Introduction of atropisomeric axes into a bent bispyridine ligand leads to the quantitative formation of a complex mixture of atropisomeric M2L4 cages upon treatment with metal ions. Whereas the isomer...

Biological receptors distinguish and bind steroid sex hormones, e.g., androgen-, progestogen-, and estrogen-type hormones, with high selectivity. To date, artificial molecular receptors have been unable to discriminate between these classes of biosubstrates. Here, we report that an artificial polyaromatic receptor preferentially binds a single molecule of androgenic hormones, known as “male” hormones (indicated with m), over progestogens and estrogens, known as “female” hormones (indicated with f), in water. Competitive experiments established the binding selectivity of the synthetic receptor for various sex hormones to be testosterone (m) > androsterone (m) >> progesterone (f) > β-estradiol (f) > pregnenolone (f) > estriol (f). These bindings are driven by the hydrophobic effect, and the observed selectivity arises from multiple CH-π contacts and hydrogen-bonding interactions in the semirigid polyaromatic cavity. Furthermore, micromolar fluorescence detection of androgen was demonstrated using the receptor containing a fluorescent dye in water.

Selective recognition of natural fatty acids is intrinsically difficult owing to the long, flexible, and poorly interactive hydrocarbon chains. Inspired by biological recognition systems, we herein demonstrate the exclusive binding of a monounsaturated fatty acid by an artificial polyaromatic receptor from a mixture of the unsaturated and corresponding saturated substrates (i.e., oleic and stearic acids) in water. The selectivity stems from multiple CH–π/π–π interactions between the host framework and the guest in its roughly coiled conformation. Moreover, competitive binding experiments elucidate higher binding affinities of the receptor for oligo‐ and polyunsaturated fatty acids (e.g., α‐linolenic acid and EPA). Within the receptor, the biosubstrates are remarkably stabilized against air, light, and heat owing to the polyaromatic shielding effect.