Chemistry - A European Journal最新文献

Chemical molecules may show very different properties in the solid state and in solution, which is mainly caused by the difference in structure between different physical states. Well-defined metal cluster molecules are ideal models for the investigation of the dynamic dissolution/crystallization process, as they usually exhibit photoluminescence (PL) that is sensitive to reversible changes in coordination geometry and multi-electron structure. Here we report the dissolution/crystallization-induced photoluminochromism (PLC) of carbon-centered Au^I ₆Cu^I ₂ clusters bearing pyridylphosphine or pyridyl N-heterocyclic carbene (NHC) ligands. These clusters, with an octahedral structure doubly capped with copper(I), exhibit greenish-yellow emission in the solid state. Remarkably, the PL of the NHC-protected clusters in solution changes only slightly, whereas the phosphine-protected clusters exhibit red PL accompanied by a large bathochromic shift (>100 nm), a reversible process upon dissolution equilibration. X-ray absorption spectroscopy and theoretical calculations suggest that the octahedral CAu^I ₆ structure in the crystal is twisted into a triangular prismatic structure in solution. This remarkable ligand effect on the dissolution/crystallization-induced PLC would provide advanced design guidance for stimuli-responsive chromic materials.

Eumelanin is a bio-pigment with remarkable photoprotective properties, whose function is tied to its complex supramolecular organization. Although hydrogen bonding and π-π interactions are recognized as key forces in shaping its architecture, their individual contributions remain poorly defined. Among its molecular precursors, the canonical monomer 5,6-dihydroxyindole (DHI) is notable for forming extensive hydrogen-bonded networks that stabilize supramolecular assemblies. To clarify how hydrogen bonding influences supramolecular topology in eumelanin precursors, we investigate selectively methylated derivatives of DHI, examining how subtle modifications to hydrogen-bonding motifs alter crystal packing, intermolecular arrangements, and optical properties. Single-crystal structures reveal that O-methylation (DMI) changes hydrogen-bonding dimensionality yet preserves helical assemblies, whereas full O- and N-methylation (DMI-Me) suppresses hydrogen-bonding, giving rise to zigzag arrangements dominated by van der Waals forces. Solid- and solution-state NMR measurements independently confirm the differences in the hydrogen-bonded assemblies. Complementary electronic spectroscopy shows that noncovalent architectures of the eumelanin derivatives exhibit pronounced excitonic coupling between neighboring chromophores. Electronic structure calculations support these observations, demonstrating that coupling originates primarily from Coulombic interactions, with minimal contributions from charge transfer. By linking molecular substitution to packing motifs and excitonic interactions, this work establishes hydrogen bonding as a design element for directing supramolecular order and emergent optoelectronic behavior in eumelanin-inspired materials.

Asymmetric transition metal catalysis represents the most reliable method for the chiral induction in organic scaffolds and to synthesize a wide array of valuable 3D-molecules. However, accessing both enantiomers of the chiral molecules from a catalyst(s) having the same chirality through ingenious stereo-control has remained a highly demanding task. Herein, we disclose the catalytic enantiodivergent synthesis of 3-vinylphthalides from arylcarboxylic acids and cyclopropenes, an efficient surrogate for vinylcarbenes. Through engineering the chiral cyclopentadienylrhodium(III) catalysts, both enantiomers have been achieved with excellent yield and enantioselectivity via regioselective C─H bond functionalization using a weakly coordinating directing group and asymmetric [4+1]-annulation. Experimental and computational investigations revealed the mechanism of the oxidative annulation and enantiodetermining ring-opening isomerization of cyclopropenes, which is governed by the stereoselective cleavage of the C─C bond. The present study opens a new avenue in asymmetric C─H bond functionalization and allows access to both enantiomers of the target molecules without altering the chirality of the ligand.

