Synthesis, Absorption, and Fluorescence-Emission Properties of 1,3,6,8-Tetraethynylpyrene and Its Derivatives: 1,3,6,8-Tetraethynylpyrene and Its Derivatives

Bottom-Up Synthesis of Twisted Porous Graphene through a Heterogeneous Scholl Reaction and Its Supercapacitor Application

Anthracene- and pyrene-based twisted porous graphene (AN-Pyre-PG) with an ordered pore structure has been synthesized through bottom-up solution phase synthesis from a conjugated microporous polymer (AN-Pyre-CMP) via a heterogeneous Scholl cyclization reaction. The regular-ordered pores embedded within the graphene structures were analyzed through a Raman spectrum, different morphological analyses, and theoretical studies. A significant change in surface area from AN-Pyre-CMP to AN-Pyre-PG was observed, from 143 to 640 m2/g, respectively. Surface area-driven capacitive properties were also observed. Twisted-structure and ordered porous graphene shows better specific capacitance compared to CMP. AN-Pyre-PG shows a specific capacitance of 629 F g-1 at 1 A g-1, with 91% retention of capacitance after 3000 charge-discharge cycles, whereas AN-Pyre-CMP shows a maximum specific capacitance of 200 F g-1 was observed at 2 A g-1.

Bromopyrene Symphony: Synthesis and Characterisation of Isomeric Derivatives at Non-K Region and Nodal Positions for Diverse Functionalisation Strategies

Pyrene, a renowned aromatic hydrocarbon, continues to captivate researchers due to its versatile properties and potential applications across various scientific domains. Among its derivatives, bromopyrenes stand out for their significance in synthetic chemistry, materials science, and environmental studies. The strategic functionalisation of pyrene at non-K region and nodal positions is crucial for expanding its utility, allowing for diverse functionalisation strategies. Bromo-substituted precursors serve as vital intermediates in synthetic routes; however, the substitution pattern of bromoderivatives significantly impacts their subsequent functionalisation and properties, posing challenges in synthesis and purification. Understanding the distinct electronic structure of pyrene is pivotal, dictating the preferential electrophilic aromatic substitution reactions at specific positions. Despite the wealth of literature, contradictions and complexities persist in synthesising suitably substituted bromopyrenes due to the unpredictable nature of substitution reactions. Building upon historical precedents, this study provides a comprehensive overview of bromine introduction in pyrene derivatives, offering optimised synthesis conditions based on laboratory research. Specifically, the synthesis of mono-, di-, tri-, and tetrabromopyrene isomers at non-K positions (1-, 3-, 6-, 8-) and nodal positions (2-, 7-) is systematically explored. By elucidating efficient synthetic methodologies and reaction conditions, this research contributes to advancing the synthesis and functionalisation strategies of pyrene derivatives, unlocking new possibilities for their utilisation in various fields.

A Stimuli-Responsive Dual-Emitting Covalent Organic Framework Shows Selective Sensing of Highly Corrosive Acidic Media via Fluorescence Turn-On Signal with White Light Emission

Luminescent covalent organic frameworks (LCOFs) have been employed as platforms for sensing analytes. Judicial incorporation of appropriate functional units inside the framework leads to the different electronic states in the presence of external stimuli, e.g., temperature, pH, etc. We report herein a new COF (TPEPy) as a solid-state acid sensor specific for the highly acidic environments that range from pH ∼0.5 to ∼3.0. This COF shows a protonation-induced reversible color change from bright yellow to deep red upon decreasing the pH from 3 to 0.5 and vice versa. No visual color change was, however, observed above pH 3.0. Photoluminescence (PL) studies show that the intrinsic emission peak of the TPEPy COF at 530 nm is shifted to 420 nm owing to the N-protonation of the imine nitrogen of COF within this pH range. Extensive studies demonstrate that the protonation behavior of the COF is counterion dependent. This was revealed when different acids, e.g., HCl, HNO3, HBr, and HI, were employed. The intensity of the proton-induced emission peak at 420 nm depends significantly upon the counterions with the order of HCl > HNO3 > HBr > HI. These anions interact with the protonated TPEPy COF by cation-anion and H-bonding interactions. Further, the pristine COF showed near white light emission at a particular pH of 2.5 (CIE coordinates 0.27, 0.32). From the PL spectrophotometric titrations, the deprotonation pKa was experimentally found to be 1.8 ± 0.02 for the TPEPy COF. The sensor reported herein is reversible, reusable, and regenerable and is useful for assessing pH fluctuations within a strongly acidic range via digital signaling.

