Charge and Spin Transport in an Organic Molecular Square

Understanding electronic communication among multiple chromophoric and redox units requires construction of well‐defined molecular architectures. Herein, we report the modular synthesis of a shape‐persistent chiral organic square composed of four naphthalene‐1,8:4,5‐bis(dicarboximide) (NDI) sides and four trans‐1,2‐cyclohexanediamine corners. Single crystal X‐ray diffraction reveals some distortion of the cyclohexane chair conformation in the solid state. Analysis of the packing of the molecular squares reveals the formation of highly ordered, one‐dimensional tubular superstructures, held together by means of multiple [C H⋅⋅⋅OC] hydrogen‐bonding interactions. Steady‐state and time‐resolved electronic spectroscopies show strong excited‐state interactions in both the singlet and triplet manifolds. Electron paramagnetic resonance (EPR) and electron‐nuclear double resonance (ENDOR) spectroscopies on the monoreduced state reveal electron sharing between all four NDI subunits comprising the molecular square.     

A Unique Blend of 2‐Fluorenyl‐2‐anthracene and 2‐Anthryl‐2‐anthracence Showing White Emission and High Charge Mobility

White‐light‐emitting materials with high mobility are necessary for organic white‐light‐emitting transistors, which can be used for self‐driven OLED displays or OLED lighting. In this study, we combined two materials with similar structures—2‐fluorenyl‐2‐anthracene (FlAnt) with blue emission and 2‐anthryl‐2‐anthracence (2A) with greenish‐yellow emission—to fabricate OLED devices, which showed unusual solid‐state white‐light emission with the CIE coordinates (0.33, 0.34) at 10 V. The similar crystal structures ensured that the OTFTs based on mixed FlAnt and 2A showed high mobility of 1.56 cm² V⁻¹ s⁻¹. This simple method provides new insight into the design of high‐performance white‐emitting transistor materials and structures.     

Significant Difference in Semiconducting Properties of Isomeric All‐Acceptor Polymers Synthesized via Direct Arylation Polycondensation

The direct arylation polycondensation (DArP) appeared as an efficient method for producing semiconducting polymers but often requires acceptor monomers with orienting or activating groups for the reactive carbon‐hydrogen (C‐H) bonds, which limits the choice of acceptor units. In this study, we describe a DArP for producing high‐molecular‐weight all‐acceptor polymers composed of the acceptor monomers without any orienting or activating groups via a modified method using Pd/Cu co‐catalysts. We thus obtained two isomeric all‐acceptor polymers, P1 and P2, which have the same backbone and side‐chains but different positions of the nitrogen atoms in the thiazole units. This subtle change significantly influences their optoelectronic, molecular packing, and charge‐transport properties. P2 with a greater backbone torsion has favorable edge‐on orientations and a high electron mobility μ_e of 2.55 cm² V^?1 s^?1. Moreover, P2‐based transistors show an excellent shelf‐storage stability in air even after the storage for 1 month.     

Analysis of Molecular Orientation in Organic Semiconducting Thin Films Using Static Dynamic Nuclear Polarization Enhanced Solid‐State NMR Spectroscopy

Molecular orientation in amorphous organic semiconducting thin‐film devices is an important issue affecting device performance. However, to date it has not been possible to analyze the “distribution” of the orientations. Although solid‐state NMR (ssNMR) spectroscopy can provide information on the “distribution” of molecular orientations, the technique is limited because of the small amount of sample in the device and the low sensitivity of ssNMR. Here, we report the first application of dynamic nuclear polarization enhanced ssNMR (DNP‐ssNMR) spectroscopy for the orientational analysis of amorphous phenyldi(pyren‐1‐yl)phosphine oxide (POPy₂). The ³¹P DNP‐ssNMR spectra exhibited a sufficient signal‐to‐noise ratio to quantify the distribution of molecular orientations in amorphous films: the P=O axis of the vacuum‐deposited and drop‐cast POPy₂ shows anisotropic and isotropic distribution, respectively. The different molecular orientations reflect the molecular origin of the different charge transport behaviors.     

4,5,9,10‐Pyrene Diimides: A Family of Aromatic Diimides Exhibiting High Electron Mobility and Two‐Photon Excited Emission

The design and synthesis of high‐performance n‐type organic semiconductors are important for the development of future organic optoelectronics. Facile synthetic routes to reach the K‐region of pyrene and produce 4,5,9,10‐pyrene diimide (PyDI) derivatives are reported. The PyDI derivatives exhibited efficient electron transport properties, with the highest electron mobility of up to 3.08 cm² V⁻¹ s⁻¹. The tert‐butyl‐substituted compounds (t‐PyDI) also showed good one‐ and two‐photon excited fluorescence properties. The PyDI derivatives are a new family of aromatic diimides that may exhibit both high electron mobility and good light‐emitting properties, thus making them excellent candidates for future optoelectronics.     

Indandione-Terminated Quinoids: Facile Synthesis by Alkoxide-Mediated Rearrangement Reaction and Semiconducting Properties

A series of 1,3-indandione-terminated π-conjugated quinoids were synthesized by alkoxide-mediated rearrangement reaction of the respective alkene precursors, followed by air oxidation. This new protocol allows access to quinoidal compounds with variable termini and cores. The resulting quinoids all show LUMO levels below −4.0 eV and molar extinction coefficients above 10⁵ L mol⁻¹ cm⁻¹. The optoelectronic properties of these compounds can be regulated by tuning the central cores as well as the aryl termini ascribed to the delocalized frontier molecular orbitals over the entire molecular skeleton involving aryl termini. n-Channel organic thin-film transistors with electron mobility of up to 0.38 cm² V⁻¹ s⁻¹ were fabricated, showing the potential of this new class of quinoids as organic semiconductors.     

