Cooperative Self‐Assembly in Linear Chains Based on Halogen Bonds

Abstract

Cooperative properties of halogen bonds were investigated with computational experiments based on dispersion-corrected relativistic density functional theory. The bonding mechanism in linear chains of cyanogen halide (XÀ CN), halocyanoacetylene (XÀ CCÀ CN), and 4-halobenzonitrile (XÀ C 6 H 4 À CN) were examined for X = H, Cl, Br, and I. Our energy decomposition and Kohn-Sham molecular-orbital analyses revealed the bonding mechanism of the studied systems. Cyanogen halide and halocyanoacetylene chains possess an extra stabilizing effect with increas-ing chain size, whereas the 4-halobenzonitrile chains do not. This cooperativity can be traced back to charge separation within the σ-electronic system by charge-transfer between the lone-pair orbital of the nitrogen (σ HOMO ) on one unit and the acceptor orbital of the CÀ X (σ* LUMO ) on the adjacent unit. As such, the HOMO-LUMO gap in the σ-system decreases, and the cooperativity increases with chain length revealing the similarity in the bonding mechanisms of hydrogen and halogen bonds.

Understanding the influence of alkali cations and halogen anions on the cooperativity of cyclic hydrogen‐bonded rosettes in supramolecular stacks

“…based on dispersion‐corrected relativistic density functional theory at the ZORA‐BLYP‐D3/TZP level for geometry optimizations and ZORA‐BLYP‐D3/TZ2P for energies. Previous works [22–24] have shown that this level of theory gives excellent understanding of bonding mechanism in hydrogen bonding and also in long range interactions within weakly‐bound complexes [11] . Furthermore, the use of the TZP basis set for large supramolecular systems has shown to furnish accurate results [16c] …”

“…Previous works [22][23][24] have shown that this level of theory gives excellent understanding of bonding mechanism in hydrogen bonding and also in long range interactions within weakly-bound complexes. [11] Furthermore, the use of the TZP basis set for large supramolecular systems has shown to furnish accurate results. [16c] The bonding energies of the dimers, the quartet and the hexamers were computed with Equation (1):…”

“…Cooperative systems can then be classified into two main categories: linear chains and cyclic arrangements. The source of cooperativity within the first group has been thoroughly studied within hydrogen, [9] pnicogen [10] and halogen‐bonded systems [11] . However, and to the best of our knowledge, there is only one record that deals with the influence of ions on linear hydrogen‐bonded arrays with positive cooperativity.…”

“…The source of cooperativity within the first group has been thoroughly studied within hydrogen, [9] pnicogen [10] and halogen‐bonded systems. [11] However, and to the best of our knowledge, there is only one record that deals with the influence of ions on linear hydrogen‐bonded arrays with positive cooperativity. Subha Mahadevi and Narahari Sastry [12] analyzed linear complexes of water, formamide and acetamide interacting at one of the extremes with Mg 2+ , Na + , H + , Cl − and OH − .…”

σ‐Electrons Responsible for Cooperativity and Ring Equalization in Hydrogen‐Bonded Supramolecular Polymers

“…The DFT‐D3(BJ) method developed by Grimme and coworkers, [18] which contains the damping function proposed by Becke and Johnson, [19] is used to describe non‐local dispersion interactions. This level is referred to as BLYP‐D3(BJ)/TZ2P and has been proven to accurately describe weak interactions [3c] . A large uncontracted relativistically optimized TZ2P Slater type orbitals (STOs) basis set containing diffuse functions were used.…”