Many aggregation-induced emission (AIE) materials are featured by the diphenylethene (DPE) moiety which exhibits rich photophysical and photochemical activities. The understanding of these activities ...behind AIE is essential to guide the design of fluorescent materials with improved performance. Herein by fusing a flexible DPE with a rigid spiro scaffold, we report a class of novel deep-blue material with solid-state fluorescent quantum yield (ΦF) up to 99.8%. Along with the AIE phenomenon, we identified a reversible photocyclization (PC) on DPE with visible chromism, which is, on the contrary, popularized in solutions but blocked by aggregation. We studied the steric and electronic effects of structural perturbation and concluded that the PC is a key process behind the RIMs (restriction of intramolecular motions) mechanism for these materials. Mitigation of the PC leads to enhanced fluorescence in solutions and loss of the AIE characteristics.
Extension of oxygen-embedded polycyclic aromatic hydrocarbons (PAHs), in particular with a defined topology, is synthetically challenging primarily because of limited regio-specific methods and poor ...solubility of PAHs. We reported herein an efficient way to construct quinoidal pentacenes and nonacenes with regular zigzag O-inserted edges. These O-embedded backbones composed of benzene, pyranyl, and cyclohexa-1,4-diene moieties provided access to a new class of longitudinally conjugated acenes with superior stability. Their structures, confirmed by single-crystal XRD analysis, indicated that they possessed rich hydrogen/halogen-bonding interactions, which likely contribute to the strengthened aggregation. In contrast to many other O-annulated PAHs generally displaying short-absorption wavelengths due to partially interrupted electron communication, the O-embedded quinoidal acene exhibited highly red-shifted absorptions (up to ∼699 nm) and narrowed energy gaps (down to ∼1.5 eV). As with more O-containing rings and quinoidal subunits in the backbone, the conjugation size was enlarged, and the molar absorption coefficients (ε) of the λmax significantly increased further, in particular, a noticeable lower-energy peak at ∼790 nm for O-doping nonacenes N1-OH/OMe. By the thin-film-based organic field-effect transistor measurements, the relatively ordered O-doping pentacene P1-OMe possessed a hole transporting efficiency (μh) of 0.00406 cm–2 V–1 s–1 in in-air fabricated devices, while O-pentacene P1-PFB with two perfluorobutoxyl substituents witnessed an improved μh up to 0.0152 cm–2 V–1 s–1. In addition, one- or two-electron oxidation of O-pentacene/nonacene generated the corresponding radical cations or dications, in which electronic properties were dependent on the number of O-containing six-membered rings and quinoidal subunits. The study provided insights into the relationships between molecule structures and optoelectronic properties for the unique class of O-embedded PAHs.
Fast and highly efficient intramolecular singlet exciton fission in a pentacene dimer, consisting of two covalently attached, nearly orthogonal pentacene units is reported. Fission to triplet ...excitons from this ground state geometry occurs within 1 ps in isolated molecules in solution and dispersed solid matrices. The process exhibits a sensitivity to environmental polarity and competes with geometric relaxation in the singlet state, while subsequent triplet decay is strongly dependent on conformational freedom. The near orthogonal arrangement of the pentacene units is unlike any structure currently proposed for efficient singlet exciton fission and may lead to new molecular design rules.
An orthogonal covalently bonded pentacene dimer (DP‐Mes) shows nearly quantitative singlet exciton fission on a sub‐picosecond timescale that is within the nuclear relxation time scale. By applying geometrical constraints, the fate of triplet–triplet annihilation is altered. These properties closely depend on molecular geometry and suggest a role for nuclear relaxation in controlling singlet exciton fission and triplet–triplet annihilation.
Singlet diradicaloids hold great potential as semiconductors for organic field‐effect transistors (OFETs). However, their relative low material and device stabilities impede the practical ...applications. Here, to achieve balanced stability and performance, two isomeric dibenzoheptazethrene derivatives with singlet diradical character were synthesized in a concise manner. Benefitting from the aromatic stabilization, both compounds display a small diradical character and large singlet–triplet gap, as corroborated by variable‐temperature electron paramagnetic resonance spectra, single‐crystal analysis, and theoretical calculations. OFET devices based on single crystals showed a high hole mobility of 0.15 cm2 V−1 s−1, which is the highest for zethrene‐based semiconductors. Both isomers exhibited remarkable material stability in air‐saturated solutions as well as excellent bias‐stress and storage stability in device under ambient air.
