Chemistry - A European Journal最新文献

Machine learning (ML) models are increasingly used in quantum chemistry, but their reliability hinges on uncertainty quantification (UQ). In this study, we compare two prominent UQ paradigms-deep evidential regression (DER) and deep ensembles-on the QM9 and WS22 datasets, with a specific emphasis on the role of post hoc calibration. Raw uncertainties from both methods were systematically miscalibrated: DER produced uncertainty estimates where data noise and model uncertainty were not cleanly separated, while ensembles produced sharper yet underconfident estimates. Applying calibration techniques such as isotonic regression (ISR), standard scaling, and GP-Normal corrected these deficiencies, aligning predicted variances with observed errors. On QM9, calibration enabled DER to filter high-confidence predictions more effectively than ensembles. On WS22, calibrated ensembles not only improved statistical reliability but also delivered substantial computational savings in active learning, reducing redundant ab initio evaluations by more than 20%. These results demonstrate that post hoc calibration is essential to transform uncertainty estimates from descriptive metrics into actionable signals, ensuring both trustworthy predictions and resource-efficient molecular modeling.

A library of novel phenylpyridine-based boron C,N-chelates bearing a mesogenic unit was synthesized and investigated to clarify how the chain type, length, and number, as well as the boron substitution (BH₂ vs. BMe₂) influence the mesomorphic and photophysical behavior. All BH₂ derivatives exhibited SmA or N phases even with short alkyl chains, whereas BMe₂ analogues remained nonmesomorphic unless a semi-perfluorinated chain was introduced, demonstrating the strong influence of boron substitution on mesophase formation. All compounds displayed intense blue emission in solution, with spectral properties primarily determined by the boron C,N core and only minor shifts induced by variation in the mesogenic unit in agreement with complementary DFT calculations. Quantum yields reached up to 100% in solution. These results demonstrate that mesomorphic behavior can be introduced and tuned while preserving the excellent photophysical performance of the boron-C,N-chelate system.

The direct functionalization of tertiary and other inert allylic C─H bonds represents one of the most attractive strategies in the construction of complicated molecules with quaternary carbon centers. Unlike approaches that rely on pre-functionalized allylic substrates, such as halides, acetates, and carbonates, allylic C─H activation provides an atom- and step-economical route to forge diverse and valuable C─C and C─X bonds. Although the functionalization of secondary allylic C─H bonds has been extensively studied and well established in recent years, the corresponding transformation of tertiary allylic C─H bonds remains considerably underdeveloped. This concept summarizes the progress and mechanistic pathways-including transition-metal insertion (via two-electron transfer) and radical-involving single-electron transfer processes-enabling the functionalization of various tertiary allylic C─H bonds. Future directions in this long-standing and challenging field are also discussed.

Donor-acceptor (D-A) conjugated polymers hold significant potential as high-potential thermoelectric (TE) materials due to their adjustable structures, efficient charge transport ability and tunable doping level. However, achieving a balance between the Seebeck coefficient (S) and electrical conductivity (σ) remains challenging. In this work, we employ thienoisoindigo (TIIG) as the acceptor and dithieno[3,2-b:2',3'-d]pyrrole (DTP) as the donor to construct two novel D-A conjugated polymers for TE application. Through introducing thiophene (T) units as spacers between DTP and TIIG, PTIIG-2T-DTP enhances the planarity of conjugated backbones compared to PTIIG-DTP. Moreover, PTIIG-2T-DTP film shows more compact packing between conjugated backbones, which improves the charge transport. Despite slightly lower doping efficiency, doped PTIIG-2T-DTP exhibits superior carrier mobility and conductivity to PTIIG-DTP. Additionally, PTIIG-2T-DTP shows a higher Seebeck coefficient at same doping concentration. Ultimately, PTIIG-2T-DTP achieves a large power factor of 23.2 µWm^-1 K^-2 with σ of 120 S cm^-1 which is much higher than that of PTIIG-DTP. This work develops an effective polymer backbone engineering strategy for developing high-performance D-A conjugated TE polymers.

The development of high-capacity and selective adsorbents for fluoride (F^-) removal is hindered by its inherent characteristics, including its small ionic radius, high charge density, strong hydration ability, high mobility and solubility, as well as the weak diffusion driving force at low concentrations. In this study, a novel composite adsorbent was prepared by loading UiO-66-NH₂ onto carboxymethylated cellulose beads (UiO-66-NH₂@CMCBs) via an in-situ generation strategy for efficient adsorption and recovery of F^-. The highly porous structure and abundant surface carboxyl groups of CMCBs provide favorable coordination sites, promoting the growth of UiO-66-NH₂. Under environmental conditions (25°C, pH 7.4), UiO-66-NH₂@CMCBs completely remove F^- from aqueous solutions with an initial concentration of 10.0 mg L^-1. Furthermore, UiO-66-NH₂@CMCBs demonstrated excellent column adsorption performance and outstanding reusability, maintaining a removal efficiency exceeding 80% after 5 cycles. These results highlight the potential of UiO-66-NH₂@CMCBs as an efficient and recyclable adsorbent for the practical treatment of fluoride-contaminated water.

