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1. Pushing the limits of the hydrogen bond enhanced halogen bond—the case of the C–H hydrogen bond

   https://doi.org/10.1039/d2sc03792k  

   Decato, Daniel A.; Sun, Jiyu; Boller, Madeleine R.; Berryman, Orion B. (September 2022, Chemical Science)

   C–H hydrogen bonds to iodine halogen bond donors are shown to improve halogen bonding and molecular preorganization. 

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2. The bond length and bond energy of gaseous CrW

   https://doi.org/10.1063/1.4952453  

   Matthew, Daniel J.; Oh, Sang Hoon; Sevy, Andrew; Morse, Michael D. (June 2016, The Journal of Chemical Physics)
3. The location of the chemical bond. Application of long covalent bond theory to the structure of silica

   https://doi.org/10.3389/fchem.2023.1123322  

   Miller, Stephen A. (February 2023, Frontiers in Chemistry)

   Oxygen is the most abundant terrestrial element and is found in a variety of materials, but still wanting is a universal theory for the stability and structural organization it confers. Herein, a computational molecular orbital analysis elucidates the structure, stability, and cooperative bonding of α-quartz silica (SiO 2 ). Despite geminal oxygen-oxygen distances of 2.61–2.64 Å, silica model complexes exhibit anomalously large O-O bond orders (Mulliken, Wiberg, Mayer) that increase with increasing cluster size—as the silicon-oxygen bond orders decrease. The average O-O bond order in bulk silica computes to 0.47 while that for Si-O computes to 0.64. Thereby, for each silicate tetrahedron, the six O-O bonds employ 52% (5.61 electrons) of the valence electrons, while the four Si-O bonds employ 48% (5.12 electrons), rendering the O-O bond the most abundant bond in the Earth’s crust. The isodesmic deconstruction of silica clusters reveals cooperative O-O bonding with an O-O bond dissociation energy of 4.4 kcal/mol. These unorthodox, long covalent bonds are rationalized by an excess of O 2 p –O 2 p bonding versus anti-bonding interactions within the valence molecular orbitals of the SiO 4 unit (48 vs. 24) and the Si 6 O 6 ring (90 vs. 18). Within quartz silica, oxygen 2 p orbitals contort and organize to avoid molecular orbital nodes, inducing the chirality of silica and resulting in Möbius aromatic Si 6 O 6 rings, the most prevalent form of aromaticity on Earth. This long covalent bond theory (LCBT) relocates one-third of Earth’s valence electrons and indicates that non-canonical O-O bonds play a subtle, but crucial role in the structure and stability of Earth’s most abundant material. 

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4. The tension-activated carbon–carbon bond

   https://doi.org/10.1016/j.chempr.2024.05.012  

   Sun, Yunyan; Kevlishvili, Ilia; Kouznetsova, Tatiana B; Burke, Zach P; Craig, Stephen L; Kulik, Heather J; Moore, Jeffrey S (June 2024, Chem)

   Mechanical force drives distinct chemical reactions; yet, its vectoral nature results in complicated coupling with reaction trajectories. Here, we utilize a physical organic model inspired by the classical Morse potential and its differential forms to identify effective force constant (keff) and reaction energy (ΔE) as key molecular features that govern mechanochemical kinetics. Through a comprehensive experimental and computational investigation with four norborn-2-en-7-one (NEO) mechanophores, we establish the relationship between these features and the force-dependent energetic changes along the reaction pathways. We show that the complex kinetic behavior of the tensioned bonds is generally and quantitatively predicted by a simple multivariate linear regression based on the two easily computed features with a straightforward workflow. These results demonstrate a general mechanistic framework for mechanochemical reactions under tensile force and provide a highly accessible tool for the large-scale computational screening in the design of mechanophores. 

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5. Bond orders of the diatomic molecules

   https://doi.org/10.1039/c9ra00974d  

   Chen, Taoyi; Manz, Thomas A. (May 2019, RSC Advances)

   Bond order quantifies the number of electrons dressed-exchanged between two atoms in a material and is important for understanding many chemical properties. Diatomic molecules are the smallest molecules possessing chemical bonds and play key roles in atmospheric chemistry, biochemistry, lab chemistry, and chemical manufacturing. Here we quantum-mechanically calculate bond orders for 288 diatomic molecules and ions. For homodiatomics, we show bond orders correlate to bond energies for elements within the same chemical group. We quantify and discuss how semicore electrons weaken bond orders for elements having diffuse semicore electrons. Lots of chemistry is effected by this. We introduce a first-principles method to represent orbital-independent bond order as a sum of orbital-dependent bond order components. This bond order component analysis (BOCA) applies to any spin-orbitals that are unitary transformations of the natural spin-orbitals, with or without periodic boundary conditions, and to non-magnetic and (collinear or non-collinear) magnetic materials. We use this BOCA to study all period 2 homodiatomics plus Mo 2 , Cr 2 , ClO, ClO − , and Mo 2 (acetate) 4 . Using Manz's bond order equation with DDEC6 partitioning, the Mo–Mo bond order was 4.12 in Mo 2 and 1.46 in Mo 2 (acetate) 4 with a sum of bond orders for each Mo atom of ∼4. Our study informs both chemistry research and education. As a learning aid, we introduce an analogy between bond orders in materials and message transmission in computer networks. We also introduce the first working quantitative heuristic model for all period 2 homodiatomic bond orders. This heuristic model incorporates s–p mixing to give heuristic bond orders of ¾ (Be 2 ), 1¾ (B 2 ), 2¾ (C 2 ), and whole number bond orders for the remaining period 2 homodiatomics. 

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