Stereoselective gridization and polygridization with centrosymmetric molecular packing

The Unexploring Optoelectronic Features in Organic Trans-Dimensional Materials of Gridofluorenes at the Nanoscale

Organic grido-architectures offer not only state-of-the-art models for exploring the complex relationships of multicarrier coherence among excitons, charges, photons, electrons, and phonons but also organic high-dimensional nanomaterials for flexible electronics and organic intelligence. Herein, we initiate the fundamental progress and perspective on gridofluorene-based zero-, one-, two-, and three-dimensional nanomolecules and their optoelectronic features. From the future point of view, the sterically trans-dimensional and hierarchically cross-scale effects of these covalent frameworks and nanostructures are discussed on their photophysical, electrical, mechanical and thermal properties. Organic multiscale systems, with the feature of synergistically molecule-programmable integration of diverse functionalities, open a bright door to flexible electronics, intelligent molecules, devices, systems, and even organobots as well as artificially intelligent and robotic chemists (AiRCs).

Non-Conjugated Gridized Nanopolymers as an Efficient Hole-Transport Material for Blue Perovskite Light-Emitting Diodes

Despite the remarkable advancements in perovskite light-emitting diode (PeLED) technology, the development of blue PeLEDs has lagged. The primary bottleneck lies in the difficulty of finding hole transport materials (HTMs) that can both match the energy levels of blue perovskite materials and exhibit efficient hole transport performance. Herein, a novel non-conjugated polyethylene carbazole-based polymer (P-AGCz) is developed that has excellent solution processability and serves as an efficient dopant-free HTM for PeLEDs. The flexible non-conjugated polyethylene backbone of P-AGCz provides exceptional film-forming capabilities. Moreover, the A-shaped carbazole-based side chains deepen the HOMO energy level and minimize the recombination energy, enhancing its ability to inject and transport holes within PeLEDs. The PeLEDs employing P-AGCz as a low-cost, dopant-free polymer HTM have attained an external quantum efficiency (EQE) of 3.26%, which is 1.54 times greater than poly(N-vinylcarbazole) (PVK)-based devices, with a brightness enhancement of 584 cd m- 2 over the PVK-based devices. Furthermore, the P-AGCz-based devices exhibit higher current efficiency at lower driving voltages, indicating reduced energy consumption and expanded potential for future applications.

C-H-activated Csp2-Csp3 diastereoselective gridization enables ultraviolet-emitting stereo-molecular nanohydrocarbons with mulitple H···H interactions

Gridization is an emerging molecular integration technology that enables the creation of multifunctional organic semiconductors through precise linkages. While Friedel-Crafts gridization of fluorenols is potent, direct linkage among fluorene molecules poses a challenge. Herein, we report an achiral Pd-PPh3-cataylized diastereoselective (>99:1 d.r.) gridization based on the C-H-activation of fluorene to give dimeric and trimeric windmill-type nanogrids (DWGs and TWGs). These non-conjugated stereo-nanogrids showcase intramolecular multiple H…H interactions with a low field shift to 8.51 ppm and circularly polarized luminescence with high luminescent dissymmetry factors (|gPL | = 0.012). Significantly, the nondoped organic light-emitting diodes (OLEDs) utilizing cis-trans-TWG1 emitter present an ultraviolet electroluminescent peak at ~386 nm (CIE: 0.17, 0.04) with a maximum external quantum efficiency of 4.17%, marking the highest record among nondoped ultraviolet OLEDs based on hydrocarbon compounds and the pioneering ultraviolet OLEDs based on macrocycles. These nanohydrocarbon offer potential nanoscafflolds for ultraviolet light-emitting optoelectronic applications.

