Field Of Molecular Recognition Research Articles

Small-molecule fluorogenic probes based on indole scaffold.

Indoles are the most versatile organic N-heterocyclic compounds widely present in bioactive natural products and used in different fields such as coordination chemistry, pharmacy, dyes, and medicine, as well as in the biology and polymer industries. More recently, the indole scaffold has been widely used in analytical chemistry for the design and development of small-molecule fluorescent chemosensors in the fields of molecular recognition and molecular imaging. The indole-based chemosensor derivatives contain heteroatoms like N-, O-, and S-, through which they interact with analytes (cations, anions, and neutral species), producing measurable analytical signals that can be used for the fluorimetric and colorimetric detection of different analytes in biological, agricultural and environmental samples. This review focuses on indole-based small-molecule fluorimetric and colorimetric chemosensors for detecting cations, anions, and neutral species in a comprehensive manner. Furthermore, the recognition mechanisms are discussed in detail, which could help researchers design and develop more powerful and efficient fluorescent chemosensors in the near future.

Enhanced molecular recognition with longer chain crosslinkers in molecularly imprinted polymers for an efficient separation of TR active substances.

Molecular imprinting technology has been widely studied as a technique to obtain molecular recognition by artificial means. Selecting functional monomers or polymerization conditions plays a key role to optimize molecularly imprinted polymer (MIP) synthesis. To date, there have been few reports well exploiting the effect of crosslinkers. Here, in this study, we synthesized the MIPs using poly(ethyleneglycol) dimethacrylate with different units of ethylene oxide (n = 1 to 23) as crosslinkers to observe the molecular recognition abilities. The MIPs were attached to the surface of mono-dispersed polymer beads. The obtained spherical MIPs and non-imprinted polymers were filled in a column for high performance liquid chromatography. Then the retention selectivity toward TR active substances was evaluated. The result revealed that the recognition ability did not improve regardless of the amount of ethylene oxide. With the crosslinker (n = 9), extremely high retention selectivity was observed, which provides at most around ten times as large imprinting factors in comparison with other MIPs. Interestingly, we obtained the highest recognition ability at around polymerization temperature from the evaluation of the recognition ability toward temperature shift using the MIP (n = 9). In general, hydrogen bonding based on MIPs provides high recognition ability at low temperature, whereas, this study indicates that the use of flexible crosslinkers may enable the synthesis of MIPs that precisely memorize the conditions of polymerization. Lastly, we simultaneously analyzed the TR active substances using the column filled with MIPs (n = 9). The result showed relatively linear correlation between the retention strength of each substance and phycological activity toward TR obtained by yeast assay. Therefore, we can conclude that an induced fit like the receptor emerged by constructing the flexible molecular recognition field.

Quantitative analysis of circular dichroism at higher-order resonance of extrinsic plasmonic chiral nanostructures using multipole decomposition combined with the optical theorem

Plasmonic chirality, which has garnered significant attention in recent years due to its ability to generate strong near-field enhancement and giant circular dichroism (CD). Currently, various theories have been proposed to explain plasmonic extrinsic chirality, however, a comprehensively quantitative explanation for the high-order optical response of extrinsic metamolecule has yet to be established. Herein, we present a concise and quantitative explanation of the giant high-order extrinsic CD of a plasmonic nanocrescent, which origins from multipole decomposition in combination with the optical theorem. Our findings indicate that the high-order resonance modes exhibit giant CD comparable to dipolar modes and can be conveniently applied to the chiral recognition of metamolecules. Furthermore, the nonradiative electric quadrupole resonance exhibits enormous electric field enhancement near metamolecule, which has great application potential in the fields of molecular recognition and sensing in the visible region.

