Detection of aliphatic aldehydes by a pillar[5]arene-based fluorescent supramolecular polymer with vaporchromic behavior

Colorimetric Detection of Furfural with Enhanced Visible Absorption of Furfural-DNPH in Basic Conditions

Furfural is an intermediary toxic aldehyde compound produced during heat-induced food processing and storage. Furfural is also formed by the degradation of cellulosic insulation in oil-immersed electric potential transformers, whose level is an important indicator of aging for replacement. In this study, we report a new means to detect the trace level of furfural in a colorimetric manner. Furfural is reacted with dinitrophenylhydrazine (DNPH) in acid solutions. The colorless furfural-DNPH compound turns orange-colored as the solution changes to basic. The delocalization of the π-electron in the DNPH-aldehyde derivatives at the basic condition causes the shift of the absorption peak from 318 to 470 nm, which renders the solution orange-colored. The color and absorbance are saturated in 20 min of incubation. There is high linearity between the absorbance and the concentration of furfural in the range of 0-0.2 mM, which enables the quantitative detection of furfural. The limit of detection is estimated to be as low as 1.76 μM for the absorbance analysis and 10 μM for the naked eyes. The colorimetric assay protocol is applicable to the detection of various aromatic aldehydes, which show strong π-electron delocalization and is not applicable to aliphatic aldehydes due to lack of delocalization. This simple assay can be conducted in typical 96-well microplates using a microplate reader, which provides a low-cost and high-throughput screening. Therefore, we believe that our method is potentially applicable for the quantitative detection of aromatic aldehydes in various samples from foods, electronic devices, and so on.

Pillararene-Based Supramolecular Polymers for Adsorption and Separation

Supramolecular polymers have attracted increasing attention in recent years due to their perfect combination of supramolecular chemistry and traditional polymer chemistry. The design and synthesis of macrocycles have driven the rapid development of supramolecular chemistry and polymer science. Pillar[n]arenes, a new generation of macrocyclic compounds possessing unique pillar-shaped structures, nano-sized cavities, multi-functionalized groups, and excellent host-guest complexation abilities, are promising candidates to construct supramolecular polymer materials with enhanced properties and functionalities. This review summarizes recent progress in the design and synthesis of pillararene-based supramolecular polymers (PSPs) and illustrates their diverse applications as adsorption and separation materials. All performances are evaluated and analyzed in terms of efficiency, selectivity, and recyclability. Typically, PSPs can be categorized into three typical types according to their topologies, including linear, cross-linked, and hybrid structures. The advances made in the area of functional supramolecular polymeric adsorbents formed by new pillararene derivatives are also described in detail. Finally, the remaining challenges and future perspectives of PSPs for separation-based materials science are discussed. This review will inspire researchers in different fields and stimulate creative designs of supramolecular polymeric materials based on pillararenes and other macrocycles for effective adsorption and separation of a variety of targets.

Synthesis of (R)-(6-Methoxyquinolin-4-yl)[(1S,2S,4S,5R)-5-vinylquinuclidin-2-yl]methanol Tetraphenylborate Ion-Pair Complex: Characterization, Antimicrobial, and Computational Study

The (R)-(6-Methoxyquinolin-4-yl)[(1S,2S,4S,5R)-5-vinylquinuclidin-2-yl]methanol (quinine)-tetraphenylborate complex was synthesized by reacting sodium tetraphenyl borate with quinine in deionized water at room temperature through an ion-pair reaction (green chemistry) at room temperature. The solid complex was characterized by several physicochemical methods. The formation of ion-pair complex between bio-active molecules and/or organic molecules is crucial to comprehending the relationships between bioactive molecules and receptor interactions. The complex under study was examined for antimicrobial activity. All theoretical calculations were carried out in vacuum and water using the B3LYP level 6-311G(d,p) levels of theory. The theoretical computation allowed for the prediction and visualization of ionic interactions, which explained the complex's stability. The results of energy optimization showed that the Q-TPB complex is stable with a negative complexation energy. The obtained geometries showed that the boron (B-) and nitrogen (N+) in piperidine of the two molecules tetraphenylborate and quinine are close to each other, which makes it possible for ions to interact. The modest energy gap between HOMO and LUMO showed that the compound was stable. The computation of the electron transitions of the two models by density functional theory (TD-DFT) in the solvent at the theoretical level B3LYP/6-311G(d,p) allowed for the detection of three UV/visible absorption bands for both models and the discovery of a charge transfer between the host and the guest. The UV absorption, infrared, and H NMR are comparable with the experimental part.

Recent Progress in the Development of Organic Chemosensors for Formaldehyde Detection

Formaldehyde has become a prominent topic of interest because of its simple molecular structure, release from various compounds in the near vicinity of humans, and associated hazards. Thus, several researchers designed sophisticated instrumentations for formaldehyde detection that exhibit real-time sensing properties and are cost-effective and portable with high detection limits. On these grounds, this review is centered on an analysis of optical chemosensors for formaldehyde that specifically fall under the broad spectrum of organic probes. In this case, this review discusses different organic functionalities, including amines, imines, aromatic pillar arenes, β-ketoesters, and β-diketones, taking part in various reaction mechanisms ranging from aza-Cope rearrangement and Schiff base and Hanztch reactions to aldimine condensation. In addition, this review distinguishes reaction mechanisms according to photophysical phenomena, that is, aggregation-induced emission, photoinduced electron transfer, and intramolecular charge transfer. Furthermore, it addresses the instrumentation involved in gas-based and liquid formaldehyde detection. Finally, it discusses the gaps in existing technologies followed by a succinct set of recommendations for future research.

The aqueous supramolecular chemistry of crown ethers

This mini-review summarizes the seminal exploration of aqueous supramolecular chemistry of crown ether macrocycles. In history, most research of crown ethers were focusing on their supramolecular chemistry in organic phase or in gas phase. In sharp contrast, the recent research evidently reveal that crown ethers are very suitable for studying abroad range of the properties and applications of water interactions, from: high water-solubility, control of Hofmeister series, "structural water", and supramolecular adhesives. Key studies revealing more details about the properties of water and aqueous solutions are highlighted.