ChemistryEurope最新文献

The Front Cover shows a magnetic molecule that is being considered for nanoscale information storage and quantum applications. An ideal molecule based on a tri-coordinated Yb^III was theorised in 2021. In their Research Article (DOI: 10.1002/ceur.202400062), Y. Sarazin, K. Bernot and co-workers show that this molecule does indeed possess the ideal electronic structure postulated, but that its performance is much weaker than expected. The anomalies observed in its infrared emission could be an experimental signature of active vibronic contributions in the molecule, detrimental to its magnetic behaviour.

The Cover Feature illustrates the unique properties of nanoconfined water that can facilitate condensation reactions, potentially leading to the formation of biopolymers in submarine hydrothermal vents. In confined nanospace, the arrangement of water molecules changes significantly, lowering the dielectric constant of water and modulating the enthalpy–entropy correlation of chemical reactions. Due to these altered properties, layered minerals with confined nanospace drive enzyme-like condensation reactions. In this Concept (DOI: 10.1002/ceur.202400038), H.-E. Lee, M. Russell and R. Nakamura explore these possibilities, offering a clue to resolving the “water paradox” in the origin of life and an innovative use of nanoconfined water as a greener solvent for polymerization chemistry.

We are reporting on the use of a low-coordinate Yb^III amide with near-ideal planar trigonal [Yb{N(SiMe₃)₂}₃] (1) and on a bipyramidal trigonal derivative [Yb{N(SiMe₂H)₂}₃ ⋅ (thf)₂] (2) that constitute quintessential cases to investigate luminescent and magnetic properties otherwise usually blurred on less symmetrical compounds. These compounds represent the first experimental objects that allow for the confirmation of the recent conjecture about best-performing SMM built on the archetypal prolate lanthanide ion. We have performed a combined theoretical, luminescent, and magnetic study on these molecules. For 1, a spectacular split of the ²F_7/2 ground state of 1312 cm⁻¹ is measured by low-temperature near-infra-red luminescence as well as the calculated pure wavefunction composition of the low-lying Kramers doublets, making this complex a textbook example of a prolate SMM. These results are corroborated by comparison with 2, that exhibits as expected a 50 % decrease of the ground state splitting compared to 1. Yet, we show that these remarkable features are insufficient to promote SMM behavior, and Orbach relaxation is unlikely to occur even on such an ideal low-coordinate SMM without control of spin-phonon coupling.

Water is the most common, yet highly peculiar, liquid on Earth. Biological systems manipulate the properties of water to perform reactions that are extremely difficult in synthetic chemistry. One such example is polymerization, which is essential for life and requires the removal of water; however, the removal of water adversely affects the redox reactions that harness the free energy to sustain life. This dichotomy in the water chemistry of life is referred to as the “water paradox”, which remains an unsolved puzzle in the origins of life research. In the present concept paper, we propose that the water paradox may be resolved if anomalous water behavior, including the extremely low dielectric constant and modulation of the enthalpy-entropy compensation relationship arising from nanoscale confinement, are considered. The unique properties of confined water allow for polymerization reactions to proceed even in water-rich hydrothermal vent (HV) environments due to the structurally aligned nanopores within HV walls. Studies of how structural changes in water networks in nano-spaces affect catalysis and free energy exchange represent the next frontier in the field of origins of life research and synthetic chemistry.

The oxygenated sesquiterpenoid (-)-integrifolian-1,5-dione, which originates from a plant that finds widespread use in South American traditional medicine, is distinguished by a rigid bicyclic framework consisting of a cyclopropane that is cis-annulated to a cyclodecane ring. The first total synthesis of this demanding target is described, which relies on a highly selective cyclopropanation reaction of an α-stannylated-α-diazoester catalyzed by a heteroleptic dirhodium paddlewheel complex, followed by an unprecedented Stille-type cross coupling of the resulting stannylated cyclopropane with methyl iodide as the electrophilic partner to form the all-carbon quaternary stereocenter at one of the bridgehead positions. Equally decisive was the bicyclization strategy based on lactonization/ring expansion that ultimately allowed the strained ten-membered carbocycle to be forged.

