Acceptor Molecules Research Articles

Nanoscale Agglomeration Mechanisms of BF‐DPB:BPyMPM Donor–Acceptor Systems for Organic Optoelectronic Devices

AbstractThe molecular order of the photo‐active molecules in organic solar cells and exciplex organic light emitting diodes based on donor–acceptor mixed systems has major influence on the performance. However, it is usually investigated only by indirect measurements or simulations. Here, low‐temperature scanning probe microscopy is used to directly image the molecular assembly, intermolecular bonding configuration, and domain interfaces of vacuum‐deposited donor and acceptor molecules BF‐DPB and BPyMPM on different single crystalline substrates with submolecular resolution. It is demonstrated that the position of the nitrogen atoms in the peripheric pyridine rings of BPyMPM molecules determines the occurrence of intermolecular C─H…N hydrogen bonds, metal coordination bonds, and related self‐assemblies. Two dominating self‐assembled structures of BF‐DPB are found, based either on its cis or trans configuration. In general a distinct increase in disorder occurs at the BF‐DPB:BPyMPM interface where scanning tunneling spectroscopy indicate an increase in the HOMO‐LUMO gap at disordered agglomerates of BF‐DPB. The crucial effect of the choice of substrate on the molecular order is illustrated. Photoluminescence measurements indicate a considerable increase in intersystem crossing in BF‐DPB due to molecule‐substrate interactions. These findings provide new insights for the targeted molecular design of active molecules and suitable contact layers in organic optoelectronic devices.

Lockable Multiple Twisting in Donor–Acceptor Molecules for Emergent Crystalline Structures and Optical Properties

Lockable Multiple Twisting in Donor–Acceptor Molecules for Emergent Crystalline Structures and Optical Properties

The Small Cycloamylose (CA15) Synthesizing Properties of 4-α-Glucanotransferase from Hyperthermophilic Archaeon Pyrobaculum arsenaticum with Its Distinct Disproportionation Activity.

4-α-Glucanotransferase (4-α-GTase, EC 2.4.1.25) facilitates the transfer of α-1,4-linked glucan to another acceptor molecule. This enzyme is widely used during starch modification to produce unique materials, such as thermoreversible gel and cyclic glucan. Because most industrial processing of starch is conducted at elevated temperatures, hyperthermophilic enzymes have received considerable attention. However, only a few of the 4-α-GTases in the glycoside hydrolase family 77 have been isolated from hyperthermophilic archaea. Here, we report for the first time the cycloamylose-forming properties of an archaeal 4-α-GTase (ParGT) isolated from Pyrobaculum arsenaticum. ParGT exhibited optimal activity at pH 6.0 and 95 °C. In particular, ParGT can synthesize small cycloamyloses (CA15-18) with unique disproportionation patterns based on its low transglycosylation activity. Structural modeling with long-chain maltooligosaccharides revealed distinct amino acid residues at the acceptor and second acarbose-binding sites of ParGT. Mutations at Y322 and P231 at the acceptor binding site reduced the disproportionation activity for long-chain maltooligosaccharides, whereas E55 at the second acarbose-binding site influenced the cycloamylose size by affecting the positioning of the 460s loop. These findings provide valuable insights into the structural features and catalytic properties of hyperthermophilic archaeal 4-α-GTase, enabling future modifications of enzymes to improve their capacity to alter starch in diverse biotechnological processes.

Ph3AsO as a Strong Hydrogen-Bond Acceptor in Cocrystals with Hydrogen Peroxide and gem-Dihydroperoxides.

Hydrogen-bonded cocrystals have attracted considerable attention as they allow fine-tuning of properties through the choice of hydrogen-bond donors and acceptors. In this study, triphenylarsine oxide (Ph3AsO) is introduced as a strong hydrogen-bond acceptor molecule. Due to its higher Lewis basicity compared to triphenylphosphine oxide (Ph3PO), it acts as a strong hydrogen-bond acceptor, which is demonstrated in six new cocrystals with H2O2 and gem-di(hydroperoxy)cycloalkanes. All cocrystals formed large, high-quality single crystals, which were analyzed by X-ray diffraction and IR spectroscopy. The cocrystal of Ph3AsO with H2O2 shows prolonged stability without loss of oxidative power. In addition, the newly formed interactions were also present in solution and were detected by NMR spectroscopy. The higher electron-donating ability of Ph3AsO compared to Ph3PO was confirmed by competition experiments. Ph3AsO exclusively binds H2O2, even in dilute aqueous solutions and in the presence of Ph3PO. This study expands the range of hydrogen-bond acceptors and demonstrates that Ph3AsO is a useful cocrystallizing tool in crystal engineering and a sensitive marker for hydrogen peroxide.

