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Abstract Mechanically interlocked molecules are a class of compounds used for controlling directional movement when barriers can be raised and lowered using external stimuli. Applied voltages can turn on redox states to alter electrostatic barriers but their use for directing motion requires knowledge of their impact on the kinetics. Herein, we make the first measurements on the movement of cyclobis(paraquat‐p‐phenylene) (CBPQT⁴⁺) across the radical‐cation state of monopyrrolotetrathiafulvalene (MPTTF) in a [2]rotaxane using variable scan‐rate electrochemistry. The [2]rotaxane is designed in a way that directs CBPQT⁴⁺to a high‐energy co‐conformation upon oxidation of MPTTF to either the radical cation (MPTTF⋅⁺) or the dication (MPTTF²⁺).¹H NMR spectroscopic investigations carried out in acetonitrile at 298 K showed direct interconversion to the thermodynamically more stable ground‐state co‐conformation with CBPQT⁴⁺moving across the oxidized MPTTF²⁺electrostatic barrier. The electrochemical studies revealed that interconversion takes place by movement of CBPQT⁴⁺across both the MPTTF^•+(19.3 kcal mol⁻¹) and MPTTF²⁺(18.7 kcal mol⁻¹) barriers. The outcome of our studies shows that MPTTF has three accessible redox states that can be used to kinetically control the movement of the ring component in mechanically interlocked molecules. 

Abstract The supramolecular recognition of anions is increasingly harnessed to achieve the self‐assembly of supramolecular architectures, ranging from cages and polymers to (pseudo)rotaxanes. The cyanostar (CS) macrocycle has previously been shown to form 2 : 1 complexes with organophosphate anions that can be turned into [3]rotaxanes by stoppering. Here we achieved steric control over the assembly of pseudorotaxanes comprising the cyanostar macrocycle and a thread that is based, for the first time, on organo‐pyrophosphonates. Subtle differences in steric bulk on the threads allowed formation of either [3]pseudorotaxanes or [2]pseudorotaxanes. We demonstrate that the threading kinetics are governed by the steric demand of the organo‐pyrophosphonates and in one case, slows down to the timescale of minutes. Calculations show that the dianions are sterically offset inside the macrocycles. Our findings broaden the scope of cyanostar‐anion assemblies and may have relevance for the design of molecular machines whose directionality is a result of relatively slow slipping. 

Abstract The recognition of boron compounds is well developed as boronic acids but untapped as organotrifluoroborate anions (R−BF₃⁻). We are exploring the development of these and other designer anions as anion‐recognition motifs by considering them as substituted versions of the parent inorganic ion. To this end, we demonstrate strong and reliable binding of organic trifluoroborates, R−BF₃⁻, by cyanostar macrocycles that are size‐complementary to the inorganic BF₄⁻progenitors. We find that recognition is modulated by the substituent's sterics and that the affinities are retained using the common K⁺salts of R−BF₃⁻anions. 

Abstract Phosphate oxyanions play central roles in biological, agricultural, industrial, and ecological processes. Their high hydration energies and dynamic properties present a number of critical challenges limiting the development of sensing technologies that are cost‐effective, selective, sensitive, field‐deployable, and which operate in real‐time within complex aqueous environments. Here, a strategy that enables the fabrication of an electrolyte‐gated organic field‐effect transistor (EGOFET) is demonstrated, which overcomes these challenges and enables sensitive phosphate quantification in challenging aqueous environments such as seawater. The device channel comprises a composite layer incorporating a diketopyrrolopyrrole‐based semiconducting polymer and a π‐conjugated penta‐t‐butylpentacyanopentabenzo[25]annulene “cyanostar” receptor capable of oxyanion recognition and embodies a new concept, where the receptor synergistically enhances the stability and transport characteristics via doping. Upon exposure of the device to phosphate, a current reduction is observed, consistent with dedoping upon analyte binding. Sensing studies demonstrate ultrasensitive and selective phosphate detection within remarkably low limits of detection of 178 × 10⁻¹²m(17.3 parts per trillion) in buffered samples and stable operation in seawater. This receptor‐based doping strategy, in conjunction with the versatility of EGOFETs for miniaturization and monolithic integration, enables manifold opportunities in diagnostics, healthcare, and environmental monitoring.