We present a small molecule sensor that provides an optical response to the presence of an organophosphorus (OP)-containing nerve agent mimic. The design contains three key features: a primary alcohol, a tertiary amine in close proximity to the alcohol, and a fluorescent group used as the optical readout. In the sensor's rest state, the lone pair of electrons of the basic amine quenches the fluorescence of the nearby fluorophore through photoinduced electron transfer (PET). Exposure to an OP nerve agent mimic triggers phosphorylation of the primary alcohol followed rapidly by an intramolecular substitution reaction as the amine displaces the created phosphate. The quaternized ammonium salt produced by this cyclization reaction no longer possesses a lone pair of electrons, and a fluorescence readout is observed as the nonradiative PET quenching pathway of the fluorophore is shut down.

Find and destroy: A series of oximes were constructed to simultaneously detect and detoxify organophosphorus‐based nerve agents. They function as optical sensors employing the oxime reactivity and incorporating a β‐hydroxyl group to undergo an intramolecular cyclization from the intermediate oxime–organophosphorus species. The generated isoxazole produces an enhanced fluorescent signal that reports on the presence and destruction of the nerve agent.

Fluorescence resonance energy transfer (FRET) was employed to monitor the dynamics of hydrogen-bonded hexameric assemblies formed from resorcin[4]arenes and pyrogallol[4]arenes. Studies were designed to provide further insights into the degree of assembly and stability of these self-assembled capsules at the micro- to nanomolar concentration ranges that are not accessible by NMR studies. The results of this investigation reveal factors that influence the self-assembly of these macrocycles into hexameric capsules. Pyrogallolarenes are very sensitive to the concentration of mixing, with an increase in the equilibration half-life from 36 min at 250 nM to 156 min at 10 microM. The resorcinarenes showed little difference in exchange rates over the same concentration range. The temperature of mixing of the macrocycles was found to be important for both systems with a 12-fold increase in exchange rates over a 20 degree range for the pyrogallolarenes and a 2-fold rate increase for the resorcinarenes over the same temperature range. The stability of the capsules to polar additives such as methanol was probed, with the pyrogallolarenes requiring a higher percentage (1.6% v/v in dichloromethane) of methanol to disassemble the capsules than the resorcinarenes (1.0% v/v in dichloromethane). Pyrogallolarenes assemble in both anhydrous and wet solvents whereas water-saturated solvents are necessary to facilitate the formation of resorcinarene capsules. In addition to these studies, evidence of strict self-sorting in the formation of distinct pyrogallolarene and resorcinarene hexamers was obtained.

Resorcinarenes were functionalized with fluorophores and fluorescence resonance energy transfer (FRET) was employed as a tool to probe the dynamic behavior of hydrogen-bonded hexameric assemblies at nanomolar concentrations. The encapsulation of a fluorescent guest inside the capsule made it possible to observe FRET across the mechanical boundary of the hexameric assembly.

Hooking up: Self‐assembly of a porphyrin amidine and fulleropyrrolidine carboxylic acid based on a two‐point amidinium–carboxylate motif leads to supramolecular dyads of high stability (Ka≈107 M−1 in toluene/acetonitrile (9:1)). The synergy of the hydrogen bonds and electrostatic interactions has been shown to be particularly beneficial in terms of electronic coupling between both electroactive components of the dyads.