Chiral recognition of neutral guests by chiral naphthotubes with a bis-thiourea endo-functionalized cavity

Developing chiral receptors with an endo-functionalized cavity for chiral recognition is of great significance in the field of molecular recognition. This study presents two pairs of chiral naphthotubes containing a bis-thiourea endo-functionalized cavity. Each chiral naphthotube has two homochiral centers which were fixed adjacent to the thiourea groups, causing the skeleton and thiourea groups to twist enantiomerically through chiral transfer. These chiral naphthotubes are highly effective at enantiomerically recognizing various neutral chiral molecules with an enantioselectivity up to 17.0. Furthermore, the mechanism of the chiral recognition has been revealed to be originated from differences in multiple non-covalent interactions. Various factors, such as the shape of cavities, substituents of guests, flexibility of host and binding modes are demonstrated to contribute to creating differences in the non-covalent interactions. Additionally, the driving force behind enantioselectivity is mainly attributed to enthalpic differences, and enthalpy -entropy compensation has also been observed to influence enantioselectivity.

Selective Potassium Chloride Recognition, Sensing, Extraction, and Transport Using a Chalcogen-Bonding Heteroditopic Receptor.

Chalcogen bonding (ChB) is rapidly rising to prominence in supramolecular chemistry as a powerful sigma (σ)-hole-based noncovalent interaction, especially for applications in the field of molecular recognition. Recent studies have demonstrated ChB donor strength and potency to be remarkably sensitive to local electronic environments, including redox-switchable on/off anion binding and sensing capability. Influencing the unique electronic and geometric environment sensitivity of ChB interactions through simultaneous cobound metal cation recognition, herein, we present the first potassium chloride-selective heteroditopic ion-pair receptor. The direct conjugation of benzo-15-crown-5 ether (B15C5) appendages to Te centers in a bis-tellurotriazole framework facilitates alkali metal halide (MX) ion-pair binding through the formation of a cofacial intramolecular bis-B15C5 M+ (M+ = K+, Rb+, Cs+) sandwich complex and bidentate ChB···X– formation. Extensive quantitative 1H NMR ion-pair affinity titration experiments, solid–liquid and liquid–liquid extraction, and U-tube transport studies all demonstrate unprecedented KCl selectivity over all other group 1 metal chlorides. It is demonstrated that the origin of the receptor’s ion-pair binding cooperativity and KCl selectivity arises from an electronic polarization of the ChB donors induced by the cobound alkali metal cation. Importantly, the magnitude of this switch on Te-centered electrophilicity, and therefore anion-binding affinity, is shown to correlate with the inherent Lewis acidity of the alkali metal cation. Extensive computational DFT investigations corroborated the experimental alkali metal cation–anion ion-pair binding observations for halides and oxoanions.

Separation of enantiomers by open‐tubular capillary electrochromatography using (R)‐1,1′‐bi‐2‐naphthol derivatives as chiral stationary phases

(R)-1,1′-Bi-2-naphthol is a kind of commonly used chiral molecule that has been widely applied in the fields of molecular recognition, materials, and asymmetric synthesis. Since there are few examples of utilizing (R)-1,1′-bi-2-naphthol derivatives used as stationary phases to resolve chiral compounds by capillary electrochromatography, three The (R)-1,1′-bi-2-naphthol derivatives were synthesized and used as stationary phases to fabricate capillary columns for chiral separation. Some of the experimental parameters for enantiomer separations were optimized. the columns exhibited good enantioselectivity for chiral alcohols, amines, ketones, and so forth. The relative standard deviation of enantiomer retention time in run-to-run, day-to-day and column-to-column experiments were 1.02, 4.45 and 5.60% using the (R)-(3,3′-di-p-cyanophenyl)-2,2′-dimethoxyl-1,1′-binaphthalene coated column, and 2.38, 3.20 and 4.94% using the (R)-(3,3′-di-p-acetylphenyl)-2,2′-dimethoxy-1,1′-binaphthalene coated column. The results indicated that the (R)-1,1′-bi-2-naphthol derivatives may have utility in capillary electrochromatography.

