Donor-acceptor Architecture Research Articles

Asymmetrically Functionalized Phenanthro[9,10-d]imidazole-Based Donor–Acceptor Architectures for High-Performance Ternary Memory Devices

Asymmetrically Functionalized Phenanthro[9,10-d]imidazole-Based Donor–Acceptor Architectures for High-Performance Ternary Memory Devices

Boron-Induced Interstitial Effects Drive Water Oxidation on Ordered Ir-B Compounds.

Interstitial filling of light atoms strongly affects the electronic structure and adsorption properties of the parent catalyst due to ligand and ensemble effects. Different from the conventional doping and surface modification, constructing ordered intermetallic structures is more promising to overcome the dissolution and reconstruction of active sites through strong interactions generated by atomic periodic arrangement, achieving joint improvement in catalytic activity and stability. However, for tightly arranged metal lattices, such as iridium (Ir), obtaining ordered filling atoms and further unveiling their interstitial effects are still limited by highly activated processes. Herein, we report a high-temperature molten salt assisted strategy to form the intermetallic Ir-B compounds (IrB1.1) with ordered filling by light boron (B) atoms. The B residing in the interstitial lattice of Ir constitutes favorable adsorption surfaces through a donor-acceptor architecture, which has an optimal free energy uphill in rate-determining step (RDS) of oxygen evolution reaction (OER), resulting in enhanced activity. Meanwhile, the strong coupling of Ir-B structural units suppresses the demetallation and reconstruction behavior of Ir, ensuring catalytic stability. Such B-induced interstitial effects endow IrB1.1 with higher OER performance than commercial IrO2, which is further validated in proton exchange membrane water electrolyzers (PEMWEs).

New conjugated copolymer MEH-PPV-P3HT with donor-acceptor system for organic optoelectronics applications: Experimental and theoretical study

Donor-acceptor architecture was designed of new diblocks copolymer MEH-PPV-P3HT synthesis. The new copolymer was elaborated through oxidative pathway. The correlation structure-properties and their potential photophysical characteristics of the obtained material were reported utilizing several characterization analyses (InfraRed, Raman, TGA, UV visible spectroscopy, as well as PL and TRPL). To define the model's geometric structure, vibrational, and optoelectronic properties of the studied copolymer, Density Functional Theory DFT and Time-dependent Density Functional Theory TD-DFT approach were carried out. The obtained copolymer exhibits great thermal stability and substantial absorption in the visible range. An energy gap lower than the original materials by the amount of 1.74 eV which proves the presence of the charge transfer process. In addition, due to Forster energy transfer from the MEH-PPV to the P3HT an enhancement of the exciton average lifetime was detected. The obtained results from the copolymer characterization suggest a potential for application in organic optoelectronic devices. A good accordance between experimental and theoretical results based DFT calculations is obtained.

Tweaking the Non-Volatile Write-Once-Read-Many-Times (WORM) Memory using Donor-Acceptor Architecture with Isatin as Core Acceptor.

Organic memory devices have attracted attention because they promise flexible electronics, low manufacturing costs, and compatibility with large-scale integration. A series of new D-A architectures were synthesized employing different donor groups and the isatin moiety as the acceptor through Suzuki-Miyaura coupling reactions. Strong intramolecular interactions were observed in the synthesized compounds, further corroborated by an optimal bandgap. The SEM investigation confirmed good molecular ordering and superior thin film surface coverage. All the compounds demonstrated notable binary Write-Once-Read-Many-Times (WORM) memory behaviour. The threshold switching voltage for these D-A systems ranged from -0.79 to -2.37 V, with the compound having isobutyl substituent showing the lowest threshold voltage and maximum ON/OFF ratio of 102, thus outperforming others. The combined effects of charge transfer and charge trapping are responsible for the resistive switching mechanism prevailing in these systems. The alterations in D-A molecules that affect molecular packing, thin film morphology, and, finally, the memory performance of the active layer are highlighted in this work.

Synthetic Strategies for 3,6-Substituted Carbazole-based Polymers and Their Opto-Electronic Applications-A Review.