Transforming Hetera-Buckybowls into Chiral Conjugated Polycycles Incorporating Epoxycyclooctadiene: a Two-Step Approach

Chiral π-conjugated polycycles have garnered increasing attention due to versatile applications in optoelectronic materials and biological sciences. In this study, we report the synthesis of chiral π-conjugated polycycles incorporating a chiral epoxycyclooctadiene moiety. Our synthetic strategy capitalizes on the novel reactions of hetera-buckybowl triselenasumanene (TSS) and is achieved in two-step manner. Firstly, the TSS is regio-selectively transformed into its ortho-quinone form. Subsequently, the nucleophilic addition reactions of TSS ortho-quinone by phenylethynides are metal ion-dependent. When utilizing (phenylethynyl)magnesium bromide as the nucleophile, two phenylethynyls are furnished onto the edged benzene ring of TSS. When the nucleophile is (phenylethynyl)lithium, a cascade of nucleophilic addition, intermolecular electron-transfer, ring-opening, and tetradehydro-Diels-Alder (TDDA) reactions occur sequentially in one-pot, ultimately affording chiral π-conjugated polycycles featuring the epoxycyclooctadiene moiety as an integral part of their backbones. This work represents a step forward in the synthesis of chiral π-conjugated polycycles using TSS as synthon.

Sulfonate-modified calixarene-based porous organic polymers for electrostatic enhancement and efficient rapid removal of cationic dyes in water

Developing of fast and efficient adsorbents for removal of low concentration refractory organics in water is significant. Herein, a novel calix[4]arene-based porous organic polymer CaPy is constructed through Sonogashira-Hagihara cross-coupling polycondensation. The strong polar sulfonate is further anchored onto the polymer skeleton of CaPy and three sulfonate-modified anionic polymers CaPy-S1, CaPy-S2, and CaPy-S3 were obtained and fully characterized. The adsorption isotherms showed that the maximum adsorption capacities of CaPy, CaPy-S1, CaPy-S2, and CaPy-S3 toward methylene blue (MB) were 270, 1454, 558 and 1381 mg g^-1, whereas those for Rhodamine B (RhB) were 183, 2653, 1132, and 1796 mg g^-1, respectively. The maximum adsorption capacity toward RhB was the highest reported vale among the currently used synthetic adsorbents. In addition, the pseudo-second-order rate constants of CaPy, CaPy-S1, CaPy-S2, and CaPy-S3 toward MB were 0.00572, 0.488, 2.24, and 0.192 g mg^-1 min^-1, respectively, and those toward RhB were 0.000234, 0.138, 0.0819, and 0.203 g mg^-1 min^-1, respectively. The pseudo-second-order rate constant of CaPy-S2 toward MB was 2.24 g mg^-1 min^-1 indicating one of the highest adsorption speeds. The activation energy of CaPy-S1 for RhB and MB were 121 and 109 kJ mol^-1, respectively, demonstrating that the adsorption of both dyes on CaPy-S1 was chemisorption process. Further, the obtained values of Gibbs free energy were negative, revealing that the adsorption process was spontaneous. This work provides an effective approach for improving adsorption performance via post-modification.

The Impact of a 1,2,3-Triazole Motif on the Photophysical Behavior of Non-K Tetrasubstituted Pyrene with a Substitution Pattern Providing the Long Axial Symmetry

1,3,6,8-Tetrasubstituted pyrene derivatives with two types of substituents (4-(2,2-dimethylpropyloxy)pyridine, 1-decyl-1,2,3-triazole, 1-benzyl-1,2,3-triazole, and pyrazole), substituted in such a way that provides the long axial symmetry, are prepared and characterized in the present study. To the best of our knowledge, the pyrene derivative containing the same heteroaryl motif (triazole) but substituted by two various alkyls, straight decyl and benzyl-based side chains (C), is reported for the first time. For comparison, compounds with one kind of triazole motif and substituted pyridine or pyrazole groups were prepared (A and B). The photophysical properties of all molecules were evaluated by thermogravimetric analysis (TGA) and UV-Vis spectroscopy (absorption and emission spectra, quantum yields, and fluorescence lifetimes). The obtained results were compared to analogues substituted at the 1,3,6,8 positions by one kind of substituent and also with all the 1,3,6,8-tetrasubstituted pyrenes reported in the literature substituted by two kinds of substituents with a substitution pattern that provides long axial symmetry. In addition, theoretical studies based on DFT and TD-DFT were performed that supported the interpretation of the experimental results. The photophysical properties of tetrasubstituted pyrene derivatives having triazole units at the 1,8-positions, respectively, and other identical substituents at the 3,6 positions show the dominance of triazole units in the pyrene framework; the dominance is even higher in the case of the substitution of 1,3,6,8 positions by triazoles, but containing two various alkyls.