Two dibenzoheptazethrene isomers with low diradical character, large singlet–triplet gaps, and narrow energy gaps were synthesized. Both compounds exhibited remarkably high stability, which allowed for the fabrication of single‐crystal field‐effect transistors in air. A hole mobility of up to 0.15 cm2 V−1 s−1 was obtained with good bias‐stress and storage stability.
We report an anti‐folded bowl‐shaped bisdibenzocorannulene (BDBC) featuring a new chair‐cyclohexane‐like hexagon as a bridge of two dibenzocorannulene moieties. The neutral compound showed multiple ...redox‐active properties and could be converted to the corresponding redox states through chemical reduction or oxidation. Chemical reduction of BDBC by stoichiometric addition of metallic potassium in the presence of 18crown‐6 ether, provided a radical anion BDBC.− and a dianion BDBC2−, respectively; while chemical oxidation by silver hexafluoroantimonate(V), converted the neutral compound to an open‐shell singlet diradical dication (BDBC..)2+. The structural consequences of both electron‐reduction and oxidation were closely related to the release of ring‐strain of the bowl‐shaped π‐scaffold and imposed steric hindrance of the hexagonal bridge. In addition, the unusual open‐shell nature of the dication could mainly be attributed to the changing of localized antiaromaticity in the closed‐shell structure to delocalized character in the biradical, and thus the emergence of weakly bonded π‐electrons.
Chemical reduction/oxidation of a new type of curved π‐network (BDBC) provided access to its multiple redox states. For the one‐electron reduced state, the BDBC.− was characterized by single‐crystal X‐ray diffraction as a solvent‐separated radical anion; while the two‐electron oxidized state was revealed as an unusual singlet diradical dication (BDBC..)2+. As a consequence of their redox behaviours, their structures and ring currents have large differences.
Open-shell diradicaloids have been intensively investigated recently due to their attractive and unique optical, electronic and magnetic properties. However, open-shell diradicaloids with non-planar ...conjugated frameworks are less studied, especially helical-shaped π systems. In this work, we synthesized tetraindeno-based singlet biradicals in a helical geometry, bridged by a curved cyclobutenyl o-quinodimethane molecule. Large diradical characters and extremely small singlet-triplet energy gaps, as well as unusual half-field transitions (forbidden ΔMs = 2) were revealed for these 3D diradicals.
Organic-inorganic lead halide perovskite solar cells (PSCs) have received much attention in the last few years due to the high power conversion efficiency (PCE). Generally, perovskite/charge ...transport layer interface and the defects at the surface and grain boundaries of perovskite film are important factors for the efficiency and stability of PSCs. Herein, we employ an extended benzopentafulvalenes compound (FDC-2-5Cl) with electron-withdrawing pentachlorophenyl group and favorable energy level as charge transfer molecule to treat the perovskite surface. The FDC-2-5Cl with pentachlorophenyl group could accept the electrons from perovskite as a p-type dopant, and passivate the surface defects. The p-type doping effect of FDC-2-5Cl on perovskite surface induced band bending at perovskite surface, which improves the hole extraction from perovskite. As a result, the PSC with FDC-2-5Cl treatment achieves a PCE of 21.16% with an enhanced open-circuit voltage (Voc) of 1.14 V and outstanding long-term stability.
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•A benzopentafulvalene compound (FDC-2-5Cl) is used to treat the perovskite film•The FDC-2-5Cl could induce p-type doping and passivation effect on perovskite film•The device with treatment achieves a PCE of 21.16% with a high Voc of 1.14 V•The unencapsulated devices with passivation exhibit outstanding stability
Energy Engineering; Surface Treatment; Energy Materials
A p-Quinodimethane-Bridged Porphyrin Dimer Zeng, Wangdong; Ishida, Masatoshi; Lee, Sangsu ...