First-Principles Investigations of Two-Sided Functionalised MoS2 Monolayer

In this computational study, we investigate two-sided functionalised MoS2 with alkali metal atoms as donors and the organic acceptor molecule F4TCNQ as an acceptor. Characterisation of functionalised MoS2 involves first-principles calculations within the density functional theory (DFT) framework with a PBE+D3 scheme to investigate the electronic structure and quantify the charge transfer in the two-sided functionalised system in comparison to the one-sided functionalised counterpart. Within the two-sided functionalised systems, there is an increase in the overall charge on MoS2 as a result of stronger electron transfer from the donor to the monolayer, additionally controlled by the ability of the acceptor to receive electrons.

The role of TCNQ for surface and interface passivation in inverted perovskite solar cells

The noticeable growth in the power conversion efficiency of solution-processed organo-inorganic halide perovskite solar cells (OIHPSCs) incited the photovoltaic community to look for limitations that hurdle the commercialization process. The surface and interface defects between the perovskite and electron transport layers are among the main challenges that cause significant non-radiative recombination losses, thereby they result in poor performance and stability. In this work, tetracyanoquinodimethane (TCNQ), a strong electron acceptor molecule, is applied at the interface between the photoactive perovskite and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) layers to modify the interface, and enhance device performance and stability. Steady-state and time-resolved photoluminescence measurements were used to characterize the role of the TCNQ passivation in reducing non-radiative recombination of charge carriers. Current density versus voltage (J-V) measurements show improvement in devices open-circuit voltage (Voc), short-circuit current density (Jsc), and fill factor (FF) for devices with TCNQ interface passivation, which is attributed to suppressed non-radiative recombination. In addition, a noticeable improvement in the device’s stability was observed. This study reveals the dual role of TCNQ passivation in improving the photoelectric properties and stability of ambient air processed perovskite devices with the pin architecture.

Fused-ring electron acceptor molecules with a narrow bandgap for near-infrared broadband ultrafast laser absorption

The nonlinear optical properties of fused-ring electron acceptors are enhanced by extending their conjugation length. And IEICO-4F with a narrow bandgap exhibits remarkable laser protection performance in the near-infrared region.

Stereoselective 1,1'-glycosylation via reactivity tuning with protecting groups.

Chemical 1,1'-glycosylation for the synthesis of non-reducing disaccharides is complicated by the need to simultaneously control the stereochemistry at two anomeric centers. While considerable progress has been made in the synthesis of α,α-disaccharides, the assembly of 1,1'-β,β- and 1,1'-β,α-linked non-reducing sugars has received comparatively less attention. Many naturally occurring non-reducing disaccharides and their biologically active mimetics feature asymmetrically located functional groups at different positions on the two pyranose rings, highlighting the demand for reliable stereoselective methods to synthesize fully orthogonally protected 1,1'-conjugated sugars suitable for targeted functionalisation to create important biomolecules. By exploiting specific electronic and torsional effects imposed by protecting groups on both glycosyl donor and lactol acceptor molecules, we achieved highly stereoselective β,β- and β,α-1,1'-glycosylation and successfully synthesised a library of fully orthogonally protected β,β- and β,α-linked diglucosamines. Our approach is based on the premise that acceptor reactivity can greatly influence the stereochemical outcome of the glycosylation reaction. We show that the tailored choice of orthogonal protecting groups can alter the anomeric preferences in lactol acceptors, stabilising specific anomeric conformations, and that protecting group-driven modulation of lactol nucleophilicity is a useful tool to achieve stereoselective 1,1'-glycosidic bond formation. Structure-activity relationships have been established for a number of fully orthogonally protected glycosyl donor-lactol acceptor pairs, with a focus on optimizing lactol acceptor nucleophilicity to facilitate stereoselective 1,1'-β,β- and 1,1'-β,α-glycosylation on the acceptor side and enhance neighboring group-driven stereoselectivity on the donor side.

