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Appropriately functionalized pillar[ n ]arenes are elegant supramolecular hosts for ion and molecule sensing. A water-soluble decaamine derivative of pillar[5]arene ( APA ) bearing triazole and amide moieties is synthesized. The ion and molecular recognition properties of APA are studied by fluorescence, UV-visible, and 1 H nuclear magnetic resonance (NMR) spectroscopy. The APA selectively detects Fe 3+ among 11 studied ions, which are important in several biological processes. Moreover, the in situ prepared Fe 3+ complex of APA ( FeAPA ) exhibits the highest responsiveness toward F - (∼12-fold) among 11 anions and cysteine (∼120-fold) among the 20 naturally occurring amino acids by a fluorescence turn-on mechanism., Competing Interests: The author declares no competing financial interest., (Copyright © 2020 American Chemical Society.)

A quinoline functionalized pillar[5]arene, QPA has been prepared and its interaction with biologically relevant ions and molecules in aqueous solution has been demonstrated. The sensor molecule, QPA has shown selectivity towards Fe 3+ among eleven metal ions studied. The Fe 3+ complex of QPA (FeQPA) selectively interacts with F - among halides by ∼4 fold fluorescence enhancement. Further, FeQPA has shown selectivity towards arginine and lysine among twenty naturally occurring amino acids. The binding of QPA with Fe 3+ has been confirmed by MALDI-TOF and 1 H NMR titrations., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Macrocyclic host structures for generating transiently bound 129 Xe have been used in various ultra-sensitive NMR and MRI applications for molecular sensing of biochemical analytes. They are based on hyperpolarized nuclei chemical exchange saturation transfer (Hyper-CEST). Here, we tested a set of water-soluble pillar[5]arenes with different counterions in order to compare their potential contrast agent abilities with that of cryptophane-A (CrA), the most widely used host for such purposes. The exchange of Xe with such compounds was found to be sensitive to the type of ions present in solution and can be used for switchable magnetization transfer (MT) contrast that arises from off-resonant pre-saturation. We demonstrate that the adjustable MT magnitude depends on the interplay of saturation parameters and found that the optimum MT contrast surpasses the CrA CEST performance at moderate saturation power. Since modification of such water-soluble pillar[5]arenes is straightforward, these compounds can be considered a promising platform for designing various sensors that may complement the field of Xe HyperCEST-based biosensing MRI., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)