Engineered non-covalent π interactions as key elements for chiral recognition

Interfacial Lithium Cations Catalyze Biomimetic Aerobic Oxygenation via Short-Range Electrostatic Interaction

Enzymes often involve short-range electrostatic interactions in the deliberate microenvironment for accelerating the catalysis. Comparatively, electrostatic interactions from ions in solutions are mostly shielded by solvent or counter-ion shells, creating negligible catalytic effects. Herein, we discovered that the interfacial Li+ cations accumulated on electrodes catalyze the selective water-involved O2 electro-reduction into peroxide anion (OOH-), forming an active side-on Li+-OOH- complex via short-range electrostatic interaction. This complex reduces the O2 reduction energy barrier and increases the nucleophilicity, expediting the aerobic oxygenation of ketones. Aside from trapping active intermediates, Li+ cations also attract the excessive water dipoles to prevent them from quenching the active Li+-OOH- complex. By using probe-assisted quantitative methods, we demonstrated the unique under-coordinative characteristics of interfacial Li+ for interacting with reaction intermediates, and the effective concentration of under-coordinative Li+ on the interface is an order of magnitude higher than in the bulk solution. These analyses provide essential evidences about the intrinsic difference between bulk ions and interfacial ions toward catalysis.

Enhancing π-π stacking by a halogen substituent in a single-molecule junction

Modulating π-π interactions and understanding their impact on charge transport at the molecular scale are critical for advancing supramolecular electronics. Herein, anthracene-based molecular wires (Py-X, X = H, F, Cl, Br) were synthesized and the effect of halogen substituents on π-π stacking was investigated. Experimental results revealed that Py-Br and Py-Cl form both monomer and π-stacked dimer junctions, while Py-H and Py-F only form monomer junctions. The bromine substituent demonstrates a unique ability to promote π-stacked dimer formation. This work provides a design strategy for the formation of π-stacked dimmers in molecular junctions, and advances the development of supramolecular electronics.

Mechanistic insights into the stereocontrolling non-covalent π interactions in Pd-catalyzed redox-relay Heck arylation reaction

The mechanism and origin of enantioselectivity of palladium-catalyzed redox-relay Heck arylation of 1,1-disubstituted homoallylic alcohols were investigated computationally. The computed mechanism consists of an initial migratory insertion, followed by a β-hydride elimination, and a subsequent re-insertion/elimination process to yield an enol intermediate, which tautomerizes to the more stable carbonyl product. Results from DFT calculations suggest that the key enantiodetermining step is the reinsertion of an alkene intermediate into the Pd-H bond, but not the initial migratory insertion of the substrate into the Pd-Aryl species. By comparing two chiral pyridine oxazoline ligands with a focus on the phenyl versus tert-butyl substituent effects, a plethora of attractive non-covalent π interactions, including CH-π interaction, lone pair-π interaction and T-shaped π-π interaction, are identified to play a key role in enabling high enantioselectivity of this reaction. This work provides mechanistic insights into the comprehensive understanding of this catalytic cascade, and highlights the significant role played by non-covalent π interactions in its enantiocontrol.

Interface Phenomena in Molecular Junctions through Noncovalent Interactions

Noncovalent interactions, both between molecules and at the molecule-electrode interfaces, play essential roles in enabling dynamic and reversible molecular behaviors, including self-assembly, recognition, and various functional properties. In macroscopic ensemble systems, these interfacial phenomena often exhibit emergent properties that arise from the synergistic interplay of multiple noncovalent interactions. However, at the single-molecule scale, precisely distinguishing, characterizing, and controlling individual noncovalent interactions remains a significant challenge. Molecular electronics offers a unique platform for constructing and characterizing both intermolecular and molecule-electrode interfaces governed by noncovalent interactions, enabling the isolated study of these fundamental interactions. Furthermore, precise control over these interfaces through noncovalent interactions facilitates the development of enhanced molecular devices. This review examines the characterization of interfacial phenomena arising from noncovalent interactions through single-molecule electrical measurements and explores their applications in molecular devices. We begin by discussing the construction of stable molecular junctions through intermolecular and molecule-electrode interfaces, followed by an analysis of electron tunneling mechanisms mediated by key noncovalent interactions and their modulation methods. We then investigate how noncovalent interactions enhance device sensitivity, stability, and functionality, establishing design principles for next-generation molecular electronics. We have also explored the potential of noncovalent interactions for bottom-up self-assembled molecular devices. The review concludes by addressing the opportunities and challenges in scaling up molecular electronics through noncovalent interactions.

