Search

Three novel azatwistarenes 5a, 8, and 13have been synthesized via the Povarov reaction and fully characterized. All of the enantiomers were separated using chiral high-performance liquid chromatography, and their optical properties were investigated through circular dichroism and circularly polarized luminescence spectra. In addition, such desired azatwistarenes have a positive response to acid in dichloromethane.

The use of harmful halogenated or aromatic solvents such as chloroform (CF), chlorobenzene (CB), and o-xylene (o-XY) is one of the greatest barriers to the industrial-scale manufacturing of high-performance organic solar cells (OSCs). Therefore, it is necessary to eliminate the effects of these solvents to ensure practical feasibility of OSCs. We found that the anthracene-terminated polymer donor and small-molecule acceptor BO-4Cl had good solubility in 3-methylthiophene (3-MeT). There were no toxicity labels in the SDS and exposure control limits for 3-MeT. An overall power conversion efficiency of 16.87% was achieved by using 3-MeT as the solvent for solar cell fabrication, which was higher than that of the cells made from CF (16.18%) and o-XY (15.69%). The best OSC based on PM6:D18:L8-BO and fabricated with 3-MeT exhibited a high PCE of 18.13%, which is one of the highest values for cells fabricated from halogen-free solvents. These results indicate that 3-MeT is an eco-friendly and low-toxicity solvent for the sustainable fabrication of the OSC active layer.

A pair of novel chiral 1-phenylethylamine-modified twistarenes (4and 11; compound 4= 9,14-di-tert-butyl-7,16-diphenyl-2-(1-phenylethyl)-1H-benzo[8',9']triphenyleno[2',3':6,7]fluoreno[2,1,9-def]isoquinoline-1,3(2H)-dione) have been synthesized and characterized, and how the solvent component affects the chirality transfer of their self-assembled processes is investigated in mixtures with THF and H2O. The ordered assembly of 11exhibits circular dichroism response. In addition, both 11aand 11bdisplay positive photoconducting behavior.

Poly-[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione))] (PM6) is one of the star molecules in organic solar cells (OSCs). However, PM6 has been suffering from molecular weight control and unreacted terminal groups. Thus, synthesizing high-quality polymers without batch-to-batch variations has been challenging for many years. Herein, a one-step protocol of both end-capping and polymerization at the same time was developed to prepare end-capped PM6 with molecular weight controlled by changing the monomer ratio. Specifically, non-end-capped PM67 and a series of PM6Enwith different molecular weights were synthesized and characterized. Our research findings indicated that (1) these copolymers’ number-average molecular weights (Mns) and weight-average molecular weights (Mws) were measured to be almost linearly increased. Although textbooks have mentioned the nonequivalent ratio monomer strategy to regulate the molecular weight of polymers, the end-capping yield has not been reported in the research of OSCs due to a lack of efficient experiments and instruments to measure the low percentage of end groups in the polymer. (2) Since the selected end-caping reagent 4′-bromobenzo-18-crown-6 (EBr) can be easily distinguished from the PM6 main backbone, we first measured the end-capping yield by both nuclear magnetic resonance (NMR) and matrix-assisted laser desorption/ionization time-of-flight mass spectra (MALDI-TOF-MS). We applied this approach for the first time to synthesize polymers with reasonable end-capping yields (40–97%) for OSCs. (3) Surprisingly, 18-crown-6 can reduce end-group defects, lower the polydispersity index (PDI) of the polymer, and achieve suitable morphology and mobility. As a result, the end-capped PM6E7-based device exhibited the best stability and power conversion efficiency (PCE) compared to those of the other end-capped or non-end-capped polymers. Both the end groups and molecular weight significantly affect the performance of the OSCs. PM6 and other copolymers could be finely tuned by subtly changing the molecular weights or end-cap groups with functional building blocks. Our research will stimulate the development of OSCs and other applications of copolymers.