Enhancing optoelectronic performance of organic solar cells: Alkoxy substitution of central cores and π-bridge units in fully non-fused ring electron acceptors

To systematically elucidate the impact of fluorination and alkoxy modification on the fully non-fused ring electron acceptors (NFREAs) for organic solar cells (OSCs), six fully NFREAs were engineered featuring a benzene core, a selenophene-thiophene unit as the π-bridge, and IC-2F end groups. The derivatives R-D2F and R-D2O were designed by introducing para-substituted fluorine and alkoxy groups onto the central benzene ring of R. Further modifications to the π-bridge of R-D2O, involving variations in the position and number of alkoxy groups, resulted in the derivatives R-DW4O, R-DN4O, and R-D6O. Molecular Dynamics (MD), Density Functional Theory (DFT), and Time-Dependent Density Functional Theory (TD-DFT) simulations were used to predict the optoelectronic properties of these compounds. A comprehensive analysis was conducted on aspects including intramolecular non-covalent interactions, transition density matrix (TDM), electron-hole distributions, charge density difference (CDD), and inter-fragment charge transfer (IFCT). Additionally, the electron transfer rate constants (Ke) and electron mobility (μe) of dimeric structures were calculated to better understand the electronic transmission behavior of these acceptor molecules. The results show that alkoxy substitution on the central core, rather than fluorine substitution, enhances planarity, strengthens intermolecular interactions, reduces the energy gap, induces a red shift in the absorption spectrum, and improves electron excitation efficiency and net charge transfer. The addition of alkoxy groups to the π-bridge further promotes non-covalent interactions, enhancing light absorption and increasing light harvesting efficiency (LHE). Among the derivatives, R-D6O, which features cooperative alkoxy substitution on both the thiophene and selenophene units, exhibits the highest electron mobility, making it a promising candidate for OSC applications. These findings provide valuable insights into the design of high-performance fully NFREAs for OSCs.

Mapping Binding Sites for Efficient Hole Extraction in Lead Halide Perovskites through Sulfur‐Based Ligand Engineering

AbstractLead halide perovskite nanocrystals (NCs) rapidly emerge as promising materials for photovoltaics. However, to fully harness their potential, efficient charge extraction is crucial. Despite rapid advancements, the specific active sites where acceptor molecules interact remain inadequately understood. Surface chemistry and interfacial properties are pivotal, as they directly impact charge transfer efficiency and overall device performance. This study identifies and maps binding sites for hole transporters, examining their influence on charge transfer dynamics through ligand engineering with 2,3‐dimercaptopropanol (DMP), a compound with a strong affinity for lead (Pb). DMP effectively passivates Pb sites in CsPbBr3 (CPB) NCs, enhancing photoluminescence (PL) by forming stable chelating bonds. DMP‐modified CPB nearly completely suppresses hole transfer to ─COOH‐functionalized ferrocene (FcA) and partially suppresses transfer to ─NMe2‐functionalized ferrocene (FcAm), suggesting an alternative hole extraction pathway for FcAm. This is further supported by enhanced hole transfer in bromine‐excess CPB (CPB‐Br(XS)) synthesized via SOBr2 treatment. The distinct binding interactions and charge transfer dynamics are validated through steady‐state and time‐resolved PL, along with transient absorption spectroscopy. These findings underscore the role of strategic ligand engineering in enhancing perovskite NC‐charge acceptor interactions, enabling better charge extraction, higher solar cell efficiency, and reduced lead toxicity through strong Pb binding.

Unlocking high-performance near-infrared photodetection: polaron-assisted organic integer charge transfer hybrids

Room temperature femtowatt sensitivity remains a sought-after attribute, even among commercial inorganic infrared (IR) photodetectors (PDs). While organic IR PDs are poised to emerge as a pivotal sensor technology in the forthcoming Fourth-Generation Industrial Era, their performance lags behind that of their inorganic counterparts. This discrepancy primarily stems from poor external quantum efficiencies (EQE), driven by inadequate exciton dissociation (high exciton binding energy) within organic IR materials, exacerbated by pronounced non-radiative recombination at narrow bandgaps. Here, we unveil a high-performance organic Near-IR (NIR) PD via integer charge transfer between Poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (C-14PBTTT) donor (D) and Tetrafluorotetracyanoquinodimethane (TCNQF4) acceptor (A) molecules, showcasing strong low-energy subgap absorptions up to 2.5 µm. We observe that specifically, polaron excitation in these radical and neutral D-A blended molecules enables bound charges to exceed the Coulombic attraction to their counterions, leading to an elevated EQE (polaron absorption region) compared to Frenkel excitons. As a result, our devices achieve a high EQE of ∼107%, femtowatt sensitivity (NEP) of ~0.12 fW Hz-1/2 along a response time of ~81 ms, at room temperature for a wavelength of 1.0 µm. Our innovative utilization of polarons highlights their potential as alternatives to Frenkel excitons in high-performance organic IR PDs.

