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The relationship between solid-state supramolecular interactions and crystal habits is highlighted based on experimental and computational analysis of the crystal structure of strong halogen-bonded (HaB) associations between iodine-containing dihalogens (ICl, IBr) with 1,4-diazabicyclo[2,2,2]octane (DABCO) as well as with substituted pyridines and phenazine. The pattern of the energy frameworks and the interplay of the attractive and repulsive interactions in the solid-state associations involving these HaB donors and acceptors directly correlated with their crystal habits. This correlation suggests that analysis of the energy framework serves as a useful tool (complementary to the earlier developed methods) to rationalize and predict the crystal habit. The X-ray structural analysis also revealed that the I⋯N distances in the complexes were in the 2.24–2.54 Å range, i.e. they were much closer to the I⋯N covalent bond length than to the van der Waals separation. The computational analysis of the nature of halogen bonding in these complexes showed delocalization of their molecular orbitals' between donor and acceptors resulting in a substantial charge transfer from the nucleophiles to dihalogens and elongation of the I⋯X bond. As a result, both I⋯N and I⋯X bonds in the strongest complexes ( e.g. , ICl with DABCO or 4-dimethylaminopyridine) are characterized by the comparable Mayer bonds orders of about 0.6, along with the electron and energy densities at their bond critical points of about 0.1 a.u. and −0.02 a.u., respectively. These data as well as the density overlap regions indicator (DORI) point to the covalency of the I⋯N bonding and suggest that the interaction within the IX complexes can be described as (unsymmetrical) hypervalent 3c/4e N⋯I⋯X bonding akin to that in trihalide or halonium ions.
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Attosecond spectroscopy reveals alignment dependent core-hole dynamics in the ICl molecule
Abstract The removal of electrons located in the core shells of molecules creates transient states that live between a few femtoseconds to attoseconds. Owing to these short lifetimes, time-resolved studies of these states are challenging and complex molecular dynamics driven solely by electronic correlation are difficult to observe. Here, we obtain few-femtosecond core-excited state lifetimes of iodine monochloride by using attosecond transient absorption on iodine 4 d −1 6 p transitions around 55 eV. Core-level ligand field splitting allows direct access of excited states aligned along and perpendicular to the ICl molecular axis. Lifetimes of 3.5 ± 0.4 fs and 4.3 ± 0.4 fs are obtained for core-hole states parallel to the bond and 6.5 ± 0.6 fs and 6.9 ± 0.6 fs for perpendicular states, while nuclear motion is essentially frozen on this timescale. Theory shows that the dramatic decrease of lifetime for core-vacancies parallel to the covalent bond is a manifestation of non-local interactions with the neighboring Cl atom of ICl.
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- Award ID(s):
- 1660417
- PAR ID:
- 10284624
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 11
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s41467-020-19496-0
