Olaf Fuhr

Phenonium ions have played a central role in physical–organic chemistry, yet their use as strategic intermediates in synthesis remains underexplored. Here, we report a phenonium‐ion‐mediated strategy for the skeletal editing of paracyclophanes. Installation of a one‐carbon handle at the aliphatic bridge, followed by direct alcohol activation with BF ₃ ·OEt ₂ under solvolysis‐avoiding conditions, generates a paracyclophane‐derived phenonium ion that undergoes regioselective ring opening by external nucleophiles. This strategy provides modular access to functionalized higher paracyclophane homologues and tolerates S‐, N‐, C‐, selenium‐, and halide‐based nucleophiles under operationally simple, gram‐scalable conditions. The sequence can be applied iteratively and extended to double bridge expansion, while reductive desulfurization furnishes the corresponding parent hydrocarbons. Mechanistic studies combining nuclear magnetic resonance spectroscopy, kinetic analysis, stereochemical probes, and density functional theory calculations support a self‐accelerating mechanism in which product water shifts BF ₃ speciation toward BF ₃ ·H ₂ O, which assists leaving‐group departure through hydrogen‐bond donation and thereby facilitates phenonium‐ion formation. Together, these results establish paracyclophane‐derived phenonium ions as controllable intermediates for skeletal editing and provide practical access to higher paracyclophane topologies with application potential in functional materials, as exemplified by a bridge‐expanded thermally activated delayed fluorescence (TADF) emitter.

The controlled construction of interwoven molecular architectures via metal coordination represents a promising strategy for the development of ordered, interwoven, two‐dimensional (2D) materials. Here, we report a bottom‐up approach to probe the relationship between molecular symmetry and interfacial 2D polymerization behavior. Two amphiphilic heteroleptic osmium(II) terpyridine complexes were designed that incorporate aldehyde and amine functionalities, asymmetric complex ( 1 ), capable of forming two imine bonds, and a symmetric analog with four reactive sites ( 2 ). Langmuir–Blodgett isotherms, Brewster angle microscopy confirmed monolayer formation. In noncontact atomic force microscopy images 1 produced discrete oligomeric aggregates, while 2 yielded extended, chain‐like polymeric structures with high surface coverage. X‐ray photoelectronic spectroscopy measurements supported the presence of polymers as a product of imine condensation. Density functional theory calculations of 1 and its dimer and tetramer were performed to assess the stability of motifs relevant to the supramolecular structures observed. Comparison of the oligomers indicates a slight thermodynamic preference for chain‐like growth over crosslinking. Although these calculations are limited, the intrinsic bias toward linear linkages is consistent with atomic force microscopy data. Together, these results suggest polymer formation through imine condensation on the water–air interface, yielding kinetically favored chain formation and expanded 2D connectivity.

Designing earth-abundant photoactive coordination complexes that combine molecular tunability with device-relevant performance is essential to advance next-generation optoelectronic and solar-energy technologies.

Understanding how nuclear spin influences electronic spin relaxation in single-molecule magnets (SMMs) is essential for advancing quantum technologies. Isotopologue coordination chemistry offers a promising route to probe nuclear-spin effects, yet its role in relaxation dynamics into Single Molecule Toroic (SMT) systems remains unexplored. Here, we study two isotopically enriched ^ADy₄ grid complexes, ¹⁶⁴Dy₄L₄ (with I = 0) and ¹⁶³Dy₄L₄ (with I = 5/2), combining μSQUID magnetometry down to 30 mK with ab initio calculations and spin-Hamiltonian modeling. Both isotopologues exhibit a pseudotoroidal ground state stabilized by noncollinear anisotropy axes and competing interactions, producing hexagonal angular maps and S-shaped hysteresis loops. The nuclear-spin-free ¹⁶⁴Dy₄L₄ displays sharp quantum tunneling of magnetization (QTM) transitions, whereas hyperfine coupling in ¹⁶³Dy₄L₄ generates a dense manifold of crossings, profoundly altering relaxation dynamics. Contrary to expectations, nuclear spins do not accelerate relaxation but promote hyperfine-mediated population transfer into the toroidal state, yielding slower dynamics and larger hysteresis openings. Temperature and sweep-rate dependences further reveal contrasting mechanisms: pure tunneling in ¹⁶⁴Dy₄L₄ versus thermally assisted processes in ¹⁶³Dy₄L₄. Overall, our findings demonstrate that nuclear spins exert a constructive and nonintuitive influence on toroidal SMMs, providing an additional lever for controlling low-temperature relaxation. Isotopically controlled lanthanide assemblies thus emerge as promising platforms for exploring quantum tunneling, spin-phonon coupling, and molecular-scale information storage/processing.

