Nature chemistry最新文献

Layered perovskites with Ruddlesden–Popper-type structures are fundamentally important for low-dimensional properties, for example, photovoltaic hybrid iodides and superconducting copper oxides. Many such halides and oxides are known, but analogous nitrides are difficult to stabilize due to the high cation oxidation states required to balance the anion charges. Here we report the high-pressure synthesis of three single-layer Ruddlesden–Popper (K₂NiF₄ type) nitrides—Pr₂ReN₄, Nd₂ReN₄ and Ce₂TaN₄—along with their structural characterization and properties. The R₂ReN₄ materials (R = Pr and Nd) are metallic, and Nd₂ReN₄ has a ferromagnetic Nd³⁺ spin order below 15 K. Thermal decomposition gives R₂ReN₃ with a Peierls-type distortion and chains of Re–Re multiply bonded dimers. Ce₂TaN₄ has a structural transition driven by octahedral tilting, with local distortions and canted magnetic Ce³⁺ order evidencing two-dimensional Ce³⁺/Ce⁴⁺ charge ordering correlations. Our work demonstrates that Ruddlesden–Popper nitrides with varied structural, electronic and magnetic properties can be prepared from high-pressure synthesis, opening the door to related layered nitride materials.

All primary chemical interactions weaken under mechanical stress, which imposes fundamental mechanical limits on the materials constructed from them. Biological materials combine plasticity with strength, for which nature has evolved a unique solution-catch bonds, supramolecular interactions that strengthen under tension. Biological catch bonds use force-gated conformational switches to convert weak bonds into strong ones. So far, catch bonds remain exclusive to nature, leaving their potential as mechanoadaptive elements in synthetic systems untapped. Here we report the design and realization of artificial catch bonds. Starting from a minimal set of thermodynamic design requirements, we created a molecular motif capable of catch bonding. It consists of a DNA duplex featuring a cryptic domain that unfolds under tension to strengthen the interaction. We show that these catch bonds recreate force-enhanced rolling adhesion, a hallmark feature of biological catch bonds in bacteria and leukocytes. This Article introduces catch bonds into the synthetic domain, and could lead to the creation of artificial catch-bonded materials.

The functional properties of organic semiconductors are defined by the interplay between optically bright and dark states. Organic devices require rapid conversion between these bright and dark manifolds for maximum efficiency, and one way to achieve this is through multiexciton generation (S₁→¹TT). The dark state ¹TT is typically generated from bright S₁ after optical excitation; however, the mechanistic details are hotly debated. Here we report a ¹TT generation pathway in which it can be coherently photoexcited, without any involvement of bright S₁. Using <10-fs transient absorption spectroscopy and pumping sub-resonantly, ¹TT is directly generated from the ground state. Applying this method to a range of pentacene dimers and thin films of various aggregation types, we determine the critical material properties that enable this forbidden pathway. Through a strikingly simple technique, this result opens the door for new mechanistic insights into ¹TT and other dark states in organic materials.

The synthesis of heteronuclear alkyne analogues incorporating heavier group 14 elements (R¹–C≡E–R², E = Si, Ge, Sn, Pb) has posed a long-standing challenge. Neutral silynes (R¹–C≡Si(L)–R²) and germynes (R¹–C≡Ge(L)–R²) stabilized by a Lewis base have achieved sufficient stability for structural characterization at low temperatures. Here we show the isolation of a base-free stannyne (R¹–C≡Sn–R²) at room temperature, achieved through the strategic use of a bulky cyclic phosphino ligand in combination with a bulky terphenyl substituent. Despite an allenic structure with strong delocalization of π-electrons, this compound exhibits adjacent ambiphilic carbon and tin centres, forming a carbon–tin multiple bond with ionic character. The stannyne demonstrates reactivity similar to carbenes or stannylenes, reacting with 1-adamantyl isocyanide and 2,3-dimethyl-1,3-butadiene. Additionally, its carbon–tin bond can be saturated by Et₃N·HCl or cleaved by isopropyl isocyanate.