Stephen Jonathan Butler

Peroxynitrite (ONOO ⁻ ) is an extremely short‐lived and highly reactive species whose biological effects depend on its local concentration at the site of formation. Consequently, detecting and quantifying ONOO ⁻ requires probes that combine high selectivity with well‐defined subcellular localization. The cell membrane is a particularly important yet underexplored interface, as it is the first barrier encountered by extracellularly generated ONOO ⁻ and determines how much of this species penetrates into the cell. Such membrane‐proximal ONOO ⁻ formation occurs during inflammatory processes and oxidative stress–based therapies, and is especially relevant in cold atmospheric plasma treatment, where complex RONS mixtures interact with the membrane before intracellular effects arise. Here, we report Eu.Chol , a luminescent europium(III) complex that integrates a phenylboronic acid ONOO ⁻ reactive motif with a cholesterol anchor to localize the probe within lipid bilayers. We demonstrate that Eu.Chol incorporates efficiently into liposomes and Jurkat cells, enabling selective, membrane‐localized ONOO ⁻ detection with minimal response to H ₂ O ₂ . These results establish a modular europium(III)‐based scaffold for targeted ONOO ⁻ sensing, enabling potential incorporation of organelle‐specific targeting groups to probe RONS dynamics at defined sub‐cellular sites.

Bimodal imaging agents that combine MRI and optical signals can improve imaging and diagnostic precision by providing complementary anatomical and molecular information. Macromolecular MRI agents can deliver higher relaxivities than small‐molecule analogues by using controlled architectures that slow rotational motion and enhance Gd(III)–water interactions. The combination of bimodal functionality with macromolecular designs represents a highly promising route to new imaging agents, but its potential has not yet been realized due to safety concerns over possible unchelated metals and difficulties in achieving reproducible large‐scale production. Here, we present a simple, reproducible method to directly incorporate isostructural Gd(III) and Tb(III) complexes into amphiphilic core–shell block copolymer nanoparticles using a single macrocyclic methacrylate ligand. This modular design enables controlled spatial positioning of each MRI‐ and luminescence agent, achieving high relaxivity up to 30.2 mM ⁻¹ s ⁻¹ per Gd(III) and long‐lived (>1.30 ms) luminescence, providing a tunable platform for dual‐modal MRI–luminescence applications.

This work investigates the use of quantum chemistry for modelling europium complexes, highlights the most effective methods and illustrates the open challenges.

This review presents recent advances in lanthanide-based anion receptors, focusing on molecules with improved anion selectivity, new mechanistic insight, and real-world sensing and imaging applications.

Synthetic anion receptors can transport anions across lipid bilayer membranes. Many anion transporters have been reported, including macrocyclic compounds. However, there are no systematic studies on how the size of macrocycles impacts their anion transport activity and selectivity. Therefore, we prepared eight amide‐based macrocyclic compounds with ring sizes ranging from 18 to 26 atoms, as well as four bis‐amides. We studied these compounds as anion receptors using chloride titrations and molecular modelling, and as anion transporters using liposomes with various fluorescent probes. Neither the size of the macrocycles nor the affinity for chloride was found to be a determining factor for chloride transport activity; pre‐organisation appears to play a more important role. Fluorination was found to have a clear positive effect on anion transport rates, with the bis‐amides performing surprisingly well compared to the macrocycles. The smallest non‐fluorinated macrocycle exhibited selectivity for chloride over hydroxide and nitrate, whereas the pentafluorophenyl bis‐amide demonstrated effective transport of bicarbonate and nitrate, likely due to anion–π interactions in addition to hydrogen bonding. The insights from this study will shape the design of future anionophores.

