Nitrogen-Containing Perylene Diimides: Molecular Design, Robust Aggregated Structures, and Advances in n-Type Organic Semiconductors

An Electric Molecular Faraday Cage

Faraday cages are essential tools for protecting conducting materials from unwanted electromagnetic radiation by redistributing charges around the cage's exterior. When integrated into nanoscale molecular circuits, particularly those with well-defined inner cavity structures, Faraday cages isolate guest molecules from external influences, thereby improving device stability and performance. The design of molecular Faraday cages involves the intersection of molecular electronics and supramolecular chemistry with the goal of safeguarding internal molecules from harmful substances. In this study, we introduce an X-shaped octacationic cyclophane, XCage8+, as an electric molecular Faraday cage. Its spacious binding cavity allows for the encapsulation of perylene diimide molecular wires. The shielding effectiveness of XCage8+ was confirmed through electrochemical gating, demonstrating that electric fields are shielded effectively. The findings of this study provide valuable insights that could inspire the development of innovative strategies for enhancing device stability and performance at the supramolecular level, paving the way for further progress in the fields of molecular electronics and quantum devices.

Supramolecular Polymorphism of the Hydrogen-Bonded C3-Symmetrical Hexadehydrotribenzo[12]annulene Derivative

The C3-symmetric hexadehydrotribenzo[12]annulene ([12]DBA) derivative (1a) with three tetradecylamide (-NHCOC14H29) chains capable of hydrogen-bonding interaction formed either a two-dimensional lamellar (LM) or a one-dimensional (1D) nanofiber (NF) molecular assembly, depending on the association state of the amide hydrogen bonds in the solution phase. The intermolecular amide hydrogen-bonding modes in the LM and NF structures were different from each other. The NF structure was metastable, 2.2 kJ mol-1 less stable than that of the LM structure, and was obtained through organogel formation. In CHCl3, 1a exhibited a 1D association behavior following the isodesmic model (K = 2.18 × 103 M-1) due to intermolecular amide hydrogen bonds, whereas the presence of CH3CN inhibited this association state. The NF structure had larger amplitude dynamics about the polar amide group than that of the LM structure, undergoing a phase transition from the NF to the LM structure upon heating. The absorption spectra of NF and solid-state LM were different from each other, exhibiting different optical properties. The coexistence of intermolecular amide hydrogen bonds and van der Waals interactions among the C3-symmetric molecules resulted in polymorphic phenomena, where energetically similar molecular assemblies were expressed.

Azuperylene: The Nonalternant Isomer of Perylene

The isoelectronic isomer of perylene, hereafter called as azuperylene, has been prepared. Electronic structure analysis reveals that the new isomer can be described as a union of two antiparallel azulenes in which the azulene-type aromatic character of the starting azulene is partially retained. Four 2,8-dialkoxy (i.e., ethoxy, n-butoxy, n-hexyloxy, and n-octyloxy) functionalized derivatives of the new isomer core have been prepared. The solid-state structures of the new compounds have been resolved showing exceptional herringbone π-π stacking ideal for charge transport. Organic field-effect transistors on sublimated substrates display an excellent hole transport mobility up to 1.03 cm2 V-1 s-1 that largely surpasses that of perylene and reveals the great potential for charge transport of this new class of nonbenzenoid compounds.

Polarization-Induced Quantum Confinement of Negative Charge Carriers by Organic Nanoporous Frameworks

We characterize the attachment of excess-electrons to organic nanoporous systems such as molecular nanohoops and models of covalent organic frameworks (COFs) using many-body methods. All the nanopore systems exhibit diffuse electronic states where the excess-electron is bound to the molecular scaffold via long-range polarization forces, and the excess-electron is predominantly localized in the interior of the nanopore or away from the molecular scaffold. Such "nanopore-bound" states show an enhanced electron-transfer coupling compared to more strongly-bound skeletal-states (or valence-bound states), where the excess-electron is confined to the molecular skeleton. For 1D assemblies of nanohoops, the bands formed from nanopore-bound states have a consistent nearly-free-electron character, indicating an efficient excited-state pathway for charge-carriers, while the bands from skeletal-states have higher effective mass along certain lattice directions. The nanopore-bound states show distinct size-dependent variations in electron affinities compared to skeletal-states and previously observed molecular quantum corral states. We conclude that nanopore-bound states emerge from polarization-induced quantum confinement, forming a distinct common feature of organic nanoporous matter with potential for efficient electron-transport.