Determining the Absolute Configuration of Small Molecules by Diffusion NMR Experiments

Enantiomers are ubiquitous in many areas of science, such as pharmaceuticals, agriculture, and food. Nuclear magnetic resonance (NMR) alone is not able to differentiate enantiomers as their spectra are identical. However, these can be distinguished using chiral auxiliaries (such as chiral complexing agents) that form diastereomeric complexes, but absolute identification is still troublesome, usually requiring a chemical reaction with a chiral derivatizing agent. Here, we propose a new method that uses a hybrid mixture of solvating agents in a simple comparison of diffusion NMR experiments, which can discriminate enantiomers in both frequency and diffusion domains, dubbed CHIMERA (CHIral Micelle Enantiomer Resolving Agent). The new method was assessed for twenty-three small chiral molecules using a combination of BINOL and (-)-DMEB, a chiral surfactant, and initial results indicate that absolute configuration can be obtained from a simple experiment.

Mechanisms for translating chiral enantiomers separation research into macroscopic visualization

Chirality is a common phenomenon in nature, including the dominance preference of small biomolecules, the special spatial conformation of biomolecules, and the biological and physiological processes triggered by chirality. The selective chiral recognition of molecules in nature from up-bottom or bottom-up is of great significance for living organisms. Such as the transcription of DNA, the recognition of membrane proteins, and the catalysis of enzymes all involve chiral recognition processes. The selective recognition between these macromolecules is mainly achieved through non covalent interactions such as hydrophobic interactions, ammonia bonding, electrostatic interactions, metal coordination, van der Waals forces, and π-π stacking. Researchers have been committed to studying how to convert this weak non covalent interaction into macroscopic visualization, which has further understood of the interactions between chiral molecules and is of great significance for simulating the interactions between molecules in living organisms. This article reviews several models of chiral recognition mechanisms, the interaction forces involved in the chiral recognition process, and the research progress of chiral recognition mechanisms. The outlook in this review points out that studying chiral recognition interactions provides an important bridge between chiral materials and the life sciences, providing an ideal platform for studying chiral phenomena in biological systems.

Lowering the affinity of single-chain monovalent BBB shuttle scFc-scFv8D3 prolongs its half-life and increases brain concentration

Monoclonal antibody therapeutics is a massively growing field. Progress in providing monoclonal antibody therapeutics to treat brain disorders is complicated, due to the impermeability of the blood-brain barrier (BBB) to large macromolecular structures. To date, the most successful approach for delivering antibody therapeutics to the brain is by targeting the transferrin receptor (TfR) using anti-TfR BBB shuttles, with the 8D3 antibody being one of the most extensively studied in the field. The strategy of fine-tuning TfR binding affinity has shown promise, with previous results showing an improved brain delivery of bivalent 8D3-BBB constructs. In the current study, a fine-tuning TfR affinity strategy has been employed to improve single-chain variable fragment (scFv) 8D3 (scFv8D3) affinity mutants. Initially, in silico protein-protein docking analysis was performed to identify amino acids (AAs) likely to contribute to 8D3s TfR binding affinity. Mutating the identified AAs resulted in decreased TfR binding affinity, increased blood half-life and increased brain concentration. As monovalent BBB shuttles are seemingly superior for delivering antibodies at therapeutically relevant doses, our findings and approach may be relevant for optimizing brain delivery.

Lone Pair-π Interactions in Organic Reactions

Noncovalent interactions between a lone pair of electrons and π systems can be categorized into two types based on the nature of π systems. Lone pair-π(C═O) interactions with π systems of unsaturated, polarized bonds are primarily attributed to orbital interactions, whereas lone pair-π(Ar) interactions with π systems of aromatic functional groups result from electrostatic attractions (for electron-deficient aryls) or dispersion attractions and Pauli repulsions (for electron-rich/neutral aryls). Unlike well-established noncovalent interactions, lone pair-π interactions have been comparatively underappreciated or less used to influence reaction outcomes. This review emphasizes experimental and computational studies aimed at integrating lone pair-π interactions into the design of catalytic systems and utilizing these interactions to regulate the reactivity and selectivity of chemical transformations. The role of lone pair-π interactions is highlighted in the stabilization or destabilization of transition states and ground-state binding. Examples influenced by lone pair-π interactions with both unsaturated, polarized bonds and aromatic rings as π systems are included. At variance with previous reviews, the present review is not structured according to the physical origin of particular classes of lone pair-π interactions but is divided into chapters according to ways in which lone pair-π interactions affect kinetics and/or selectivity of reactions.