High-Performance Supercapacitor Electrodes Prepared From Dispersions of Tetrabenzonaphthalene-Based Conjugated Microporous Polymers and Carbon Nanotubes

In this study, we prepared a series of conjugated microporous polymers (CMPs) through Sonogashira-Hagihara cross-couplings of a tetrabenzonaphthalene (TBN) monomer with pyrene (Py), tetraphenylethylene (TPE), and carbazole (Car) units and examined their chemical structures, thermal stabilities, morphologies, crystallinities, and porosities. TBN-TPE-CMP possessed a high surface area (1150 m2 g-1) and thermal stability (Td10 = 505 °C; char yield = 68 wt %) superior to those of TBN-Py-CMP and TBN-Car-CMP. To improve the conductivity of the TBN-CMP materials, we blended them with highly conductive single-walled carbon nanotubes (SWCNTs). Electrochemical measurements revealed that the TBN-Py-CMP/SWCNT nanocomposite had high capacitance (430 F g-1) at a current density of 0.5 A g-1 and outstanding capacitance retention (99.18%) over 2000 cycles; these characteristics were superior to those of the TBN-TPE-CMP/SWCNT and TBN-Car-CMP/SWCNT nanocomposites.

Green synthesis of AgNP-ligand complexes and their toxicological effects on Nilaparvata lugens

BACKGROUND

Despite developments in nanotechnology for use in the pharmaceutical field, there is still a need for implementation of this technology in agrochemistry. In this study, silver nanoparticles (AgNPs) were successfully prepared by a facile and an eco-friendly route using two different ligands, 2'-amino-1,1':4',1″-terphenyl-3,3″,5,5″-tetracarboxylic acid (H4L) and 1,3,6,8-tetrakis (p-benzoic acid)-pyrene (TBAPy), as reducing agents. The physiochemical properties of the as-obtained AgNPs were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The toxicity of H4L-AgNP and TBAPy-AgNP against the brown planthopper (BPH, Nilaparvata lugens) was also measured.

RESULTS

SEM and TEM analyses demonstrated the formation of quasi-spherical AgNP structures in the presence of H4L and TBAPy. Insecticidal assays showed that TBAPy is less effective against N. lugens, with a median lethal concentration (LC50) of 810 mg/L, while the toxicity of H4L increased and their LC50 reached 786 mg/L 168 h posttreatment at a high concentration of 2000 mg/L. H4L-AgNPs were also highly toxic at a low concentration of 20 mg/L, with LC50 =  ~ 3.9 mg/L 168 h posttreatment, while TBAPy-AgNPs exhibited less toxicity at the same concentration, with LC50 =  ~ 4.6 mg/L.

CONCLUSIONS

These results suggest that the synthesized AgNPs using the two ligands may be a safe and cheaper method compared with chemical insecticides for protection of rice plants from pests and has potential as an effective insecticide in the N. lugens pest management program.

One-pot synthesis of dicyclopenta-fused peropyrene via a fourfold alkyne annulation

A novel dicyclopenta-fused peropyrene derivative 1 was synthesized via a palladium-catalyzed four-fold alkyne annulation of 1,3,6,8-tetrabromo-2,7-diphenylpyrene (5) with diphenylacetylene. The annulative π-extension reaction toward 1 involved a twofold [3 + 2] cyclopentannulation and subsequent twofold [4 + 2] benzannulation. The structure of 1 is unambiguously confirmed by X-ray crystallography; 1 adopted a twisted geometry due to the steric hindrance of the phenyl rings and the hydrogen substituents at the bay regions. Notably, compound 1 exhibits a narrow energy gap (1.78 eV) and a lower LUMO energy level than the parent peropyrene without the fusion of the five-membered rings. In addition, the effects of the peri-fused pentagons on the aromaticity and molecular orbitals of 1 were evaluated by theoretical calculations. This work presents an efficient method to develop π-extended aromatic hydrocarbons with cyclopenta moieties.