Unveiling the Centrosymmetric Effect in the Design of Narrowband Fluorescent Emitters: From Single to Double Difluoroboron Cores

Narrowband fluorescent emitters are receiving significant attention due to the great potential for creating ultrahigh-definition organic light-emitting diode displays (UHD-OLED). Unveiling innovative mechanisms to design new high-performance narrowband fluorescent emitters is a concerted endeavor in both academic and industrial circles. Theoretical calculations reveal that the centrosymmetric dianilido-bipyridine boron difluoride framework (cs-DAPBF2) exhibits significantly reduced structural relaxation compared to previously reported asymmetric structures with monofluoroboron cores, creating new opportunities for the development of narrowband fluorescent emitters. In this work, we present a dual chelation-assisted C-H/C-H homocoupling strategy to efficiently synthesize the 3,3'-amino-2,2'-bipyridine skeleton, enabling the straightforward construction of a series of symmetric cs-DAPBF2-based fluorescent emitters. Through molecular optimization, we have developed a high-performance narrowband green fluorescent emitter, cs-DMeAPBF2-MP, which demonstrates a narrow full width at half-maximum (fwhm) of 20 nm, a high photoluminescence quantum yield (ΦPL) of 98%, a large molar absorptivity (ε) of 2.10 × 104 M-1 cm-1, and a high horizontal dipole ratio (Θ//) of 77%. These properties make cs-DMeAPBF2-MP a promising candidate for fabricating high-efficiency, narrowband green organic light-emitting diodes (OLEDs) with minimal efficiency roll-off. This study represents the first successful application of the DAPBF2 architecture in the design of narrowband fluorescent emitters for high-performance OLEDs.

Molecular Design of n-Type Organic Semiconductors with Ultralow Electron Reorganization Energies

Bottom-up design of n-type organic semiconductors with salient electron-transport properties is of fundamental importance. Here, with the aid of density functional theory, we demonstrate that condensing odd-membered carbon rings (5MR/7MR) to small polycyclic aromatic hydrocarbons (PAHs) can endow molecules with ultralow electron reorganization energies (λ < 100 meV). Studying 60 molecules, we find that introducing polycyclic fragments with built-in 5MR and 7MR to linear PAHs at the Cα,β positions or to nonlinear PAHs in D2h symmetry constitutes molecules with λ as low as 65 meV. A joint ACID and NICS analysis proves that the stronger the molecular aromaticity, the lower the λ will be. This is contrary to what has been previously found for p-type molecules. Furthermore, we propose "acupoints" on molecules for N-doping and cyanation, which can be used to precisely locate the substitution sites to reduce the LUMO energies (in favor of electron injection and air stability) of low-λ molecules while it does not elevate λ. These findings would help to reduce the synthetic blindness/cost and contribute to the bottom-up design of n-type small-molecule organic semiconductors.

Visible Light-Sensitized CO2 Methanation along a Relaxed Heat Available Route

In photocatalysis, the resulted heat by the relaxation of most of incident light no longer acts as the industrially favorite driving force back to the target photo-reaction due to more or less the negative relation between photocatalytic efficiency and temperature. Here, we reported a visible light-sensitized protocol that completely reversed the negatively temperature-dependent efficiency in photo-driven CO2 methanation with saturated water vapor. Uniform Pt/N-TiO2/PDI self-assembly material decisively injects the excited electron of PDI sensitizer into N-TiO2 forming Ti-H hydride which is crucially temperature-dependent nucleophilic species to dominate CO2 methanation, rather than conventionally separated and trapped electrons on the conductor band. Meanwhile, the ternary composite lifts itself temperature from room temperature to 305.2 °C within 400 s only by the failure excitation upon simulated sunlight of 2.5 W/cm2, and smoothly achieves CO2 methanation with a record number of 4.98 mmol g-1 h-1 rate, compared to less than 0.02 mol g-1 h-1 at classic Pt/N-TiO2/UV photocatalysis without PDI sensitization. This approach can reuse ~53.9 % of the relaxed heat energy from the incident light thereby allow high-intensity incident light as strong as possible within a flowing photo-reactor, opening the most likely gateways to industrialization.

