Bismuth-containing functional polymers: Molecular design strategies and synthetic challenges

2D molecular crystals (2DMCs) have attracted considerable attention because of their unique optoelectronic properties and potential applications. Taking advantage of the solution processability of organic semiconductors, solution self-assembly is considered an effective way to grow large-area 2DMCs. However, this route is largely blocked because a precise molecular design towards 2DMCs is missing and little is known about the relationship between 2D solution self-assembly and molecular structure. A "phase separation" molecular design strategy towards 2DMCs is proposed and layer-by-layer growth of millimeter-sized monolayer or few-layer 2DMCs is realized. High-performance organic phototransistors are constructed based on the 2DMCs with unprecedented photosensitivity (2.58 × 107 ), high responsivity (1.91 × 104 A W-1 ), and high detectivity (4.93 × 1015 Jones). This "phase separation" molecular design strategy provides a guide for the design and synthesis of novel organic semiconductors that self-assemble into large-area 2DMCs for advanced organic (opto)electronics.

Multiresonant thermally activated delayed fluorescence (MR‐TADF) materials have emerged as next‐generation OLED emitters owing to their narrowband emission, high color purity, and potential for 100% exciton utilization. Among the various MR‐TADF scaffolds, carbonyl/nitrogen‐based, quinolino[3,2,1‐de]acridine‐5,9‐dione (QAO) cores have attracted significant attention due to their modularity and electronic tunability. This review article presents a systematic analysis of recent advancements in QAO‐based emitters, categorized into three molecular design strategies: core locking, core substitution, and core extension. Core locking enhances rigidity, minimizes vibrational loss, and narrows emission profiles critically mandated by blue‐emitting MR‐TADF systems. Substitution at key positions enables fine control over emission wavelength, Δ E ST , and photoluminescence quantum yield (Φ PL ). Core extension via π ‐conjugation elongation or fused aromatic units leads to improved device efficiencies and diverse emission colors, including green and deep‐blue electroluminescence. Collectively, these strategies have produced emitters with Φ PL exceeding 90%, EQEs above 30%, and full‐width half maximums as low as 20 nm. We conclude by highlighting current limitations, including RISC bottlenecks, doping concentration effects, and synthetic challenges, while proposing design pathways toward next‐generation multifunctional, solution‐processable, and chiral MR‐TADF materials. This review article provides a roadmap for advancing carbonyl‐nitrogen based MR‐TADF emitters toward high‐performance OLED technologies.

Generally, different isoforms of proteins exert separate biological functions. However, due to similar structures and identical catalysis functions, distinguishing isoforms is challenging. Summarizing a molecular design strategy has great significance in developing a protein-specific fluorescent probe. Usually, recognition of a group was deemed to be the key to a protein isoform-specific response. However, some novel literature reported that fluorophore could play a vital role in the protein isoform-specific response. It means that any part of the fluorescent probe could affect the detected properties. In this work, we report the generation of the first probe to specifically recognize HexA(β-N-acetylhexosaminidase A), Hex-C4, by adjusting the length of the linker. Hex-C4 exhibits specific recognition of HexA both in vitro and in living cells. The integration of the fluorescent spectrum and the MD (molecular dynamics) results provide two factors for the molecular design of isoform-specific fluorescent probes. One is the interaction between tetraphenyl ethylene (AIE fluorogen) and amino acid residues, and the other is the interaction between amino acid residues and the binding group. In this work, a powerful tool to detect HexA in living cells is reported for the first time. Further, a workable molecular design strategy for protein isoform-specific fluorescent probes is summarized.

Recent Advances in Molecular Design of Organic Thermoelectric Materials

Molecular design of ternary copolymers with high photothermal performance in the near-infrared window for effective treatment of gliomas in vivo.

The excited-state manipulation of the phosphorescent iridium(III) complexes plays a vital role in their photofunctional applications. The development of the molecular design strategy promotes the creative findings of novel iridium(III) complexes. The current molecular design strategies for iridium(III) complexes mainly depend on the selective cyclometalation of the ligands with the iridium(III) ion, which is governed by the steric hindrance of the ligand during the cyclometalation. Herein, a new molecular design strategy (i.e., random cyclometalation strategy) is proposed for the effective excited-state manipulation of phosphorescent cyclometalated iridium(III) complexes. Two series of new and separable methoxyl-functionalized isomeric iridium(III) complexes are accessed by a one-pot synthesis via random cyclometalation, resulting in a dramatic tuning of the phosphorescence peak wavelength (∼57 nm) and electrochemical properties attributed to the high sensitivity of their excited states to the position of the methoxyl group. These iridium(III) complexes show intense phosphorescence ranging from the yellow (567 nm) to the deep-red (634 nm) color with high photoluminescence quantum yields of up to 0.99. Two deep-red emissive iridium(III) complexes with short decay lifetimes are further utilized as triplet emitters to afford efficient solution-processed electroluminescence with reduced efficiency roll-offs.