Two novel helical heteronanographenes bearing a [6]helicene unit (3aand 5a) have been synthesized, and their molecular structures are unambiguously determined via single-crystal X-ray diffraction analyses. Density functional theory calculations suggest that the as-prepared compounds have isomerization barriers of 29.02 kcal/mol for 3aand 34.07 kcal/mol for 5a, respectively. Optical enantiomers of 5aexhibit appealing chiroptical properties.

Two novel double π-extended [n]helicene (n= 5, 6) derivatives (7band 9) including pentagonal rings have been synthesized and characterized. Both of them have three isomers containing two enantiomers (P6), (M6), and a diastereoisomer in a meso form (P,M). X-ray single crystal analyses suggest that molecules 7band 9exhibit offset packing models of (P6,P5)- and (M6,M5)-isomers. Optical resolution of the resultant compound 7bwas finished, and their chiroptical properties, as well as the DFT calculations, were also examined.

We have designed and synthesized three novel twistacene-modified enlarged pentagon-containing π-systems (6and 9) with mismatched structures. The introduction of electron-withdrawing cyclopenta rings in the parent skeleton effectively stabilizes the electron-rich arenes. Their optoelectronic properties were studied via ultraviolet–visible (UV–vis) absorption spectra, fluorescence spectra, cyclic voltammetry, and density functional theory (DFT) calculation. In addition, chemical oxidation of the as-prepared compounds with nitrosonium hexafluoroantimonate could form the corresponding cationic radicals.

Four chalcogenophene-fused acenes containing O, S, Se, or Te, respectively, were presented, and the chalcogenophene effect on linear and nonlinear optics was systematically investigated. Their excited-state absorption performance and two-photon absorption (TPA) capacity could be modulated by the incorporating chalcogen atoms. The experimental results showed that the heavy chalcogen facilitated the intersystem crossing resulting in the presence of the triplet state absorption for PyPSeand PyPTe, and the TPA capacity gradually increased with the atomic size of the chalcogens. The theoretical calculation inferred that their nonlinear optical performance was closely related to the contributions of the chalcogenophene component to heterotwistacenes in the final excited state. In addition, PyPTewas able to work under various laser pulses from femtoseconds to nanoseconds.

Four substituted twistacenes decorated with different twisted π-conjugated units are synthesized to investigate their structure–property relationship. To improve the nonlinear optical (NLO) response of these twistacenes, phenyl, naphthyl, anthryl, and pyrenyl are selected as the twisted units to gradually increase the population of π-electrons. Broadband excited-state absorption (ESA) and reverse saturable absorption (RSA) of these compounds show a significant enhancement in femtosecond transient absorption spectra (TAS) and multiwavelength Z-scan experiments, respectively. The photophysical mechanism exhibits a typical feature of two-photon absorption (TPA)-induced ESA (TPA-ESA) on the singlet state. With the analysis of the electron transition calculated by the time-dependent density functional theory (TD-DFT), it can be inferred that TPA and ESA of these twistacenes are modulated by intramolecular charge transfer (ICT) and local excitation (LE), respectively. The TPA cross sections of these twistacenes at 515 nm are dramatically enhanced from 214 to 534 GM by introducing ICT, while the ESA cross sections are significantly increased from 1.2 × 10–21to 6.5 × 10–21m2at 690 nm via strengthening LE with the π–π* feature. The result indicates that not only can TPA and ESA be enhanced simultaneously but also the selective modulation of the nonlinear optical (NLO) properties can be achieved in such kinds of compounds.

Two novel [5]helicene derivatives (labeled 5and 8) have been successfully synthesized and characterized. The structural analyses, photophysical properties, along with density functional theory calculations for unveiling the helicity inversion and equilibrium of the diastereomers, were investigated in a comparative manner. In addition, chemical oxidation of them indicated that molecule 8exhibited the formation of the radical cation at room temperature.

A family of chiral nanographenes bearing [6]helicene units has been synthesized via the classical Scholl reaction. Inserting the [6]helicene unit into the parent nanographene skeleton can result in different structural topologies and optoelectric properties. Moreover, the isolated enantiomers exhibit attractive chiroptical properties.