Molecular "backbone surgery" of electron-deficient heteroarenes based on dithienopyrrolobenzothiadiazole: conformation-dependent crystal structures and charge transport properties

Electron-deficient heteroarenes based on dithienopyrrolobenzothiadiazole (BTP) have been highly attractive due to their fascinating packing structures, broad absorption profiles, and promising applications in non-fullerene organic solar cells. However, the control of their crystal structures for superior charge transport still faces big challenges. Herein, a conformation engineering strategy is proposed to rationally manipulate the single crystal structure of BTP-series heteroarenes. The parent molecule BTPO-c has a 3D network crystal structure, which originates from its banana-shaped conformation. Subtracting one thiophene moiety from the central backbone leads to a looser brickwork crystal structure of the derivative BTPO-z because of its interrupted angular-shaped conformation. Further subtracting two thiophene moieties results in the derivative BTPO-l with a compact 2D-brickwork crystal structure due to its quasi-linear conformation with a unique dimer packing structure and short π-π stacking distance (3.30 Å). Further investigation of charge-transport properties via single-crystal organic transistors demonstrates that the compact 2D-brickwork crystal structure of BTPO-l leads to an excellent electron mobility of 3.5 cm2 V-1 s-1, much higher than that of BTPO-c with a 3D network (1.9 cm2 V-1 s-1) and BTPO-z with a looser brickwork structure (0.6 cm2 V-1 s-1). Notably, this study presents, for the first time, an elegant demonstration of the tunable single crystal structures of electron-deficient heteroarenes for efficient organic electronics.

Engineered solid-state aggregates in brickwork stacks of n-type organic semiconductors: a way to achieve high electron mobility

Efficient, economically viable n-type organic semiconductor materials suitable for solution-processed OFET devices with high electron mobility and ambient stability are scarce. Merging these attributes into a single molecule remains a significant challenge and a careful molecular design is needed. To address this, synthetic viability (achievable in fewer than three steps) and using cost-effective starting materials are crucial. Our research presents a strategy that meets these criteria using naphthalene diimide (NDI) core structures. The approach involves a simple synthesis process with a cost of $ 5-10 per gram for the final products. This paper highlights our success in scaling up the production using affordable known reagents, creating ambient condition solution-processed OFET devices with impressive electron mobility, on-off current ratio (1 cm2 V-1 s-1 and I on/I off ∼ 109) and good ambient stability (more than 100 h). We conducted a comprehensive study on EHNDIBr2, a material that demonstrates superior performance due to its unique supramolecular arrangement in its brickwork stack. This was compared with two similar structures to validate our findings. The superior performance of EHNDIBr2 is attributed to the effective interlocking of charge-hopping units within the NDI core in its brickwork stack. Our findings include detailed electronic, spectroscopic, and microscopic analyses of these layers.

Electronically and geometrically complementary perylenediimides for kinetically controlled supramolecular copolymers

The synthesis of 3,4,9,10-benzo[d,e]isoquinolino[1,8-g,h]quinoline-tetracarboxylic diimide (BQQDI) 1 endowed with peripheral trialkoxybenzamide fragments is reported and its self-assembling features investigated. The peripheral benzamide moieties generate metastable monomeric species that afford a kinetically controlled supramolecular polymerization. The electron-withdrawing character of 1 in comparison with previously reported PDIs 2, together with the similar geometry, makes this dye an optimal candidate to perform seeded supramolecular copolymerization yielding four different supramolecular block copolymers. Whilst heteropolymers poly-1-co-2a, poly-2a-co-1 and poly-1-co-2b present an H-type arrangement of the monomeric units, heteropolymer poly-2b-co-1, prepared by seeding the chiral, metastable monomers of 2b with achiral seeds of 1, produces chiral, J-type aggregates. Interestingly, the monosignated CD signal of pristine poly-2b changes to a bisignated CD signal most probably due to the formation of columnar domains around the seeds of 1 which implies the blocky nature of the supramolecular copolymers formed.