Layer‐Defining Strategy to Grow Two‐Dimensional Molecular Crystals on a Liquid Surface down to the Monolayer Limit

Two‐dimensional molecular crystals (2DMCs) open a new door for the controllable growth of 2D materials by molecular design with a energy gap and solution processability. However, the growth of 2DMCs with defined molecular layers remains full of challenges. Herein, we report a novel method to produce various 2DMCs with a defined number of molecular layers. When the surface tension and viscosity are tuned to control the spreading of the solution on the liquid surface, large‐area quasi‐freestanding 2DMCs from bulk size down to the monolayer limit are obtained, which makes it possible to probe the intrinsic layer‐dependent optoelectronic properties of organic semiconductors down to the physical limit, and paves the way for the application of 2DMCs in new optoelectronic devices and technologies.     

A Corrole-Based Covalent Organic Framework Featuring Desymmetrized Topology

Herein, for the first time, we present the successful synthesis of a novel two-dimensional corrole-based covalent organic framework (COF) by reacting the unusual approximately T-shaped 5,10,15-tris(p-aminophenyl)corrole H₃TPAPC with terephthalaldehyde, which adopts desymmetrized hcb topology and consists of a staggered AB stacking structure with elliptical pores. The resultant corrole-based COF, TPAPC-COF , exhibits high crystallinity and excellent chemical stability. The combination of extended π-conjugated backbone and interlayer noncovalent π–π interactions endows TPAPC-COF with excellent absorption capability in the entire visible-light and even near-infrared regions. Moreover, this work suggests the promise of TPAPC-COF as a new class of photoactive material for efficient singlet-oxygen generation with potential photodynamic therapy application as demonstrated by in vitro anticancer studies.     

BowtieArene: A Dual Macrocycle Exhibiting Stimuli-Responsive Fluorescence

Although highly useful in supramolecular chemistry, pillararenes lack a fluorophore in their skeleton. Here we present BowtieArene, a novel fluorescent dual macrocycle, featuring a central tetraphenylethylene-derived fluorophore and two pillar-like, pentagon-shaped cavities which are comparable to pillar[5]arene. This concisely prepared, figure-of-eight molecule exhibits vapor absorption and host–guest capabilities, as well as intriguing switchable fluorescence. The fluorochromism of BowtieArene can be triggered by multiple external stimuli including solvent, vapor, and mechanical force, with excellent reversibility and stability. Experimental and theoretical evidence indicate that the fluorochromism should be closely related to molecular packing.     

Heptagon‐Embedded Pentacene: Synthesis,Structures, and Thin‐Film Transistors of Dibenzo[d,d′]benzo[1,2‐a:4,5‐a′]dicycloheptenes

This study presents a new class of conjugated polycyclic molecules that contain seven‐membered rings, detailing their synthesis, crystal structures and semiconductor properties. These molecules have a nearly flat C₆‐C₇‐C₆‐C₇‐C₆ polycyclic framework with a p‐quinodimethane core. With field‐effect mobilities of up to 0.76 cm² V⁻¹ s⁻¹ as measured from solution‐processed thin‐film transistors, these molecules are alternatives to the well‐studied pentacene analogues for applications in organic electronic devices.     

Interplay Between J‐ and H‐Type Coupling in Aggregates of π‐Conjugated Polymers: A Single‐Molecule Perspective

Strong dipole–dipole coupling within and between π‐conjugated segments shifts electronic transitions, and modifies vibronic coupling and excited‐state lifetimes. Since J‐type coupling between monomers along the conjugated‐polymer (CP) chain and H‐type coupling of chromophores between chains of a CP compete, a superposition of the spectral modifications arising from each type of coupling emerges, making the two couplings hard to discern in the ensemble. We introduce a single‐molecule H‐type aggregate of fixed spacing and variable length of up to 10 nm. HJ‐type aggregate formation is visualized intuitively in the scatter of single‐molecule spectra.     

Stable Heterometallic Cluster-Based Organic Framework Catalysts for Artificial Photosynthesis

A series of stable heterometallic Fe₂M cluster-based MOFs ( NNU-31-M , M=Co, Ni, Zn) photocatalysts are presented. They can achieve the overall conversion of CO₂ and H₂O into HCOOH and O₂ without the assistance of additional sacrificial agent and photosensitizer. The heterometallic cluster units and photosensitive ligands excited by visible light generate separated electrons and holes. Then, low-valent metal M accepts electrons to reduce CO₂, and high-valent Fe uses holes to oxidize H₂O. This is the first MOF photocatalyst system to finish artificial photosynthetic full reaction. It is noted that NNU-31-Zn exhibits the highest HCOOH yield of 26.3 μmol g⁻¹ h⁻¹ (selectivity of ca. 100 %). Furthermore, the DFT calculations based on crystal structures demonstrate the photocatalytic reaction mechanism. This work proposes a new strategy for how to design crystalline photocatalyst to realize artificial photosynthetic overall reaction.