To realize the relationship of structure and property, four novel twistacene-functionalized arenes, namely, 1,4-bis(2,7-di-tert-butyl-9,14-bis(4-(tert-butyl)phenyl)dibenzo[de,qr]tetracen-11-yl)buta-1,3-diyne (4), 1,4-bis(3,5,10,12-tetra-tert-butyltribenzo[a,d,g]coronen-16-yl)buta-1,3-diyne (7), 1,4-bis(2,7-di-tert-butyl-9,14-bis(4-(tert-butyl)phenyl)dibenzo[de,qr]tetracen-10-yl)buta-1,3-diyne (10), 1,4-bis(3,5,10,12-tetra-tert-butyltribenzo[a,d,g]coronen-15-yl)buta-1,3-diyne (13), linked with butadiyne as π bridges have been strategically synthesized and characterized. The nonlinear optical properties are detailly examined in solution through the open-aperture Z-scan method in a comparative manner, indicating that molecules 4and 7exhibit better nonlinear optical responses than 10and 13. Among them, 4and 7exhibit excellent optical limiting responses with limiting thresholds of 0.17 and 0.19 J/cm2, respectively, being superior to the state-of-the-art material C60. The ultrafast transient absorption test and DFT calculations suggest that the nonlinear absorption mechanisms belong to TPA-induced ESA. In addition, the effective percentage calculated from TD-DFT can provide a brief glance to evaluate the optical limiting performance.

A highly thermally stable twistarene, namely 11,16‐di‐tert‐butyl‐9,18‐diphenylbenzo[kl]benzo[8,9]triphenyleno[2,3‐b]xanthene (BTX), has been synthesized via a simple reaction, and its structure was unambiguously determined by single crystal X‐ray analysis with a twisted angle of 37.9° between plane C1‐C2‐C4 and plane C16‐C17‐C24. More interestingly, molecule BTXcould self‐assembly into nanowires and nanospheres via simple reprecipitation, which were characterized by scanning electron microscope (SEM), UV‐vis absorption and emission spectra. The fabricated electroluminescent devices based on BTXas active ingredient presented a maximum brightness of 4355 cd m−2(bias voltage at 9.0 V) with CIE coordinate of (0.14, 0.53). Bright twist: A pyran‐embedded arene was synthesized and possessed a twisted topological structure with a twist angle of 37.9°. This molecule could self‐assembly into nanowires and nanoparticles by tuning the solvent type and ratio. More interestingly, the optimized devices using it as emitter exhibited green electroluminescence with a maximum brightness of 4355 cd m−2.

Acenes, usually defined as segments of “graphene”, consist of linearly annulated benzene rings, and have attracted considerable interest in both theoretical research and practical applications. However, these compounds generally have undesirable features such as poor solubility, easy oxidation and photodimerization. Thus, scientists have to invest much effort to address these problems and experimentally achieve the desired electronic properties to meet various demands. Herein, we summarize recent progress in the synthesis of pyrene‐functionalized acenes and heteroacenes through the use of pyrene diketone and pyrene tetraketone building blocks. Moreover, the physical properties and applications of these semiconductors in organic semiconductor devices are also described. You′re creating a‐cene! Recent progress in synthetic efforts to access pyrene‐functionalized acenes and heteroacenes from pyrene diketone and pyrene tetraketone building blocks is reviewed. The favorable physical properties and applications of these materials in organic semiconductor devices are also described.

