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Photophysical Impact of Diacetylenic Conjugation on Classical Donor-Acceptor Electronic Energy Pair
摘要： Organic fluorophores with extended π-conjugation are important for their wide-spread applications. The present work provides photophysical insights of a diacetylene bridged classical donor-acceptor electronic energy pair, naphthalene-pyrene, in comparison with its part molecular structures, naphthyl and pyrenyl acetylenes as well as parent naphthalene and pyrene chromophores. The diacetylenic dye loses individual spectral identities of the donor and acceptor fluorophores exhibiting a locally excited (LE) emission (~411 nm) from the overall molecular entity with high fluorescence quantum yields (0.55–0.84) in non-aqueous media. In contrast to parent pyrene, the hybrid derivative shows strongly allowed S0→S1 transition. In mixed-aqueous media, the dye forms J-aggregates displaying a new red-shifted absorption (~425 nm) as well as emission (~510 nm) band. Unlike the hybrid dye, the naphthyl and pyrenyl acetylenes do not form aggregates. In the aggregate state of the hybrid fluorophore, electronic energy transfer takes place from the naphthyl moiety to pyrenyl ring. The excited state photophysical properties of the dye is exploited to vapor sensing in solid state.
关键词： vapor sensing,Organic fluorophores,donor-acceptor electronic energy pair,diacetylene bridged,naphthalene-pyrene,locally excited emission,J-aggregates,electronic energy transfer,π-conjugation,fluorescence quantum yields
更新于2025-09-23 15:19:57
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The characterization of electronic defect states of single and double carbon vacancies in graphene sheets using molecular density functional theory
摘要： A detailed picture of the electronic states manifolds of single- and double-vacancy defects in molecular models of graphene based on polycyclic aromatic hydrocarbons (PAHs) is presented. DFT calculations using various density functionals including long-range corrected ones have been performed for pyrene, circumpyrene and 7a,7z-periacene. It has been found for pyrene defect models that DFT results reproduced well the set of closely-spaced singlet and triplet states predicted by the CCSD(T) and previous MRCI + Q calculations, indicating the applicability of DFT for accessing the excited states manifolds also for larger graphene models. For the single-carbon vacancy defect, all structures have a triplet ground state. As expected, in the largest system, 7a,7z-periacene-1C, the lowest lying states are much closer in energy. For all double-vacancy defect structures, a significant rearrangement of the electronic states with increasing size of the sheet is observed. The closed-shell 1Ag state in the smallest systems is destabilised in the extended 7a,7z-periacene system, which has the 3B2u state as the ground state. As observed for the single-vacancy defect, the lowest lying states are closer in energy for the larger systems, since there are more π orbitals close in energy available. For all states, the formation of the bridging bonds for the double vacancy leads to distances shorter than for the single vacancy defect indicating a larger rigidity of the former structure which does not allow stronger distortions.
关键词： polycyclic aromatic hydrocarbons,Excited states,Periacenes,DFT,pyrene
更新于2025-09-19 17:15:36
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Chromophore Arrays Constructed in the Major Groove of DNA Duplexes Using a Post-Synthetic Strategy
摘要： The construction of zipper-like chromophore-arrays in the major groove of duplex DNA remains a challenge because only a few chromophores for this application have been discovered. To address the challenge, dual-chromophore labeled DNAs having a self-complementary sequence were prepared using a solid-phase, post-synthetic, copper-catalyzed, alkyne-azide cycloaddition. The resulting chromophore-arrays on the labeled DNA duplexes were characterized. The dual-tetraphenylethene (TPE) or dual-pyrene (Py) labeled DNA formed self-complementary B-form duplexes and resulted in the construction of chromophore-arrays in the major groove. The TPE-arrays, in which TPEs were arranged in a zipper-like fashion, slightly destabilized the duplex because of their bulkiness and exhibited aggregation-induced-emission. The Py-arrays, in which Pys were not arranged in a zipper-like fashion, had no effect on duplex stability and exhibited weak excimer emission because Py was sufficiently small for free rotation in the major groove.
关键词： Click chemistry,Aggregation,Tetraphenylethene,Pyrene,Oligonucleotides
更新于2025-09-19 17:15:36
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The maximum rectification ratio of pyrene-based molecular devices: a systematic study
摘要： We apply the NEGF + DFT technique to study the effect of anchoring groups on the electronic transport properties of a single pyrene molecule attached to two Au electrodes via three different anchoring groups (namely NO2, NH2 and CN). More specifically, we investigate the effect of asymmetric electrode coupling together with B and N doping on rectification ratio of a pyrene-based molecular device. The results indicate that the rectification ratio can be tuned by selecting configurations of maximum difference in the coupling parameters in the two sides of the gold electrodes, and its magnitude depends on the strength of the electronic coupling of the pyrene molecule to the gold electrodes. In addition, we observe that doping the molecule with B and N atoms decreases the coupling parameters by creating a resonant peak close to the Fermi level.
