we fabricated air-stable CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> quantum dots with a tunable size from 6.6 to 13.3 nm by selecting
noncoordinated acetonitrile as a good solvent through ligand-assisted
precipitation synthesis. The fabrication can be processed under ambient
conditions, and the resulting CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> quantum dots exhibit tunable emission with high photoluminescence
quantum yields (maximum of âź46%) as well as good stability.
Moreover, the quantum confinement effects in CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> quantum dots were discussed by correlating
the size-dependent photoluminescence properties with theoretical calculations,
which can be described by the infinite quantum well approximation
model
Quantitation of Albumin in Serum Using âTurn-onâ Fluorescent Probe with Aggregation-Enhanced Emission Characteristics
An aggregation-enhanced emission
active luminogen named as sodium 4,4â˛4âł-(3,4-diphenyl-1<i>H</i>-pyrrole-1,2,5-triyl)Âtribenzoate (DP-TPPNa) with propeller
construction was synthesized and developed as a âturn onâ
fluorescent probe for in situ quantitation of albumin in blood serum.
The DP-TPPNa fluorescence intensity was linearly correlated with the
concentration of two serum albumins, bovine serum albumin (BSA) and
human serum albumin (HSA), in pure PBS buffer in the ranges of 2.18â70
and 1.68â100 Îźg/mL, respectively. The detection limits
were as low as 2.18 Îźg/mL for BSA and 1.68 Îźg/mL for HSA.
The response time of fluorescence to serum albumin (SA) was very short
(below 6 s), which achieved real-time detection. It also showed high
selectivity to SA because other components in serum barely interfere
with the detection of DP-TPPNa to SA, enabling in situ quantitative
detection of SA without isolation from serum. DP-TPPNa was successfully
applied for the quantitative detection of BSA in fetal bovine serum.
The mechanism of fluorescent turn-on behavior was elucidated utilizing
an unfolding process induced by guanidine hydrochloride, which revealed
a capture process via selective hydrophobic interaction and hydrogen
bonding between luminogen and SA
Patient disposition and reasons for discontinuation.
<p>RBV, ribavirin; TVR, telaprevir.</p