The use of conducting polymers in devices makes them desirable due to their allowance for the fabrication of flexible, lightweight, and potentially inexpensive devices. This review explores the synthetic strategies and characterizations of 3,6-substituted carbazole-based polymers, emphasizing the influence of these modifications on their electronic structure and absorption properties. Polymers containing carbazole substituents are widely studied due to their unique optical and electronic properties, high electron-donating ability, and photoconductivity. The structural adaptability of the carbazole with the 3,6-substitution makes it as an outstanding candidate for their integration into polymers and also possesses improved stability and triplet energy. The role of intramolecular charge transfer (ICT) was highlighted by donor-acceptor architectures with tailoring energy levels to extract their advantageous physicochemical characteristics and optimized performances. Collectively, this comprehensive review delves into the burgeoning field of 3,6-substituted carbazole-based polymers and their crucial role in advancing optoelectronic applications. By amalgamating materials design, synthetic strategies, and application-driven insights, the review serves as a valuable resource for researchers to understand the structure-property relationships and foster innovative solutions for next-generation opto-electronic applications.

Enhanced Visible Light Absorption in Heteroleptic Cuprous Phenanthrolines.

This work presents a series of Cu(I) heteroleptic 1,10-phenanthroline chromophores featuring enhanced UVA and visible-light-harvesting properties manifested through vectorial control of the copper-to-phenanthroline charge-transfer transitions. The molecules were prepared using the HETPHEN strategy, wherein a sterically congested 2,9-dimesityl-1,10-phenanthrolne (mesPhen) ligand was paired with a second phenanthroline ligand incorporating extended π-systems in their 4,7-positions. The combination of electrochemistry, static and time-resolved electronic spectroscopy, 77 K photoluminescence spectra, and time-dependent density functional theory calculations corroborated all of the experimental findings. The model chromophore, [Cu(mesPhen)(phen)]+ (1), lacking 4,7-substitutions preferentially reduces the mesPhen ligand in the lowest energy metal-to-ligand charge-transfer (MLCT) excited state. The remaining cuprous phenanthrolines (2-4) preferentially reduce their π-conjugated ligands in the low-lying MLCT excited state. The absorption cross sections of 2-4 were enhanced (εMLCTmax = 7430-9980 M-1 cm-1) and significantly broadened across the UVA and visible regions of the spectrum compared to 1 (εMLCTmax = 6494 M-1 cm-1). The excited-state decay mechanism mirrored those of long-lived homoleptic Cu(I) phenanthrolines, yielding three distinguishable time constants in ultrafast transient absorption experiments. These represent pseudo-Jahn-Teller distortion (τ1), singlet-triplet intersystem crossing (τ2), and the relaxed MLCT excited-state lifetime (τ3). Effective light-harvesting from Cu(I)-based chromophores can now be rationalized within the HETPHEN strategy while achieving directionality in their respective MLCT transitions, valuable for integration into more complex donor-acceptor architectures and longer-lived photosensitizers.

Multi-heteroatom doped nanographenes: enhancing photosensitization capacity by forming an electron donor-acceptor architecture.

Systematically tuning and optimizing the properties of synthetic nanographenes (NGs) is particularly important for NG applications in diverse areas. Herein, by devising novel electron donor-acceptor (D-A) type structures, we reported a series of multi-heteroatom-doped NGs possessing an electron-rich chalcogen and electron-deficient pyrimidine or pyrimidinium rings. Comprehensive experimental and theoretical investigations revealed significantly different physical, optical, and energetic properties compared to the non-doped HBC or chalcogen-doped, non-D-A analogues. Some intriguing properties of the new NGs such as unique electrostatically oriented molecular stacking, red-shifted optical spectra, solvatochromism, and enhanced triplet excitons were observed due to the formation of the D-A electron pattern. More importantly, these D-A type structures can serve as photosensitizers to generate efficiently reactive-oxygen species (ROS), and the structure-related photosensitization capacity that strengthens the electron transfer (ET) process leads to significantly enhanced ROS which was revealed by experimental and calculated studies. As a result, the cell-based photodynamic therapy (PDT) indicated that the cationic NG 1-Me+ is a robust photosensitizer with excellent water-solubility and biocompatibility.