关键词： Non-equilibrium Green's function method,Molecular junction,Pyrene,Doping,Rectification ratio
更新于2025-09-19 17:15:36
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An efficient new dual fluorescent pyrene based chemosensor for the detection of bismuth (III) and aluminium (III) ions and its applications in bio-imaging
摘要： A new simple pyrene based schiff base chemosensor 1 (nicotinic acid pyren-1-ylmethylene-hydrazide) has been constructed and is prepared from 1-pyrenecarboxaldehyde and nicotinic hydrazide. Notably, the chemosensor 1 exhibited remarkable colour changes while in the presence of trivalent metal ions like Bi3+ & Al3+ ion in DMSO-H2O, (1:1 v/v, HEPES = 50 mM, pH = 7.4). The UV-Vis spectral investigation of chemosensor 1 showed that the maximum absorption peak appeared at 378 nm. In emission studies, chemosensor 1 develops weak fluorescence, while upon the addition of Bi3+ and Al3+ ions, it exhibits an enhancement of fluorescence intensity. Nevertheless, rest of metal ions have no changes in the emission spectra. The association constant of chemosensor 1 for binding to Bi3+ & Al3+ system had a value of 1.27 × 104 M-1 and 1.53 × 104 M-1. The detection limits were 0.12 μM for Bi3+ and 0.17 μM for Al3+ respectively. The overall results reveal that chemosensor 1 can act as a dual-channel, highly selective, and sensitive probe for Bi3+ and Al3+ ions. Moreover, the fluorescence imaging of chemosensor 1 was applied in RAW 264.7 cell line and cytotoxicity assay prove that this chemosensor 1 is non-toxic as well as highly biocompatible.
关键词： Pyrene Schiff base,Spectroscopic studies,Live cell imaging,PET,Bi3+ and Al3+ detection
更新于2025-09-19 17:15:36
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Blue electroluminescent materials based on indeno[1,2-a]arene derivatives for Organic Light-Emitting Diodes
摘要： In this study, as a continuous effort for searching efficient blue-emitting materials, we designed and synthesized materials based on indeno[1,2-a]arene. OLED devices using these materials were fabricated in the following sequence; ITO (180 nm)/N,N’-diphenyl-N,N’-(2-napthyl)-(1,1’-phenyl)-4,4’-diamine (NPB) (50 nm)/emitting materials (30 nm)/4,7-diphenyl-1,10-phenanthroline (Bphen) (30 nm)/Liq/Al (2/100 nm). Particularly, a device using 7,7-dimethyl-7H-indeno[1,2-a]pyrene as emitter showed maximum values of luminous efficiency, power efficiency, and external quantum efficiency of 1.10 cd/A, 0.49 lm/W, 1.47% at 20 mA/cm2, respectively with CIE (x,y) coordinates of (0.15, 0.08) at 6.0V.
关键词： pyrene,blue OLED,electroluminescence,fluorescence,indeno[1,2-a]arene derivatives
更新于2025-09-19 17:13:59
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Solvation Controlled Excited-State Planarization in a Pusha??Pull Pyrene Dye
摘要： The excited state deactivation pathway of the push–pull pyrene derivative (EPP), a molecule emitting bright red fluorescence, has been studied in several solvents using quantum chemical calculations, femtosecond time-resolved fluorescence up-conversion spectroscopy and femtosecond transient absorption spectra (fs-TA). From the steady-state spectra, EPP has shown a strong negatively solvatochromic behavior of the absorption spectra and a non-solvatochromic emission spectra, revealing the decreased dipole moment upon excitation. Femtosecond up-conversion measurements have shown interesting rise-decay kinetics at red emission side and fs-TA spectra also feature the SE (Stimulated emission) formed and new ESA (Excited State Absorption) developed in all investigated solvents. The careful analysis of the data gathered from fluorescence up-conversion and fs-TA spectra, supported by DFT quantum chemical calculations and temperature-dependent fluorescence measurements, unambiguously pointed out the excited state relaxation pathway of EPP is controlled by solvent stabilized planar intramolecular charge transfer (PICT) dynamics. This finding confirms the surrounding solvents as a significant factor that affects the rate of excited state conformation changes.
