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A novel strategy to design "turn-on" fluorescent receptors for G-quadruplexes of DNA is presented, which relies on the connection of phosphate binding macrocycles (PBM) with naphthalimide dyes. A new PBM-dye family was synthesized and evaluated in terms of binding and detection of nucleotides and DNA G-quadruplexes of different topologies.

Pyrene‐based cyclophanes have been synthesized with the aim to realize a bellows‐type sensing mechanism for the ratiometric detection of nucleotide concentrations in a buffered aqueous solution. The sensing mechanism involves the encapsulation of a nucleobase between two pyrene rings, which affects the monomer‐excimer equilibrium of the receptor in the excited state. The nature of the spacer and its connection pattern to pyrene rings have been varied to achieve high selectivity for ATP. The 1,8‐substituted pyrene‐based cyclophane with the 2,2’‐diaminodiethylamine spacer demonstrates the best selectivity for ATP showing a 50‐fold increase in the monomer‐excimer emission ratio upon saturation with the nucleotide. The receptor can detect ATP within the biological concentrations range over a wide pH range. NMR and spectroscopic studies have revealed the importance of hydrogen bonding and stacking interactions for achieving a required receptor selectivity. The probe has been successfully applied for the real‐time monitoring of creatine kinase activity., Bellows‐type sensing mechanism: the effect of amine spacers in pyrene‐based cyclophanes has been studied to reveal best structures for ratiometic detection of ATP through a guest‐dependent monomer‐excimer equilibrium.

Phosphonates have found broad commercial applications as scale inhibitors in reverse osmosis facilities, boilers, heat exchangers, evaporation plants, and oilfields. Irrespective of their long-term use, there is a cogent need to detect phosphonates in aqueous solution “online” to control their actual concentration in industrial water treatment. Towards this goal, a novel fluorescent-labeled monomer M containing a triamine subunit and 1,8-naphthalimide with an allyl group has been synthesized and found to exhibit a selective fluorescence enhancement with phosphonates in the presence of other anions. The absorption and fluorescence properties of M as well as its effective stability constants with various phosphonates have been studied in a wide pH range. M has been implemented in the synthesis of cryopolymers, which can detect phosphonates in aqueous solution. The presented results provide an important contribution to the future design of fluorescent polymer probes for antiscalants.

Supramolecular recognition of perrhenate is a challenging task due to therelatively large size and low charge density of this anion. In this work, we design and synthesize a family of helix-like synthetic receptors that can bind perrhenate by forming hydrogen bonds with all four oxygen atoms of the anion. Among the investigated rigid helix-forming subunit derived from 1,1′-ferrocenedicarboxylic acid, 1,3-phenylenediacetic acid and 2,2′-(ethyne-1,2-diyl)dibenzoic acid, the latter one shows the best selectivity for perrhenate recognition. However, the receptor based on 1,1′-ferrocenedicarboxylic acid demonstrates selectivity to bind chloride in a 1:2 fashion. The properties of the receptors are investigated in the acetonitrile solution by using NMR, UV–Vis, and in the solid state by single crystal X-ray analysis.

Control of isomerization of a receptor bearing multiple light-switchable subunits in a confined space is critical for the design of synthetic molecular machines. Toward this goal, a new azacryptand containing three azobenzene subunits has been developed, and its photoisomerization in an aqueous solution has been studied depending on anion coordination and recognition by a larger hostcucurbit[8]­uril (CB[8]). The cryptand in its hexaprotonated form shows considerable affinity for fluoride and perchlorate, which in turn affects the isomer distribution of the receptor under UV-light irradiation, stabilizing the isomers of the cryptand with Z-configurations. CB[8] was found to be able to encapsulate the isomers of the cryptand by forming a Matryoshka-type complex. The irradiation of a 10:1 CB[8]–cryptand mixture has led to a selective conversion of the cryptand to the E,E,Z isomer inside CB[8]. It has been demonstrated that the addition of fluoride to the resulted complex induces the release of the cryptand as a major E,E,E isomer, while other studied anions were ineffective in this reaction. To our knowledge, this work presents a first example of a host-controlled photoisomerization of an anion receptor bearing multiple switching azobenzenes that model the function of naturally occurring chaperones.

Synthesis and anion binding properties of hybrid macrocycles containing ammonium and hydrogen bond donor groups are reported. Receptor properties were studied in a 10 mM MES buffer solution at pH 6.2, at which the receptors carry two positive charges at the secondary amine groups. Receptor 1 was found to bind fluoride with the highest affinity (105 M–1) and selectivity among the synthesized receptors. It was the only receptor that demonstrated fluorescence increase upon addition of fluoride. Other titration experiments with halides and oxyanions led to an anion-induced aggregation and fluorescence quenching. The mechanism of the particular turn-on fluorescence for fluoride was explained by the ability of receptor 1 to encapsulate several fluoride anions. Multiple anion coordination resulted in the protonation of the tertiary amine group and subsequent hindering of the PET process. 1H and 19F NMR titrations, single-crystal X-ray structure of chloride complex, and DFT calculation suggest that 1 can perfectl...