Type I photosensitizers (PSs), due to reduced dependence on O2, have outstanding prospects for cancer treatment. However, it is difficult to manipulate electron transfer of molecules during excited state transitions (T1-S0), which makes it a challenging task to systematically create type I PSs, especially with a deficiency of an instructive molecular construction strategy. Herein, for the first time, we proposed the "electron reservoir-pump-integrated" molecular design strategy, that is, "electron reservoir" and "electron pump" were dexterously fused in one appropriate dye, which greatly facilitated the creation of type I PS molecules through the manipulation of spatial electron flow (verified by the density functional theory and spectral experiments). On this basis, we constructed a series of organic small-molecule type I PSs; especially, the prominent type I PS Cy5-NF could specifically produce a large amount of O2•- under 660 nm laser irradiation. Notably, without the sulfonic acid groups (electron reservoir) or the electron-withdrawing group (electron pump), both derivatives of Cy5-NF are unable to generate O2•-, which fully validated the above strategy. More encouragingly, Cy5-NF could effectively destroy cytomembranes under irradiation and further lead to pyroptosis of tumor cells, which not only ablated the primary/distant tumors but also halted tumor metastasis to the different organs via enhancing CD4+ and CD8+ T cell infiltration-mediated long-term immunological memory. Notably, the "electron reservoir-pump-integrated" strategy represents a kind of modular approach for constructing organic small-molecule type I PSs, potentially offering valuable guidance for future type I PS development.

Photoactive molecules that reversibly switch upon visible light irradiation are one of the most attractive targets for biological as well as imaging applications. One possible approach to prepare such photoswitches is to extend π-conjugation length of molecules and shift the absorption bands to longer wavelengths. Although several attempts have been demonstrated based on this approach for diarylethene (DAE) photoswitches, photoreactivity of the DAE derivatives is dramatically suppressed when the conjugation length is extended by connecting aromatic dyes at the side positions of aryl groups in the DAE unit. In this study, we successfully prepared a visible-light reactive DAE derivative by introducing an aromatic dye at the reactive carbon atom of the DAE unit, optimizing orbital level of each component, and controlling the mutual orientation of the aromatic dye and the DAE unit. The DAE derivative (3) undergoes a photocyclization reaction upon irradiation with 560 nm light and the closed-isomer converts to the open-ring isomer upon irradiation with 405 nm light. The high photoconversion yields (>90%) were achieved for both photocyclization and photocycloreversion reactions. The photoreactivity induced by visible light irradiation and the molecular design strategy were discussed based on theoretical calculations.

Atomically dispersed Zn moieties are efficient active sites for accelerating the electrode kinetics of carbons for sodium-ion hybrid capacitors (SIHCs), but the low utilization and symmetric configuration of Zn single-atom greatly hamper the Na ion storage capability. Herein, a molecular design strategy is employed to synthesize high-density Zn single atoms with asymmetric Zn-N3 S coordination embedded in nitrogen/sulfur codoped carbon (Zn-N3 S-NSC). The key to this strategy lies in the Zn power-catalyzed condensation of trithiocyanuric acid molecules to generate S-doped g-C3 N4 , which can in situ coordinate with Zn sources to form Zn-N3 S moieties during pyrolysis. By virtue of the highly exposed Zn-N3 S moieties, Zn-N3 S-NSC presents ultrahigh reactivity, efficient electron transfer, and decreased ion diffusion barriers for SIHCs, rendering an impressive energy density of 215Whkg-1 and a maximum power density of 15625 Wkg-1 . Moreover, the pouch cell displays a high capacity of 279mAhg-1 after 4000cycles. This work provides a new avenue for the regulation of the coordination configuration of single metal atoms in carbons toward high-performance electrochemical energy technologies at the molecular level.

Two-dimensional conductive metal-organic frameworks (2D c-MOFs), which feature high electrical conductivity and large charge carrier mobility, hold great promise in electronics and optoelectronics. Nevertheless, the limited solubility of commonly used planar ligands inevitably brings challenges in synthesis and purification and causes laborious coordination conditions for screening. Moreover, most reported 2D c-MOFs are polycrystalline powders with relatively low crystallinity and irregular morphology, hindering the unveiling of the detailed structure-function relationship. Herein, we developed a "rotor-stator" molecular design strategy to construct 2D c-MOFs using a delicately designed nonplanar biscarbazole ligand (8OH-DCB). Benefiting from the special "rotor-stator" structure of the ligand, crystals of Cu-DCB-MOF were successfully prepared, allowing for the precise determination of their crystal structure. Interestingly, the crystals of Cu-DCB-MOF can be obtained in various organic solvents, indicating excellent solvent compatibility. The versatility of the "rotor-stator" molecular design strategy was further demonstrated by another two new ligands with a "rotor-stator" structure, and afford corresponding 2D c-MOF crystals (Cu-DCBT-MOF and Cu-DCBBT-MOF). The current work presents a facile approach toward the rational design and direct construction of highly crystalline 2D c-MOFs using nonplanar ligands.