关键词： solvation controlled,push–pull pyrene derivative,excited state deactivation,planar intramolecular charge transfer,femtosecond spectroscopy
更新于2025-09-19 17:13:59
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Optoelectronic properties and aggregation effects on the performance of planar versus contorted pyrene-cored perylenediimide dimers for organic solar cells
摘要： In this work, we present a new strategy to develop small molecules based on perylenediimde (PDI) with fused and contorted conjugated backbones as electron acceptors for fullerene-free organic solar cells. The two new electron acceptors, 27-Py-PDI and 49-Py-PDI, containing binary PDI units fused with pyrene at different positions were structurally isomers, which were investigated systematically. Theoretical calculations indicated that the two positional isomers exhibit distinct molecular geometries (planar for 27-Py-PDI vs contorted for 49-Py-PDI), which lead to huge differences on their synthetic methods, aggregation effects and their optoelectronic properties. The effects of structural isomerism on the molecular geometry, optical spectra, energy levels, charge carrier mobility and the morphology discrepancies as well as the corresponding photovoltaic performance were fully investigated. Temperature-dependent 1H NMR and the film UV-vis spectroscopy were used to study the molecular aggregation behaviors. Calculations of nuclear independent chemical shifts (NICS) indicate significant difference of the aromaticity between the isomers. Blended with donor materials of PTB7-Th to fabricate the inverted solar cells, an encouraging PCE of 4.53% along with an impressive open-circuit voltage (VOC) of 1.0 V (higher than the other acceptors based on PDIs and the PC71BM) were achieved by using 49-Py-PDI, which were superior to those of its isomer 27-Py-PDI (2.51%). The work suggests that introducing rigid and contorted features into fully fused acceptors based on PDI motifs can enhance the interface energy gap (?EDA), extend the π-delocalization and decrease the conformational disorder resulting into improved VOC without sacrificing JSC in OPV devices. This design strategy by introducing rigid and steric hindrance to increase intermolecular strain to construct fully ring fused contorted acceptors is an effective approach for the development of novel NFAs.
关键词： fused perylenediimides,pyrene core,non-fullerene acceptors,contorted conformation
更新于2025-09-19 17:13:59
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Fluorination of pyrene-based organic semiconductors enhances the performance of light emitting diodes and halide perovskite solar cells
摘要： In this work, a fluorinated pyrene-based organic semiconductor (L-F) has been designed and synthesized starting from a low-cost pyrene core functionalized with triphenilamine substituents at 1,3,6,8 positions (L-H), obtained via Suzuki coupling reactions. Its performance when used as green emitter in organic light emitting diodes (OLEDs) or as dopant-free hole-transporting material (HTM) in halide perovskite solar cells (PSCs) is higher than the L-H counterpart, in spite of its lower bulk hole-mobility (7.0 x 10-6 cm2/Vs) with respect to L-H (1.9 x 10-4 cm2/Vs). In fact, the OLED devices based on L-F active layer showed excellent green emission (brightness and current efficiency were1759.8 cd/m2 and 3.7 cd/A, respectively) at a 4.5 V turn-on voltage. When the molecules were employed as a dopant-free HTM in PSCs, L-F led to a power conversion efficiency (PCE) and open circuit voltage (Voc) of 5.9 % and 1.07 V, respectively, thus outperforming those of corresponding devices based on L-H (PCE = 5.0% and Voc = 0.87 V) under similar experimental conditions (AM 1.5G and 100 mW cm2). We attribute the enhancements of L-F-based optoelectronic devices (OLEDs and PSCs) to the observed better quality of theL-F films. The promising performance of L-F indicates that fluorination of small molecules can be an effective strategy to achieve low-cost and high-performing materials for energy harvesting and display-based organic electronic devices.
关键词： pyrene,perovskite solar cells,hole transporting material,triphenylamine,fluorination,dopant-free,organic light emitting diodes
更新于2025-09-12 10:27:22
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Deep Red Iridium(III) Complexes Based on Pyrene-Substituted Quinoxaline Ligands for Solution-Processed Phosphorescent Organic Light-Emitting Diodes
摘要： In this paper, we systemically investigated the photoelectric properties of three new deep-red quinoxaline-based iridium(III) complexes: Ir-0, Ir-1, and Ir-2. (MPQ)2Ir(dpm) (Ir-0) bore a 2-methyl-3-phenyl-quinoxaline cyclometalated ligand, while (c-PyMPQ)2Ir(dpm) (Ir-1) and (t-PyMPQ)2Ir(dpm) (Ir-2) possessed a 1-pyrene substituent that connected at the 6/7 position of the corresponding ligands. The configurations of the latter two complexes were well-confirmed by single-crystal X-ray diffraction, and both of them had large dihedral angles between the quinoxaline and pyrene units, preventing the emission peaks of the three complexes from being altered too much. Based on the density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, we concluded that the emission of all complexes originated predominantly from the triplet metal-to-ligand/intraligand charge transfer (3MLCT/3ILCT) state of the non-pyrene-substituted counterpart Ir-0 core. Interestingly, we also obtained another type of pyrene-stacking characteristic crystal of Ir-1, which had an emission resembled the phosphorescence observed in thin film. The easily formed pyrene-stacking configuration would most probably limit their device performance at a higher concentration. Moreover, the fabricated organic light-emitting diodes (OLEDs) using these materials achieved considerable device performance at a low doping concentration of 0.5 wt %. This work provides an approach for reasonably designing large fused-ring-substituted quinoxaline ligands of iridium complexes.
关键词： Pyrene-Substituted Quinoxaline Ligands,Deep Red Iridium(III) Complexes,Solution-Processed Phosphorescent Organic Light-Emitting Diodes
更新于2025-09-12 10:27:22