Self-Assembly Behavior, Aggregation Structure, and the Charge Carrier Transport Properties of S-Heterocyclic Annulated Perylene Diimide Derivatives

The construction of high-performance n-type semiconductors is crucial for the advancement of organic electronics. As an attractive n-type semiconductor, molecular systems based on perylene diimide derivatives (PDIs) have been extensively investigated over recent years. Owing to the fascinating aggregated structure and high performance, S-heterocyclic annulated PDIs (SPDIs) are receiving increasing attention. However, the relationship between the structure and the electrical properties of SPDIs has not been deeply revealed, restricting the progress of PDI-based organic electronics. Here, we developed two novel SPDIs with linear and dendronized substituents in the imide position, named linear SPDI and dendronized SPDI, respectively. A series of structural and property characterizations indicated that linear SPDI formed a long-range-ordered crystalline structure based on helical supramolecular columns, while dendronized SPDI, with longer alkyl side chains, formed a 3D-ordered crystalline structure at a low temperature, which transformed into a hexagonal columnar liquid crystal structure at a high temperature. Moreover, no significant charge carrier transport signal was examined for linear SPDI, while dendronized SPDI had a charge carrier mobility of 3.5 × 10-3 cm2 V-1 s-1 and 2.1 × 10-3 cm2 V-1 s-1 in the crystalline and liquid crystalline state, respectively. These findings highlight the importance of the structure-function relationship in PDIs, and also offer useful roadmaps for the design of high-performance organic electronics for down-to-earth applications.

Functionalized Phenanthrene Imide-Based Polymers for n-Type Organic Thin-Film Transistors

High-performing n-type polymers are crucial for the advance of organic electronics field, however strong electron-deficient building blocks with optimized physicochemical properties for constructing them are still limited. The imide-functionalized polycyclic aromatic hydrocarbons (PAHs) with extended π-conjugated framework, high electron deficiency and good solubility serve as promising candidates for developing high-performance n-type polymers. Among the PAHs, phenanthrene (PhA) features a well-delocalized aromatic π-system with multiple modifiable active sites . However, the PhA-based imides are seldom studied, mainly attributed to the synthetic challenge. Herein, we report two functionalized PhAs, CPOI and CPCNI, by simultaneously incorporating imide with carbonyl or dicyanomethylene onto PhA. Notably, the dicyanomethylene-modified CPCNI exhibits a well stabilized LUMO energy level (-3.84 eV), attributed to the synergetic inductive effect from imide and cyano groups. Subsequently, based on CPOI and CPCNI, two polymers PCPOI-Tz and PCPCNI-Tz were developed. Applied to organic thin-film transistors, owing to the strong electron-deficiency of CPCNI, polymer PCPCNI-Tz shows an improved electron mobility and largely decreased threshold voltage compared with PCPOI-Tz. This work affords two structurally novel electron-deficient building blocks and highlights the effectiveness of dual functionalization of PhAs with strong electron-withdrawing groups for devising n-type polymers.

Diselenophene-Dithioalkylthiophene Based Quinoidal Small Molecules for Ambipolar Organic Field Effect Transistors

This work presents a series of novel quinoidal organic semiconductors based on diselenophene-dithioalkylthiophene (DSpDST) conjugated cores with various side-chain lengths (-thiohexyl, -thiodecyl, and -thiotetradecyl, designated DSpDSTQ-6, DSpDSTQ-10, and DSpDSTQ-14, respectively). The purpose of this research is to develop solution-processable organic semiconductors using dicyanomethylene end-capped organic small molecules for organic field effect transistors (OFETs) application. The physical, electrochemical, and electrical properties of these new DSpDSTQs are systematically studied, along with their performance in OFETs and thin film morphologies. Additionally, the molecular structures of DSpDSTQ are determined through density functional theory (DFT) calculations and single-crystal X-ray diffraction analysis. The results reveal the presence of intramolecular S (alkyl)···Se (selenophene) interactions, which result in a planar SR-containing DSpDSTQ core, thereby promoting extended π-orbital interactions and efficient charge transport in the OFETs. Moreover, the influence of thioalkyl side chain length on surface morphologies and microstructures is investigated. Remarkably, the compound with the shortest thioalkyl chain, DSpDSTQ-6, demonstrates ambipolar carrier transport with the highest electron and hole mobilities of 0.334 and 0.463 cm2 V-1 s-1 , respectively. These findings highlight the excellence of ambipolar characteristics of solution-processable OFETs based on DSpDSTQs even under ambient conditions.