Self-Polymerized Tough and High-Entanglement Zwitterionic Functional Hydrogels

Zwitterionic hydrogels exhibit great potential in biomedical applications due to their antifouling properties and biocompatibility. However, the single-network structure of pure zwitterionic hydrogels leads to a low toughness and strength, limiting their application in biomedical fields. In this work, a high entanglement sulfobetaine methacrylate-dopamine hydrogel (SBMA-DA-PE) with low cross-linker content and high monomer concentration is prepared by using a dopamine oxidative radical polymerization method. Compared to a regular zwitterionic hydrogel, the SBMA-DA-PE hydrogel exhibits a 5-fold increase in tensile fracture stress and a 10-fold increase in compressive fracture stress. The SBMA-DA-PE hydrogel possesses excellent mechanical properties (the maximum compressive stress ≥4.85 MPa, the maximum compressive strain ≥90%). Besides, the non-covalent interactions between catechol or ortho-quinones within the SBMA-DA-PE hydrogel, combined with strong intermolecular electrostatic interactions, endow the SBMA-DA-PE hydrogel with great self-healing capabilities and fatigue resistance. The SBMA-DA-PE hydrogel demonstrates low swellability and possesses good antifouling properties. Furthermore, the good printability and conductivity of the tough SBMA-DA-PE hydrogel endows it with new possibilities for developing biological 3D scaffolds and electronic devices. Overall, this work provides new insights into the preparation of zwitterionic hydrogels with high mechanical strength and multi-functionality for biomedical applications.

Light-Up Fluorescence and Circularly Polarized Luminescence in Achiral Interlocked Framework via Adaptive Lone Pair-π Interaction Confinement

Interactions between lone pairs and aromatic π systems are significant across biology and self-assembled materials. Herein, employing an achiral confinement metal-organic framework (MOF) encapsulates guest molecules, it is successfully realized that lone pair (lp)-π interaction induces fluorescence "turn-on" and circularly polarized luminescence for the first time. The MOFs synthesized based on naphthalenediimide show nearly non-emissive, which can be light-up by introducing acetone or ester guests containing lone pairs-π interaction. Furthermore, the introduction of a series of lp-rich chiral esters induces supramolecular chirality as well as circularly polarized luminescence in achiral MOFs, while also observing chiral adaptability. This work first demonstrates the luminescence and chiral induction via lone pair electrons-π interactions, presenting a fresh paradigm for the advancement of chiroptical materials.

Chiral Macrocycles for Enantioselective Recognition

The efficient synthesis of chiral macrocycles with highly enantioselective recognition remains a challenge. We have addressed this issue by synthesizing a pair of chiral macrocycles, namely, R/S-BINOL[2], achieving total isolated yields of up to 62% through a two-step reaction sequence. These macrocycles are readily purified by column chromatography over silica gel without the need for chiral separation, thus streamlining the overall synthesis. R/S-BINOL[2] demonstrated enantioselective recognition toward chiral ammonium salts, with enantioselectivity (KS/KR) values reaching up to 13.2, although less favorable separations were seen for other substrates. R/S-BINOL[2] also displays blue circularly polarized luminescence with a |glum| value of up to 2.2 × 10-3. The R/S-BINOL[2] macrocycles of this study are attractive as chiral hosts in that they both display enantioselective guest recognition and benefit from a concise, high-yielding synthesis. As such, they may have a role to play in chiral separations.

Tracking Noncovalent Interactions of π, π-Hole, and Ion in Molecular Complexes at the Single-Molecule Level

Noncovalent interactions involving aromatic rings, such as π-stacking and π-ion interactions, play an essential role in molecular recognition, assembly, catalysis, and electronics. However, the inherently weak and complex nature of these interactions has made it challenging to study them experimentally, especially with regard to elucidating their properties in solution. Herein, the noncovalent interactions between π and π-hole, π and cation, and π-hole and anion in molecular complexes in nonpolar solution are investigated in situ through single-molecule electrical measurements in combination with theoretical calculations. Specifically, phenyl and pentafluorobenzyl groups serve as π and π-hole sites, respectively, while Li+ and Cl- are employed as the cation and anion. Our findings reveal that, in comparison with homogeneous π···π interactions, heterogeneous π···π-hole and π···cation interactions exhibit greater binding energies, resulting in a longer binding lifetime of the molecular junctions. Meanwhile, π···Li+ and π-hole···Cl- interactions present significantly distinct binding characteristics, with the former being stronger but more flexible than the latter. Furthermore, by changing the molecular components, similar conductivity can be achieved in both molecular dimers or sandwich complexes. These results provide new insights into π- and π-hole-involved noncovalent interactions, offering novel strategies for precise manipulation of molecular assembly, recognition, and molecular device.

