N-type high mobility emissive organic semiconductor materials (HMEOSCs) are pivotal for advancing logic circuits and sensors. Nevertheless, their development faces the great challenge in achieving both high carrier mobility and strong luminescent properties, attributed to the limitations of intrinsic molecular structure and solid-state stacking. In this study, a series of fluorinated diphenylanthracene isomers (1,5-, 2,6-, and 9,10-DPA-F) were theoretically designed, with their charge transport and fluorescence properties systematically investigated via first-principles calculations. Additionally, crystal growth morphologies were modeled to establish multiscale structure-property relationships. The results show that the perfluorination of aryl substituents were demonstrated to effectively reduce LUMO energy levels, enhance electron injection capabilities, and elevate fluorescence quantum yields beyond 70 %. However, it also brings the problems of larger reorganization energy and intermolecular sliding along the long axis. Building on this foundation, molecular redesign strategies focused on 2,6-DPA-F were developed to suppress electronic reorganization energy. Moreover, we also clarified the reason by crystal morphology growth why high mobility molecules 1,5-DPA-F and 9,10-DPA-F (mu(e)s>1 cm(2)V(-1)s(-1)) have not yet obtained experimental measurement values. This work elucidates the influence of multi-scale factors (molecular structure-stacking-morphology) on the transport properties, and opens up new avenues and perspectives for the design of n-type HMEOSCs.

This study employs DFT and TDDFT methods to explore how -OH substitution at different positions and solvent polarity modulate the ESIPT mechanisms and photophysical properties of dual proton-transfer-site TFAQ derivatives. Results indicate that all intramolecular hydrogen bonds (IHBs) are strengthened upon photoexcitation. The introduction of the -OH group makes a net enhancement of IHB1 but induces a pronounced strengthening of IHB2. Hole-electron analysis confirms LE nature for all compounds. The potential energy curves (PECs) demonstrate that the -OH substitution imposes kinetic restrictions on the ESIPT process along the IHB1 pathway. Consequently, the TFAQ derivatives undergo ESIPT preferentially along IHB2, followed by IHB1. Furthermore, increasing solvent polarity promotes the ESIPT process. Spectral simulations reveal red shifts in keto forms, along with large Stokes shifts for all molecules. This study demonstrates the tunability of ESIPT through substitution position and solvent engineering, providing valuable insights for designing dual proton-transfer-site TFAQ based fluorescent materials.

Iridium-based photosensitizers have attracted significant attention in photodynamic therapy (PDT) due to their exceptional photophysical properties and chemical stability, as well as tunable phosphorescence emission spectrum and high triplet state production yields. Photosensitizers with large two-photon absorption (TPA) and mitochondrial targeting capabilities are particularly promising for clinical PDT, as they enable deeper tissue penetration and reduced damage to normal cells. In this study, we theoretically studied photophysical, photodynamic properties and photosensitization reaction mechanism of a series of iridium-based photosensitizers with modified C^N and N^N ligands (a2-a6, b1/b1-r and b2/b2-r) by TDDFT/DFT methods. The photophysical properties, including one- and two-photon absorption spectra, frontier molecular orbitals, and singlet and triplet excitation energies, were calculated. Additionally, rate constants for intersystem crossing, fluorescence, and phosphorescence, along with water solubility and lipophilicity metrics (logP), were determined to assess both efficacy and biocompatibility. The results elucidate the modulation roles of the chelated ligands and ancillary ligands in TP-PDT efficiency, indicating that the asymmetric iso-fused-benzene ring modification to the N^N ligand is a robust design strategy for comprehensively enhancing photosensitization performance. Complexes a2, b2 and b1-r show greater promise as candidates for two-photon PDT photosensitizers, owing to their large TPA cross-sections, extended triplet state lifetimes, and balanced water solubility and lipophilicity. Notably, the b1-r complex can undergo both Type I and Type II PDT photosensitization mechanisms, which will help address the issue of drug resistance arising from the hypoxic environment in deep-seated tumors.