Molecular Packing and Solid-State Photophysical Properties of 1,3,6,8-Tetraalkylpyrenes

The relationship between the photophysical properties and molecular orientation of 1,3,6,8-tetraalkylpyrenes in the solid state is described herein. The introduction of alkyl groups with different chain structures (in terms of length and branching) did not affect the photophysical properties in solution, but significantly shifted the emission wavelengths and fluorescence quantum yields in the solid state for some samples. Pyrenes bearing ethyl, isobutyl, or neopentyl groups at the 1-, 3-, 6-, and 8-positions showed similar emission profiles in both the solution and solid states. In contrast, pyrenes bearing other alkyl groups exhibited an excimer emission in the solid state, similar to that of the parent pyrene. On studying the photophysical properties in the solid state with respect to the obtained crystal structures, the observed solid-state photophysical properties were found to depend on the relative position of the pyrene chromophores. The solid-state photophysical properties can be controlled by the alkyl groups, which provide changing crystal packing. Among the pyrenes tested, 1,3,6,8-tetraethylpyrene showed the highest fluorescence quantum yield of 0.88 in the solid state.

Thioether-Crown-Rich Calix[4]arene Porous Polymer for Highly Efficient Removal of Mercury from Water

A rational design of adsorbents with high uptake efficiency and fast kinetics for highly toxic pollutants is a key challenge in environmental remediation. Here, we report the design of a well-defined thioether-crown-rich porous calix[4]arene-based mesoporous polymer S-CX4P and its utility in removal of highly relevant toxic mercury (Hg²⁺) from water. The polymer shows an exceptional, record-high uptake efficiency of 1686 mg g^-1 and the fastest initial adsorption rate of 278 mg g^-1 min^-1. Remarkably, S-CX4P can effectively remove Hg²⁺ from high concentration (5 ppm) to below the acceptable limit for drinking water (2 ppb) even in the presence of other competitive metals at high concentrations. In addition, the polymer can be easily regenerated at room temperature and reused multiple times with negligible loss in uptake rate and efficiency. The results demonstrate the potential of rationally designed thioether-crown-rich polymers for high performance mercury removal.

Alkyloxy modified pyrene fluorophores with tunable photophysical and crystalline properties

Alkyloxy modified 4,5,9,10-tetrasubstituted pyrenes display tunable photophysical and crystalline properties depending on the alkyl chains attached at the polyaromatic core.

Pyrene-cored covalent organic polymers by thiophene-based isomers, their gas adsorption, and photophysical properties

Two new pyrene‐cored covalent organic polymers (COPs), CK‐COP‐1 and CK‐COP‐2, were synthesized via the one‐step polymerization of two thiophene‐based isomers, 1,3,6,8‐tetra(thiophene‐2‐yl) pyrene (L₁) and 1,3,6,8‐tetra(thiophene‐3‐yl) pyrene (L₂). The resulting pyrene‐cored COPs exhibit rather different surface areas of 54 m² g⁻¹ and 615 m²g⁻¹ for CK‐COP‐1 and CK‐COP‐2, respectively. The CO₂ uptake capacities of CK‐COP‐1 and CK‐COP‐2 also show different values of 2.85 and 9.73 wt % at 273 K, respectively. Furthermore, CK‐COP‐2 offers not only a larger CO₂ adsorption capacity but also a better CO₂/CH₄ selectivity at 273 K compared with CK‐COP‐1. CK‐COP‐1 and CK‐COP‐2 also exhibit considerable differences in their photophysical property. The different structure and properties of CK‐COPs could be attributed to the isomer effect of their corresponding thiophene‐based monomers. © 2017 Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2383–2389

New thiophene-functionalized pyrene, peropyrene, and teropyrene via a two- or four-fold alkyne annulation and their photophysical properties

We synthesized thiophene-functionalized pyrene, peropyrene, and teropyrene through a two- or four-fold alkyne annulation reaction promoted by triflic acid. All of the target compounds were fully characterized spectroscopically, and the structure of the peropyrene analogue was unambiguously confirmed by X-ray crystallography. A significant red shift in the absorption and emission properties as a function of extended conjugation was observed by UV–vis and fluorescence spectroscopy. This alkyne annulation strategy is a useful method for the conversion of smaller polycyclic aromatics to larger ones, such as nanographenes.

Extended cavity pyrene-based iptycenes for the turn-off fluorescence detection of RDX and common nitroaromatic explosives

Extended cavity pyrene-based iptycenes were synthesized for the turn-off fluorescence detection of RDX and common nitro-aromatic explosives.