Buckybowl Molecular Tweezers for Recognition of Fullerenes

Buckybowl tweezers are a relatively young research area closely associated with the development of non-planar polycyclic aromatic systems and supramolecular chemistry. Since the appearance of the first prototypes in the early 2000s, the tweezers have undergone evolutionary changes. Nowadays they are able to effectively interact with fullerenes and the results opened up prospects for development in the field of sensing, nonlinear optics, and molecular switchers. In the present study, examples of corannulene-based and other buckybowl tweezers for the recognition of C60 and C70 fullerenes were summarized and analyzed. The main structural components of the tweezers were also reviewed in detail and their role in the formation of complexes with fullerenes was evaluated. The revealed structural patterns should trigger the development of novel recognition systems and materials with a wide range of applications.

TKI type switching overcomes ROS1 L2086F in ROS1 fusion-positive cancers

The grammar in this abstract is generally correct, but there's a minor issue with sentence structure in one part. Here's a slightly revised version with improved grammar and flow:ROS1 tyrosine kinase inhibitors (TKIs) are highly effective in ROS1-positive non-small cell lung cancer, but resistance remains a challenge. We investigated the activity of various TKIs against wildtype and mutant ROS1, focusing on the emerging L2086F resistance mutation. Using Ba/F3 and NIH3T3 cell models, CRISPR/Cas9-edited isogenic wildtype and mutant patient-derived cell lines, and in vivo tumor growth studies, we compared type I TKIs (crizotinib, entrectinib, taletrectinib, lorlatinib, and repotrectinib) to type II TKIs (cabozantinib and merestinib) and the type I FLT3 inhibitor gilteritinib. The ROS1 L2086F mutant kinase showed resistance to type I TKIs, while type II TKIs retained activity. Gilteritinib inhibited both wildtype and L2086F mutant ROS1 but was ineffective against the G2032R mutation. Structural analyses revealed distinct binding poses for cabozantinib and gilteritinib, explaining their efficacy against L2086F. Clinical cases demonstrated cabozantinib's effectiveness in patients with TKI-resistant, ROS1 L2086F mutant NSCLCs. This study provides the first comprehensive report of ROS1 L2086F in the context of later-generation TKIs, including macrocyclic inhibitors. While cabozantinib effectively inhibits ROS1 L2086F, its multi-kinase inhibitor nature highlights the need for more selective and better-tolerated TKIs to overcome kinase-intrinsic resistance. Gilteritinib may offer an alternative for targeting ROS1 L2086F with distinct off-target toxicities, but further studies are required to fully evaluate its potential in this setting.

Recent Advances in π-Stacking Interaction-Controlled Asymmetric Synthesis

The π-stacking interaction is one of the most important intramolecular and intermolecular noncovalent interactions in organic chemistry. It plays an important role in stabilizing some structures and transition states in certain reactions via both intramolecular and intermolecular interactions, facilitating different selectivities, such as chemo-, regio-, and stereoselectivities. This minireview focuses on the recent examples of the π-stacking interaction-controlled asymmetric synthesis, including auxiliary-induced asymmetric synthesis, kinetic resolution, asymmetric synthesis of helicenes and heterohelicenes, and multilayer 3D chiral molecules.

Highly Enantioselective Dihydroxylation of 1,1-Disubstituted Aliphatic Alkenes Enabled by Orchestrated Noncovalent π-Interactions

The elusive nature of noncovalent π-interactions leads to their infrequent use as a design element in challenging chemical reactions. Stereocontrolling models based on coordinated noncovalent π-interactions were used for the asymmetric dihydroxylation of 1,1-disubstituted aliphatic alkenes. By introduction of a substituted phthalazine ring into the alkene substrates, the enantioselectivity reached 99% under the catalysis of bis-cinchona alkaloid ligands. Density functional theory calculations indicated a well-orchestrated, π-π interaction-directed "sandwich-like" transition state.