Dimeric Acceptors Using Different Central Linkers to Manipulate Electronic and Morphological Properties

AbstractDimerized acceptors show promise in combining the high performance of small‐molecule non‐fullerene acceptors (NFAs) with the excellent stability of polymer acceptors. The central linking units that connect two acceptor molecules together have a profound impact on dimeric acceptor properties and structure‐performance relationships in blended thin films. It is seen that different linkers significantly affect the electronic properties and morphology in blended thin film. The electron‐donating linker elevates the absorption coefficient, affords a lower bandgap, and reduces energy loss, and thus better photovoltaic device performance. Better fibrillar morphology can be obtained. The best material DY‐EDOT‐based device shows a power conversion efficiency (PCE) of 18.21%, an open‐circuit voltage (Voc) of 0.924 V, a short‐circuit current density (Jsc) of 25.20 mA cm−2, a fill factor (FF) of 78.19%, which is among the highest value for dimerized acceptors. This study reveals the fundamental importance of linker units in determining the dimerized acceptor properties and provides useful strategies for developing oligomeric and polymeric acceptors, which is critical in simultaneously improving the performance and stability of organic solar cells (OSCs).

Role of 'pi-Stacked Self-Assembly' in Governing the Dynamics of Photoinduced Electron Transfer Events in Nanocarbon-Derived Donor-Acceptor Conjugates and Hybrids

Supramolecular donor-acceptor nanostructures formed from the intermolecular association of either repeated units of redox- and photo-active molecular monomers or with the association of components of the same molecule are of greater significance due to their importance in understanding the complex photo- and electrochemical events occurring in biology. One such supramolecular organization is the ‘photosynthetic antenna-reaction center’ found in green plants and bacteria which is involved in converting sunlight into chemical energy that drives life as we know it on our planet. Several attempts have been made to mimic aspects of this complex photo-active machinery.1-4 In the present contribution, we discuss our latest work on self-assembled, multi-modular systems. Two key examples will be highlighted, viz., (i) covalently linked fullerene-bisstyrylBODIPY-(zinc porphyrin)2 binding to single-wall carbon nanotubes and (ii) fullerene-(zinc porphyrin)2 self-assembling to form supramolecular donut structures.5 Photodynamics of these complex structures about stabilizing the charge-separated states through sequential electron transfer will be highlighted in this presentation. D’Souza, F.; Sandanayaka, A. S. D.; Ito, O. ‘SWNT-Based Supramolecular Nanoarchitectures with Photosensitizing Donor and Acceptor Molecules’ Phys. Chem. Letts. 2010, 1. 2586-2593.B. KC, G. N. Lim, and F. D’Souza, ‘Accelerated Charge Separation in Graphene Decorated Multi-Modular Tripyrene-Subphthalocyanine-Fullerene Donor-Acceptor Hybrids,’ Angew. Chem. Int. Ed. 2015, 54, 5088-5092.Barrejon, L. M. Arellano, F. D’Souza, F. Langa, ‘Bidirectional charge transfer in carbon-based hybrid nanomaterials’ Nanoscale, 2019, 11, 14978-14992.Kazemi, Y. Jang, A. Liyanage, P. A. Karr, and F. D’Souza, A Carbon Nanotube Binding Bis(pyrenylstyryl)BODIPY-C60 Nano Tweezer: Charge Stabilization through Sequential Electron Transfer, Angew. Chem. Int. Ed. 2022, 61, e202212474 (1-7).Caballero, M. Barrejón, J. Cerdá, J. Aragó, S. Seetharaman, P. de la Cruz, E. Ortí, F. D’Souza, and F. Langa, Self-Assembly-Directed Organization of a Fullerene−Bisporphyrin into Supramolecular Giant Donut Structures for Excited-State Charge Stabilization, J. Am. Chem. Soc. 2021, 143, 11199−11208. Figure 1

Unlocking the Full Redox Capability of Organic Charge‐Transfer Complex in High‐Loading Electrodes for Organic Rechargeable Batteries

