Ambipolar macrocycle derived from spiro-xanthene and carbazole: synthesis, structure-property relationships, electronic properties and host-guest investigation

For the first time, we present the detailed synthesis, photophysical, electrochemical, host-guest and charge transport properties of spiro[fluorene-9,9'-xanthene] (SFX) and carbazole macrocycle SPS-NR-02. The electron and hole transport values measured using the space charge limited current (SCLC) method resulted in ambipolar charge transport with an electron to hole mobility ratio of 0.39.

One-Step Catalyst-Transfer Macrocyclization: Expanding the Chemical Space of Azaparacyclophanes

In this paper, we report on a one-step catalyst-transfer macrocyclization (CTM) reaction, based on the Pd-catalyzed Buchwald-Hartwig cross-coupling reaction, selectively affording only cyclic structures. This route offers a versatile and efficient approach to synthesize aza[1n]paracyclophanes (APCs) featuring diverse functionalities and lumens. The method operates at mild reaction temperatures (40 °C) and short reaction times (∼2 h), delivering excellent isolated yields (>75% macrocycles) and up to 30% of a 6-membered cyclophane, all under nonhigh-dilution concentrations (35-350 mM). Structural insights into APCs reveal variations in product distribution based on different endocyclic substituents, with steric properties of exocyclic substituents having minimal influence on the macrocyclization. Aryl-type endocyclic substituents predominantly yield 6-membered macrocycles, while polycyclic aromatic units such as fluorene and carbazole favor 4-membered species. Experimental and computational studies support a proposed mechanism of ring-walking catalyst transfer that promotes the macrocycle formation. It has been found that the macrocyclization is driven by the formation of cyclic conformers during the oligomerization step favoring an intramolecular C-N bond formation that, depending on the cycle size, hinges on either preorganization effect or kinetic increase of the reductive elimination step or a combination of the two. The CTM process exhibits a "living" behavior, facilitating sequential synthesis of other macrocycles by introducing relevant monomers, thus providing a practical synthetic platform for chemical libraries. Notably, CTM operates both under diluted and concentrated regimes, offering scalability potential, unlike typical macrocyclization reactions usually operating in the 0.1-1 mM range.

The Synthesis of a Multiple D-A Conjugated Macrocycle and Its Application in Organic Photovoltaic

As a novel class of materials, D-A conjugated macrocycles hold significant promise for chemical science. However, their potential in photovoltaic remains largely untapped due to the complexity of introducing multiple donor and acceptor moieties into the design and synthesis of cyclic π-conjugated molecules. Here, we report a multiple D-A ring-like conjugated molecule (RCM) via the coupling of dimer molecule DBTP-C3 as a template and thiophenes in high yields. RCM exhibits a narrow optical gap (1.33 eV) and excellent thermal stability, and shows a remarkable photoluminescence yield (ΦPL ) of 11.1 % in solution, much higher than non-cyclic analogues. Organic solar cell (OSC) constructed with RCM as electron acceptor shows efficient charge separation at donor-acceptor band offsets and achieves a power conversion efficiency (PCE) of 14.2 %-approximately fourfold higher than macrocycle-based OSCs reported so far. This is partly due to low non-radiative voltage loss down to 0.20 eV and a high electroluminescence yield (ΦEL ) of 4×10-4 . Our findings emphasize the potential of D-A cyclic conjugated molecules in advancing organic photovoltaic technology.

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.

Butterfly-Like Triarylamines with High Hole Mobility and On/Off Ratio in Bottom-Gated OFETs

Highly π-extended butterfly-shaped triarylamine dyads with aryleneethynylene spacer were constructed using an efficient synthetic route. These aryleneethynylene-bridged dyads are highly fluorescent and exhibited high HOMO levels, and low bandgaps, which are suitable for high-performance p-type OFETs. The field-effect transistors were fabricated through a solution-processable method and exhibited promising p-type performance with field-effect mobility up to 4.3 cm² /Vs and high I_on/off of 10⁸ under ambient conditions.