Conjugated microporous copolymer networks with enhanced gas adsorption

Conjugated microporous copolymer networks show a high specific surface area of up to 2241 m² g⁻¹ and a high CO₂ uptake of 4.57 mmol g⁻¹ (1.13 bar/273 K) with a H₂ uptake of 2.24 wt% (1.13 bar/77.3 K).

Anomalous coarsening driven by reversible charge transfer at metal-organic interfaces

The unique electronic properties and functional tunability of polycyclic aromatic hydrocarbons have recently fostered high hopes for their use in flexible, green, portable, and cheap technologies. Most applications require the deposition of thin molecular films onto conductive electrodes. The growth of the first few molecular layers represents a crucial step in the device fabrication since it determines the structure of the molecular film and the energy level alignment of the metal-organic interface. Here, we explore the formation of this interface by analyzing the interplay between reversible molecule-substrate charge transfer, yielding intermolecular repulsion, and van der Waals attractions in driving the molecular assembly. Using a series of ad hoc designed molecules to balance the two effects, we combine scanning tunnelling microscopy with atomistic simulations to study the self-assembly behavior. Our systematic analysis identifies a growth mode characterized by anomalous coarsening that we anticipate to occur in a wide class of metal-organic interfaces and which should thus be considered as integral part of the self-assembly process when depositing a molecule on a conducting surface.

Intramolecular excimer formation in hexakis(pyrenyloxy)cyclotriphosphazene: photophysical properties, crystal structure, and theoretical investigation

A hexakis(pyrenyloxy)cyclotriphosphazene was synthesized by the reaction of N₃P₃Cl₆ with 2-hydroxypyrene, and its excimer emission has been investigated.

Fluorescence enhancement of pyrene chromophores induced by alkyl groups through σ-π conjugation: systematic synthesis of primary, secondary, and tertiary alkylated pyrenes at the 1, 3, 6, and 8 positions and their photophysical properties

We have systematically synthesized 1-, 3-, 6-, and 8-alkyl-substituted pyrene derivatives using the latest synthesis methods and investigated the effects of alkyl substitution on the photophysical properties of the pyrene chromophore. Like the trimethylsilyl group, which is known to enhance the fluorescence properties of some chromophores through σ*-π* conjugation, alkyl groups (primary, secondary, and tertiary) enhanced the fluorescence quantum yield of the pyrene chromophore through σ-π conjugation in most cases. While these enhancements in the fluorescence quantum yield were beyond expectations, the results were supported by absolute measurements. These results also indicate that ubiquitous alkyl groups can be used to tune the photophysical properties of the pyrene chromophore, as well as to improve the solubility or prevent aggregation. In other words, they can be used to develop new photofunctional materials.

Large electronic bandwidth in solution-processable pyrene crystals: the role of close-packed crystal structure

We examine the interdependence of structural and electronic properties of two substituted pyrene crystals by means of combined spectroscopic probes and density-functional theory calculations. Substituted pyrenes are useful model systems to unravel the interplay of crystal structure and electronic properties in organic semiconductors. To study the effect of steric encumbrance on the crystalline arrangement of two 1,3,6,8-tetraalkynylpyrene derivatives, one features linear n-hexyl side groups while the other contains branched trimethylsilyl groups. Both derivatives form triclinic crystal structures when grown from solution, but the electronic dispersion behavior is significantly different due to differences in π-π overlap along the π-stacking axis. Both systems display dispersion of around 0.45 eV in the valence band, suggesting a high intrinsic hole mobility. However, the direction of the dispersion is different: it is primarily along the π-stacking axis in the trimethylsilyl-substituted derivative, but less aligned with this crystal axis in the hexyl-substituted molecule. This is a direct consequence of the differences in co-facial π electron overlap revealed by the crystallographic studies. We find that photophysical defects, ascribed to excimer-like states, point to the importance of localized trap states.

Synthesis and third-order nonlinear optical properties of novel ethynyl-linked heteropentamer composed of four porphyrins and one pyrene

Novel heteropentameric porphyrins-pyrene arrays, in which four meso-tetraphenyl porphyrins are linked to the center unit of pyrene by four acetylenyl bonds, were designed and synthesized. The newly synthesized heteropentameric compounds have been characterized by a wide range of spectroscopic methods. The third-order nonlinear optical (NLO) properties of both the metal-free and zinc compounds of the three-dimensional arrays were investigated by Z-scan experiments, showing enhanced NLO properties compared with that of the porphyrin and pyrene monomers.