Insight into the effect of side chains on thermal transport of organic semiconductors

Understanding the correlation mechanism of side chains on thermal transport of organic semiconductors is crucial for functionalized organic electronics. In this study, phenyl and alkyl side chains, two representatives of side chain engineering, are chosen to modify dinaphtho-[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT) to synthesize Ph-DNTT and C10-DNTT. The thermal conductivities of the three organic semiconductors exhibit obvious anisotropy, and the corresponding relationships are along-chain > inter-chain > cross-chain. The phenyl side chains enhance the thermal conductivity in the along-chain direction and degrade it in the inter-chain direction, while the alkyl side chains hinder thermal transport. In the cross-chain direction, side chains have a slight effect on thermal transport. The structure orientation consistency between the phenyl side chains and the main chains in Ph-DNTT leads to phonon coupling in the along-chain direction, which improves phonon transport. In the inter-chain direction, the combined effect of the phonon group velocity and phonon participation ratio causes the thermal conductivity degeneracy of Ph-DNTT. For C10-DNTT, the vibrational mismatch between the alkyl side chains and the main chains results in the degradation of thermal transport in the along-chain and inter-chain directions. In the cross-chain direction, the nonbonding interaction dominates the energy transfer in the three organic semiconductors, which induces inferior phonon transport properties and weak effects of side chains.

Electric-Field Effects on the Internal Charge Reorganization Energies of Crystalline Organic Semiconductors

The synergistic effects of molecular packing and external electric fields (EEFs, including axial and nonaxial fields) on the internal charge reorganization energies (λ) of typical p-type SMOS have been investigated. Combined quantum and molecular mechanics calculations show that, for all-ring-fused rigid molecules single-molecule approximation and neglect of EEFs are adequate for computing λ, while for nonrigid molecules with inter-ring carbon-carbon (IRCC) linkers, the above simplifications may cause a significant deviation from the actual λ. For nonrigid molecules, solid-state packing can prevent "bad" EEFs (Fz and Fyz) from enhancing λ (adverse to charge transfer), while it allows λ to be greatly reduced (in favor of charge transfer) if "good" EEFs (Fx, Fxy, Fxz and Fxyz) are imposed. Last, a simple strategy that can divide λ into each subring contribution for IRCC-linked molecules has been proposed.

Asymmetrically Functionalized Electron-Deficient π-Conjugated System for Printed Single-Crystalline Organic Electronics

Large-area single-crystalline thin films of n-type organic semiconductors (OSCs) fabricated via solution-processed techniques are urgently demanded for high-end electronics. However, the lack of molecular designs that concomitantly offer excellent charge-carrier transport, solution-processability, and chemical/thermal robustness for n-type OSCs limits the understanding of fundamental charge-transport properties and impedes the realization of large-area electronics. The benzo[de]isoquinolino[1,8-gh]quinolinetetracarboxylic diimide (BQQDI) π-electron system with phenethyl substituents (PhC2 -BQQDI) demonstrates high electron mobility and robustness but its strong aggregation results in unsatisfactory solubility and solution-processability. In this work, an asymmetric molecular design approach is reported that harnesses the favorable charge transport of PhC2 -BQQDI, while introducing alkyl chains to improve the solubility and solution-processability. An effective synthetic strategy is developed to obtain the target asymmetric BQQDI (PhC2 -BQQDI-Cn ). Interestingly, linear alkyl chains of PhC2 -BQQDI-Cn (n = 5-7) exhibit an unusual molecular mimicry geometry with a gauche conformation and resilience to dynamic disorders. Asymmetric PhC2 -BQQDI-C5 demonstrates excellent electron mobility and centimeter-scale continuous single-crystalline thin films, which are two orders of magnitude larger than that of PhC2 -BQQDI, allowing for the investigation of electron transport anisotropy and applicable electronics.