One-pot synthesis of conjugated triphenylamine macrocycles and their complexation with fullerenes

Triphenylamine derivates have been utilized as building blocks in hole-transporting materials. Herein, we describe the synthesis of three octyl-derived conjugated triphenylamine macrocycles with different sizes, and a 4-(2-ethylhexyloxy)-substituted cyclic triphenylamine hexamer using a palladium-catalyzed C–N coupling reaction. These conjugated triphenylamine macrocycles not only have interesting structures, but also are capable of complexing with C₆₀, C₇₀ and PC₆₁BM. Their binding stoichiometries with fullerenes were all determined to be 1 : 1 by an emission titration method. The association constants of these complexes were measured to be in the range of 0.115–1.53 × 10⁵ M⁻¹ depending on the cavity size of the triphenylamine macrocycles and the volume of the fullerenes. The space-charge-limited current properties of the complexes were further investigated using the fabricated ITO/PEDOT:PSS/active layer/Au devices.

Cyclic triphenylamine (TPA) oligomers synthesized by C–N coupling were found to be capable of complexing with fullerenes, and the applications in optoelectronic devices were investigated by using the fabricated ITO/PEDOT:PSS/active layer/Au devices.

High performance p-channel and ambipolar OFETs based on imidazo[4,5-f]-1,10-phenanthroline-triarylamines

A series of phenanthroline functionalized triarylamines (TAA) has been designed and synthesised to evaluate their OFET characteristics. Solution processed OFET devices have exhibited p-channel/ambipolar behaviour with respect to the substituents, in particular methoxyphenyl substitution resulted with highest mobility (μ h) up to 1.1 cm2 V-1 s-1 with good I on/off (106) ratio. These compounds can be potentially utilized for the fabrication of electronic devices.

Light-controlled morphologies of self-assembled triarylamine-fullerene conjugates

A family of triarylamine-fullerene conjugates has been synthesized and shown to self-assemble upon light stimulation in chlorinated solvents. This light-induced process primarily involves excitation of triarylamine derivatives, which then oxidize and stack with their neutral counterparts to form charge transfer complexes in the form of p-conducting channels, while fullerenes are consequently enforced in coaxial n-conducting columnar arrangements. These supramolecular heterojunctions can be organized over very long distances in micrometric fibers when a controlled amount of photons is provided from a white light source to initiate the process. Surprisingly, when sunlight or UV light is used instead, the nanostructuration leads to monodisperse spherical objects due to the nature of the nucleation-growth process involved in the stacks formation. This control over the supramolecular morphology of organic self-assemblies using the nature of light is of general interest for the design of functional responsive materials.

Synthesis and optical properties of a new triphenylamine-p-phenylenevinylene-small molecule with applications in high open-circuit voltage organic solar cells

Fluorescence quenching studies enabled us to preview applications of a new small molecule as electron-donor in OSCs. Planar heterojunction cells are also shown.

Control over nanostructures and associated mesomorphic properties of doped self-assembled triarylamine liquid crystals

We have synthesized a series of triarylamine-cored molecules equipped with an adjacent amide moiety and dendritic peripheral tails in a variety of modes. We show by (1) H NMR and UV/Vis spectroscopy that their supramolecular self-assembly can be promoted in solution upon light stimulation and radical initiation. In addition, we have probed their molecular arrangements and mesomorphic properties in the bulk by integrated studies on their film state by using differential scanning calorimetry (DSC), variable-temperature polarizing optical microscopy (VT-POM), variable-temperature X-ray diffraction (VT-XRD), and atomic force microscopy (AFM). Differences in the number and the disposition of the peripheral tails significantly affect their mesomorphic properties associated with their lamellar- or columnar-packed nanostructures, which are based on segregated stacks of the triphenylamine cores and the lipophilic/lipophobic periphery. Such structural tuning is of interest for implementation of these soft self-assemblies as electroactive materials from solution to mesophases.