Accurate monitoring of adenosine triphosphate (ATP)-the universal energy currency of cells-is essential for elucidating cellular metabolism and disease progression. However, the high basal concentration of intracellular ATP (1-10 mM) and variable probe uptake during imaging have hampered the development of reliable fluorescent sensors. Although DNA aptamer-based probes provide excellent selectivity, conventional turn-on designs often lack internal calibration, and Förster resonance energy transfer-based ratiometric probes typically exhibit limited signal changes. We report a ratiometric DNA duplex sensor comprising a Cy5-labeled ATP aptamer and a thiazole orange (TO)-labeled exciton-controlled hybridization-sensitive fluorescent oligonucleotide (ECHO) probe. Upon ATP binding, the aptamer structure switches and releases the reporter strand, resulting in a pronounced decrease in TO fluorescence while the Cy5 signal remains constant. Rational insertion of a polythymidine spacer effectively suppressed undesired TO-to-Cy5 energy transfer, enabling a reliable ratiometric Cy5/ECHO readout. The sensor operates robustly across physiological ATP concentrations, exhibits high nucleotide selectivity and satisfactory serum stability, and shows minimal cytotoxicity. Live-cell flow cytometry and confocal imaging further confirmed that cancer cells displayed significantly higher Cy5/ECHO ratios than normal fibroblasts. This internally self-calibrating aptamer sensor thus provides a powerful platform for intracellular ATP imaging and cancer diagnostics.

Thiazolinochlorin compounds bearing sulfoxide and sulfone moieties were prepared by selective sulfur-oxidation with m-chloroperoxybenzoic acid. The oxidation state of the sulfur atom directly affected the optical properties of the thiazolinochlorin compounds, which were investigated through computational calculations. The structures of zinc complexes of these compounds were drastically changed by the oxidation state of the sulfur atom. Notably, nonoxidized thiazolinochlorin afforded a π-cation complex with elimination of the alkoxy group. The detailed structure and optical properties of the complexes in solution were investigated and compared with those of neutral zinc complexes derived from sulfoxide and sulfone compounds. Furthermore, the π-cation complex underwent self-aggregation, enabling the absorption of near-infrared light.

Sulfoquinovose (SQ) is a major biogenic sulfonated sugar whose degradation fuels microbial sulfur and carbon cycling. In the sulfoglycolytic Entner-Doudoroff (sulfo-ED) pathway, 2-keto-3,6-dideoxy-6-sulfogluconate (KDSG) is cleaved by KDSG aldolase to yield pyruvate and sulfolactaldehyde, yet the structure and mechanism of this enzyme have remained unclear. We report the biochemical and structural characterization of a metal-dependent KDSG aldolase from Pseudomonas putida using chemo-enzymatically synthesized KDSG. The enzyme forms a homohexamer, with a (β/α)₈ TIM-barrel monomer assembling as a 'dimer-of-trimers'. The enzyme exhibits optimal activity in the presence of Co²⁺ or Mn²⁺, consistent with other class II aldolases. Kinetic analysis revealed millimolar-range K_M values for KDSG and modest cross-reactivity with the related glycolytic intermediate, 2-keto-3,6-deoxy-6-phosphogluconate (KDPG). Crystal structures of the apo and Co²⁺•pyruvate-bound forms (2.85 Å and 2.80 Å) show a metal-coordinated active site at the subunit interface, with conserved residues mediating metal binding and catalysis, providing insights into the mechanism of sulfonate-specific aldol cleavage. Sequence-similarity network and genome-context analyses show that KDSG aldolases are widespread among Proteobacteria and typically cluster with sulfo-ED pathway genes. These results define the structural and mechanistic basis of KDSG aldolases and inform on their roles in bacterial sulfur metabolism.