Aqueous Zn-I₂ batteries suffer from short cycle life due to zinc (Zn) dendrite growth and polyiodide shuttle-induced corrosion. To address these key challenges, a multifunctional protective film of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIMTFSI) ionic liquid, denoted as IL@Zn, was constructed on the Zn anode surface via a tape-casting method to improve the cycle life of Zn-I₂ batteries. EMIM⁺ cations preferentially adsorb on Zn, creating a water-lean inner Helmholtz plane (IHP) and providing steric hindrance for uniform Zn nucleation, while hydrophobic TFSI^- anions enrich at the surface to build a water-repellent interface that excludes H₂O and suppresses parasitic reactions. Moreover, EMIM⁺ hinders iodine dissolution and forms an EMIM⁺-I₃ ^- dominant phase, mitigating the polyiodide shuttle and the associated Zn corrosion. Consequently, IL@Zn symmetric cells deliver over 350 h of stable cycling at 5.0 mA cm^-2. Zn-I₂ full cells with IL@Zn anodes retain 82% capacity after 2000 cycles at 2 A g^-1 and exhibit higher Coulombic efficiency (CE) after self-discharge than cells with unprotected Zn anodes. This work demonstrates a facile strategy for aqueous Zn-I₂ batteries that effectively addresses the challenges of dendrite formation and the shuttle effect.

Understanding and controlling the reactivity of radical species remains a major challenge in many chemical reactions, with the goal of steering and precisely tuning key processes. Recognized as a simple and efficient method for the preparation of 2D nanomaterials, diazonium electrografting is a prime example of a functionalization technique that still requires deeper mastery to meet the demands of future bottom-up approaches. In this work, supported by multiphysics simulations, we achieve an unprecedented understanding of the grafting mechanism involved in nitrobenzene diazonium electrografting and its impact on the resulting nanofilm composition. It is demonstrated that film growth arises from a competition between aryl and diazenyl radicals, leading to the incorporation of variable amounts of azo-bridged nitrophenyl units. By implementing control strategies using radical scavengers and redox inhibitors, corroborated by simulations, we show that diazenyl radicals are preferentially grafted at the substrate/film interface rather than within the film structure itself. Finally, we demonstrate that selective trapping of aryl radicals over diazenyl radicals enables the formation of azo-enriched films, thus opening the way for precise tuning of film composition and selective radical reactivity.

Recent development in the field of organic luminescent materials has gained tremendous attention, particularly due to the materials which exhibit efficient room temperature phosphorescence (RTP). The extensive research in the field has led to variety of metal-free pure organic systems exhibiting excellent performance such as high quantum yield, longer lifetime, and afterglow at ambient conditions. A wide range of strategies were developed to enhance the RTP efficiency, among which the incorporation of chalcogen atoms such as O, S, Se, and Te at bridging position in pure organic system has emerged as a promising strategy. The bridging of the chalcogens atoms not only facilitates the strong spin orbit coupling (SOC) and efficient intersystem crossing (ISC), but also provide more rigid molecular framework to reduce the nonradiative decay pathways and stabilizes the triplet excitons, resulting in RTP with higher quantum yield and longer lifetime. This review focuses on the development of bridged chalcogen-containing pure organic RTP materials with various strategies to achieve more efficient RTP and their applications. In particular, we discuss and compare a broad range of chalcogen containing organic phosphors, highlighting their structural differences and design strategies that affect the phosphorescence under ambient condition.

We describe here the first report on the alkaline earth-catalyzed regioselective synthesis of trisubstituted allenes from sec-propargyl alcohols (PAs) and active methyl ketones/electron-rich arenes. Unlike previous methods, the current approach does not require the protection of alcohol, heating, transition metal catalysts, or solvents. The reaction mechanism is proposed based on deuterium labelling, step-wise synthesis, and isolation of intermediates. The current protocol exhibits a broad substrate scope, high reaction yields, and enables gram-scale synthesis. Besides, we also demonstrated the one-pot cyclization of these allenes to obtain tetrahydroindoles and fused furans.

Chiral secondary amines in lactams are commonly used as chiral organocatalysts (MacMillan catalysts) in a broad range of transformations. The related thiolactam derivatives are less explored although possessing some significantly differing properties originating from the stereoelectronic characteristics of sulfur. In the present study, we present a streamlined synthesis and application of imidazolidine-4-thiones from naturally abundant L-phenylalanine. Suitable substituents enable asymmetric Diels-Alder reactions with high enantioselectivity and yield. Here, we discovered the formation of a novel bicyclic thiolactam aldehyde motif in absence of the diene. The obtained hetero-bicycle, with four consecutive stereocenters, is formed in high yield and stereoselectivity from imidazolidine-4-thione and two cinnamaldehyde units, whereas the first gen. MacMillan catalyst shows no reactivity. We propose a mechanism of formation which is supported by DFT calculations, revealing a combination of thermodynamic and kinetic factors for the observed selectivity. Our results demonstrate the surprising versatility of imidazolidine-4-thiones, as this compound class can not only engage as a catalyst but can simultaneously participate as a reagent to form complex structures. The hetero-bicyclic skeleton is accessible in a single step and allows for facile structural modifications.