A Discrete 3d–4f Metallacage as an Efficient Catalytic Nanoreactor for a Three-Component Aza-Darzens Reaction

The exploration and development of coordination nanocages can provide an approach to control chemical reactions beyond the bounds of the flask, which has aroused great interest due to their significant applications in the field of molecular recognition, supramolecular catalysis, and molecular self-assembly. Herein, we take the advantage of a semirigid and nonsymmetric bridging ligand (H5L) with rich metal-chelating sites to construct an unusual and discrete 3d-4f metallacage, [Zn2Er4(H2L)4(NO3)Cl2(H2O)]·NO3·xCH3OH·yH2O (Zn2Er4). The 3d-4f Zn2Er4 cage possesses a quadruple-stranded structure, and all of the ligands wrap around an open spherical cavity within the core. The self-assembly of the unique cage not only ensures the structural stability of the Zn2Er4 cage as a nanoreactor in solution but also makes the bimetallic lanthanide cluster units active sites that are exposed in the medium-sized cavity. It is important to note that the Zn2Er4 cage as a homogeneous catalyst has been successfully applied to catalyze three-component aza-Darzens reactions of formaldehyde, anilines, and α-diazo esters without another additive under mild conditions, displaying better catalytic activity, higher specificity, short reaction time, and low catalyst loadings. A possible mechanism for this three-component aza-Darzens reaction catalyzed by the Zn2Er4 cage has been proposed. These experimental results have demonstrated the great potential of the discrete 3d-4f metallacage as a host nanoreactor for the development of supramolecular or molecular catalysis.

Benzimidazole appended optical sensors for ionic species: Compilation of literature reports from 2017 to 2022

Rigorous advancement in the area of generation of optical (colorimetric/fluorescent) chemosensors has seen brilliant success as vibrant tools for the selective and sensitive tracking of analytes (cations and/or anions etc.) since the advent of supramolecular chemistry. Several benzimidazole derivatives and their impending significance in field of molecular recognition have been reported in this literature review, which point to the vitality of the chemosensing area. The present review delivers comprehensions into different benzimidazole based derivatives with varied structural modulations by pyridine, coumarin, pyrazole, pyrene, carbazole and Schiff base functionalities for optical detection of a variety of analytes (metal ions and/or anions). The discussed literature reports will excavate new avenues and enable research fraternities to develop superlative chemosensors with enhanced sensitivity and selectivity. This review highlights the development of various benzimidazole appended optical chemosensors for various metal ions and anions since 2017.

Recent developments in calix[4]pyrrole (C4P)-based supramolecular functional systems

Recent advances with calix[4]pyrrole-based supramolecular functional entities in the fields of molecular recognition (receptors, sensors, and metal ion caged systems), self-assembly (polymers), photo/pH-responsive molecular switches and catalysis are reviewed.

Super-assembly of freestanding graphene oxide-aramid fiber membrane with T-mode subnanochannels for sensitive ion transport

Biomimetic nacre-like membranes composed of two-dimensional lamellar sheets and one-dimensional nanofibers exhibit high mechanical strength and excellent stability. Thus, they show substantial application in the field of membrane science and water purification. However, the limited techniques for the assembly of two-dimensional lamellar membranes and one-dimensional nanofibers hamper their development and application. Herein, we developed a nacre-like and freestanding graphene oxide/aramid fiber membrane with abundant T-mode subnanochannels by introducing aramid fibers into graphene oxide interlamination via the super-assembly interaction between graphene oxide and aramid fibers. Benefiting from the presence of stable and adjustable sub-nanometer-size ion transport channels, the graphene oxide/aramid fiber composite membrane exhibited excellent mono/divalent ion selectivity of 3.51 (K+/Mg2+), which is superior to that of the pure graphene oxide membrane. The experimental results suggest that the mono/divalent ion selectivity is ascribed to the subnanochannels in the graphene oxide/aramid fiber composite membrane, electrostatic repulsion interaction and strong interaction between the divalent metal ion and carboxyl groups. Moreover, the composite membrane exhibited remarkable charge selectivity with a K+/Cl- ratio of up to ∼158, indicating that this graphene oxide/aramid fiber composite membrane has great potential for application in energy conversion. This study provides an avenue to prepare freestanding and nacre-like composite membranes with abundant T-mode ion transport channels for ion recognition and energy conversion, which also shows great application prospects in the field of membrane science and water purification.

Self-Assembly of Complementary Components Using a Tripodal Bismuth Compound: Pnictogen Bonding or Coordination Chemistry?

