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 UV–vis 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 alkyne–aldehyde monomers and aniline derivatives under the catalysis of Lewis acid B­(C₆F₅)₃. The polymerization was conducted in dichloroethane at 100 °C for 36 h under air atmosphere, affording polyquinolines with molecular weights up to 13 100 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 coordination–insertion 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 Flu′Ln­(CH₂SiMe₃)₂(THF)_n (<b>1</b>–<b>10</b>) with an activator (such as [Ph₃C]­[B­(C₆F₅)₄] (<b>A</b>), [PhNHMe₂]­[B­(C₆F₅)₄] (<b>B</b>), or B­(C₆F₅)₃ (<b>C</b>)) and Al^<i>i</i>Bu₃. The homopolymerization of CHD afforded poly­(CHD)­s with complete 1,4 selectivity (1,4 selectivity up to 100%). The copolymerization of CHD with styrene gave new random CHD–S copolymers with CHD content ranging from 22 to 74 mol % containing 1,4-linked CHD–CHD, alternating CHD–S, and syndiotactic S–S sequences unavailable previously. The activity of the copolymerization and the comonomer compositions and sequences of the resulting CHD–S 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 C–C double bonds of the random CHD–S 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 coordination–insertion 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 Flu′Ln­(CH₂SiMe₃)₂(THF)_n (<b>1</b>–<b>10</b>) with an activator (such as [Ph₃C]­[B­(C₆F₅)₄] (<b>A</b>), [PhNHMe₂]­[B­(C₆F₅)₄] (<b>B</b>), or B­(C₆F₅)₃ (<b>C</b>)) and Al^<i>i</i>Bu₃. The homopolymerization of CHD afforded poly­(CHD)­s with complete 1,4 selectivity (1,4 selectivity up to 100%). The copolymerization of CHD with styrene gave new random CHD–S copolymers with CHD content ranging from 22 to 74 mol % containing 1,4-linked CHD–CHD, alternating CHD–S, and syndiotactic S–S sequences unavailable previously. The activity of the copolymerization and the comonomer compositions and sequences of the resulting CHD–S 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 C–C double bonds of the random CHD–S 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 Donor–Acceptor 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 donor–acceptor 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 donor–acceptor alignments, whereas electron-accepting buckyballs were spatially confined within the nanochannels via covalent anchoring on the channel walls. The donor–acceptor heterojunctions trigger photoinduced electron transfer and allow charge separation with radical species delocalized in the π-arrays, whereas the charge separation efficiency was dependent on the buckyball content. This new donor–acceptor strategy explores both skeletons and pores of COFs for charge separation and photoenergy conversion

Tuning the Luminescence of Metal–Organic Frameworks for Detection of Energetic Heterocyclic Compounds

Herein we report three metal–organic frameworks (MOFs), TABD-MOF-1, -2, and -3, constructed from Mg²⁺, Ni²⁺, and Co²⁺, respectively, and deprotonated 4,4′-((<i>Z</i>,<i>Z</i>)-1,4-diphenylbuta-1,3-diene-1,4-diyl)­dibenzoic 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 cm² testing strip) and parts per billion-scale sensitivity by spectroscopy via pronounced fluorescence emission

Tuning the Luminescence of Metal–Organic Frameworks for Detection of Energetic Heterocyclic Compounds

Herein we report three metal–organic frameworks (MOFs), TABD-MOF-1, -2, and -3, constructed from Mg²⁺, Ni²⁺, and Co²⁺, respectively, and deprotonated 4,4′-((<i>Z</i>,<i>Z</i>)-1,4-diphenylbuta-1,3-diene-1,4-diyl)­dibenzoic 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 cm² testing strip) and parts per billion-scale sensitivity by spectroscopy via pronounced fluorescence emission

Colloidal Synthesis of Air-Stable CH₃NH₃PbI₃ 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 CH₃NH₃PbBr₃ quantum dots, the fabrication of stable iodide-based CH₃NH₃PbI₃ quantum dots remains a great challenge because of their sensitivity to moisture in the open air. Even in a glovebox, the colloidal CH₃NH₃PbI₃ 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 CH₃NH₃PbI₃ in reprecipitation synthesis. By gaining chemical insight into the coordination effects, we can explain the degradation of CH₃NH₃PbI₃ 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 CH₃NH₃PbI₃ 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 CH₃NH₃PbI₃ quantum dots exhibit tunable emission with high photoluminescence quantum yields (maximum of ∼46%) as well as good stability. Moreover, the quantum confinement effects in CH₃NH₃PbI₃ 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 “Turn-on” Fluorescent Probe with Aggregation-Enhanced Emission Characteristics

An aggregation-enhanced emission active luminogen named as sodium 4,4′4″-(3,4-diphenyl-1<i>H</i>-pyrrole-1,2,5-triyl)­tribenzoate (DP-TPPNa) with propeller construction was synthesized and developed as a “turn on” 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 2.18–70 and 1.68–100 μg/mL, respectively. The detection limits were as low as 2.18 μg/mL for BSA and 1.68 μg/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