AbstractOrganic charge‐transfer complex (OCTC) comprising redox‐active donor and acceptor molecules is a promising electrode material group, potentially resolving issues of low power and inferior cycle stability of organic electrodes in rechargeable batteries. Strong intermolecular interactions in OCTC such as π–π interaction and hydrogen bonding enable high electronic conductivity and suppress solubility to solvents. However, full redox activities of OCTC have not been achieved yet despite the inherent redox capabilities of respective donor and acceptor molecules. Here, it is revealed that the limited redox activities of OCTC stem from electrolyte‐incorporated complex formation, which weakens the characteristic intermolecular interactions, thereby hindering the redox reaction, particularly in Li‐based electrolytes. It is further shown that tailoring electrolyte types, specifically using Zn‐aqueous electrolytes, can substantially mitigate the complex formation and unlock the four‐electron redox activity of OCTC (phenazine (PNZ)‐7,7,8,8‐tetracyanoquinodimethane (TCNQ), that is, PNZ–TCNQ), with superior cycle stability retaining 88% of maximum capacity over 100 cycles. Surprisingly, the full redox reaction achieves an unprecedentedly high electrode‐level energy density, delivering ≈10 mAh cm−2 of areal capacity (580 µm‐thick electrodes) in Zn‐aqueous batteries. The findings elucidate the complex interplay between organic electrodes and electrolytes in the charge storage mechanism, highlighting the importance of electrolyte design in developing organic electrode materials.

Donor–Acceptor Type Solvatochromic Flavonoid Materials Fluorphores for Polarity Sensing and Real‐Time Temperature Monitoring

AbstractElectron donor–acceptor (D–A) molecules are emerging tools for designing sensitive luminogens, attracting significant research attention. However, due to poor quantum yields under certain conditions, current D–A fluorophores often suffer from fluorescence quenching in practical applications. Developing new D–A dyes and functional composites is crucial for expanding their applications. Here, a novel donor–acceptor type flavonoid dye molecule, namely “AFL”, exhibiting both polarity‐dependent fluorescence emission wavelength shift and viscosity‐dependent intensity change, for polarity measurement and temperature sensing is designed and synthesized. Because the intramolecular charge transfer (ICT) can be enhanced by a decrease of excited state energy caused in high‐polarity organic solvents, AFL undergoes fluorescence emission wavelength shift that shows fluorescence color response to solvents of different polarities and hence differentiates between them. Moreover, the actual temperature can be monitored by the as‐designed AFL@tetradecanoic acid (AFL@TA) sensor. By combining with TA, viscosity sensitively changes upon the temperature change of insoluble composites, thus realizing the fluorescence intensity response to temperature. Remarkable recyclable performance and satisfactory mechanical properties are integrated. This study provides a promising approach to developing a new D–A fluorescent probe and furnishes perspectives on the potential of such D–A type flavonoid material in stimuli‐responsive systems with a focus on visualization sensing technology.

Origin of the intermolecular forces that produce donor–acceptor stacks in π-conjugated charge-transfer complexes

The attraction between π-conjugated planar electron donor and acceptor molecules that form many stable charge-transfer (CT) complexes has been explained by quantum chemical CT interactions, although the fundamental origin remains unclear. Here, we demonstrate the mechanism of CT complex formation by potential energy map analysis for TTF–CA and BTBT–TCNQ, using energy decomposition of intermolecular interaction by symmetry-adapted perturbation theory (SAPT) combined with coupled cluster calculation. We find that the source of attraction between donor and acceptor molecules is ascribed primarily to the dispersion force and also to the electrostatic force. In contrast, the contribution of CT interactions to the attractive forces is minimal. We demonstrate that the highly directional feature of the exchange repulsion force, coupled with the attractive dispersion and electrostatic forces, is crucial in determining the intermolecular arrangements of actual CT crystals. These findings are key for understanding the unique structural and electronic properties of π-conjugated CT complexes.

Charge-transfer interactions between antibiotics and small organic acids: Spectroscopic characterization and computational investigation