To realize the high reactivity of large acenes, doping heteroatoms into the skeleton of acene is an appealing strategy. Thus herein a novel annulated dioxin derivative containing thirteen six‐membered rings (DPyP) in one row has been synthesized and characterized. The resulting molecule presented maximum absorption and emission peaks at 611 nm and 655 nm in dichloromethane, respectively, and its decomposition temperature was stable up to 343 °C (5% weight loss). Furthermore, the organic light‐emitting diode fabricated with DPyPas an emitter exhibited a promising electroluminescent performance with the maximum red brightness of 301 cd m−2with CIE of (0.71, 0.28). A novel annulated dioxin derivativecontaining thirteen six‐membered rings (DPyP) in one row has been synthesized and characterized. The resulting molecule presented maximum absorption and emission peaks at 611 nm and 655 nm in dichloromethane. The fabricated device with DPyPas an emitter exhibited a promising red electroluminescence.

Three novel end‐capping twistacene derivatives with phenyl (PyDP), naphthyl (PyDN), and anthryl groups (PyDA) have been designed and synthesized. Given the crystallographic analyses, the as‐prepared molecules exhibited a twisted topological structure with the torsion angles of 35.99° for PyDP and 45.85° for PyDA. In addition, there is no π‐stacking interaction in PyDP. However, PyDA displayed π‐stacking interactions between the terminal intermolecular anthracene groups. The electroluminescent performance of OLEDs shows that devices with PyDP and PyDA outperform the PyDN‐based device, which is attributable to their higher fluorescence quantum yields. The maximum EQE value for PyDP reaches 3.10 %, which illustrates that the terminal substituent can affect the performance of OLEDs to a certain extent. The end‐capping twistaceneswith phenyl (PyDP), naphthyl (PyPN), and anthryl (PyDA) groups, which emitted strong blue fluorescence, have been synthesized and characterized,. The device performances of PyDP/PyDA acenes outperformed that of PyDN, which might be attributed to their higher fluorescence quantum yields. The maximum external quantum efficiency (EQE) value for PyDP reached 3.1 %, illustrating that the terminal substituent could affect the performance of OLEDs to a certain extent.

A series of functionalized benzofuran derivatives (2, 3, 4) have been strategically synthesized and characterized via NMR spectra and high resolution mass spectrometry. To enhance the solubility in organic common solvents, long alkyl groups were introduced into the parent skeletons in compounds 2 b, 3 b, 4 b. The photophysical properties were examined in a comparative manner. The self‐assembly behaviors were further studied, indicating that the regular nanostructures could be tuned by the change of the ratio of THF and cetyltrimethylammonium bromide (CTAB) aqueous solution. Moreover, 3 bpresented nonlinear optical (NLO) response recorded through open‐aperture Z‐scan way. The threshold of 3 bwas 2.08 J/cm2, which is lower than that of the state‐of‐the‐art material C60(4.01 J/cm2) under the similar operation condition, implying that such molecule might be promising optical limiting (OL) materials. A family of functionalized benzofuran derivatives have been synthesized in this work. Subsequently, the photophysical, electrochemical properties and self‐assembly behaviors were examined in detail. Compound 3 bexhibits excellent OL performance better than reference molecule fullerene (C60).

Two pairs of isomers of heptagon-embedded helical arenes (3/6and 10/13) have been strategically prepared, where the molecular structures of 3and 13have been identified through single crystal X-ray diffraction analysis. The effect of the heptagon unit on the physical properties of 3, 6, 10, and 13is investigated in a comparative manner, and the results indicate that the optical enantiomers of 13obtained from HPLC exhibit promising chiroptical properties.

Four novel unsymmetrical heteroacenes containing five-membered heterocycles (OPyN, TPyN, TPyC, TPyO) have been synthesized and characterized. The formed molecules exhibited twisted structures, determined by crystal analysis and showed blue/green fluorescence in dichloromethane and in thin film. Compounds OPyN and TPyN were selectively used as active ingredients, and the fabricated devices displayed promising electroluminescent performance.