Chemistry : a European journal,
December 2, 2013, Letnik:
19, Številka:
49
Journal Article
Recenzirano
A p‐quinodimethane (p‐QDM)‐bridged porphyrin dimer 1 has been prepared for the first time. An unexpected Michael addition reaction took place when we attempted to synthesize compound 1 by reaction of ...the cross‐conjugated keto‐linked porphyrin dimers 8 a and 8 b with alkynyl/aryl Grignard reagents. Alternatively, compound 1 could be successfully prepared by intramolecular Friedel–Crafts alkylation of the diol‐linked porphyrin dimer 14 with concomitant oxidation in air. Compound 1 shows intense one‐photon absorption (OPA, λmax=955 nm, ε=45400 M−1 cm−1) and a large two‐photon absorption (TPA) cross‐section (σ(2)max=2080 GM at 1800 nm) in the near‐infrared (NIR) region due to its extended π‐conjugation and quinoidal character. It also exhibits a short singlet excited‐state lifetime of 25 ps. The cyclic voltammogram of 1 displays multiple redox waves with a small electrochemical energy gap of 0.86 eV. The ground‐state geometry, electronic structure, and optical properties of 1 have been further studied by density functional theory (DFT) calculations and compared with those of the keto‐linked dimer 8 b. This research has revealed that incorporation of a p‐QDM unit into the porphyrin framework had a significant impact on its optical and electronic properties, leading to a novel NIR OPA and TPA chromophore.
Fused porphyrin dimer: A p‐quinodimethane‐bridged porphyrin dimer 1 (see figure) has been prepared by an intramolecular Friedel–Crafts alkylation approach. Compound 1 shows intense one‐photon absorption (λmax=955 nm) and a large two‐photon absorption cross‐section (σ(2)max= 2080 GM (at 1800 nm)) in the near‐infrared region.
A “turn‐on” fluorescent sensing strategy was developed for ultrasensitive detection of heavy metal mercury ion (Hg2+) directly in water. It utilized an aqueous soluble aggregation‐induced emission ...(AIE)‐active probe, named 1,1,2,2‐tetrakis(4‐(1H‐tetrazol‐5‐yl)phenyl)ethene (TPE‐4TA), composing of a luminescent tetraphenylene core and multiple anionic tetrazolate spawns. The probe retained dark when molecularly dissolved in water. However, mercury ions can ligate with multiple tetrazolate groups to form infinite coordination polymer particles spontaneously, thus inducing a fluorogenic AIE response for in situ analysis. Moreover, by embedding this AIE sensing molecules in a hydrophilic polyvinyl alcohol substrate, the resulting hydrogel film allowed in situ detection of Hg2+ on a laser‐induced fluorescence analysis setup in aqueous environment. This strategy worked effectively in common aqueous environments with pH from 4 to 7.5 and showed high sensitivity (limit of detection down to 0.38 ppb/1.9 nM), good selectivity and a wide linearity range for quantification. This work may lead to a reliable and promising platform for on‐site environmental water analysis.
On‐site analysis of toxic metal spices is increasingly important and demands sensitive, reliable, and convenient methods directly in the aqueous environment because of their variable chemo‐physical states. Here, we report a new fluorescent turn‐on mercury sensing system by making use of a specific tetrazolate‐Hg coordination‐triggered aggregation‐induced emission process. By further formulating with a hydrogel host, it allowed for efficient analysis of environmental samples using a LIFs instrument.
The synthesis of high-spin polycyclic hydrocarbons is very challenging due to their extremely high reactivity. Herein, we report the synthesis and characterization of a kinetically blocked ...1,14:11,12-dibenzopentacene, DP-Mes, which represents a rare persistent triplet diradical of a non-Kekule polycyclic benzenoid hydrocarbon. In contrast to its structural isomer 1,14:7,8-dibenzopentacene (heptazethrene) with a singlet biradical ground state, DP-Mes is a triplet diradical as confirmed by ESR and ESTN measurements and density functional theory calculations. DP-Mes also displays intermolecular antiferromagnetic spin interactions in solution at low temperature.
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