High-efficiency electrocatalysts targeting oxygen evolution (OER) and reduction reactions (ORR) are essential for breakthrough renewable energy technologies. We systematically investigated the impact of 17 axial ligands (X = F, Cl, Br, I, O2, O, OH, OOH, OCH3, NH2, NO2, CN, SCN, SCH3, SCH2CH3, CHO, CH3) on the OER/ORR performance of CuN4 and CuN3H2 single-atom catalysts employing density functional theory (DFT). The calculations revealed that the introduction of axial ligand results in changed adsorption strength. In the CuN4 system, axial ligands systematically weakened *O adsorption while strengthening *OH and *OOH adsorption. Similarly, in the CuN3H2 system, axial ligands systematically strengthened *O, *OH and *OOH adsorption. As a result, CuN3H2 (HOER = 0.76 V/HORR = 0.41 V) and CuN4-O2 (HOER = 0.63 V/HORR = 0.59 V) shows balanced catalytic performance in both OER and ORR, indicating these materials are strong candidates for bifunctional OER/ORR electrocatalysis. These findings contribute key knowledge relevant to designing Cu-N-C catalysts for renewable energy applications. The design principle expands new possibilities for designing high-performance Cu-N-C bifunctional SACs in OER and ORR.

The excited state intramolecular proton transfer (ESIPT) process and fluorescent properties of trifluoroanthraquinone (TFAQ) derivatives are investigated by introducing 1'-methyl-2', 3', 4'-trihydropyridine or 3'-hydroxylpyridine to the 2, 3-positions or 7, 8-positions with time-dependent density functional theory (TD-DFT) methods. Through the analysis of geometric parameters and infrared (IR) vibrational spectra, it is evident that the hydrogen bonds (HBs) are strengthened in the S1 state, providing the driving force for the ESIPT behavior. Next, frontier molecular orbitals (FMOs) and hole-electron analyses reveal dynamically distinct intramolecular charge transfer characteristics (ICTC). Furthermore, scanning of the potential energy curves (PECs) reveals that TFAQ-C more readily exists in a stable enol form in the S1 state. Finally, the photophysical properties demonstrate that TFAQ and TFAQ-C have dual fluorescent emission, and TFAQ-C-enol can act as a promising ambipolar material. This work provides robust insights for the design and development of novel TFAQ-derived WOLED materials.

Karakus et al. synthesized a turn-on fluorescence probe 3-(cyanooxy)-hydroxyflavone (FLVN-OCN) based on excited state intramolecular proton transfer (ESIPT) for detection of H2S. However, both sensing mechanism of FLVN-OCN and ESIPT mechanism of sensing product (3-HF) remain poorly understood. Additionally, CC bond was introduced to investigate the conjugated effects on sensing mechanism, ESIPT process and photophysical properties with time-dependent density functional theory (TD-DFT) method. The results found that (1) the fluorescence quenching of the probes was photoinduced electron transfer (PET) mechanism. (2) the introduction of CC bond had little effect on the sensing mechanism of FLVN-OCN substituents. (3) the extent of ESIPT attenuation exhibited a positive correlation with the length of CC bond chain. The theoretical findings provided a practical and guiding design strategy for the subsequent development of novel ESIPT-based fluorescent probes for H2S detection.

Curved polycyclic aromatic hydrocarbons (PAHs) exhibit distinctive geometric and electronic structures, rendering them highly promising for addressing solubility and air stability challenges encountered by large linear pi-conjugated organic semiconductors. In this study, a series of surface-curved PAHs and heteroatom-doped derivatives are selected and designed, and the relationship between their electronic structures and charge transport properties is investigated using density functional theory. The effects of sulfur/oxygen (S/O), nitrogen (N) and boron (B) doping on charge transport performance are further explored. The results indicate that curved PAHs exhibit enhanced solubility and stability, with molecular curvature significantly influencing charge transport properties. PAHs of series A with deeper bowl depths (d > 1.0 & Aring;) and their N/B dopants tend to form quasi-one-dimensional, slightly sliding, compact pi-stack structures with concave-to-convex configurations, exhibiting superior hole transport properties compared to those with shallower bowl-like structures (0.5 & Aring; < d < 1.0 & Aring;) and loose stacking motifs (B2, B4, B6). S/O doping between benzene rings to form seven-membered rings can significantly reduce the bowl shaped depth (d < 1.0 & Aring;) but increases reorganization energy, promoting 2D pi-pi stacking. However, the N/B atom at the edges or core of the PAHs can fine-tune the bowl shaped depth, and suppress the increase in hole reorganization energy caused by S/O doping, maintaining the hole reorganization energy of heteroatom-doped PAHs (ca. 200 meV), which is essential for high mobility materials. Introducing S/O/N atoms can increase the bandgap and enhance the optical stability of PAHs. In summary, simultaneous incorporation of sulfur (inhibiting intermolecular rotational motion) and boron (enhancing intermolecular overlap and transfer integrals) in derivative B5 leads to a substantial hole mobility enhancement (3.49 cm(2) V-1 s(-1)). These findings demonstrate that strategic heteroatom doping and curvature control synergistically optimize the charge transport functionality of curved PAH semiconductors.