Triple pnictogen bonding refers to the ability of a pnictogen atom to engage in three simultaneous pnictogen bonds (PnBs) to a complementary partner through a single pnictogen atom. This supramolecular strategy was recently introduced as a unique facet of pnictogen bonding as compared to other named supramolecular interactions. Here, the ability of bismuth to participate in this phenomenon is demonstrated using Bi((NC9H7)3CH3). The study reveals that Bi engages in stronger PnBs than the analogous Sb system. The results have been contrasted with Bi systems that form strong coordination bonds, and analysis of the electron density along the bond path reveals key differences. The solution behavior of these newly synthesized supramolecules were studied by PFGSE NMR spectroscopy and they are found to remain intact in solution. Molecular design strategies that allow for triple pnictogen bonding should find use in the fields of molecular recognition and crystal engineering.

Macrocycles in Bioinspired Catalysis: From Molecules to Materials.

Macrocyclic compounds have been studied extensively as the host molecules in supramolecular chemistry. Their structural characteristics make macrocycles desirable in the field of molecular recognition, which is the key to high catalytic efficiencies of natural enzymes. Therefore, macrocycles are ideal building blocks for the design of bioinspired catalysts. This mini review highlights recent advances ranging from single-molecule to metal-organic framework materials, exhibiting multilevel macrocycle catalysts with unique catalytic centers and substrate-binding affinities.

Name reactions: strategies in the design of chemodosimeters for analyte detection

The design and synthesis of suitable chemodosimeters for the detection of toxic analytes has become challenging for new researchers nowadays in the molecular recognition field.

François N. Diederich: Pioneer of carbon allotropes and molecular recognition

Francois Nico Diederich, an iconic organic chemist who innovated and created in the fields of molecular recognition and host–guest chemistry, new allotropes of carbon and novel carbon-rich molecules, and drug activity and design, passed away on September 23, 2020 in Zurich, Switzerland at the age of 68, after battling an aggressive cancer. Francois N. Diederich. Reproduced with permission from ref. 1. Francois Diederich in the Chemistry Library at UCLA, 1980. Image credit: Marion C. Peters (Librarian Emeritus, University of California, Los Angeles, CA). Francois and Georgine Diederich at UCLA in 2019. Image credit: Penny Jennings (University of California, Los Angeles, CA). A proud native of Luxembourg, Diederich became known the world over both for his chemical discoveries and for his warm, lively, and interactive personality. Educated first in Luxembourg and then earning his diploma and doctorate at the University of Heidelberg, Germany with Heinz Staab, Diederich gained early fame for the first synthesis in 1978 of a hydrocarbon that Staab had named “Kekulene” to honor the discoverer of the structure of benzene. Kekulene, containing 12 fused benzene rings in a planar circular structure, was resynthesized and studied by single-molecule imaging in 2019, and found to have the structural details predicted by Diederich and Staab. By conquering the synthesis of this molecule, Diederich became enamored of carbon-rich molecules that he studied throughout his career. Diederich was a postdoctoral fellow with Orville L. Chapman at the University of California, Los Angeles (UCLA) from 1979 to 1981, and had fruitful interactions with Donald Cram, UCLA professor, who was on his way to the Nobel Prize in 1987 for host–guest chemistry. This field was another one in which Diederich became a world leader. Both of us (K.N.H. and J.F.S.) had similarly memorable educational interactions with Cram (and with Diederich!) at various times in … [↵][1]1To whom correspondence may be addressed. Email: houk{at}chem.ucla.edu. [1]: #xref-corresp-1-1

Development of a Raltegravir-based Photoaffinity-Labeled Probe for Human Immunodeficiency Virus-1 Integrase Capture.

Photoaffinity labeling (PAL) is one of the upcoming and powerful tools in the field of molecular recognition. It includes the determination of dynamic parameters, such as the identification and localization of the target protein and the site of drug binding. In this study, a photoaffinity-labeled probe for full-length human immunodeficiency virus-1 integrase (HIV-1 IN) capture was designed and synthesized, following the structure of the FDA-approved drug Raltegravir. This photoprobe was found to retain the HIV IN inhibitory potential in comparison with its parent molecule and demonstrates the ability to label the HIV-1 IN protein. Putative photoprobe/inhibitor binding sites near the catalytic site were then identified after protein digestion coupled to mass and molecular modeling analyses.

The dark side of disulfide-based dynamic combinatorial chemistry.