Dual state emissive tridentate imidazopyridines with applications in acidochromism, metal ions detection, data encryption, and bioimaging

Four novel tridentate scaffolds IP-nTPA (n = 1, 4, 8, and 12), in which 2,6-bis(imidazo [1,2-a]pyridin-2-yl)pyridine and alkoxyl-substituted triphenylamine (TPA) are utilized as electron-donor and electron-acceptor, respectively, have been synthesized. Due to the inclusion of flexible alkoxyl chain to suppress π–π stacking in solids, IP-nTPA (n = 1, 4, 8) displayed efficient fluorescence in both solution and solid state. Meanwhile, IP-nTPA demonstrated an obvious solvatochromism with red-shifted emission when increasing solvent polarity, which is associated with the formed intramolecular charge transfer (ICT) states in the donor-acceptor (D-A) architecture. Theoretical calculations and single crystal structure analysis were utilized to interpret the emission behaviors in both solution and solid state. Importantly, IP-4TPA was chosen as the candidate to exhibit reversible acidichromism, metal ions detection, and information security application. Finally, the bioimaging application of IP-nTPA in PC-3 cells was investigated, which showed excellent biocompatibility and cell permeability.

Investigating the Effect of Cross-Conjugation Patterns on the Optoelectronic Properties of 7,7′Isoindigo-Based Materials

Isoindigo (IID) is widely used as a building block for the fabrication of organic semiconductor devices. Understanding the impact of cross-conjugation and linear conjugation on the optoelectronic properties of disubstituted IID is of great importance for the design of improved materials. In this study, phenyl and thienyl groups were substituted at the cross-conjugated 7,7′ position of IID to generate three novel organic semiconductor structures with a donor–acceptor architecture. The optoelectronic properties of this IID derivative were investigated and compared with those of the 6,6′ linearly conjugated IID analogs using UV–Vis spectroscopy and cyclic voltammetry. The experimental results were compared using density functional theory calculations to provide structure–property relationships based on substitution types and attachment sites for IID. The frontier orbital energy levels of the material did not vary dramatically with the position of the substituent, while the type of substituent showed a more significant influence on the HOMO’s energy level and oscillator strength. Phenyl-disubstituted 7,7′ IID (7Ph7′Ph) and thienyl-disubstituted 7,7′ IID (7Th7′Th) materials were used as electron transport layers in perovskite solar cells with a power conversion efficiency of 5.70% and 6.07%, respectively. These observations enhance our understanding of the electronic structure and optoelectronic properties of IID, guiding the design of the next generation of IID-based semiconductors.

Modulating the Room Temperature Phosphorescence by Tweaking SOC and P = X Interactions (X = O, S, and Se) in Phosphoramides: Magnetic Circularly Polarized Luminescence from Achiral Phosphoramides

AbstractHerein, the synthesis, structure, room temperature phosphorescence, and magnetic chiroptical properties of phosphoramides 1‐6 with donor–acceptor architecture are reported.5). The electronic interactions between donor phenothiazine (PTZ) and acceptor (C6H5)n‐P = X (n = 1, 2; X = O, S, and Se)moieties in 1–6 are modulated by varying the number of donor units. The Lewis acidity of the phosphorus center is controlled by the nature of heteroatoms and the number of phenyl moieties attached to it. All compounds exhibit phosphorescence in the solid state under ambient conditions with a photoluminescence lifetime in the millisecond range (≈8–40 ms). The energy of the phosphorescence bands and their excited state lifetimes are governed by the P=X units. The phosphorescence features observed for 1–6 are in complete contrast to the observations noted for (PTZ)3P = X (X = O, S, and Se), where the phosphorescence process is completely controlled by the PTZ moiety, and there is a negligible contribution from the P = X moiety. Thus, the present and earlier studies together reveal that the steric crowding and the number of C6H5 moieties around the P = X unit play a crucial role in controlling the electronic coupling between the donor and acceptor moieties in phosphoramides containing non‐planar donor moieties. Furthermore, for the first time, the magnetic chiroptical properties of achiral phosphoramides 1–6, exhibiting a luminescence dissymmetry factor (gMCPL) in the order of 10−3 (≈4.0 × 10−3–7.4 × 10−3) are demonstrated.