Copper(I) complexes exhibit efficient luminescent properties, such as thermally activated delayed fluorescence (TADF), making them attractive for applications in organic light-emitting diodes or sensors. While copper(I) complexes with 2-pyridyl phosphine ligands have been well studied, this work explores the effect of positional isomerism by using 3-pyridyl phosphine instead of 2-pyridyl phosphine, leading to a previously unreported double-bridged distorted tetrahedral structure with an unusually long average of the Cu···Cu distance of 6.238 Å. This new structural motif, enabled by the unique coordination behavior of the 3-pyridyl ligand, leads to excitation-dependent emission behavior with typical TADF behavior and photoluminescence quantum yields ranging from 0.11 to 0.83. Quantum mechanical calculations indicate that the excited-state transitions exhibit primarily metal-to-ligand and halide-to-ligand charge transfer character or a combination of both, which enhances the TADF response. This study highlights how small changes in the ligand topology can lead to fundamentally different coordination modes and photophysical response. The results offer structure-property relationships for copper(I)-based emitters and the development of future ligand derivatives for tunable optical properties.

Magneto-optical correlations linking effective ligand-field (LF) symmetry and magnetization relaxation are presented for an emissive mononuclear Dy( iii) compound functioning as a single-molecule magnet (SMM).

We report the synthesis and characterization of a series of Eu-labeled cyclic peptoids and evaluate their potential as luminescent probes for biological applications. Our results suggest that Eu-peptoid hybrids represent a promising class of luminescent probes for bioimaging, with potential applications in disease diagnosis, drug discovery, and fundamental biological research.

The impact of the decoration of the multiresonant thermally activated delayed fluorescence (MR‐TADF) core DiKTa with 9,9′‐spirobifluorene (SBF) groups is investigated with respect to the impact of number, position, and incorporation‐type of the SBF unit on the photophysical and optoelectronic properties. This approach allows for the development of narrowband, high‐efficiency organic light emitting diodes (OLEDs) with moderate efficiency roll‐off. The MR‐TADF emitters DiKTaSBF , 3‐SBF‐DiKTa , 7‐SBF‐DiKTa , and 7‐SBF‐DiKTaSBF , differ in the number, position, and incorporation‐type of the SBF unit. Sky‐blue OLEDs with DiKTaSBF and 3‐SBF‐DiKTa show superior performance with maximal external quantum efficiencies (EQE _max ) of 26.1 and 27.0%, respectively, while all four families of OLEDs show a moderate efficiency roll‐off. Narrowband emissions with full‐width at half maximum (FWHM) of 32 and 35 nm are observed for 7‐modified emitters, whereas for the devices with emitters containing SBF groups at the 3‐position show a broadened emission, with FWHM of ≈50 nm. These findings highlight the effect of the regiochemistry of the SBF group on the optoelectronic properties and the corresponding impact on the performance of the OLEDs.

Iron(II)-based spin-crossover (SCO) complexes are promising candidates for several applications—for example, as switching and memory elements in molecule-based information processing architectures. Consequently, the spin-state switching characteristics of such complexes have been studied at the bulk, thin-film, and single-molecule levels. In an effort to link the bulk and single-molecule switching regimes, we have studied three mononuclear iron(II) complexes composed of 2,6-bis(pyrazol-1-yl)pyridine (BPP)-based ligands L1-L3. Complex 1—[Fe(L1)2](BF4)2·CH3CN—underwent bistable spin-state switching with a transition temperature (T1/2) of 253 K and a thermal hysteresis width (ΔT1/2) of 5 K. Complex 2—[Fe(L2)2](BF4)2·CH3CN—showed two-step bistable switching—T1/2 = 258 K (step 1) and 206 K (step 2)—with wide ΔT1/2—40 K (step 1) and 56 K (step 2)—at a scan rate of 0.25 K/min. Remarkably, widening of ΔT1/2 with slow scan rates, below 1 K/min, is noted for 2. In contrast, 3—[Fe(L3)2](BF4)2·2CH3CN—showed lattice-solvent-dependent spin-state switching; loss of lattice solvent resulted in a high spin (HS) phase that underwent gradual and incomplete switching. Single-molecule transport studies of 2 and 3 functionalized with thiomethyl (SMe) anchoring groups indicate charge transport through segments of the molecules attributed to the partially stretched configurations of the complexes in the junctions.