Poor charge injection and transport at the electrode/semiconductor contacts has been so far a severe performance hurdle for bottom-contact bottom-gate (BCBG) organic field-effect transistors (OFETs). Here, we have developed a simple, economic, and effective method to improve the carrier injection efficiency and obtained high-performance devices with low cost and widely used source/drain (S/D) electrodes (Ag/Cu). Through the simple electrode etching process, the work function of the electrodes is more aligned with the semiconductors, which reduces the energy barrier and facilitates the charge injection. Besides, the formation of the thinned electrode edge with desirable micro/nanostructures not only leads to the enlarged contact side area beneficial for the carrier injection but also is in favor of the molecular self-organization for continuous crystal growth at the contact/active channel interface, which is better for the charge injection and transport. These effects give rise to the great reduction of contact resistance and the amazing improvement of the low-cost bottom-contact configuration OFETs performance.

Five novel organic conjugated derivatives containing multifraction twisted acene units have been synthesized and characterized. These compounds and the model molecule 2-methyl-5,12-diphenyl-6:7,10:11-bisbenzotetracene emit strong blue light in diluted solution with quantum yields of 0.21–0.67, while in the solid state, except for the 1,2,3,4,5,6-hexa(2-(5,12-diphenyl-6:7,10:11-bis(4′-tert-butylbenzo)tetracene))benzene, green luminance is seen. The experimental results also indicate that the multifraction structure leads to a significant fluorescence enhancement (over two times) compared to the monomer, which might be attributed to the formation of delocalized excited state in multibranch structures. The quantum-chemical calculation implies that only two branches are involved in formation of the delocalized system for the multibranched derivatives. Furthermore, the organic light-emitting diode (OLED) devices using compounds 1,4-di(2-(5,12-diphenyl-6:7,10:11-bis(4′-tert-butylbenzo)tetracene))benzene, 1,3-di(2-(5,12-diphenyl-6:7,10:11-bis(4′-tert-butylbenzo)tetracene))benzene, and 1,3,5-tri(2-(5,12-diphenyl-6:7,10:11-bis(4′-tert-butylbenzo)tetracene))benzene as emitters exhibit good electroluminescent performance. Our systematic studies might provide more chances to challenge the rational design and synthesis of new- and high-generation branched dendrimers.

6,8,15,17-Tetraaza-1.18,4.5,9.10,13.14-tetrabenzoheptacene (TTH, 1) has been prepared and characterized by single-crystal X-ray structure analysis. A phototransistor device based on TTHsingle crystal demonstrated that TTHshowed a good performance in signal amplification under the photoconductive effect as well as photocontrolled switches.

Let's twist again: A “clean reaction” strategy based on thermally eliminating lactam bridges from a soluble acene precursor through a retro‐Diels–Alder reaction gives a new, stable, green heptatwistacene (see structure). The molecule has a twist angle of 23.49°, is very stable even in air, and has an optical band gap of 1.82 eV.

A novel compound, 5,7,14,16‐tetraphenyl‐8:9,12:13‐bisbenzo‐hexatwistacene (TBH), has been successfully synthesized through a retro‐Diels–Alder reaction. Single‐crystal structure analysis indicated that TBHhas a twisted configuration with a torsion angle of 27.34°. The HOMO–LUMO gap of TBHcalculated from the difference between the half‐wave redox potentials (E1/2ox=+0.40 eV and E1/2red=−1.78 eV) is 2.18 eV, which is in good agreement with the band gap (2.19 eV) derived from the UV/Vis absorption data. In addition, organic light‐emitting devices using TBHas emitter have been fabricated. The results revealed that TBHis a promising red light‐emitting candidate for applications in organic light‐emitting diodes.

Recent studies have demonstrated that single‐walled carbon nanotube (SWCNT) films can be doped by a nitric/sulfuric acid treatment to significantly improve its conductivity. However, the sheet resistance is still too high for many applications. Here we report on a simple treatment using a piranha mixture that could further enhance SWCNT film conductivity. The high redox potentials of hydrogen peroxides combined with the acidity of sulfuric acid enabled strong p‐doping of the carbon nanotube films. Absorption peak suppression and a G‐band shift provided proof of strong p‐doping of the SWCNT films.