Heterometallic AuI 6 AgI 6 Macrocyclic Cluster Templated by a Supramolecular Melamine Dimer

The application of supramolecular templates in aligning atomically precise heterometal arrays is important for pursuing functional materials. Herein, we report that a bilayered supramolecular tri-deprotonated melamine dimer functions as an effective template in the construction of a heterometallic gold(I)-silver(I) macrocyclic cluster [μ6 -(C3 N6 H3 )3- ]2 -AuI 6 AgI 6 . X-ray single crystal structural analysis showed that a crown-like AuI 6 AgI 6 macrocycle is aligned around two parallelly stacked μ6 -(C3 N6 H3 )3- moieties hold together with π-π interactions. Theoretical calculations revealed that the [μ6 -(C3 N6 H3 )3- ]2 motif dominantly contributes to the near-occupied orbitals in the electronic structure, which is closely related to its luminescence properties. This work demonstrates that the supramolecular templates containing multiple symmetric binding sites may present a facile approach in the construction of functional metal clusters.

Insights into non-covalent interactions in dicopper(II,II) complexes bearing a naphthyridine scaffold: anion-dictated electrochemistry

A family of bis(μ-hydroxido)dicopper(II,II) complexes bearing a naphthyridine-based scaffold has been synthesized and characterized. Cyclic voltammetry reveals that the nature of the anions present in the complexes plays a pivotal role in their electrochemical properties. X-ray diffraction, spectroscopic and electrochemical analysis data support the formation of intimate ion pairs by non-covalent interactions driving to a ca. 270 mV difference for the potential required to monooxidize the CuIICuII species.

Engineering π-Conjugation of Phenylalanine Derivatives for Controllable Chiral Folding and Self-Assemblies

π-π stacking interaction is an attractive interaction that involves aromatic groups containing π-conjugated domains. It is a promising strategy for stabilizing folded structures with interesting chiroptical properties and manipulating the supramolecular chiral self-assembly process. In this study, we report the engineering of π-conjugated amino acids that utilize π-π stacking interactions to manipulate chiral folding as well as self-assembly evolution. Stepwise conjugation of phenyl, naphthyl, and pyrenyl to N-terminal phenylalanine derivatives witnessed the folding through intramolecular π-interactions in solution phase, which facilitated the formation of chiral geometry and the emergence of chiral optics. Introduction of aromatic domains efficiently lowers the critical aggregation concentration in the aqueous media. Molecular folding enables a special concentration-dependent self-assembly, whereby the supramolecular chirality accomplished inversion with the evolution of helical nanoarchitectures. This work develops a strategy to engineer π-conjugated amino acids with controllable folding behaviors, which also offers implications for the rational design of functional chiral materials.

α-Methylbenzylamine Functionalized Crown-Ether-Appended Calix[4]arene Phase Transfer Catalyst for Enantioselective Henry Reaction

In this letter, we designed a highly selective α-methylbenzylamine functionalized crown-ether-appended calix[4]arene derived phase transfer catalyst for asymmetric nitroaldol reaction to provide the desired nitroaldol adducts in high yields (up to 99 % yield) with good to excellent enantioselectivities (up to 99.8 % ee).

L-ribose specific recognition surface constructed by pillar[5]arene-based host-guest interaction

In living organisms, chiral molecules have specific chiral conformations that produce different physiological effects. Ribose is one of the components of RNA, which mainly plays a role in regulating biological activity. Inspired by the biological recognition of sugars, functional chiral surfaces for recognizing L-ribose through non-covalent interactions were constructed. In the strategy of this study, a functional chiral gold surface based on host-guest interactions was constructed through the assembly of the host molecule single-function alynyl pillar[5]arene(SAP5) and the guest molecule (S) -mandelate-violet (SMV). The association constant of SMV and SAP5 was calculated to be 2.95×104 M-1, with a binding ratio of 1:1. By impedance and contact angle detection, the constructed functional interface has good detection effect on L-ribose in the range of 1×10-7 M to1× 10-2 M. In addition, CV was disassembled from the aromatic cavity of pillar[5]arene after adding zinc powder and it can repeat five times with good recyclability, thus achieving the organic combination of interface recognition and intelligence.

Facile Blending Strategy for Boosting the Conjugated Polymer Semiconductor Transistor's Mobility

The optimization of field-effect mobility in polymer field-effect transistors (FETs) is a critical parameter for advancing organic electronics. Today, many challenges still persist in understanding the roles of the design and processing of semiconducting polymers toward electronic performance. To address this, a facile approach to solution processing using blends of PDPP-TVT and PTPA-3CN is developed, resulting in a 3.5-fold increase in hole mobility and retained stability in electrical performance over 3 cm2 V-1 s-1 after 20 weeks. The amorphous D-A conjugated structure and strong intramolecular polarity of PTPA-3CN are identified as major contributors to the observed improvements in mobility. Additionally, the composite analysis by X-ray photoelectron spectroscopy (XPS) and the flash differential scanning calorimetry (DSC) technique showed a uniform distribution and was well mixed in binary polymer systems. This mobility enhancement technique has also been successfully applied to other polymer semiconductor systems, offering a new design strategy for blending-type organic transistor systems. This blending methodology holds great promise for the practical applications of OFETs.

