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1. Dynamic Entwined Topology in Helical Covalent Polymers Dictated by Competing Supramolecular Interactions

   https://doi.org/10.1002/anie.202403599  

   Wayment, Lacey J.; Teat, Simon J.; Huang, Shaofeng; Chen, Hongxuan; Zhang, Wei (March 2024, Angewandte Chemie International Edition)

   Abstract Naturally occurring polymeric structures often consist of 1D polymer chains intricately folded and entwined through non‐covalent bonds, adopting precise topologies crucial for their functionality. The exploration of crystalline 1D polymers through dynamic covalent chemistry (DCvC) and supramolecular interactions represents a novel approach for developing crystalline polymers. This study shows that sub‐angstrom differences in the counter‐ion size can lead to various helical covalent polymer (HCP) topologies, including a novel metal‐coordination HCP (m‐HCP) motif. Single‐crystal X‐ray diffraction (SCXRD) analysis of HCP−Na revealed that double helical pairs are formed by sodium ions coordinating to spiroborate linkages to form rectangular pores. The double helices are interpenetrated by the unreacted diols coordinating sodium ions. The reticulation of the m‐HCP structure was demonstrated by the successful synthesis of HCP−K. Finally, ion‐exchange studies were conducted to show the interconversion between HCP structures. This research illustrates how seemingly simple modifications, such as changes in counter‐ion size, can significantly influence the polymer topology and determine which supramolecular interactions dominate the crystal lattice. 

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2. From weak to strong interactions: structural and electron topology analysis of the continuum from the supramolecular chalcogen bonding to covalent bonds

   https://doi.org/10.1039/d1cp05441d  

   Miller, Daniel K.; Chernyshov, Ivan Yu.; Torubaev, Yury V.; Rosokha, Sergiy V. (April 2022, Physical Chemistry Chemical Physics)

   The relationship between covalent and supramolecular bonding, and the criteria of the assignments of different interactions were explored via the review of selenium and tellurium containing structures in the Cambridge Structural Database and their computational analysis using Quantum Theory of Atoms in Molecules (QTAIM). This combined study revealed continuums of the interatomic Se⋯Br and Te⋯I distances, d Ch⋯X , in the series of associations from the sums of the van der Waals radii of these atoms ( r Ch + r X ) to their covalent bond lengths. The electron densities, ρ ( r ), at Bond Critical Points (BCPs) along the chalcogen bond paths increased gradually from about 0.01 a.u. common for the non-covalent interactions to about 0.1 a.u. typical for the covalent bonds. The log  ρ ( r ) values fell on the same linear trend line when plotted against normalized interatomic distances, R XY = d Ch⋯X /( r Ch + r X ). The transition from the positive to negative values of the energy densities, H ( r ), at the BCPs (related to a changeover of essentially non-covalent into partially covalent interactions) were observed at R XY ≈ 0.80. Synchronous changes of bonding characteristics with R XY (similar to that found earlier in the halogen-bonded systems) designated normalized interatomic separation as a critical factor determining the nature of these bondings. The uninterrupted continuums of Te⋯I and Se⋯Br bond lengths and BCPs’ characteristics signified an intrinsic link between limiting types of bonding involving chalcogen atoms and between covalent and supramolecular bonding in general. 

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3. Anion-binding catalyst designs for enantioselective synthesis

   Visco, M. D.; Attard, J. W.; Guan, Y.; Mattson, A. E. (January 2017, Tetrahedron letters)

   Select hydrogen bond donors can catalyze reactions of ion pairs through the recognition of anions. This mode of action can be exploited in enantioselective catalysis if a suitable chiral hydrogen bond donor is applied. Beyond just anionic recognition, an enantioselective anion-binding catalyst often must host numerous non-covalent interactions, including hydrogen bonding, general base, π-π, and π-cation, to achieve high levels of enantiocontrol. Anion-binding catalysts can be strategically designed to support those non-covalent interactions required to render a process highly stereoselective. Tactics applied in anion-binding catalyst development include enhancing arene substituents for improved π-stacking, linking two anion-binding units together on a single scaffold, expanding types of functional groups for anion recognition, and building frameworks with bifunctional modes of action. The intent of this digest is to highlight observations that suggest as anion-binding catalyst designs advance, their associated synthetic methodologies for complex molecule construction become increasingly impressive. 

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4. Global Minimum Search and Bonding Analysis of Tl ₂ H _x and Tl ₃ H _y (x=0–6; y=0–5) Series

   https://doi.org/10.1002/cphc.202300332  

   Pozdeev, Anton_S; Rublev, Pavel; Boldyrev, Alexander_I; Rao, Yi (July 2023, ChemPhysChem)

   Abstract A remarkable distinction between boron and carbon hydrides lies in their extremely different bonding patterns and chemical reactivity, resulting in diverse areas of application. Particularly, carbon, characterized by classical two‐center – two‐electron bonds, gives rise to organic chemistry. In contrast, boron forms numerous exotic and non‐intuitive compounds collectively called non‐classical structures. It is reasonable to anticipate that other elements of Group 13 exhibit their own unusual bonding patterns; however, our knowledge of the hydride chemistry for other elements in Group 13 is much more limited, especially for the heaviest stable element, thallium. In this work, we performed a conformational analysis of Tl₂H_xand Tl₃H_y(x=0–6, y=0–5) series via Coalescence Kick global minimum search algorithm, DFT, andab initioquantum chemistry methods; we investigated the bonding pattern using the AdNDP algorithm, thermodynamic stability, and stability toward electron detachment. All found global minimum structures are classified as non‐classical structures featuring at least one multi‐center bond. 

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5. The pivotal role of non-covalent interactions in single-molecule charge transport

   https://doi.org/10.1039/D3QM00210A  

   Ayinla, Ridwan Tobi; Shiri, Mehrdad; Song, Bo; Gangishetty, Mahesh; Wang, Kun (May 2023, Materials Chemistry Frontiers)

   Integrating multidisciplinary efforts from physics, chemistry, biology, and materials science, the field of single-molecule electronics has witnessed remarkable progress over the past two decades thanks to the development of single-molecule junction techniques. To date, researchers have interrogated charge transport across a broad spectrum of single molecules. While the electrical properties of covalently linked molecules have been extensively investigated, the impact of non-covalent interactions has only started to garner increasing attention in recent years. Undoubtedly, a deep understanding of both covalent and non-covalent interactions is imperative to expand the functionality and scalability of molecular-scale devices with the potential of using molecules as active components in various applications. In this review, we survey recent advances in probing how non-covalent interactions affect electron transmission through single molecules using single-molecule junction techniques. We concentrate on understanding the role of several key non-covalent interactions, including π–π and σ–σ stacking, hydrogen bonding, host–guest interactions, charge transfer complexation, and mechanically interlocked molecules. We aim to provide molecular-level insights into the structure–property relations of molecular junctions that feature these interactions from both experimental and theoretical perspectives. 

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