Linear fused acenes exhibit excellent charge transport properties but suffer from poor solubility and stability. This study investigates “H-type” acene derivatives to address the poor solubility and stability of linear acenes by Marcus theory and kinetic Monte Carlo simulations. The findings reveal that “H-type” conjugation enhances photostability, oxidative stability, and solubility compared to linear acenes, with series a exhibiting superior solubility. The reorganization energy decreases with molecular extension, following trends similar to linear acenes. Key electronic structure differences were identified: thiophene substitution (series b) localizes the highest occupied molecular orbital (HOMO) on the bridging carbon atoms, while benzene substitution (series a) localizes it on the central acene core. Crucially, a strong correlation is established between the molecular structure parameter |ΔR| and crystal packing modes: |ΔR|<0.7 yields 1D/2D stacking; 0.7<|ΔR|<1.1 produces herringbone packing; and |ΔR|>1.1 leads to beneficial pitched π-stacking. Mobility calculations showed benzene-extended derivatives exhibit strong anisotropy. Thiophene expansion (b-3) reduces anisotropy, and benzothiophene (b-3*) improves the anisotropic mobility of molecules. This is attributed to favorable S…C interactions that suppress detrimental molecular slip. These results provide a critical theoretical framework for future development of “H-type” acene materials.

In response to the increasing demand for renewable energy technologies, it has become imperative to develop low-cost, efficient, and stable bifunctional electrocatalysts for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Here, construct a series of 2D-0D heterostructures, TMN4-O-C58BN and explore their stability and catalytic properties through density functional theory (DFT). Our results indicate that ORR prefer to produce H2O via four-electron pathway rather than H2O2 through two-electron pathway for most of catalysts. It further demonstrates that CoN4-O-C58BN and IrN4-O-C58BN are potential OER and ORR (four-electron pathway) bifunctional catalysts because of no by-product H2O2 and extremely low overpotentials (eta) (0.34/0.32 V) and (0.30/0.39 V). On the other hand, ZnN4-O-C58BN displays higher activity for H2O2 production with a small two-electron ORR overpotential (0.20 V). Lastly, the results indicate that moderate values of the Bader charge and dband center in transition metal atoms are key factors determining the intrinsic activities of TMN4-O-C58BN catalysts. This work broadens the perception of constructing 2D-0D heterostructures as stable and efficient eletrocatalysts in various electrochemical fields.

The enhancement of the optoelectronic properties of organic conjugation materials through boron doping may reshape current understanding, with boron-doped polycyclic aromatic hydrocarbons (PAHs) poised to be high-performance organic optoelectronic materials. However, the impact of boron doping on charge transport remains underexplored. In this study, the effects of diboron doping, including both dense and dispersed doping, along with further π-extension on the electronic structure, stacking pattern, and charge transport of perylene-based PAHs were systematically investigated using density-functional theory. The results indicate that diboron doping can switch the molecular packing from herringbone to π-stacking, which increases the transfer integrals and significantly improves the mobility. Furthermore, it is revealed that intermolecular B···B and B···C interactions promote the formation of π-π stacking by symmetry-adapted perturbation theory and Hirshfeld surface analysis. In addition, densely doped B2-TBPA exhibits a one-dimensional intrinsic hole mobility of up to 40.86 cm2 V-1 s-1, while B2-HBP with π-extension and dispersed diboron doping exhibits pitched-π stacking, allowing it to display potential for bipolar transport. Monte Carlo and molecular dynamics simulations further demonstrate that diboron-doped PAHs offer more stable charge transport with reduced thermal disorder. This research provides new insights for the experimental design and synthesis of high-performance organic semiconductor devices.