Flexible and sewable electrode based on Ni-Co@PANI-salphen composite-coated on textiles for wearable supercapacitor

Flexible electrodes with high deformability and energy density are critical for electronic textiles. The key factor for achieving high-performance supercapacitors with superior power and energy density is the evaluation of materials that exhibit exceptional capacitive performance. Herein, we have prepared Ni-Co nanoparticles at the surface of polyaniline-salphen (Ni-Co@PS). Then, followed by casting Ni-Co@PS on a conductive carbon cloth (CC) as a substrate through a facile in-situ polymerization strategy. The morphologies of Ni-Co@PS composite were characterized by different methods such as FE-SEM, XPS, XRD, BET, and electrochemical methods. This nanocomposite showed high tolerability and a large surface area with excellent behavior as a new nanomaterial for supercapacitor application. Thus, the optimum composite designed with a metal ratio (nickel-cobalt 3:1 w/w) satisfactorily possesses a specific capacitance of up to 549.994 C g-1 (1447.2 F g-1) under 0.5 A g-1 and long-term cyclic stability featuring capacity retention of 95.9% after 5000 cycles at a current density of 9.0 A g-1. The Ni-Co@PS-CC, is a material with great potential as an electrode in asymmetric wearable supercapacitor (AWSC) apparatus, demonstrating a remarkable specific capacity of 70.01, and accompanied by an energy density of 23.46 Wh k g-1 at a power density of 800 W k g-1.

Chiral Materials: Progress, Applications, and Prospects

Chirality is a universal phenomenon in molecular and biological systems, denoting an asymmetric configurational property where an object cannot be superimposed onto its mirror image by any kind of translation or rotation, which is ubiquitous on the scale from neutrinos to spiral galaxies. Chirality plays a very important role in the life system. Many biological molecules in the life body show chirality, such as the "codebook" of the earth's biological diversity-DNA, nucleic acid, etc. Intriguingly, living organisms hierarchically consist of homochiral building blocks, for example, l-amino acids and d-sugars with unknown reason. When molecules with chirality interact with these chiral factors, only one conformation favors the positive development of life, that is, the chiral host environment can only selectively interact with chiral molecules of one of the conformations. The differences in chiral interactions are often manifested by chiral recognition, mutual matching, and interactions with chiral molecules, which means that the stereoselectivity of chiral molecules can produce changes in pharmacodynamics and pathology. Here, the latest investigations are summarized including the construction and applications of chiral materials based on natural small molecules as chiral source, natural biomacromolecules as chiral sources, and the material synthesized by design as a chiral source.

Ligand and Substituent Effect on Regium-π Bonding in Cu and Ag π-Conjugated Complexes: A Density Functional Study

Density functional theory investigation of regium (Rg)-π bonding using the RgL-X model system, where Rg = Cu and Ag; L = CN, NO2, and OH; X = π-conjugated system (benzene, cyanobenzene, benzoic acid, pyridine, 2-methoxy aniline, 1,4-dimethoxy benzene, and cyclophane), has been performed. Conclusive evidence of the Rg-π bond has been provided by analysis of molecular electrostatic potential surfaces, Rg-π bond length, interaction energy (ΔE), second-order perturbation energy (E2), charge transfer (Δq), quantum theory of atom in molecules, and noncovalent interaction plots for 42 structural arrangements with varying ligands and the substituted aromatic ring. The Rg-π bond length in the optimized model systems varies from 2.03 to 2.12 Å in Cu complexes (1-21) and from 2.26 to 2.38 Å in Ag complexes (22-42) at the PBE0-D3 functional. While the ligand (L) attached to the Rg metal has a bargaining effect on the strength of the Rg-π bond (in the order of -OH > -CN = -NO2), the π-conjugated systems have a diminutive effect. Two X-ray crystal structures (CUCSOI and AHIDQU) having the Rg-π bond, accessed from Cambridge Crystallographic Data Centre (CCDC), are discussed here to signify the influence of Rg-π bonding on the crystal structure.