Recent molecular design strategies for efficient photodynamic therapy and its synergistic therapy based on AIE photosensitizers

The development of high-performance blue organic light-emitting diodes (OLEDs) is impeded by the scarcity of molecular scaffolds for ultranarrow multiple-resonance thermally activated delayed fluorescence (MR-TADF) emitters and their inherent tendency to suffer from aggregation-induced broadening and quenching in solid films. To intrinsically address these dual challenges, we report a "soft constraints" molecular design strategy that strategically enhances intramolecular noncovalent interactions. By appending tailored donor (carbazole) or acceptor (triazine) units to the MR-TADF core, this architecture not only directly suppresses key high-frequency vibrations (e.g., C─N stretching) to achieve an impressively narrow emission with a full width at half-maximum (FWHM) of 19nm in solution, but also effectively inhibits detrimental π…π stacking between the emissive cores. The resulting emitters Cz‑TBN and TRZ‑TBN retain ultranarrow emission (FWHM ≈ 23nm) and high external quantum efficiencies (up to 40.5%) in OLEDs across a broad doping range (1-10 wt%); theTRZ‑TBNdevice also reaches a record power efficiency (67.9lmW-1) for blue MR-OLEDs. This work offers a generalizable strategy for the rational design of high-performance blue emitters.

ConspectusPolymer-based organic field-effect transistors (OFETs) have attracted great attention owing to their significantly improved performance and the recently emerged prospects for broad applications. The charge carrier mobility of polymer-based OFETs has been improved from 10–5 to more than 10 cm2 V–1 s–1 over the past three decades. With the carrier mobility close to or higher than that of amorphous silicon, the application fields of polymer-based OFETs have been extended from sensing to logic or drive circuits. During OFET operation, the charge carriers are successively injected in and then transferred across the semiconducting channel under an external electric field. The behavior of the charge carriers is determined by both charge injection and charge transport. Well-matched frontier molecular orbital (FMO) energy levels and optimized hierarchical structures of semiconducting polymers are essential for the realization of high-performance polymer-based OFETs.In this Account, we mainly demonstrate our recent progress in molecular design strategies and fabrication processing methods for high-performance semiconducting polymers. Moreover, we provide some examples of integrated applications of polymer-based OFETs. The convenient FMO energy level modulation and excellent molecular designability of donor–acceptor (D–A) conjugated polymers facilitate studies on their performance enhancement in OFETs. Proper molecular design of the D–A polymer backbone and side chain can significantly contribute to charge injection enhancement, transport pathway establishment, and trap reduction, thereby resulting in efficient charge transport. Moreover, special fabrication processes of OFET devices can further enhance the charge transport by optimizing the hierarchical structures of semiconducting polymers, thereby enhancing their carrier mobility and stability. By employing high-performance semiconducting polymers as the semiconducting channel of OFETs, various applications can be implemented. These applications range from small-scale logic signal processing and periodic signal generation to complex visual perception systems, indicating broad application prospects in human life. The works on performance improvement and functional utilization of the semiconducting polymers in OFETs might provide insights for molecular design strategies and applications for future plastic electronics.

Electrostatic interactions between biological molecules are crucially influenced by their aqueous environment, with efficient and accurate models of solvent effects required for robust molecular design strategies. Continuum electrostatic models provide a reasonable balance between computational efficiency and accurate system representation. In this article, I review two specific molecular design strategies, charge optimization and combinatorial design, paying particular attention to how the continuum framework (also briefly described herein) successfully enables both theoretical insights and molecular designs and presents a challenge in design applications due to what I call “the isostericity constraint.” Efforts to work around the isostericity constraint and other challenges are discussed. Additionally, particular emphasis is placed on using such models in the rational design of particularly tight, specific, or promiscuous interactions, in keeping with the increased sophistication of current molecular design applications.

Organic persistent luminescence (pL) systems with photoresponsive dynamic features have valuable applications in the fields of data encryption, anticounterfeiting, and bioimaging. Photoinduced radical luminescent materials have a unique luminous mechanism with the potential to achieve dynamic pL. It is extremely challenging to obtain radical pL under ambient conditions; on account of it, it is unstable in air. Herein, a new semialiphatic polyimide-based polymer (A0) is developed, which can achieve dynamic pL through reversible conversion of radical under photoexcitation. A "joint-donor-spacer-acceptor" molecular design strategy is applied to effectively modulate the intramolecular charge-transfer and charge-transfer complex interactions, resulting in effective protection of the radical generated under photoirradiation. Meanwhile, polyimide-based polymers of A1-A4 are obtained by doping different amine-containing fluorescent dyes to modulate the dynamic afterglow color from green to red via the triplet to singlet Förster resonance energy-transfer pathway. Notably, benefiting from the structural characteristics of the polyimide-based polymer, A0-A4 have excellent processability, thermal stability, and mechanical properties and can be applied directly in extreme environments such as high temperatures and humidity.