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Let Digons be Bygones: The Fate of Excitons in Curved π-Systems
摘要： We explore the diverse origins of unpolarized absorption and emission of molecular polygons, consisting of π-conjugated oligomer chains held in a bent geometry by strain controlled at the vertex units. For this purpose, we make use of atomistic nonadiabatic excited-state molecular dynamics simulations of a bichromophore molecular polygon (digon) with bent chromophore chains. Both structural and photoexcited dynamics were found to affect polarization features. Bending strain induces exciton localization on individual chromophore units of the conjugated chains. The latter display different transition dipole moment orientations, a feature not present in the linear oligomer counterparts. In addition, bending makes exciton localization very sensitive to molecular distortions induced by thermal fluctuations. The excited-state dynamics reveals an ultrafast intramolecular energy redistribution that spreads the exciton equally among spatially separated chromophore fragments within the molecular system. As a result, digons become virtually unpolarized absorbers and emitters, in agreement with recent experimental studies on the single-molecule level.
关键词： transition dipole moment,unpolarized absorption and emission,π-conjugated oligomer chains,molecular polygons,nonadiabatic excited-state molecular dynamics,exciton localization
更新于2025-09-10 09:29:36
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Ultrapure Films of Polythiophene Derivatives are Born on a Substrate by Liquid Flow
摘要： Almost all ?lms of conjugated polymers are composed of mixtures of two di?erent structures called H- or J-aggregates, which are side-by-side and head-to-tail structures, respectively, between polymer chains. The mixture of H- and J-aggregates is responsible for the mixed optical and/or electrical properties of a conjugated polymer ?lm. If a highly puri?ed conjugated polymer ?lm composed of only a single species of aggregate was obtained, its properties would enable the realization of new soft electronics, such as ?exible solar cells, wearable sensors, and arti?cial skin. However, there have been no reports on a method to prepare such a highly puri?ed polymer ?lm so far. Here, we show a facile method to obtain an ultrapure 99.8% H-aggregate polymer ?lm by dropping a solution of poly(3-hexylthiophene) (P3HT) on a substrate at room temperature, inspired by the co?ee-ring e?ect.According to contact angle measurements, photoluminescence and Raman spectroscopy, and X-ray di?raction, a critical step for achieving the ultrapure H-aggregate ?lm was a two-step drying process of the polymer solution droplet on a speci?c substrate. The pinning of the droplet caused this drying process and yielded a ?ow-induced extension of the P3HT chains on the substrate, followed by the formation of ultrapure H-aggregates. We also found a 6-fold enhancement in carrier density using the ultrapure (99.8%) H-aggregate P3HT ?lm. Furthermore, ?ve conjugated polymers of polythiophene derivatives, used as state-of-the-art polymer solar cells, revealed the same trends to ultrapure H-aggregates, whose structure enhances performance of solar cell. The proposed method could provide a new approach to make solution-processable ?lms for next-generation soft and ?exible electronics.
关键词： π-conjugated polymer,contact angle,aggregate,soft electronics,co?ee ring
更新于2025-09-10 09:29:36
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Attachment of a 1,8-Naphthalimide Moiety to a Conjugated Polythiophene Efficiently Improves the Sensing Abilities of Naphthalimide-Based Materials
摘要： A novel polythiophene-based conjugated polymer bearing 1,8-naphthalimide-based pendants is prepared by a two-step modification of regioregular poly[3-(6-bromohexyl)thiophene] involving a nucleophilic substitution reaction of the bromide end-groups with sodium azide followed by a robust, copper-catalyzed Huisgen click reaction with a novel 1,8-naphthalinmide derivative containing an active, N-substituted propyne group. Both the polymer and the highly luminescent-active synthesized dye are extensively studied in solution by UV–vis spectroscopy, photoluminescence, NMR, light-scattering and isothermal titration calorimetry. The materials prepared are considered potential chemosensors for different transition metals, such as Fe2+, Co2+, Ni2+, Cu2+, Zn2+, and Cd2+. Luminescence quenching shows that these materials have a higher sensitivity to Fe2+ than to the other metal ions tested. Moreover, the 1,8-naphthalimide-based conjugated polymer is more efficiently quenched by Fe2+ metal ions, at a significantly lower concentration and with a higher binding constant than its parent 1,8-naphthalimide derivative, thus indicating a high potential for sensor development.