In the quest for advanced resistive memory devices, the rational design of π-conjugated small molecules is increasingly recognized as an effective approach to achieving high-performance, non-volatile data storage. Herein, we report the design and synthesis of a series of D-A-D' and D-π-A-π-D' type molecules featuring dibenzothiophene sulfone as the central acceptor, marking its debut application in organic resistive memory device applications. The molecules were unsymmetrically functionalized through the incorporation of different donor units such as tert- butylphenyl, triphenylamine, and methoxyphenyl units. Furthermore, the incorporation of acetylene bridges enhanced π-conjugation and facilitated intramolecular charge transfer. Photophysical and electrochemical studies revealed intramolecular charge-transfer characteristics and band gap values in the range of 3.0-3.8 eV. All fabricated devices displayed non-volatile binary WORM memory behavior with ON/OFF ratios up to 10⁴, low threshold voltages as low as -1.52 V, and substantial stability over 100 cycles with retention time of 4000 s. Notably, asymmetric compounds containing triphenylamine donor exhibited superior memory performance. Density functional theory studies further validated the proposed charge transfer and charge trapping mechanism. These results establish dibenzothiophene sulfone-based donor-acceptor systems as promising candidates for next-generation organic memory technologies.

The detection of unilateral kidney injury remains challenging owing to the intrinsic compensatory mechanism of the kidneys. Noninvasive kidney imaging using renal-clearable near-infrared (NIR) agents has shown promise in evaluating renal function. To enable accurate detection of unilateral kidney injury, herein, we developed a high-contrast NIR imaging agent of 800CW-Au by conjugating IRDye800CW with renal-clearable gold nanoparticles (Au₂₅SG₁₈). Compared with free IRDye800CW, the pharmacokinetics of the dye was significantly tailored after conjugation on Au₂₅SG₁₈, resulting in enhanced blood retention, reduced vascular extravasation, and lower affinity with background tissue. Consequently, 800CW-Au achieved noninvasive kidney imaging with contrast enhancement > 100% for up to 12 h, much longer than the previously reported zwitterionic ZW800-1 (∼10 min) and PEGylated IRDye800CW (∼4 min). We then established two representative mouse models of unilateral kidney injuries, including unilateral ureteral obstruction and ischemia-reperfusion injury. According to its kinetics of renal enhancement and derived parameters, 800CW-Au sensitively detected the functional impairment in the injured kidney and the compensatory hyperfiltration in the contralateral kidney, which the conventional blood biomarkers and global glomerular filtration rate were all insensitive to detect. This strategy of our work will provide guidance for developing renal NIR agents and advance the noninvasive detection of unilateral kidney injury.

Micro-mesoporous Ti-MWW zeolites with a hierarchical structure were synthesized to overcome the diffusion limitations in the epoxidation reaction involving large-molecules. One-pot dissolution-recrystallization process of three-dimensional Ti-MWW constructed bimodal pores and abundant Ti sites on the external surface of Ti-MWW, which were efficient for cumene hydroperoxide-based propylene epoxidation to propylene oxide (PO), achieving a high PO yield as 91%, far superior to the sole 35% performance value afforded by the pristine Ti-MWW catalyst. Poisoning experiments confirm that the reaction predominantly occurs on the external surface. The recrystallization process further increases the fraction of open Ti sites, boosting epoxidation activity. Moreover, the robust zeolite framework endowed superior stability compared to the conventional mesoporous titanosilicate catalysts, remaining high activity under harsh conditions.

Zinc-based flow batteries (ZFBs) have emerged as promising energy storage systems due to their high theoretical gravimetric capacity, low electrochemical potential, natural abundance of zinc, and cost-effectiveness. However, their widespread adoption is hindered by the persistent issue of zinc dendrite formation. Herein, we report a facile yet effective strategy to suppress dendrite formation by introducing polyquaternium-6 (PQ-6) as a functional electrolyte additive. Spectroscopic and electrochemical analyses reveal that PQ-6 preferentially adsorbs at the electrode-electrolyte interface, forming a dynamic barrier that modulates the zincate ion diffusion from a two-dimensional (2D) to a three-dimensional (3D) mode and promotes homogeneous nucleation. Consequently, the PQ-6 modified alkaline zinc-iron flow battery (AZIFB) exhibits exceptional cycling stability (nearly 400 h, 1200 cycles) while maintaining high energy efficiency (70.37%) at a current density of 80 mA cm^-2. This work not only provides an effective strategy for mitigating zinc dendrite growth but also advances the development of sustainable and high-performance zinc-based flow batteries.