During the last two decades, disulfide-based dynamic combinatorial chemistry has been extensively used in the field of molecular recognition to deliver artificial receptors for molecules of biological interest. Commonly, the nature of library members and their relative amounts are provided from HPLC-MS analysis of the libraries, allowing the identification of potential binders for a target (bio)molecule. By re-investigating dynamic combinatorial libraries generated from a simple 2,5-dicarboxy-1,4-dithiophenol building block in water, we herein demonstrated that multiple analytical tools were actually necessary in order to comprehensively describe the libraries in terms of size, stereochemistry, affinity, selectivity, and finally to get a true grasp on the different phenomena at work within dynamic combinatorial systems.

Study of the self-association of molecular tweezers bearing two different arms: influence of the stereoelectronic effects of the arm substituents

In the general field of molecular recognition, the self-assembly of a tweezer bearing a R(+) usnic acid arm and a substituted 1,8-naphthalimide moiety as a second arm was investigated through a 1H NMR study. Two self-association modes were evidenced: either the usnic acid arms (mode A) or the naphthalimide ones (mode B) were face to face in the center of the dimer. The existence of a third non-symmetrical mode (mode C) has not been evidenced experimentally. The behavior of these tweezers was discussed taking into account the electronic density of the naphtalimide arms and the slow mode A/mode B exchange rate (EXSY experiments). Only the mode A was observed when naphthalimide was either non-substituted (1) or substituted by Br (2). With one or two electrodonating substituents (OCH3 (3) or (OCH3)2 (4) or N(CH3)2 (5)) both modes A and B occured in a 50/50 ratio. This ratio depended on temperature for tweezer 3.

Coumarin-Based Small-Molecule Fluorescent Chemosensors.

Coumarins are a very large family of compounds containing the unique 2H-chromen-2-one motif, as it is known according to IUPAC nomenclature. Coumarin derivatives are widely found in nature, especially in plants and are constituents of several essential oils. Up to now, thousands of coumarin derivatives have been isolated from nature or produced by chemists. More recently, the coumarin platform has been widely adopted in the design of small-molecule fluorescent chemosensors because of its excellent biocompatibility, strong and stable fluorescence emission, and good structural flexibility. This scaffold has found wide applications in the development of fluorescent chemosensors in the fields of molecular recognition, molecular imaging, bioorganic chemistry, analytical chemistry, materials chemistry, as well as in the biology and medical science communities. This review focuses on the important progress of coumarin-based small-molecule fluorescent chemosensors during the period of 2012-2018. This comprehensive and critical review may facilitate the development of more powerful fluorescent chemosensors for broad and exciting applications in the future.

Electrochemical Activation of TTF‐Based Halogen Bond Donors: A Powerful, Selective and Sensitive Analytical Tool for Probing a Weak Interaction in Complex Media

AbstractHerein we demonstrate the electrochemical activation and detection of intermolecular halogen bonding (XB) in solution by generating the cation radical of iodo‐trimethyltetrathiafulvalene (I‐Me3TTF•+) in the presence of various Lewis‐basic anions. This work is leading to the endorsement and generalization of the concept of electrostimulating XB for molecular recognition by adjusting the properties of the XB donor via the electrochemical reversible generation of charged species. The formation of the interaction between I–Me3TTF•+ and Lewis bases has been investigated by cyclic voltammetry allowing to quantify the strength of the interaction (KOx=100 to 400 M−1 and ΔG=−12 to −15 kJ mol−1). Moreover spectroelectrochemical measurements along with TD‐DFT calculations have confirmed XB formation upon generation of the radical cation. The present work opens broad perspectives for the development of redox switchable XB donors in the field of molecular recognition in chemical and biological systems where non‐covalent interactions are usually key governing parameters.

The Solvatochromic Materials: A Progress Review

Solvatochromic compounds attracted more and more attentions in the application of fluorescent probe, indicator, chromogenic reagent, molecular recognition field and so on. Although sovatochromic effects have been discovered for more than a century, they are still difficult to understand and even more difficult to predict. This review introduced organometallic complexes and organic compounds of solvatochromic materials and highlight the latest progress in recent years, and the molecular structure design and solvatochromic properties are discussed.