关键词： Stern–Volmer constant,polythiophene,1,8-naphthalimide,photoluminescence quenching,conjugated polymers
更新于2025-09-10 09:29:36
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A 3-Dimensional Fully Conjugated Carbaporphyrin Cage
摘要： A fully conjugated 3-dimensional (3D) expanded carbaporphyrin (2) was prepared in a one-pot procedure that involves a reaction between a dibenzo[g,p]chrysene-bearing tetrapyrrole precursor (1) and pentafluorobenzaldehyde, followed by oxidation. Single crystal X-ray diffraction analysis revealed that 2 possesses a cage-like structure consisting of four dipyrromethenes and two bridging dibenzo[g,p]chrysene units. As prepared, 2 is nonaromatic as inferred from UV-vis-NIR and 1H NMR spectroscopy and a near-zero (-1.75) nucleus-independent chemical shift (NICS) value. In contrast, after protonation with trifluoroacetic acid (TFA), the cage gains global aromatic character as inferred from the large negative NICS value (-11.63) and diatropic ring current observed in the anisotropy of the induced current density (ACID) plot, as well as the ca. 8-fold increase in the excited state lifetime. In addition, the size of the cavity increases to ca. 143 ?3 upon protonation as deduced from a single crystal X-ray diffraction analysis. To our knowledge, this is the largest carbaporphyrin prepared to date and the first with a fully conjugated 3D cage structure whose size and electronic features may be tuned through protonation.
关键词： protonation,fully conjugated,cage-like structure,aromaticity switching,3D expanded carbaporphyrin
更新于2025-09-09 09:28:46
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Butterfly in a Flask: Irregular Nanographenes by Highly Regioselective Domino Benzannulation
摘要： A highly regioselective domino benzannulation reaction of conjugated 1,3-diynes was developed by Chalifoux and co-workers to access irregular nanographene moieties. Notably, to demonstrate the efficiency of the reaction, a chiral butterfly-shaped ligand precursor was successfully synthesized through a fourfold alkyne benzannulation of a bis-buta-1,3-diyne. This method opens new avenues for tuning and studying the properties of nanographenes as a function of shape.
关键词： conjugated diynes,domino benzannulation,nanographenes
更新于2025-09-09 09:28:46
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Synthesis of C-C bonded Two-dimensional Conjugated Covalent Organic Framework Films via Suzuki Polymerization on Liquid/liquid Interface
摘要： Synthesis of free standing two-dimensional (2D) conjugated covalent organic framework (COF) films linked by C-C bonds can be considered as a holy grail of synthetic chemistry. However, reactions for their synthesis are quite rare. Herein we developed a very simple and mild strategy to synthesize them via the Nobel Prize reaction (Suzuki polymerization) on water/toluene interface in a fridge. The versatility of this strategy was proved by the successful synthesis of two different 2D-COF films: a porous graphene and a porphyrin-contained 2D-COF. Both 2D-COF films have large lateral size and their crystalline domains were visualized by high resolution TEM. Based on the wide compatibility of Suzuki reaction, our breakthrough work opened a door for the synthesis of various 2D conjugated COF films. For application studies, the porous graphene exhibits a good carrier mobility which is much higher than -C=N- linked 2D COF films and a good catalytic activity for hydrogen evolution reaction which is comparable with nitrogen or phosphorus doped graphene.
关键词： porous graphene,interface,porphyrin,2D conjugated COF,Suzuki polymerization
更新于2025-09-09 09:28:46
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Impact of Molecular Order on Polaron Formation in Conjugated Polymers
摘要： The nature of polaron formation has profound implications on the transport of charge carriers in conjugated polymers, but still remains poorly understood. Here we develop in situ electrochemical resonant Raman spectroscopy, a powerful structural probe that allows direct observation of polaron formation. We report that polaron formation in ordered poly(3-hexyl)thiophene (P3HT) polymer domains (crystalline phase) results in less pronounced changes in molecular conformation, indicating smaller lattice relaxation, compared to polarons generated in disordered polymer domains (amorphous phase) for which we observe large molecular conformational changes. These conformational changes are directly related to the effective conjugation length of the polymer. Furthermore, we elucidate how blending the P3HT polymer with phenyl C-61 butyric acid methyl ester (PCBM) affects polaron formation in the polymer. We find that blending disturbs polymer crystallinity, reducing the density of polarons that can form upon charge injection at the same potential, whilst the lost capacity is partly restored during post-deposition thermal annealing. Our study provides direct spectroscopic evidence for a lower degree of lattice reorganisation in crystalline (and therefore more planarised) polymers than in conformationally disordered polymers. This observation is consistent with higher charge carrier mobility and better device performance commonly found in crystalline polymer materials.