Strategically incorporating Se into B/N-heteropolycyclic frameworks is key to modulating multiple resonance (MR) systems and developing high-performance TADF materials. Combining density functional theory and spin-component scaled coupled cluster calculations, this study reveals the TADF mechanism regulated by the heavy-atom effect in model molecule BNSSe, and designs two types of high-performance MR-TADF materials based on BNSSe. (1) The blue-emission molecule 1 (469 nm) achieves complementary short-range charge transfer/long-range charge transfer advantages via three para-B-π-N units. Its reverse intersystem crossing rate (k RISC) reaches 108 s-1 (three orders of magnitude higher than BNSSe), benefiting from the synergy of a reduced singlet-triplet energy gap, moderately enhanced spin-orbit coupling (SOC), and suppressed structural relaxation. (2) The red-emission molecules 2-7 (≈630 nm) were further developed via a delicately designed π-bonding/non-bonding molecular orbital hybridization strategy. This series of molecules not only maintain a high radiative decay rate but also effectively inhibit the non-radiative decay process, and their design concept is expected to break through the constraints of the traditional energy gap law. Theoretical studies reveal that the spatial position of heteroatoms can modulate molecular geometry and induce axial redistribution of frontier molecular orbital electron density, thereby selectively enhancing the contribution of Se atoms to the excited-state transition orbitals and enabling precise regulation of SOC strength. This work not only deepens the theoretical understanding of the heavy-atom effect mechanism but also provides a new strategy for developing high-performance MR-TADF materials through the targeted regulation of SOC and k RISC via atomic site engineering.

Singlet oxygen (1O2) is well known in cancer photodynamic therapy, however, its real-time monitoring still faces certain challenges. In the past decades, a great deal of phenoxy-dioxetane-based chemiluminescence probes had become widespread to detect 1O2. However, much detail in this process is still unclear, for instance, the oxygen addition reaction happened in ground state or singlet biradical state. In this work, take SOCL as an example, the chemiluminescent mechanisms were studied by DFT and TDDFT method. The results found that both the neutral and anionic SOCL undergoes an oxygen addition reaction at ground state, not singlet biradical state. In the gas phase, DMSO and water, the deprotonation process makes the intrinsic barrier of anionic SOCL smaller than that of neutral SOCL. Moreover, the solvents can greatly reduce the reaction barrier and change the potential determining steps oxygen addition reaction. In contrast, the solvents have almost no effect on the decomposition mechanism.

Two-coordinated carbene-metal-amide (CMA) complexes represent an important class of thermally activated delayed fluorescence (TADF) emitters, yet the underlying mechanisms governing their high efficiency remain to be fully elucidated. Here, we report a systematic theoretical study of two CMA complexes (M = Cu(I), Ag(I)) supported by a cyclic alkyl(amino)carbene (CAAC) ligand and a carbazolyl amide donor. We find that delayed fluorescence arises from ligand-centered intermolecular charge transfer with minimal involvement of the metal in frontier orbitals or spin-orbit coupling. Remarkably, efficient reverse intersystem crossing is facilitated by the presence of near-degenerate T1 and T2 states, enabled by a mirrored hole-electron distribution reminiscent of the multiple-resonance effect observed in B/N systems. This unique electronic characteristic promotes intramolecular short-range charge transfer and enhances triplet-to-singlet spin-flip processes, ultimately leading to a high photoluminescence quantum yield. Our results uncover a previously overlooked TADF mechanism in CMA emitters and offer a design strategy for efficient metal-assisted TADF materials through tailored electronic degeneracy and spatial overlap.

This study systematically investigates the synergetic effect of atomic electronegativity, substitution position and solvent polarity on the regulation of the excited-state intramolecular proton transfer (ESIPT) mechanism in 1-(trifluoroacetylamino)anthraquinone (TFAQ) derivatives. Through analyses of geometric parameters, infrared (IR) vibrational spectra, reduced density gradient (RDG) plots, and topological characteristics, we confirmed that the intramolecular hydrogen bonds (IHBs) are enhanced from the ground state (S0) to the first singlet excited state (S1) in cyclohexane (CYH), dimethyl sulfoxide (DMSO) and water (H2O). More specifically, the IHBs in the S1 state weaken with increasing electronegativity. IHBs are strengthened with increasing solvent polarity from CYH to DMSO. The meta- and para-substituted derivatives display a stronger IHB enhancement effect in DMSO and H2O than the ortho-substituted derivatives. Fluorescence spectral analyses revealed that TFAQ, TFAQ-N, m-TFAQ-N, and p-TFAQ-N display dual fluorescence emission in DMSO and H2O. Finally, the scanned potential energy curves (PECs) indicate that the enhanced electronegativity of substituent atoms imposes certain restrictions on ESIPT, making meta- and para-substituted derivatives conducive to ESIPT. We anticipate this study will provide valuable insights for the design and development of novel TFAQ-based white-light organic light-emitting diodes (WOLEDs).