π-Stacking among the Anthracenyl Groups of a Copper Complex Resulted in Doubling of Unit Cell Volume To Provide New Polymorphs

Two polymorphs of the 9-N-(3-imidazolylpropylamino)methylanthracene (Hanthraimmida) containing hydrated copper(II)-2,6-pyridinedicarboxylate complex are reported. The two polymorphs have either lamellar or Herringbone arrangements of π-stacks among the anthracenyl groups of organocation. The difference between the two polymorphs originated from having face-to-face stacking arrangements between the two anthracenyl groups of the symmetry independent cations within the unit cell in one of the polymorphs. The π-stacked anthracenyl groups in consecutive layers of the polymorphs are oriented in one direction in the polymorph designated as P1, whereas the polymorph designated as P2 has such orientations in opposite directions. The unit cell volume of the polymorph P2 (Z = 4) has approximately twice the volume of the polymorph P1 (Z = 2); it happend due to coalescence of two unit cells of P1 in the ab-crystallographic plane. A mixed methanol/water solvate of the copper complex is also reported. It has a channel-like arrangement of the cations; has the anions and the solvents within the cation embraced channel-like enclosures. This complex is unstable, once taken out from the methanol solvent, it transforms in real time to P2 by replacements of the methanol molecules by water molecules.

Noncovalent bonding assessment by pair distribution function

Noncovalent interactions are essential in the formation and properties of a diverse range of materials. However, reliably identifying noncovalent interactions remains challenging using conventional methods such as X-ray diffraction, especially in nanocrystalline, poorly crystalline or amorphous materials which lack long-range lattice periodicity. Here, we demonstrate the accurate determination of deviations in the local structure and tilting of aromatic rings during the temperature-induced first order structural transition in the 1 : 1 adduct of 4,4'-bipyridinium squarate (BIPY:SQA) from the low temperature form HAZFAP01 to high temperature HAZFAP07 by X-ray pair distribution function. This work demonstrates how pair distribution function analyses can improve our understanding of local structural deviations resulting from noncovalent bonds and guide the development of novel functional materials.

Click synthesis, antimicrobial, DNA photocleavage and computational studies of oxindole-tethered 1H-1,2,3-triazoles

Aim: To obtain new hybrids derived from isatin and triazole. Materials & methods: A series of oxindole-1-H-1,2,3-triazole hybrids (4a-l) were synthesized from 3-sulfenylated N-propargylated oxindoles and organic azides employing Cu(I)-catalyzed azide-alkyne cycloaddition. These compounds were evaluated in vitro for antimicrobial activity by the standard serial dilution method and DNA photocleavage activity. Results: Antimicrobial assay revealed that compounds 4l and 4f exhibited promising efficacy against Candida albicans and Rhizopus oryzae, respectively, with a minimum inhibitory concentration value of 0.0008 μmol/mL. Compounds 4h and 4k completely degraded plasmid DNA. Further molecular docking of compounds with 1KZN (4j and 4k) and 5TZ1 (4h and 4l) revealed good binding interactions. Conclusion: Results of the current research can help in the development of new antimicrobial agents with high efficacy.

Bracelet-like Complexes of Lithium Fluoride with Aromatic Tetraamides, and Their Potential for LiF-Mediated Self-Assembly: A DFT Study

Geometries and binding energies of complexes between a LiF molecule and a model aromatic tetraamide are obtained using various DFT methods. The tetraamide consists of a benzene ring and four amides positioned so that the LiF molecule can bind via Li⋯O=C or N-H⋯F interactions. The complex with both interactions is the most stable one, followed by the complex with only N-H⋯F interactions. Doubling the size of the former resulted in a complex with a LiF dimer sandwiched between the model tetraamides. In turn, doubling the size of the latter resulted in a more stable tetramer with bracelet-like geometry having the two LiF molecules also sandwiched but far apart from each other. Additionally, all methods show that the energy barrier to transition to the more stable tetramer is small. The self-assembly of the bracelet-like complex mediated by the interactions of adjacent LiF molecules is demonstrated by all computational methods employed.

Ligand-induced activation and G protein coupling of prostaglandin F2α receptor

Prostaglandin F_2α (PGF_2α), an endogenous arachidonic acid metabolite, regulates diverse physiological functions in many tissues and cell types through binding and activation of a G-protein-coupled receptor (GPCR), the PGF_2α receptor (FP), which also is the primary therapeutic target for glaucoma and several other diseases. Here, we report cryo-electron microscopy (cryo-EM) structures of the human FP bound to endogenous ligand PGF_2α and anti-glaucoma drugs LTPA and TFPA at global resolutions of 2.67 Å, 2.78 Å, and 3.14 Å. These structures reveal distinct features of FP within the lipid receptor family in terms of ligand binding selectivity, its receptor activation, and G protein coupling mechanisms, including activation in the absence of canonical PIF and ERY motifs and G_q coupling through direct interactions with receptor transmembrane helix 1 and intracellular loop 1. Together with mutagenesis and functional studies, our structures reveal mechanisms of ligand recognition, receptor activation, and G protein coupling by FP, which could facilitate rational design of FP-targeting drugs.