Solution-Processed Pure Red TADF Organic Light-Emitting Diodes With High External Quantum Efficiency and Saturated Red Emission Color.

In spite of recent research progress in red thermally activated delayed fluorescence (TADF) emitters, highly efficient solution-processable pure red TADF emitters are rarely reported. Most of the red TADF emitters reported to date are designed using a rigid acceptor unit which renders them insoluble and unsuitable for solution-processed organic light-emitting diodes (OLEDs). To resolve this issue, a novel TADF emitter, 6,7-bis(4-(bis(4-(tert-butyl)phenyl)amino)phenyl)-2,3-bis(4-(tert-butyl)phenyl)quinoxaline-5,8-dicarbonitrile (tBuTPA-CNQx) is designed and synthesized. The highly twisted donor-acceptor architecture and appropriate highest occupied molecular orbital/lowest unoccupied molecular orbital distribution lead to a very small singlet-triplet energy gap of 0.07eV, high photoluminescence quantum yield of 92%, and short delayed fluorescence lifetime of 52.4µs. The peripheral t-butyl phenyl decorated quinoxaline acceptor unit and t-butyl protected triphenylamine donor unit are proven to be useful building blocks to improve solubility and minimize the intermolecular interaction. The solution-processed OLED based on tBuTPA-CNQx achieves a high external quantum efficiency (EQE) of 16.7% with a pure red emission peak at 662 nm, which is one of the highest EQE values reported till date in the solution-processed pure red TADF OLEDs. Additionally, vacuum-processable OLED based on tBuTPA-CNQx exhibits a high EQE of 22.2% and negligible efficiency roll-off.

Squaraine-fullerene conjugate for single component organic solar cells

The donor (D) acceptor (A) architecture of squaraine-fullerene conjugate (SQ-Full) was developed for single-component organic solar cell (SC–OSCs) devices. The SQ-Full dyad showed three absorption bands centered around 330 nm, 396 nm, and 712 nm, extending to 850 nm. We have fabricated SC-OSCs and achieved an overall power conversion efficiency of 5.21% after solvent vapor annealing (SVA) of the active layer. This is the highest efficiency available in the reported literature for small molecules and squaraine-based SC-OSC.

Construction of Ordered Atomic Donor–Acceptor Architectures in bcc IrGa Intermetallic Compounds toward Highly Electroactive and Stable Overall Water Splitting

AbstractBenefiting from ordered atomic structures and strong d‐orbital interactions, intermetallic compounds (IMCs) are promising electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, the body‐centered cubic IrGa IMCs with atomic donor–acceptor architectures are synthesized and anchored on the nitrogen‐doped reduced graphene oxide (i.e., IrGa/N‐rGO). Structural characterizations and theoretical calculations reveal that the electron‐rich Ir sites are atomically dispersed in IrGa/N‐rGO, facilitating the electron transfer between Ir atoms and adsorbed species, which can efficiently decrease the energy barriers of the potential determining step for both HER and OER. Impressively, the IrGa/N‐rGO||IrGa/N‐rGO exhibits excellent performance for overall water splitting in alkaline medium, requiring a low cell voltage of 1.51 V to achieve 10 mA cm−2, meanwhile, exhibiting no significant degradation for 100 h. This work demonstrates that the rational design of noble metal electrocatalysts with donor–acceptor architectures is beneficial for catalytic reactions in energy conversion applications.