Tetraazacoronenes and Their Dimers, Trimers and Tetramers

Tetraazacoronenes were synthesized from bay-functionalized tetraazaperylenes by Zr-mediated cyclization and four-fold Suzuki-Miyaura cross coupling. In the Zr-mediated approach, an η4 -cyclobutadiene-zirconium(IV) complex was isolated as an intermediate to cyclobutene-annulated derivatives. Using bis(pinacolatoboryl)vinyltrimethylsilane as a C2 building block gave the tetraazacoronene target compound along with the condensed azacoronene dimer as well as higher oligomers. The series of extended azacoronenes show highly resolved UV/Vis absorption bands with increased extinction coefficients for the extended aromatic cores and fluorescence quantum yields of up to 80 % at 659 nm.

N-Type Doping of Naphthalenediimide-Based Random Donor-Acceptor Copolymers to Enhance Transistor Performance and Structural Crystallinity

An integrated strategy of molecular design and conjugated polymer doping is proposed to improve the electronic characteristics for organic field effect transistor (OFET) applications. Here, a series of soluble naphthalene diimide (NDI)-based random donor-acceptor copolymers with selenophene π-conjugated linkers and four acceptors with different electron-withdrawing strengths (named as rNDI-N/S/NN/SS) are synthesized, characterized, and used for OFETs. N-type doping of NDI-based random copolymers using (12a,18a)-5,6,12,12a,13,18,18a,19-octahydro-5,6-dimethyl-13,18[1',2']-benzenobisbenzimidazo[1,2-b:2',1'-d]benzo[i][2.5]benzodiazocine potassium triflate adduct (DMBI-BDZC) is successfully demonstrated. The undoped rNDI-N, rNDI-NN, and rNDI-SS samples exhibit ambipolar charge transport, while rNDI-S presents only a unipolar n-type characteristic. Doping with DMBI-BDZC significantly modulates the performance of rNDI-N/S OFETs, with a 3- to 6-fold increase in electron mobility (μ_e) for 1 wt % doped device due to simultaneous trap mitigation, lower contact resistance (R_C), and activation energy (E_A), and enhanced crystallinity and edge-on orientation for charge transport. However, the doping of intrinsic pro-quinoidal rNDI-NN/SS films exhibits unchanged or even reduced device performance. These findings allow us to manipulate the energy levels by developing conjugated copolymers based on various acceptors and quinoids and to optimize the dopant-polymer semiconductor interactions and their impacts on the film morphology and molecular orientation for enhanced charge transport.

Recent Research Progress of Organic Small-Molecule Semiconductors with High Electron Mobilities

Organic electronics has made great progress in the past decades, which is inseparable from the innovative development of organic electronic devices and the diversity of organic semiconductor materials. It is worth mentioning that both of these great advances are inextricably linked to the development of organic high-performance semiconductor materials, especially the representative n-type organic small-molecule semiconductor materials with high electron mobilities. The n-type organic small molecules have the advantages of simple synthesis process, strong intermolecular stacking, tunable molecular structure, and easy to functionalize structures. Furthermore, the n-type semiconductor is a remarkable and important component for constructing complementary logic circuits and p-n heterojunction structures. Therefore, n-type organic semiconductors play an extremely important role in the field of organic electronic materials and are the basis for the industrialization of organic electronic functional devices. This review focuses on the modification strategies of organic small molecules with high electron mobility at molecular level, and discusses in detail the applications of n-type small-molecule semiconductor materials with high mobility in organic field-effect transistors, organic light-emitting transistors, organic photodetectors, and gas sensors.

Electron-Deficient Benzo[de]isoquinolino[1,8-gh]quinoline Diamide π-Electron Systems

Synthetically versatile electron-deficient π-electron systems are urgently needed for organic electronics, yet their design and synthesis are challenging due to the low reactivity from large electron affinities. In this work, we report a benzo[de]isoquinolino[1,8-gh]quinoline diamide (BQQDA) π-electron system. The electron-rich condensed amide as opposed to the generally-employed imide provides a suitable electronic feature for chemical versatility to tailor the BQQDA π-electron system for various electronic applications. We demonstrate an effective synthetic method to furnish the target BQQDA parent structure, and highly selective functionalization can be performed on bay positions of the π-skeleton. In addition, thionation of BQQDA can be accomplished under mild conditions. Fine-tuning of fundamental properties and supramolecular packing motifs are achieved via chemical modifications, and the cyanated BQQDA organic semiconductor demonstrates a high air-stable electron-carrier mobility.