Molecular Understanding of Adhesion of Epoxy Resin to Graphene and Graphene Oxide Surfaces in Terms of Orbital Interactions

The adhesion mechanism of epoxy resin (ER) cured material consisting of diglycidyl ether of bisphenol A (DGEBA) and 4,4'-diaminodiphenyl sulfone (DDS) to pristine graphene and graphene oxide (GO) surfaces is investigated on the basis of first-principles density functional theory (DFT) with dispersion correction. Graphene is often used as a reinforcing filler incorporated into ER polymer matrices. The adhesion strength is significantly improved by using GO obtained by the oxidation of graphene. The interfacial interactions at the ER/graphene and ER/GO interfaces were analyzed to clarify the origin of this adhesion. The contribution of dispersion interaction to the adhesive stress at the two interfaces is almost identical. In contrast, the DFT energy contribution is found to be more significant at the ER/GO interface. Crystal orbital Hamiltonian population (COHP) analysis suggests the existence of hydrogen bonding (H-bonding) between the hydroxyl, epoxide, amine, and sulfonyl groups of the ER cured with DDS and the hydroxyl groups of the GO surface, in addition to the OH-π interaction between the benzene rings of ER and the hydroxyl groups of the GO surface. The H-bond has a large orbital interaction energy, which is found to contribute significantly to the adhesive strength at the ER/GO interface. The overall interaction at the ER/graphene is much weaker due to antibonding type interactions just below the Fermi level. This finding indicates that only dispersion interaction is significant when ER is adsorbed on the graphene surface.

A Cost Effective Scheme for the Highly Accurate Description of Intermolecular Binding in Large Complexes

There has been a growing interest in quantitative predictions of the intermolecular binding energy of large complexes. One of the most important quantum chemical techniques capable of such predictions is the domain-based local pair natural orbital (DLPNO) scheme for the coupled cluster theory with singles, doubles, and iterative triples [CCSD(T)], whose results are extrapolated to the complete basis set (CBS) limit. Here, the DLPNO-based focal-point method is devised with the aim of obtaining CBS-extrapolated values that are very close to their canonical CCSD(T)/CBS counterparts, and thus may serve for routinely checking a performance of less expensive computational methods, for example, those based on the density-functional theory (DFT). The efficacy of this method is demonstrated for several sets of noncovalent complexes with varying amounts of the electrostatics, induction, and dispersion contributions to binding (as revealed by accurate DFT-based symmetry-adapted perturbation theory (SAPT) calculations). It is shown that when applied to dimeric models of poly(3-hydroxybutyrate) chains in its two polymorphic forms, the DLPNO-CCSD(T) and DFT-SAPT computational schemes agree to within about 2 kJ/mol of an absolute value of the interaction energy. These computational schemes thus should be useful for a reliable description of factors leading to the enthalpic stabilization of extended systems.

Asymmetric Dihydroxylation-Based Kinetic Resolution of Allylic Amides Enabled by Noncovalent π-Interactions

While Sharpless asymmetric dihydroxylation is widely utilized to convert various alkenes into diols with excellent enantioselectivies, kinetic resolution by means of this fundamental catalysis has generally proven to be ineffective. Here we report that, by relying on noncovalent π-interactions that purposely include the substrate's stereocenter in the corresponding catalyst-substrate interaction framework, AD-based kinetic resolution of allylic amides is realized. This method enables such versatile chiral building blocks to be easily accessed with excellent enantiomeric excesses (ee's).

Scissor-like Face to Face π-π Stacking: A Surprising Preference Induced by the Isocyano Group in the Self-Assembled Dimer of Phenyl Isocyanide

Phenyl isocyanide has been chosen as a prototype to probe the π-π interaction modulated by the -NC group, which has a chameleonic nature with two main resonance forms showing a triple bond and being carbenoid. The rotational spectroscopic investigation complemented with theoretical analyses indicates that the phenyl isocyanide dimer has a scissor-like configuration controlled by dispersive forces along with the formation of π-π stacking. This is the first rotational spectroscopic evidence, to the best of our knowledge, that the mono-substitution by an -NC group on benzene can activate the meta position in forming noncovalent interactions. This work also provides experimental evidence on the importance of substituent effects in modulating π-π stacked structures, as well as practical proof of a biased interaction behavior of isocyanide-substituted aromatic molecules.