One-Pot Synthesis and Excited-State Dynamics of Null Exciton-Coupled Diketopyrrolopyrroles Oligo-Grids

Exciton coupling in molecular aggregates plays a vital role in impacting and fine-tuning optoelectronic materials and their efficiencies in devices. A versatile platform to decipher aggregation-property relationships is built around multichromophoric architectures. Here, a series of cyclic diketopyrrolopyrrole (DPP) oligomers featuring nanoscale gridarene structures and rigid bifluorenyl spacers are designed and synthesized via one-pot Friedel-Crafts reaction. DPP dimer [2]Grid and trimer [3]Grid, which are cyclic rigid nanoarchitectures of rather different sizes, are further characterized via steady-state and time-resolved absorption and fluorescence spectroscopies. They exhibit monomer-like spectroscopic signatures in the steady-state measurements, from which null exciton couplings are derived. Moreover, in an apolar solvent, high fluorescence quantum yields and excited-state dynamics that resembled DPP monomer are gathered. In a polar solvent, the localized singlet excited state on a single DPP dissociates into the adjacent null coupling DPP with charge transfer characteristics. This pathway facilitates the evolution of the symmetry-broken charge-separated state (SB-CS). Notable is the fact that the SB-CS of [2]Grid is, on one hand, in equilibrium with the singlet excited state and promotes, on the other hand, the formation of the triplet excited state with a yield of 32% via charge recombination.

In Situ Super-Hindrance-Triggered Multilayer Cracks for Random Lasing in π-Functional Nanopolymer Films

In situ self-assembly of semiconducting emitters into multilayer cracks is a significant solution-processing method to fabricate organic high- Q lasers. However, it is still difficult to realize from conventional conjugated polymers. Herein, we create the molecular super-hindrance-etching technology, based on the π-functional nanopolymer PG-Cz, to modulate multilayer cracks applied in organic single-component random lasers. Massive interface cracks are formed by promoting interchain disentanglement with the super-steric hindrance effect of π-interrupted main chains, and multilayer morphologies with photonic-crystal-like ordering are also generated simultaneously during the drop-casting method. Meanwhile, the enhancement of quantum yields on micrometer-thick films ( Φ = 40% to 50%) ensures high-efficient and ultrastable deep-blue emission. Furthermore, a deep-blue random lasing is achieved with narrow linewidths ~0.08 nm and high-quality factors Q ≈ 5,500 to 6,200. These findings will offer promising pathways of organic π-nanopolymers for the simplification of solution processes applied in lasing devices and wearable photonics.

Cubic Nanogrids for Counterbalance Contradiction among Reorganization Energy, Strain Energy, and Wide Bandgap

Molecular cross-scale gridization and polygridization of organic π-backbones make it possible to install 0/1/2/3-dimensional organic wide-bandgap semiconductors (OWBGSs) with potentially ZnO-like fascinating multifunctionality such as optoelectronic and piezoelectronic features. However, gridization effects are limited to uncover, because the establishment of gridochemistry still requires a long time, which offers a chance to understand the effects with a theoretical method, together with data statistics and machine learning. Herein, we demonstrate a state-of-the-art 3D cubic nanogridon with a size of ∼2 × 2 × 1.5 nm³ to examine its multigridization of π-segments on the bandgap, molecular strain energy (MSE), as well as reorganization energy (ROE). A cubic gridon (CG) consists of a four-armed bifluorene skeleton and a thiophene-containing fused arene plane with the Csp³ spiro-linkage, which can be deinstalled into face-on or edge-on monogrids. As a result, multigridization does not significantly reduce bandgaps (E_g ≥ 4.03 eV), while the MSE increases gradually from 4.72 to 23.83 kcal/mol. Very importantly, the ROE of a CG exhibits an extreme reduction down to ∼28 meV (λ⁺) that is near the thermal fluctuation energy (∼26 meV). Our multigridization results break through the limitation of the basic positively proportional relationship between reorganization energies and bandgaps in organic semiconductors. Furthermore, multigridization makes it possible to keep the ROE small under the condition of a high MSE in OWBGS that will guide the cross-scale design of multifunctional OWBGSs with both inorganics' optoelectronic performance and organics' mechanical flexibility.