The ring-annelation modification of phenyl and naphthyl on excited-state intramolecular proton transfer (ESIPT) and photophysical properties of seven 10-hydroxybenzo[h]quinoline (HBQ) derivatives were investigated by density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. Potential energy curve (PEC) analysis suggests that proton transfer is more probable in the excited state for all studied molecules. In particular, for HBQ, HBQ-B, HBQ-C, HBQ-D, HBQ-C-2, the ESIPT can occur spontaneously. Naphthyl both at the 8, 9-position and 2, 3-position of HBQ are unfavorable for the formation of keto form tautomer in excite state. Absorption and fluorescence spectra analyses demonstrate that the absorption and emission wavelength increase with extending the conjugation effect. It also found that 3, 4 -position of HBQ is very important for near-infrared emission.

Multi-resonance thermally activated delayed fluorescence (MR-TADF) materials have garnered significant research interest owing to their remarkably narrow emission spectra with full width at half maximum (FWHM) below $40~\text{nm}$, demonstrating substantial advantages over conventional donor-acceptor (D--A) type TADF materials in spectral purity. However, conventional N--B--N resonant framework materials are fundamentally constrained by their intrinsically low reverse intersystem crossing rates ($k_{\text{RISC}} < 10^{3}~\text{s}^{-1}$), presenting a persistent challenge for achieving high-efficiency TADF. This study proposes a triple collaborative design strategy based on CzBN to break through this limitation: (1) Enhance the separation of HOMO and LUMO by $\pi$-conjugation expansion and reduce $\Delta E_{\text{ST}}$; (2) Introduce O/S heteroatoms to control the excited state charge transfer (CT) characteristics and further reduce $\Delta E_{\text{ST}}$; (3) Enhance the spin-orbit coupling (SOC) effect through the synergy of extended $\pi$-system and heteroatoms. Based on this, five new MR-TADF molecules were designed and studied. Among them, the $k_{\text{RISC}}$ of CzBN\_S reached $3.48 \times 10^{6}~\text{s}^{-1}$, two orders of magnitude higher than CzBN, while maintaining $\Delta E_{\text{ST}} < 0.1~\text{eV}$ and FWHM at $40~\text{nm}$.

Bimetallic atomic catalysts were widely used in oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) because of the synergistic effect between two metal atoms and the high metal loading. However, there were still many questions which could not find satisfactory answers in the catalyst process. For example, were there one or dual active site? What was the impact of the synergistic effect on electronic properties, catalytic activity, reaction mechanism? In order to solve these questions, the FeCo bimetallic atom catalysts with adjacent Fe-N4-C and Co-N4-C structures as dual active sites for OER/ORR was studied through density functional theory (DFT) calculations. Both the ORR and OER theoretical overpotential (HORR and HOER) of the dual active centers structure, FeCoN8C-Dual was between single active site structure. FeCoN8C-Dual expressed a comparable HORR with Pt and a superior OER catalytic activity than IrO2. For ORR and OER in alkaline medium, the kinetic catalytic performance of FeCoN8C-Dual was higher than that of the single metal active site model, when two metal active sites were used at the same time.

Single-atom catalysts (SACs) have attracted significant attention due to their high atomic utilization and tunable coordination environment. However, the catalytic mechanisms related to the active center and coordination environment remain unclear. In this study, we systematically investigated the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) catalytic activities of NiN4, NiN3, NiN3H2, NiN4X, NiN3X, and NiN3H2X (X denotes axial ligand) through density functional theory (DFT) calculations. This study unveils two distinct reaction pathways for ORR and OER, involving proton-electron pairs adsorbed from both the solution and the catalyst surface. The overpotential is the key parameter to evaluate the catalytic performance when proton-electron pairs are adsorbed from the solution. NiN3 and NiN3H2 show promise as pH-universal bifunctional electrocatalysts for both ORR and OER. On the other hand, when proton-electron pairs are adsorbed from the catalyst surface, the reaction energy barrier becomes the crucial metric for assessing catalytic activity. Our investigation reveals that NiN3H2 consistently exhibits optimal ORR activity across a wide pH range, regardless of the source of proton-electron pair (solvent or catalyst surface).