Receptors bearing hydrogen and halogen bond donors for recognition of perrhenate and pertechnetate were designed and studied. Acyclic hosts with N-H and C-H binding sites showed the best selectivity for TcO4- and ReO4- over spherical and more basic tetrahedral anions.

New naphthalimide-based receptors for anions have been synthesized. Efficient synthetic routes have been discovered to functionalize the naphthalimide core with branched polyamines. Binding and sensing properties of the receptors were studied by potentiometric, NMR and fluorescence titrations. The receptors bind selectively to the pyrophosphate anion in buffered aqueous solutions. The receptors with more than six amine groups in the structure demonstrated the highest affinities for pyrophosphate. The fluorescence response towards anions was found to be dependent on the position of the amine groups relative to the naphthalimide core, and on the pH of the buffered solution. Three sensing mechanisms have been found that explain fluorescence responses of receptors towards anions in an aqueous solution.

A new amido−amine cage receptor, which combines 1,8‐anthracene diacarboxamide subunit and a polyammonium azamacrocycle, is reported. Bearing both the hydrogen bond donor and the acceptor binding sites, the receptor is able to bind phosphate selectively under neutral (pH 7.2) aqueous conditions. The recognition events for phosphate and dicarboxylates are accomplished by a fluorescence enhancement in the anthracene emission. As revealed by experimental and theoretical studies, phosphate and oxalate show different recognition modes. Phosphate demonstrates hydrogen bond acceptor properties, while the coordination of oxalate favours the protonation of the receptor., Anion sensing: Cage receptor based on 1,8‐anthracene dicarboxamide has been designed for anion recognition under neutral aqueous conditions. The difference in recognition modes between oxalate and phosphate has been elucidated by theoretical and experimental methods.

The Front Cover shows the authors’ association of fluorescence anion sensing with pearl hunting – the activity of recovering pearls from wild molluscs. In the presented work, the group of Kataev has developed a new water‐soluble amido‐amine azacryptand bearing a fluorescence anthracene dicarboxamide fragment. With the help of the fluorescent receptors (a hand) one can catch the phosphate anion (a glowing pearl) and visualize this binding event. The recognition of phosphate and oxalate has led to a fluorescent enhancement in a selective manner; however, the anions have demonstrated different recognition modes. More information can be found in the Communication by Boris S. Mozorov et al. on page 171 in Issue 2, 2020 (DOI: https://doi.org/10.1002/open.201900309).[Image: see text]

Herein we describe the design, synthesis, and anion binding properties of bicyclic receptors with two or three anthracenes, which show a turn-on fluorescence response in the presence of nitrate and chaotropic anions in a buffered aqueous solution. The receptor with two anthracenes binds nitrate with 10

Bicyclic receptors bearing anthracene as a strap were designed for selective oxalate binding in a buffered aqueous solution. The receptors were found to possess two mechanisms of fluorescence response depending on the pH of a buffered solution. Receptor 2 binds oxalate at pH 6.2 showing a 10-fold fluorescence enhancement and a two orders of magnitude selectivity over other anions.

Novel naphthalimide-functionalized bisphosphonates with different spacer length have been designed and synthesized. The spectroscopic properties, dissociation constants and complexation behavior with calcium(II) have been studied in aqueous solution. It has been shown that the length of the spacer has a dramatic effect on the fluorescence, Ca2+ binding properties and solubility of Ca2+ complexes in aqueous solution. New fluorescent bisphosphonates have been found to provide a perfect contrasting of inorganic industrial fouling (barite) and human tissue calcification (hydroxyapatite). The affinity of the fluorescent bisphosphonates for the bone matrix in the presence of human fibroblast cells has been tested in vitro with hydroxyapatite crystals imitated the human bone. Microscopic fluorescence analysis has demonstrated that fluorescent bisphosphonates are able to bind efficiently and selectively to the hydroxyapatite in the presence of human fibroblast cells.

Nucleotides are constituents of nucleic acids and they have a variety of functions in cellular metabolism. Synthetic receptors and sensors are required to reveal the role of nucleotides in living organisms and mechanisms of signal transduction events. In recent years, a large number of nucleotide-selective synthetic receptors have been devised, which utilize different molecular designs and sensing mechanisms. This Minireview presents recent progress in the design of synthetic molecular receptors for selective recognition of nucleotides in aqueous solution. The binding properties of receptors and the origins of their selectivity for a particular nucleotide are discussed.

New polymer cryogels based on N,N-dimethylacrylamide and allyl derivatives of 1,8-naphthalimide have been synthesized. They have intense fluorescence in the visible region of the spectrum. The influence of synthesis conditions on the properties of the resulting products has been studied. The maximum yield of the gel fraction and the minimum degree of swelling of the crosslinked polymer are observed during the lowtemperature (–20°C) synthesis of cryogels. Their fluorescence depends on the monomer content reaching the maximum value at concentrations of N,N-dimethylacrylamide and a fluorophore-containing monomer of 1.0 and 1.0 × 10–3 mol/L, respectively.

Design of PET probes for anions working in an aqueous buffered solution is described. The design has been used to develop selective fluorescent probes for sulfate and pyrophosphate. The relationship between the selectivity of receptors towards anions, their conformation, fluorescence response and the pH of the solution has been studied in detail.