关键词： electrochemical resonant Raman spectroscopy,conjugated polymers,polaron formation,molecular order,PCBM,charge transport,P3HT
更新于2025-09-09 09:28:46
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Probing Exciton Delocalization in Organic Semiconductors: Insight from Time-Resolved Electron Paramagnetic Resonance and Magnetophotoselection Experiments
摘要： Delocalization of excited states of organic semiconductors is directly related to their e?ciency in devices. Time-resolved electron paramagnetic resonance spectroscopy provides unique capabilities in this respect because of its high spectral resolution and capability to probe the geometry and extent of excitons. Using magnetophotoselection experiments, the mode of exciton delocalization, along the backbone or parallel to the π?π stacking direction of the conjugated polymers, can be revealed. We demonstrate the robustness of this approach by applying it to building blocks of a prototypical conjugated polymer showing a symmetry of their excited states being far from ideal for this experiment. This renders magnetophotoselection superior to other approaches because it is applicable to a wealth of other organic semiconductors. The insight gained into exciton delocalization is crucial to the structure?function relationship of organic semiconductors and directly relevant for developing highly e?cient materials.
关键词： time-resolved electron paramagnetic resonance,conjugated polymers,exciton delocalization,organic semiconductors,magnetophotoselection
更新于2025-09-09 09:28:46
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Hybrid Nanomaterials of Conjugated Polymers and Albumin for Precise Photothermal Therapy
摘要： Heretofore, conjugated polymers (CPs) attract considerable attention in photothermal therapy (PTT). Although various CPs with different structures have been reported, the suboptimal circulation persistence and biodistribution limit their efficacy in tumor treatment. Human serum albumin (HSA), an endogenous plasm protein, has been widely functioned as a carrier for therapeutic agents. Herein, we construct nanocomplexs C16 pBDP@HSA NPs from hydrophobic 4, 4-difluoro-4-bora-3a, 4adiaza-s-indacene (BODIPY)-containing CPs and HSA, which exhibit robust stability in physiological conditions and excellent photothermal activity upon irradiation. The high photothermal conversion efficiency of 37.5 %, higher than that of other reported PTT agents such as gold nanorods, phosphorus quantum dots and 2D materials, results in the potent photocytotoxicity towards cancer cells. Simultaneously, C16 pBDP@HSA NPs’ capabilities of near infrared fluorescence and photoacoustic imaging can provide guidance to the PTT. The outstanding inhibition of tumor growth results from great photothermal activity, the benefited accumulation in tumor and optimal timing of treatment. To the best of our knowledge, this is the first study which combines the BODIPY-based CPs and HSA in one nanostructure and finds application in cancer treatment. Moreover, this article also offers a new strategy for other insoluble macromolecules to explore more biomedical applications.
关键词： photothermal therapy,albumin,hybrid nanoparticles,conjugated polymers,BODIPY
更新于2025-09-09 09:28:46
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Torsionally induced exciton localization and decoherence in <i>π</i> -conjugated polymers
摘要： We develop a model of excitons coupled to the rotational motion of monomers to study the torsionally induced relaxation and decoherence of excitons in π-conjugated polymers. The model assumes that the monomer units are described by elastically uncoupled harmonic oscillators and that there is a linear exciton-roton coupling. Although the rotational degrees of freedom are much slower than the exciton, so that the adiabatic approximation is generally expected to be valid, we also investigate possible quantized roton corrections via coupled time evolving block decimation-Ehrenfest equations of motion. For the relaxation of the lowest-excited exciton, we find that (1) for a polymer chain with a ground state spiral torsional conformation, the equilibrium angular displacement of each monomer is proportional to the difference of the exciton bond-orders on the neighboring bridging bonds. Consequently, this displacement vanishes in the long chain limit and a classical (Landau) exciton-polaron is not formed. (2) For a polymer chain with a ground state staggered torsional conformation, the equilibrium angular displacement of each monomer is proportional to the sum of the exciton bond-orders on the neighboring bridging bonds. Consequently, there is significant angular displacement and local planarization causing exciton density localization. A classical (Landau) exciton-polaron is formed where the staggered angular displacement is proportional to the exciton density. (3) Generally, in the adiabatic limit, the decay of off-diagonal long-range order (i.e., exciton decoherence) mirrors the localization of the exciton density. However, quantum corrections to the rotational motion alter this adiabatic prediction because of correlated exciton-roton dynamics within the first rotational half-period. In particular, exciton-polaron quasiparticle formation causes more rapid and oscillatory exciton decoherence and slower exciton density localization.
关键词： π-conjugated polymers,exciton,decoherence,torsional relaxation,Landau exciton-polaron
更新于2025-09-04 15:30:14