Thermodynamic-dominated stereoselective meshing of molecular nano-links based on fluorenes

The path-selectivity and stereoselectivity of gridization pathways into fluorene-based Drawing Hand Grids (DHGs-F) are precisely modulated through tuning acid conditions and side-chain effects. BF3•OEt2 supports the realization of the gridization path (rac-DHG1-F, yield: 82%, meso-DHG1-F, yield: 11%). On the contrary, CF3SO3H will lead to the enhancements in polymerization pathways (about 85% yield). When the side chain is a methoxy group, rac-DHG1-F and meso-DHG1-F will be obtained. However, when the side chain is a group without an oxygen atom, only rac-DHG1-F can be obtained (de = 100%). Moreover, through excitonic physical proper-ties, rac-DHGs-F exhibits a more π-electronic delocalization, potentially serving as the intriguing tactic strategy to modulate the optoelectronic properties.

Gridization-Driven Mesoscale Self-Assembly of Conjugated Nanopolymers into Luminescence-Anisotropic Photonic Crystals

Organic semiconducting emitters integrated with butterfly-mimetic photonic crystals (PhCs) are fascinating for dramatic advantages over light outcoupling efficiency and multifunctional strain sensors, as well as the key step toward electrically pumped lasers. Herein, an unprecedentedly direct mesoscale self-assembly into 1D PhCs is reported through a covalently gridization-driven approach of wide-bandgap conjugated polymers. A simple solvent-casting procedure allows for in situ self-assembly of the state-of-the-art conjugated nanopolymer, poly{[4-(octyloxy)-9,9-diphenylfluoren-2,7-diyl]grid}-co-{[5-(octyloxy)-9,9-diphenylfluoren-2,7-diyl]grid} (PODPFG), into well-defined multilayer architectures with an excellent toughness (30-40 J m^-3 ). This ordered meso-architecture shows a typical Bragg-Snell diffraction behavior to testify the PhC nature, along with a high effective refractive index (1.80-1.88) and optical transmittance (85-87%). The PhC films also exhibit an angle-dependent blue/green photoluminescence switching, an electroluminescence efficiency enhancement by 150-250%, and an amplified spontaneous emission enhancement with ultralow waveguide loss coefficient (2.60 cm^-1 ). Gridization of organic semiconductors offers promising opportunities for cross-scale morphology-directed molecular design in multifunctional organic mechatronics and intelligences.

Cross-Scale Synthesis of Organic High-k Semiconductors Based on Spiro-Gridized Nanopolymers

High dielectric constants in organic semiconductors have been identified as a central challenge for the improvement in not only piezoelectric, pyroelectric, and ferroelectric effects but also photoelectric conversion efficiency in OPVs, carrier mobility in OFETs, and charge density in charge-trapping memories. Herein, we report an ultralong persistence length (l p ≈ 41 nm) effect of spiro-fused organic nanopolymers on dielectric properties, together with excitonic and charge carrier behaviors. The state-of-the-art nanopolymers, namely, nanopolyspirogrids (NPSGs), are synthesized via the simple cross-scale Friedel-Crafts polygridization of A2B2-type nanomonomers. The high dielectric constant (k = 8.43) of NPSG is firstly achieved by locking spiro-polygridization effect that results in the enhancement of dipole polarization. When doping into a polystyrene-based dielectric layer, such a high-k feature of NPSG increases the field-effect carrier mobility from 0.20 to 0.90 cm2 V-1 s-1 in pentacene OFET devices. Meanwhile, amorphous NPSG film exhibits an ultralow energy disorder (<50 meV) for an excellent zero-field hole mobility of 3.94 × 10-3 cm2 V-1 s-1, surpassing most of the amorphous π-conjugated polymers. Organic nanopolymers with high dielectric constants open a new way to break through the bottleneck of efficiency and multifunctionality in the blueprint of the fourth-generation semiconductors.