Bridged photosensitizer-catalyst systems are promising models to study photocatalytic hydrogen evolution. However, the systems in the literature structurally diverse and therefore hard to compare. Many systems show highly complex photophysics including several accepting orbitals for the excited state, as a result catalytic activity is hard to predict. Here we present a bimetallic Ru−Pt photocatalyst bearing peripheral spectator ligands at the ruthenium(II) photocenter as a member of the Ru-tpphz-Pt family. Consequently, it features a single acceptor tpphz ligand and so-called unidirectional electron transfer, i. e., electron transfer without co-occurring transfer to peripheral ligands, from the excited state. Thus – and in contrast to recently used peripheral ligands – the new spectator ligands do not disrupt electron transfer towards the catalytic center. By comparison to known systems, this facilitates unprecedented insight into the importance of electron transfer from the bridge to the catalytic center moving towards more rational design of oligonuclear photocatalysts.

Carbohydrate-based ionic liquids and salts (CHILS) have recently emerged as an uprising sub-class of ionic liquids. Their starting materials are available in abundant natural resources from plants and fauna. Carbohydrates are not only sustainable; they also exhibit natural chirality. To use this, novel glucosyl imidazolium NTf₂ ionic liquids were synthesized and applied as organocatalysts in aza-Diels-Alder reactions in this work, where we used aldimines and Danishefsky's diene as substrates. We investigated the structure-activity relationships of these glucosyl imidazolium NTf₂ organocatalysts through several functionalizations on the carbohydrate and the imidazole and compared them with common metal catalysts and ionic liquids. Our organocatalysts improved the yield of the model aza-Diels-Alder reaction highly and also had a positive effect on the overall diastereomeric excess.

Sulfur-containing functional groups (SFGs) are increasingly important for modern medicinal chemistry and their large structural diversity provides many opportunities for lead optimization. In an effort to simplify the access to the full set of SFGs, we report herein a versatile strategy utilizing (hetero)aryl trityl sulfides (ArSCPh₃) as the common precursors. We developed a mild and high yielding Pd-catalyzed thiotritylation cross-coupling methodology to afford ArSCPh₃ compounds from (hetero)aryl bromides and iodides. Efficient chemoselective derivatizations provided access to eight different SFGs and sulfur(VI) fluorine exchange (SuFEx) hubs, which open up further downstream derivatizations towards the full set of SFGs. Thereby obtainable sulfur motifs include aryl sulfur pentafluorides (ArSF₅), aryl tetrafluoro-λ⁶-sulfanyl chlorides (ArSF₄Cl), aryl sulfonimidoyl fluorides (ArS(O)(NR)F), aryl sulfonyl fluorides (ArSO₂F), aryl sulfonic acids (ArSO₃H), and aryl sulfinyl fluorides (ArSOF), which are all valuable functional groups in modern drug discovery.

We report the first synthesis of a water-soluble [9]cycloparaphenylene derivative containing three hydrindacene (1,2,3,5,6,7-hexahydro-s-indacene) units with four carboxylates at the 2,6-positions via a macrocyclic gold complex. This crown-shaped macrocyclic compound exhibits remarkable water solubility, of up to 16 mmol L⁻¹ (2.6 g/100 mL), as well as strong visible fluorescence in water (λ_em=447 nm, ϕ_F=0.64, brightness (ϵ×ϕ_F)=5.1×10⁴). This molecule effectively encapsulates cationic guest compounds, such as methyl viologen dichloride, as indicated by a change in visible fluorescence.

The Front Cover highlights the core transformation that occurs in a polycyclic aromatic hydrocarbon with a central eight-membered ring (tetrabenzocyclooctatetraene) upon chemical reduction. The dial at the bottom illustrates the controlled addition of charge to the system. In the charge states—neutral, anionic, and dianionic—the eight-membered ring core is highlighted in red, yellow, or green, respectively. These “stoplight” colors emphasize the experimental observations described in the paper, whereby going from the neutral to the monoanionic form results in only a small structural perturbation of the carbon framework, whereas the addition of the second electron triggers the formation of an energetically favorable “butterfly” dianion with a new C−C bond. Thus, the central eight-membered ring is transformed into two fused five-membered rings. More information can be found in the Research Article by R. Gershoni-Poranne, M. A. Petrukhina and co-workers (DOI: 10.1002/ceur.202400055).