Fluorescent indolo[2,3-b]quinoxalin-2-yl(phenyl)methanone dyes: photophysical, AIE activity, electrochemical, and theoretical studies

Herein, we have synthesized four indolo[2,3-b]quinoxalin-2-yl)(phenyl)methanone derivatives by cyclocondensation. The photophysical studies of dyes in various solvents and neat solid film exhibit typical electronic spectra with inbuilt intramolecular charge transfer (ICT) (λmax: 397–490 nm) confirming donor–acceptor architecture. Herein, dyes fluoresce in the blue-orange region (λEmax: 435–614) on excitation at their ICT maxima in toluene, ethyl acetate, chloroform, DMSO, and neat solid film. Two dyes, which exhibit good emission intensity in all mediums, were studied for aggregation-induced emission (AIE) effect. Electrochemical studies indicate the dyes possess relatively low lying LUMO (− 3.65 to − 3.98 eV) comparable to reported n-type/electron-transporting materials. The HOMO and LUMO energy levels were evaluated by DFT and TD-DFT calculations. TGA analysis shows the dyes exhibit good thermal stability. The characteristic optoelectronic properties and thermal stability signify these dyes are potential candidates for their application in optoelectronics.Graphical abstract

Polymer Dots as Photoactive Membrane Vesicles for [FeFe]-Hydrogenase Self-Assembly and Solar-Driven Hydrogen Evolution.

A semiartificial photosynthesis approach that utilizes enzymes for solar fuel production relies on efficient photosensitizers that should match the enzyme activity and enable long-term stability. Polymer dots (Pdots) are biocompatible photosensitizers that are stable at pH 7 and have a readily modifiable surface morphology. Therefore, Pdots can be considered potential photosensitizers to drive such enzyme-based systems for solar fuel formation. This work introduces and unveils in detail the interaction within the biohybrid assembly composed of binary Pdots and the HydA1 [FeFe]-hydrogenase from Chlamydomonas reinhardtii. The direct attachment of hydrogenase on the surface of toroid-shaped Pdots was confirmed by agarose gel electrophoresis, cryogenic transmission electron microscopy (Cryo-TEM), and cryogenic electron tomography (Cryo-ET). Ultrafast transient spectroscopic techniques were used to characterize photoinduced excitation and dissociation into charges within Pdots. The study reveals that implementation of a donor–acceptor architecture for heterojunction Pdots leads to efficient subpicosecond charge separation and thus enhances hydrogen evolution (88 460 μmolH2·gH2ase–1·h–1). Adsorption of [FeFe]-hydrogenase onto Pdots resulted in a stable biohybrid assembly, where hydrogen production persisted for days, reaching a TON of 37 500 ± 1290 in the presence of a redox mediator. This work represents an example of a homogeneous biohybrid system combining polymer nanoparticles and an enzyme. Detailed spectroscopic studies provide a mechanistic understanding of light harvesting, charge separation, and transport studied, which is essential for building semiartificial photosynthetic systems with efficiencies beyond natural and artificial systems.

Probing Charge Management across the π-Systems of Nanographenes in Regioisomeric Electron Donor-Acceptor Architectures.

Inspired by light-induced processes in nature to mimic the primary events in the photosynthetic reaction centers, novel functional materials combine electron donors and acceptors, i.e., (metallo)porphyrins (ZnP) and fullerenes (C60), respectively, with emerging materials, i.e., nanographenes. We utilized hexa-peri-hexabenzocoronene (HBC) due to its versatility regarding functionalization and physicochemical properties, to construct three regioisomeric ZnP-HBC-C60 conjugates, which foster geometrical diversity by arranging ZnP and C60 in ortho-, meta-, and para-positions to each other. The corresponding hexaarylbenzene (HAB) motifs, with an interrupted π-system, were also prepared. Transient absorption measurements disclosed the fast population of charge transfer as well as singlet and triplet charge-separated states. With the help of density functional theory (DFT) calculations, we further conceive the communication across the HBCs and HABs. This work reveals the impact of both the geometrical arrangement with respect to through-space versus through-bond interactions and the structural rigidity/flexibility on the charge management across the different π-systems.