Facile Synthesis of Bis-pentafluoroarylated Anthracene Derivatives for N-type Organic-Field-Effect Transistor Applications

Diphenylanthracene (DPA) and its derivatives are promising semiconducting materials for p-type organic-field-effect transistors (OFETs). In this study, to develop n-type semiconducting materials with an anthracene core, pentafluorobenzene was introduced into anthracene by C-H direct arylation, enabling the synthesis of various bis(pentafluorophenyl)anthracene (DPA-F) derivatives. The high reactivity of the pentafluorobenzene C-H bond allows direct arylation for synthesizing DPA-F derivatives in a single step. The introduction of strong electron-withdrawing pentafluorophenyl groups provides the anthracene derivatives with n-type semiconducting properties, in contrast to the p-type properties of the parent DPAs. Among the synthesized compounds, 2,6-bis(pentafluorophenyl)anthracene shows a high electron mobility of 0.12±0.02 cm² /Vs and an on/off ratio>10⁶ in OFETs. The high crystallinity results in the smooth electron transport. This study provides a facile synthetic method for n-type semiconducting materials and insights into the molecular design of the positional effects of aromatic substituents on anthracene.

Diazazethrene bisimide: a strongly electron-accepting π-system synthesized via the incorporation of both imide substituents and imine-type nitrogen atoms into zethrene

The development of highly electron-accepting π-systems is a fundamentally challenging issue despite their potential applications as high-performance n-type organic semiconductors, organic rechargeable batteries, and stable redox-active organocatalysts. Herein, we demonstrate that the incorporation of both imide substituents and imine-type nitrogen atoms into zethrene affords the strongly electron-accepting π-system diazazethrene bisimide (DAZBI). DAZBI has a low-lying LUMO (-4.3 eV vs. vacuum) and is readily reduced by the weak reductant l-ascorbic acid to afford the corresponding dihydro species. The injection of two electrons into DAZBI provides the corresponding dianion. These reduced species display remarkable stability, even under ambient conditions, and an intense red fluorescence. A DAZBI dimer, which was also synthesized, effectively accommodated four electrons upon electron injection.

Quantitative Prediction of Charge Mobilities and Theoretical Insight into the Regulation of Site-Specific Trifluoromethylethynyl Substitution to Electronic and Charge Transport Properties of 9,10-Anthraquinone

Herein, we systematically studied the electronic and conducting properties of 9,10-anthraquinone (AQ) and its derivatives and discussed the substitute-site effects on their organic field-effect transistor (OFET) properties in detail. Our calculation results show the influence of different substitute sites on the ionization potential (IP), electronic affinity (EA), reorganization energy (λ), electronic couplings (V), and anisotropic mobility (μ) of semiconducting materials, which mainly originates from the variations of the frontier molecular orbital charge distributions, the steric hindrance, and the conjugate degree. Combining quantum-chemical calculations with charge transfer theory, we simulated the intermolecular hopping rate in the organic crystals of AQ derivatives and predicted the fluctuation range of three-dimensional (3D) anisotropic charge carrier mobility for the first time. Our calculation results well reproduced the experimental observations and provided evidence for the determination of the optimal OFET conduction plane and channel direction relative to the crystal axis.

Solution-Processed Isoindigo- and Thienoisoindigo-Based Donor-Acceptor-Donor π-Conjugated Small Molecules: Synthesis, Morphology, Molecular Packing, and Field-Effect Transistor Characterization