Six new charge-transfer complexes using ofloxacin (OFL) and sulfamethazine (SMR) as electron donors and coumaric acid (COA), cinnamic acid (CNA), and salicylic acid (SAA) as acceptors via equimolar mixture have been synthesized. The experiment used UV–vis spectroscopy to determine the formation of the complex in methanol through the presence of a new broad absorption band with a maximum wavelength in the 200–400 nm range. The molecular composition of the charge-transfer complexes was determined by the spectrophotometric titration method and found to be 1:1 (donor: acceptor). These complexes have been characterized by infrared (FTIR) and scanning electron microscopy (SEM). In the FTIR spectra, the CT complexes showed a wavelength shift compared to the reactants. The complexes exhibited various morphologies by SEM, including spherical particles, short rods, and flattened shapes. Additionally, quantum chemical calculations at the DFT/B3LYP level of theory investigated the complexes' steady-state structures, energies, and charge densities. The intermolecular binding energies was negative, indicating that the reactions of the six complexes proceeded spontaneously. There was strong van der Waals forces and hydrogen bonds between the donor and acceptor, which contributed to the complexes' strong molecular stability. The CN and NH groups in the donor molecule, and the -COOH group in the acceptor molecule, played key roles in the complexation process. DFT calculation results were appropriate to support our experimental results. This study highlights the molecular mechanisms of donor and acceptor action in charge-transfer interactions, providing a theoretical basis for the synthesis of antibiotic complexes and the removal of antibiotics.

Highly Efficient Organic Solar Cells with the Highly Crystalline Third Component as a Morphology Regulator.

The morphology of the active layer is crucial for highly efficient organic solar cells (OSCs), which can be regulated by selecting a rational third component. In this work, the highly crystalline nonfullerene acceptor BTP-eC9 is selected as the morphology regulator in OSCs with PM6:BTP-BO-4Cl as the main system. The addition of BTP-eC9 can prolong the nucleation and crystallization progress of acceptor and donor molecules, thereby enhancing the order of molecular arrangement. Meanwhile, the nucleation and crystallization time of the donor is earlier than that of the acceptors after introducing BTP-eC9, which is beneficial for obtaining a better vertical structural phase separation. The exciton dissociation, charge transport, and charge collection are promoted effectively by the optimized morphology of the active layer, which improves the short-circuit current density and filling factor. After introducing BTP-eC9, the power conversion efficiencies (PCEs) of the ternary OSCs are improved from 17.31% to 18.15%. The PCE is further improved to 18.39% by introducing gold nanopyramid (Au NBPs) into the hole transport layer to improve photon utilization efficiency. This work indicates that the morphology can be optimized by selecting a highly crystalline third component to regulate the nucleation and crystallization progress of the acceptor and donor molecules.

Luminescent anthracene-based elastic mixed molecular crystals for flexible and FRET-assisted optical waveguides

Abstract Optical waveguides based on elastic molecular crystals are of interest as flexible and compact optical communication materials. Low emission efficiency is often a problem in terms of communication signal strength, and an increase in the loss factor α due to fluorescence reabsorption in the crystal reduces the photon transport efficiency. Here, we report the development and improvement of Förster resonance energy transfer (FRET)-assisted optical waveguides using anthracene-based elastic mixed molecular crystals. 9,10-Dicyanoanthracene was selected as the dopant for solution-grown crystallization of 9,10-dibromoanthracene. 1H NMR measurements of the obtained crystals showed that the acceptor doping to be 1% to 5%. Elastic behavior was observed even when doped with a few percent of the acceptor. The quantum efficiency was 0.016, a dramatic improvement over the previous luminescent elastic mixed molecular crystals (0.004). The α value (92 dB/cm) of this crystal containing 1%-doped 9,10-dicyanoanthracene is much lower than that of the crystal consisting of only 9,10-dibromoanthracene (1258 dB/cm) due to the reduced reabsorption in the FRET system. We have demonstrated a practical approach toward developing improved fluorescent, highly efficient, and flexible optical waveguides by constructing the mixed crystal structure by selecting appropriate acceptor molecules and their low doping ratios.

Photomodulation of Charge Transfer through Excited‐State Processes: Directing Donor‐Acceptor Binding Dynamics

AbstractModulating charge transfer (CT) interactions between donor and acceptor molecules may give rise to unique dynamic changes in physicochemical properties, exhibiting great importance in supramolecular chemistry and materials science. In this work, we demonstrate the first instance of reversible photomodulation of donor‐acceptor (D−A) CT interaction in the solid state. Pyridinium‐based chromophore featuring π‐conjugated D−A structures can not only function as a good electron acceptor to undergo photoinduced electron transfer (ET) or engage in intermolecular CT interaction, but also exhibit unique dual emission depending on the excitation wavelengths. The rotatable C−C single bonds within D−A pairs enhance the tunability of molecular structure. Through the synergy of a photoinduced ET and an excited‐state conformational change, the intermolecular CT interaction can be switched on and off by alternate light irradiation to enable reversibly modulation of the affinity between donor and acceptor molecules, accompanied by visual color switching and fluorescence on‐off as feedback signals.