Covalent nanosynthesis of fluorene-based macrocycles and organic nanogrids

Gridization is an alternative way to create macromolecules of various sizes in addition to linear and dendritic polymerization as well as cyclization. Organic nanogrids are an expanding family of macrocycle-like closed structures at the nanoscale, but with a series of well-defined extension edges and vertices. Cyclic nanogrids can be used as nanoscale building blocks for the fabrication of not only rotaxanes, catenanes, knots, 3D cages, but also nanopolymers, covalent organic frameworks (COFs), metal-organic frameworks (MOFs), and complex molecular cross-scale architectures. In this review, the history of fluorene-based macrocycles has first been explored, followed by the development of the synthetic methodologies; in particular, fluorene-based nanogrids are highlighted owing to their features and applications. Typically, fluorenes are fused arenes with a hybrid entity between tetrahedral Csp³ and Csp². Four ingenious connection modes of fluorene-based macrocycles, including 2,7-, 3,6-, 9,9-, and 2,9-linkages, fully demonstrate the geometric possibilities of the macrocycles and nanogrids. Such fluorene-based nanogrids will give birth to organic intelligence.

Spiro-based diamond-type nanogrids (DGs) via two ways: 'A1B1'/'A2 + B2' type gridization of vertical spiro-based fluorenol synthons

Regular or well-defined nanogrids with atomically precise extension sites offer an opportunity for covalent nano-architectures as well as frameworks. Previously, we discovered organic nanogrids based on the 2,7-linkage of fluorene via Friedel-Crafts gridization. However, the regularity of nanogrids is not always based on the actual molecular backbone, which leads to ineffective linkage for the more regular complex nanogrids such as nano-windows. Herein, we report the introduction of spirobifluorene, which has more orthogonal shapes, to fix the backbone of nanogridons with regards to the diarylfluorenes. The diamond-type nanogridons (DGs) obtained as a result have the potential feature of cross extension, which is different from their ladder-type counterparts, although they both have four well-defined extension sites. In order to screen efficient monogridon modules, we designed two types of DGs (spiro[fluorene-9,8'-indeno[2,1-b]thiophene] (SFIT)-based DGs-1 and spirobifluorene-based DGs-2) and compared their synthetic routes. The results show that the Friedel-Crafts (F-C) gridization of the A₁B₁ synthon (A₁B₁ mode) offers DGs-1 in 44-50% yields, while the F-C gridization of A₂ + B₂ synthons (A₂ + B₂ mode) is more efficient and gives DGs-2 in 64% yield. Furthermore, unlike in the A₁B₁ mode, the dehydroxylated byproduct and linear polymers were not observed in the A₂ + B₂ mode.

Iodide ion receptors: shape-persistent macrocycles of syn/anti configurations

A local induced fit mechanism following a conformational selection in the recognition of iodide anions is reported.

Over one century after discovery: pyrylium salt chemistry emerging as a powerful approach for the construction of complex macrocycles and metallo-supramolecules

Over one century after its discovery, pyrylium salt chemistry has been extensively applied in preparing light emitters, photocatalysts, and sensitizers. In most of these studies, pyrylium salts acted as versatile precursors for the preparation of small molecules (such as furan, pyridines, phosphines, pyridinium salts, thiopyryliums and betaine dyes) and poly(pyridinium salt)s. In recent decades, pyrylium salt chemistry has emerged as a powerful approach for constructing complex macrocycles and metallo-supramolecules. In this perspective, we attempt to summarize the representative efforts of synthesizing and self-assembling large, complex architectures using pyrylium salt chemistry. We believe that this perspective not only highlights the recent achievements in pyrylium salt chemistry, but also inspires us to revisit this chemistry to design and construct macrocycles and metallo-supramolecules with increasing complexity and desired function.