Molecular design and precise control of thin-film morphology and crystallinity of solution-processed small molecules are important for enhancing charge transport mobility of organic field-effect transistors and gaining more insight into the structure-property relationship. Here, two donor-acceptor-donor (D-A-D) architecture small molecules TRA-IID-TRA and TRA-TIID-TRA comprising an electron-donating triarylamine (TRA) and two different electron-withdrawing cores, isoindigo (IID) and thienoisoindigo (TIID), respectively, were synthesized and characterized. Replacing the phenylene rings of central IID A with thiophene gives a TIID core, which reduces the optical band gap and upshifts the energy levels of frontier molecular orbitals. The single-crystal structures and grazing-incidence wide-angle X-ray scattering (GIWAXS) analysis revealed that TRA-TIID-TRA exhibits the relatively tighter π-π stacking packing with preferential edge-on orientation, larger coherence length, and higher crystallinity due to the noncovalent S···O/S···π intermolecular interactions. The distinctly oriented and connected ribbon-like TRA-TIID-TRA crystalline film by the solution-shearing process achieved a superior hole mobility of 0.89 cm² V^-1 s^-1 in the organic field-effect transistor (OFET) device, which is at least five times higher than that (0.17 cm² V^-1 s^-1) of TRA-IID-TRA with clear cracks. Eventually, rational modulation of fused core in the π-conjugated D-A-D small molecule provides a new understanding of structural design for enhancing the performance of solution-processed organic semiconductors.

Crystal structure of the cocrystal 2,4,6-triamino-1,3,5-triazine – 1H-isoindole-1,3(2H)-dione – methanol (1/1/1), C12H15N7O3

C12H15N7O3, P21/c (no. 14), a = 7.1782(3) Å, b = 16.6800(6) Å, c = 12.1070(5) Å, β = 92.030(2)°, V = 1448.69(10) Å3, Z = 4, Rgt (F) = 0.0449, wRref (F 2) = 0.1220, T = 296(2) K.

Materials nanoarchitectonics in a two-dimensional world within a nanoscale distance from the liquid phase

Promoted understanding of nanotechnology has enabled the construction of functional materials with nanoscale-regulated structures. Accordingly, materials science requires one-step further innovation by coupling nanotechnology with the other materials sciences. As a post-nanotechnology concept, nanoarchitectonics has recently been proposed. It is a methodology to architect functional material systems using atomic, molecular, and nanomaterial unit-components. One of the attractive methodologies would be to develop nanoarchitectonics in a defined dimensional environment with certain dynamism, such as liquid interfaces. However, nanoarchitectonics at liquid interfaces has not been fully explored because of difficulties in direct observations and evaluations with high-resolutions. This unsatisfied situation in the nanoscale understanding of liquid interfaces may keep liquid interfaces as unexplored and attractive frontiers in nanotechnology and nanoarchitectonics. Research efforts related to materials nanoarchitectonics on liquid interfaces have been continuously made. As exemplified in this review paper, a wide range of materials can be organized and functionalized on liquid interfaces, including organic molecules, inorganic nanomaterials, hybrids, organic semiconductor thin films, proteins, and stem cells. Two-dimensional nanocarbon sheets have been fabricated by molecular reactions at dynamically moving interfaces, and metal-organic frameworks and covalent organic frameworks have been fabricated by specific interactions and reactions at liquid interfaces. Therefore, functions such as sensors, devices, energy-related applications, and cell control are being explored. In fact, the potential for the nanoarchitectonics of functional materials in two-dimensional nanospaces at liquid surfaces is sufficiently high. On the basis of these backgrounds, this short review article describes recent approaches to materials nanoarchitectonics in a liquid-based two-dimensional world, i.e., interfacial regions within a nanoscale distance from the liquid phase.

Donor-Acceptor Hybrid Heterostructures: An Emerging Class of Photoactive Materials with Inorganic and Organic Semiconductive Components

Just as the heterojunctions in physics, donor-acceptor (D-A) heterostructures are an emerging class of photoactive materials fabricated from two semiconductive components at the molecular level. Among them, D-A hybrid heterostructures from organic and inorganic semiconductive components have attracted extensive attention in the past decades due to their combined advantages of high stability for the inorganic semiconductors and modifiability for the organic semiconductors, which are particularly beneficial to efficiently achieve photoinduced charge separation and transfer upon irradiations. In this review, by analogy with the heterojunctions in physics, a definition of the D-A heterostructures and their general design and synthetic strategies are given. Meanwhile, the D-A hybrid heterostructures are focused on and their recent advances in potential applications of photochromism, photomodulated luminescence, and photocatalysis summarized.