Halogen-Bonded Assemblies of Arylene Imides and Diimides: Insight from Electronic,Structural, and Computational Studies |
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Authors: | Dr Kalyanashis Mandal Dr Deepak Bansal Yogendra Kumar Rustam Dr Jyoti Shukla Dr Pritam Mukhopadhyay |
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Institution: | 1. Supramolecular and Material Chemistry Lab, School of Physical Sciences, Jawaharlal Nehru University, Delhi, 110067 India;2. Institute of Resource Ecology, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany |
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Abstract: | Halogen-bonding interactions in electron-deficient π scaffolds have largely been underexplored. Herein, the halogen-bonding properties of arylene imide/diimide-based electron-deficient scaffolds were studied. The influence of scaffold size, from small (phthalimide) to moderately sized (pyromellitic diimide or naphthalenediimides) to large (perylenediimide), axial-group modification, and number of halo substituents on the halogen bonding and its self-assembly was probed in a set of nine compounds. The structural modification leads to tunable optical and redox properties. The first reduction potential ranges between −1.09 and −0.17 V (vs. SCE). Two of the compounds, that is, 6 and 9 , have deep-lying LUMOs with values reaching −4.2 eV. Single crystals of all nine systems were obtained, which showed Br ⋅⋅⋅ O, Br ⋅⋅⋅ Br, or Br ⋅⋅⋅ π halogen-bonding interactions, and a few systems are capable of forming all three types. These interactions lead to halogen-bonded rings (up to 12-membered), which propagate to form stacked 1D, 2D, or corrugated sheets. A few outliers were also identified, for example, molecules that prefer C−H ⋅⋅⋅ O hydrogen bonding over halogen bonding, or noncentrosymmetric rather than centrosymmetric organization. Computational studies based on Atoms in Molecules and Natural Bond Orbital analysis provided further insight into the halogen-bonding interactions. This study can lead to a predictive design tool-box to further explore related systems on surfaces reinforced by these weak directional forces. |
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Keywords: | halogen bonding imides noncovalent interactions quantum-chemical calculations self-assembly |
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