Tuning the photocatalytic properties of porphyrins for hydrogen evolution reaction: An in-silico design strategy

Porphyrins constitute a class of attractive materials for harvesting sunlight and promote chemical reactions following their natural activity for the photosynthetic process in plants. In this work, we employ an in-silico design strategy to propose novel porphyrin-based materials as photocatalysts for hydrogen evolution reaction (HER). More specifically, a set of meso-substituted porphyrins with donor-acceptor architecture are evaluated within the density functional theory (DFT) framework, according to these screening criteria: i) broad absorption spectrum in the ultraviolet–visible (UV–Vis) and near infrared (NIR) range, ii) suitable redox potentials to drive the uphill reaction that lead to molecular hydrogen formation, iii) low exciton binding free energy ( E b ), and iv) low hydrogen binding free energy (ΔG H ), a quantity that should present low HER overpotentials, ideally ΔG H = 0. The outcomes indicate that the Se-containing compound, where the donor ligands are attached to the porphyrin core by the spacer, outstands as the most promising candidate that is presented in this work. It displays a broad absorption in the visible and NIR regions to up to 1000 nm, suitable catalytic power, low E b (in special in high dielectric constant environment, such as water) and the lowest ΔG H = +0.082 eV. This is comparable, in absolute values, to the value exhibited by platinum (ΔG H = −0.10 eV), one of the most efficient catalysts for HER. • Novel porphyrin-based materials are proposed as photocatalysts for HER. • The screening strategy includes the UV–Vis absorption profile, catalytic power and ΔG H . • All candidates have catalytic power for electron transfer. • The Se-based compound is the most promising candidate in the series. • Nitrogen is the most relevant catalytic site for hydrogen production in these materials.

Thermally induced charge transfer in a quinoid-bridged linear Cu3 compound.

Charge transfer always occurs in molecular valence tautomers, leading to the redistribution of electron density and exhibiting electrical, optical, and magnetic properties, and can be further controlled by multiple external stimuli such as temperature, light and electric field. The design of molecule-based materials capable of charge transfer remains a challenge. Herein, a linear Cu3 compound [(CH3)3NCH2CH2Br]2[Cu3L4(H2O)2] (H2L = chloranilic acid) (1) with a multi-center donor-acceptor architecture was constructed using the redox-active chloranilic acid quinoid ligand. Temperature-dependent dielectric measurement was performed to capture the charge transfer valence tautomer transition because it is difficult to detect this transition by crystal structure and magnetism analysis. Temperature-dependent XPS and EPR further confirmed that the charge transfer valence tautomer transition is based on the CuII-L2- to CuI-L-˙ multi-center charge transfer. Thus, the present work builds a charge transfer compound with a multi-center donor-acceptor architecture and proves that dielectric measurement is a very effective means to detect charge transfer.

Phenothiazine-Based Luminophores with AIE, Solvatochromism, and Mechanochromic Characteristics.

Aggregation-induced emission (AIE) fluorescent molecules with unique photoelectric properties have received extensive attention due to the wide range of applications. In this work, two novel phenothiazine-based luminophores DPE-PTZ-Cl and DPE-PTZ-CF3 were designed based on the frontier molecular orbital (FMO) theory and construction strategy of AIEgens. As expected, both of the luminophores displayed typical AIE behavior and realized the spatial separation of FMOs, which was confirmed by the positive solvatochromism behavior. Their AIE properties could be attributed to the twisted three-dimensional (3D) conformation. Such a conformation resulted from "butterfly-like" phenothiazine and a multirotor structure of diphenylethylene. The spatial separation of FMOs originated from the push-pull electronic synergistic effect of the donor-acceptor (D-A) architecture. Interestingly, DPE-PTZ-Cl also showed a rare blue-shifted mechanochromic (MC) luminescence property. Single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD) experiments were carried out to reveal that the phase transformation between crystalline and amorphous states was responsible for the peculiar solid-state luminescence phenomenon.

One molecule to light it all: The era of dual-state emission

One molecule to light it all: The era of dual-state emission