Bacteria play a crucial role in maintaining human health, particularly within the microbiome of the gastrointestinal tract and skin. However, pathogenic species such as Escherichia coli , Staphylococcus aureus , and Salmonella can disrupt this balance, leading to severe infections and contributing to the global rise of antimicrobial resistance (AMR). Rapid and species‐selective bacterial detection is therefore critical for effective diagnosis and control of healthcare infections. Fluorescence‐based sensing has emerged as a promising strategy for rapid, sensitive, and cost‐effective detection of bacterial species. Polymer‐based materials are particularly interesting due to their tunable chemistry, structural versatility, and enhanced stability. By integrating fluorophores with functional polymer backbones, these systems can interact selectively with bacterial surfaces through electrostatic, hydrophobic, and directed hydrogen‐bonding interactions, enabling non‐disruptive interactions and detection. This review highlights advances in fluorescent polymeric materials for bacterial sensing, classifying systems by polymer type and outlining design strategies that control selectivity, sensitivity, and photophysical behavior. Emphasis is placed on fully synthetic polymers that achieve bacterial recognition without biological components, offering new pathways toward non‐toxic, responsive bacterial sensors.

Lanthanide(III) complexes are invaluable tools for probing protein structure and dynamics, enabling precise distance measurements and site‐specific labeling across electron paramagnetic resonance (EPR), nuclear magnetic resonance (NMR), and luminescence‐based techniques. Designing an optimal lanthanide tag requires high thermodynamic and kinetic stability, minimal linker flexibility, and rapid, quantitative reactivity under mild conditions. Herein, a short series of Ln(III) complexes developed as efficient protein tags is reported, each showing high chemoselectivity for cysteine and enabling labeling in aqueous solution under mild conditions (pH 8, 37 °C). Subtle modifications to the reactive arm of the parent Ln.L1 complex has a pronounced effect on tagging kinetics, with Tb.QuNO achieving >95% labeling of the free amino acid cysteine within 10 min. The more compact and readily synthesized Gd.PyNO also labels efficiently and exhibits a narrow EPR linewidth (3.1 mT average at Q‐band across three protein‐labeled samples), making it an optimal choice for many EPR applications. These findings highlight the critical role of linker design in lanthanide‐based probes for EPR spectroscopy and biological imaging.

Synthetic anion receptors can transport anions across lipid bilayer membranes. Many anion transporters have been reported, including macrocyclic compounds. However, there are no systematic studies on how the size of macrocycles impacts their anion transport activity and selectivity. Therefore, we prepared eight amide-based macrocyclic compounds with ring sizes ranging from 18 to 26 atoms, as well as four bis-amides. We studied these compounds as anion receptors using chloride titrations and molecular modelling, and as anion transporters using liposomes with various fluorescent probes. Neither the size of the macrocycles nor the affinity for chloride were found to be determining factors for chloride transport activity; preorganisation appears to play a more important role. Fluorination was found to have a clear positive effect on anion transport rates, with the bis-amides performing surprisingly well compared to the macrocycles. The smallest non-fluorinated macrocycle exhibited selectivity for chloride over hydroxide and nitrate, whereas the pentafluorophenyl bis-amide demonstrated effective transport of bicarbonate and nitrate, likely due to anion-pi interactions in addition to hydrogen bonding. The insights from this study will shape the design of future anionophores.

The selective recognition of adenosine diphosphate (ADP) in water presents a significant challenge for synthetic supramolecular chemistry, driven by its biological importance in cellular energy transfer and enzymatic signaling pathways. Discriminating ADP from structurally similar anions such as ATP requires a high degree of host–guest complementarity. We recently developed [Eu.ADPGlow]⁻, a luminescent Eu(III) complex bearing two 6‐substituted quinolyl‐phenoxyacetate arms, which create a binding site at the central Eu(III) ion that accommodates ADP. Binding induces a tight interaction in water, involving both metal coordination and π–π stacking, switching the emission on with a 33‐fold enhancement. Here, we examine how systematic changes in ligand geometry influence anion selectivity, by synthesizing four new Eu(III) complexes with pendant arms at the 4‐ or 7‐positions of the quinoline scaffold. The 4‐substituted systems provide a more accessible binding site and bind ADP, ATP, and AMP with limited selectivity between them, while the 7‐substituted analogues impose steric hindrance at the Eu(III) center, resulting in minimal response to all tested anions. Only the 6‐substituted complex [Eu.ADPGlow]⁻ achieves optimal geometrical complementarity for ADP binding. These findings reinforce the importance of steric and geometric control in the design of selective lanthanide probes for biological anions in water.