Two novel shapes of 9,10-diphenylanthracene (DPA) micro/nanostructures: octahedron and sphere together with microrod and nanowire have been synthesized via a surfactant-assisted self-assembling process. These micro/nanostructures have been characterized by UV−vis, fluorescence spectra, X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and transmission electron microscope (TEM). Our results indicated that the absorption and emission spectra of as-prepared particles were slightly blue-shift when the shape of DPA particles changed from octahedron to microrod and finally to nanowire. This result could be explained by the different growth directions of DPA micro/nanostructures. To study the relationship between shape and devices’ performance, the heterojunction light emitting diode (LED) devices of quartz/ITO/organic particles/n-SiC/Ti(10 nm)/Au(120 nm) have been prepared. The testing results showed that the different shapes of DPA micro/nanostructures did affect the performance of diodes and the nanowire was the best shape for the heterojunction light emitting diode (LED) devices.

We report the synthesis and characterization of a novel, stable and blue heteroacene, 2‐methyl‐1,4,6,7,8,9‐hexaphenylbenz(g)isoquinolin‐3(2H)‐one (BIQ 3). BIQ 3, with its relatively small π framework, has an absorption λmaxat 620 nm, which is larger than that of pentacene (λmax=582 nm), but BIQ 3is more stable. The solutions of BIQ 3are observed without any noticeable photobleaching on the order of days. In the solid state, it is very stable at ambient conditions and can be stored indefinitely. Owing to its pyridone end unit, BIQ 3can display different resonance structures in different solvents (aprotic and protic) or Lewis acids to give different colors. The attractive stability exhibited by BIQ 3is very desirable in organic semiconductor devices. Herein, we investigated a simple heterojunction photovoltaic device based on BIQ 3as an electron donor and [6,6]‐phenyl‐C61butyric methyl ester as an electron acceptor. Our results show that this type of heteroacene could be a good candidate as a charge‐transport material in organic semiconductor devices.

An asymmetric twistacene, 1′,4′‐diphenyl‐naphtho‐(2′.3′:1.2)‐pyrene‐6′‐nitro‐7′‐methyl carboxylate (tetracene 2), was synthesized by using benzyne‐trapping chemistry. Its structure, determined by X‐ray crystallography, confirmed that this material has a twisted topology with torsion angles as high as 23.8(3)°. Organic light‐emitting devices using tetracene 2as either charge‐transporting materials or emitters have been fabricated. The results indicate that this material has bipolar transporting behavior in these devices.

Hot Rod: Using the reprecipitation method, microrods of 2,5‐dibromo‐3,4‐ethylenedioxythiophene (DBEDOT) were prepared in aqueous solution. The as‐synthesized microrods were found to polymerize in aqueous solution after heated at 75 °C for 4 hours.

Three end‐capping aceneswith phenyl (PyDP), naphthyl (PyDN), and anthryl groups (PyDA) have been designed and synthesized. The crystallographic analyses show that the as‐prepared molecules exhibit twisted topological structures. The electroluminescent performance of OLEDs shows that devices with PyDP and PyDA outperform the PyDN‐based device, suggesting that the terminal substituent can affect the performance of OLEDs to a certain extent. More information can be found in the Full Paper by Wenming Su and Jinchong Xiao et al. on page 424 in Issue 2, 2018(DOI: 10.1002/ajoc.201700576).

A series of twistacene-functionalized dendrimers were successfully synthesized and characterized. The model molecule DBPy has a twisted configuration with a torsional angle of 27.69° between pyrene and naphthalene units. The resulting compounds TPPh, TTPy, OTPy and TOPhP can self-assemble into organic nanoparticles through re-precipitation method and emit strong blue, cyan, green and red fluorescence in water, respectively. Additionally, the obtained multicolor nanoparticles showed low cytotoxicity and good photostability that selectively flow into the membrane and cytoplasm of HeLa cells, indicating the feasibility and efficiency in fluorescence imaging. This study might be a new avenue for the design of three-dimensional branched conjugated molecule and specific location imaging in living cell.